// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/service.h"

#include <memory>
#include <utility>

#include "include/dart_api.h"
#include "include/dart_native_api.h"
#include "platform/globals.h"

#include "platform/unicode.h"
#include "vm/base64.h"
#include "vm/compiler/jit/compiler.h"
#include "vm/cpu.h"
#include "vm/dart_api_impl.h"
#include "vm/dart_api_message.h"
#include "vm/dart_api_state.h"
#include "vm/dart_entry.h"
#include "vm/debugger.h"
#include "vm/heap/safepoint.h"
#include "vm/isolate.h"
#include "vm/kernel_isolate.h"
#include "vm/lockers.h"
#include "vm/malloc_hooks.h"
#include "vm/message.h"
#include "vm/message_handler.h"
#include "vm/native_arguments.h"
#include "vm/native_entry.h"
#include "vm/native_symbol.h"
#include "vm/object.h"
#include "vm/object_graph.h"
#include "vm/object_id_ring.h"
#include "vm/object_store.h"
#include "vm/parser.h"
#include "vm/port.h"
#include "vm/profiler.h"
#include "vm/profiler_service.h"
#include "vm/reusable_handles.h"
#include "vm/service_event.h"
#include "vm/service_isolate.h"
#include "vm/source_report.h"
#include "vm/stack_frame.h"
#include "vm/symbols.h"
#include "vm/timeline.h"
#include "vm/type_table.h"
#include "vm/version.h"

namespace dart {

#define Z (T->zone())

DECLARE_FLAG(bool, trace_service);
DECLARE_FLAG(bool, trace_service_pause_events);
DECLARE_FLAG(bool, profile_vm);
DEFINE_FLAG(charp,
            vm_name,
            "vm",
            "The default name of this vm as reported by the VM service "
            "protocol");

DEFINE_FLAG(bool,
            warn_on_pause_with_no_debugger,
            false,
            "Print a message when an isolate is paused but there is no "
            "debugger attached.");

#ifndef PRODUCT
// The name of this of this vm as reported by the VM service protocol.
static char* vm_name = NULL;

static const char* GetVMName() {
  if (vm_name == NULL) {
    return FLAG_vm_name;
  }
  return vm_name;
}

ServiceIdZone::ServiceIdZone() {}

ServiceIdZone::~ServiceIdZone() {}

RingServiceIdZone::RingServiceIdZone()
    : ring_(NULL), policy_(ObjectIdRing::kAllocateId) {}

RingServiceIdZone::~RingServiceIdZone() {}

void RingServiceIdZone::Init(ObjectIdRing* ring,
                             ObjectIdRing::IdPolicy policy) {
  ring_ = ring;
  policy_ = policy;
}

char* RingServiceIdZone::GetServiceId(const Object& obj) {
  ASSERT(ring_ != NULL);
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  ASSERT(zone != NULL);
  const intptr_t id = ring_->GetIdForObject(obj.raw(), policy_);
  return zone->PrintToString("objects/%" Pd "", id);
}

// TODO(johnmccutchan): Unify embedder service handler lists and their APIs.
EmbedderServiceHandler* Service::isolate_service_handler_head_ = NULL;
EmbedderServiceHandler* Service::root_service_handler_head_ = NULL;
struct ServiceMethodDescriptor;
const ServiceMethodDescriptor* FindMethod(const char* method_name);

// Support for streams defined in embedders.
Dart_ServiceStreamListenCallback Service::stream_listen_callback_ = NULL;
Dart_ServiceStreamCancelCallback Service::stream_cancel_callback_ = NULL;
Dart_GetVMServiceAssetsArchive Service::get_service_assets_callback_ = NULL;
Dart_EmbedderInformationCallback Service::embedder_information_callback_ = NULL;

// These are the set of streams known to the core VM.
StreamInfo Service::vm_stream("VM");
StreamInfo Service::isolate_stream("Isolate");
StreamInfo Service::debug_stream("Debug");
StreamInfo Service::gc_stream("GC");
StreamInfo Service::echo_stream("_Echo");
StreamInfo Service::graph_stream("_Graph");
StreamInfo Service::logging_stream("Logging");
StreamInfo Service::extension_stream("Extension");
StreamInfo Service::timeline_stream("Timeline");

const uint8_t* Service::dart_library_kernel_ = NULL;
intptr_t Service::dart_library_kernel_len_ = 0;

static StreamInfo* streams_[] = {
    &Service::vm_stream,      &Service::isolate_stream,
    &Service::debug_stream,   &Service::gc_stream,
    &Service::echo_stream,    &Service::graph_stream,
    &Service::logging_stream, &Service::extension_stream,
    &Service::timeline_stream};

bool Service::ListenStream(const char* stream_id) {
  if (FLAG_trace_service) {
    OS::PrintErr("vm-service: starting stream '%s'\n", stream_id);
  }
  intptr_t num_streams = sizeof(streams_) / sizeof(streams_[0]);
  for (intptr_t i = 0; i < num_streams; i++) {
    if (strcmp(stream_id, streams_[i]->id()) == 0) {
      streams_[i]->set_enabled(true);
      return true;
    }
  }
  if (stream_listen_callback_) {
    Thread* T = Thread::Current();
    TransitionVMToNative transition(T);
    return (*stream_listen_callback_)(stream_id);
  }
  return false;
}

void Service::CancelStream(const char* stream_id) {
  if (FLAG_trace_service) {
    OS::PrintErr("vm-service: stopping stream '%s'\n", stream_id);
  }
  intptr_t num_streams = sizeof(streams_) / sizeof(streams_[0]);
  for (intptr_t i = 0; i < num_streams; i++) {
    if (strcmp(stream_id, streams_[i]->id()) == 0) {
      streams_[i]->set_enabled(false);
      return;
    }
  }
  if (stream_cancel_callback_) {
    Thread* T = Thread::Current();
    TransitionVMToNative transition(T);
    return (*stream_cancel_callback_)(stream_id);
  }
}

RawObject* Service::RequestAssets() {
  Thread* T = Thread::Current();
  Object& object = Object::Handle();
  {
    Api::Scope api_scope(T);
    Dart_Handle handle;
    {
      TransitionVMToNative transition(T);
      if (get_service_assets_callback_ == NULL) {
        return Object::null();
      }
      handle = get_service_assets_callback_();
      if (Dart_IsError(handle)) {
        Dart_PropagateError(handle);
      }
    }
    object = Api::UnwrapHandle(handle);
  }
  if (object.IsNull()) {
    return Object::null();
  }
  if (!object.IsTypedData()) {
    const String& error_message = String::Handle(
        String::New("An implementation of Dart_GetVMServiceAssetsArchive "
                    "should return a Uint8Array or null."));
    const Error& error = Error::Handle(ApiError::New(error_message));
    Exceptions::PropagateError(error);
    return Object::null();
  }
  const TypedData& typed_data = TypedData::Cast(object);
  if (typed_data.ElementSizeInBytes() != 1) {
    const String& error_message = String::Handle(
        String::New("An implementation of Dart_GetVMServiceAssetsArchive "
                    "should return a Uint8Array or null."));
    const Error& error = Error::Handle(ApiError::New(error_message));
    Exceptions::PropagateError(error);
    return Object::null();
  }
  return object.raw();
}

static uint8_t* allocator(uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
  void* new_ptr = realloc(reinterpret_cast<void*>(ptr), new_size);
  if (new_ptr == NULL) {
    OUT_OF_MEMORY();
  }
  return reinterpret_cast<uint8_t*>(new_ptr);
}

static void PrintMissingParamError(JSONStream* js, const char* param) {
  js->PrintError(kInvalidParams, "%s expects the '%s' parameter", js->method(),
                 param);
}

static void PrintInvalidParamError(JSONStream* js, const char* param) {
  js->PrintError(kInvalidParams, "%s: invalid '%s' parameter: %s", js->method(),
                 param, js->LookupParam(param));
}

static void PrintIllegalParamError(JSONStream* js, const char* param) {
  js->PrintError(kInvalidParams, "%s: illegal '%s' parameter: %s", js->method(),
                 param, js->LookupParam(param));
}

static void PrintUnrecognizedMethodError(JSONStream* js) {
  js->PrintError(kMethodNotFound, NULL);
}

static void PrintSuccess(JSONStream* js) {
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "Success");
}

static bool CheckDebuggerDisabled(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  if (!isolate->compilation_allowed()) {
    js->PrintError(kFeatureDisabled, "Debugger is disabled in AOT mode.");
    return true;
  }
  if (isolate->debugger() == NULL) {
    js->PrintError(kFeatureDisabled, "Debugger is disabled.");
    return true;
  }
  return false;
}

static bool CheckCompilerDisabled(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  if (!isolate->compilation_allowed()) {
    js->PrintError(kFeatureDisabled, "Compiler is disabled in AOT mode.");
    return true;
  }
  return false;
}

static bool CheckProfilerDisabled(Thread* thread, JSONStream* js) {
  if (Profiler::sample_buffer() == NULL) {
    js->PrintError(kFeatureDisabled, "Profiler is disabled.");
    return true;
  }
  return false;
}

static bool GetIntegerId(const char* s, intptr_t* id, int base = 10) {
  if ((s == NULL) || (*s == '\0')) {
    // Empty string.
    return false;
  }
  if (id == NULL) {
    // No id pointer.
    return false;
  }
  intptr_t r = 0;
  char* end_ptr = NULL;
#if defined(ARCH_IS_32_BIT)
  r = strtol(s, &end_ptr, base);
#else
  r = strtoll(s, &end_ptr, base);
#endif
  if (end_ptr == s) {
    // String was not advanced at all, cannot be valid.
    return false;
  }
  *id = r;
  return true;
}

static bool GetUnsignedIntegerId(const char* s, uintptr_t* id, int base = 10) {
  if ((s == NULL) || (*s == '\0')) {
    // Empty string.
    return false;
  }
  if (id == NULL) {
    // No id pointer.
    return false;
  }
  uintptr_t r = 0;
  char* end_ptr = NULL;
#if defined(ARCH_IS_32_BIT)
  r = strtoul(s, &end_ptr, base);
#else
  r = strtoull(s, &end_ptr, base);
#endif
  if (end_ptr == s) {
    // String was not advanced at all, cannot be valid.
    return false;
  }
  *id = r;
  return true;
}

static bool GetInteger64Id(const char* s, int64_t* id, int base = 10) {
  if ((s == NULL) || (*s == '\0')) {
    // Empty string.
    return false;
  }
  if (id == NULL) {
    // No id pointer.
    return false;
  }
  int64_t r = 0;
  char* end_ptr = NULL;
  r = strtoll(s, &end_ptr, base);
  if (end_ptr == s) {
    // String was not advanced at all, cannot be valid.
    return false;
  }
  *id = r;
  return true;
}

// Scans the string until the '-' character. Returns pointer to string
// at '-' character. Returns NULL if not found.
static const char* ScanUntilDash(const char* s) {
  if ((s == NULL) || (*s == '\0')) {
    // Empty string.
    return NULL;
  }
  while (*s != '\0') {
    if (*s == '-') {
      return s;
    }
    s++;
  }
  return NULL;
}

static bool GetCodeId(const char* s, int64_t* timestamp, uword* address) {
  if ((s == NULL) || (*s == '\0')) {
    // Empty string.
    return false;
  }
  if ((timestamp == NULL) || (address == NULL)) {
    // Bad arguments.
    return false;
  }
  // Extract the timestamp.
  if (!GetInteger64Id(s, timestamp, 16) || (*timestamp < 0)) {
    return false;
  }
  s = ScanUntilDash(s);
  if (s == NULL) {
    return false;
  }
  // Skip the dash.
  s++;
  // Extract the PC.
  if (!GetUnsignedIntegerId(s, address, 16)) {
    return false;
  }
  return true;
}

// Verifies that |s| begins with |prefix| and then calls |GetIntegerId| on
// the remainder of |s|.
static bool GetPrefixedIntegerId(const char* s,
                                 const char* prefix,
                                 intptr_t* service_id) {
  if (s == NULL) {
    return false;
  }
  ASSERT(prefix != NULL);
  const intptr_t kInputLen = strlen(s);
  const intptr_t kPrefixLen = strlen(prefix);
  ASSERT(kPrefixLen > 0);
  if (kInputLen <= kPrefixLen) {
    return false;
  }
  if (strncmp(s, prefix, kPrefixLen) != 0) {
    return false;
  }
  // Prefix satisfied. Move forward.
  s += kPrefixLen;
  // Attempt to read integer id.
  return GetIntegerId(s, service_id);
}

static bool IsValidClassId(Isolate* isolate, intptr_t cid) {
  ASSERT(isolate != NULL);
  ClassTable* class_table = isolate->class_table();
  ASSERT(class_table != NULL);
  return class_table->IsValidIndex(cid) && class_table->HasValidClassAt(cid);
}

static RawClass* GetClassForId(Isolate* isolate, intptr_t cid) {
  ASSERT(isolate == Isolate::Current());
  ASSERT(isolate != NULL);
  ClassTable* class_table = isolate->class_table();
  ASSERT(class_table != NULL);
  return class_table->At(cid);
}

// TODO(johnmccutchan): Split into separate file and write unit tests.
class MethodParameter {
 public:
  MethodParameter(const char* name, bool required)
      : name_(name), required_(required) {}

  virtual ~MethodParameter() {}

  virtual bool Validate(const char* value) const { return true; }

  virtual bool ValidateObject(const Object& value) const { return true; }

  const char* name() const { return name_; }

  bool required() const { return required_; }

  virtual void PrintError(const char* name,
                          const char* value,
                          JSONStream* js) const {
    PrintInvalidParamError(js, name);
  }

  virtual void PrintErrorObject(const char* name,
                                const Object& value,
                                JSONStream* js) const {
    PrintInvalidParamError(js, name);
  }

 private:
  const char* name_;
  bool required_;
};

class DartStringParameter : public MethodParameter {
 public:
  DartStringParameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool ValidateObject(const Object& value) const {
    return value.IsString();
  }
};

class DartListParameter : public MethodParameter {
 public:
  DartListParameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool ValidateObject(const Object& value) const {
    return value.IsArray() || value.IsGrowableObjectArray();
  }
};

class NoSuchParameter : public MethodParameter {
 public:
  explicit NoSuchParameter(const char* name) : MethodParameter(name, false) {}

  virtual bool Validate(const char* value) const { return (value == NULL); }

  virtual bool ValidateObject(const Object& value) const {
    return value.IsNull();
  }
};

class BoolParameter : public MethodParameter {
 public:
  BoolParameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool Validate(const char* value) const {
    if (value == NULL) {
      return false;
    }
    return (strcmp("true", value) == 0) || (strcmp("false", value) == 0);
  }

  static bool Parse(const char* value, bool default_value = false) {
    if (value == NULL) {
      return default_value;
    }
    return strcmp("true", value) == 0;
  }
};

class UIntParameter : public MethodParameter {
 public:
  UIntParameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool Validate(const char* value) const {
    if (value == NULL) {
      return false;
    }
    for (const char* cp = value; *cp != '\0'; cp++) {
      if (*cp < '0' || *cp > '9') {
        return false;
      }
    }
    return true;
  }

  static uintptr_t Parse(const char* value) {
    if (value == NULL) {
      return -1;
    }
    char* end_ptr = NULL;
    uintptr_t result = strtoul(value, &end_ptr, 10);
    ASSERT(*end_ptr == '\0');  // Parsed full string
    return result;
  }
};

class Int64Parameter : public MethodParameter {
 public:
  Int64Parameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool Validate(const char* value) const {
    if (value == NULL) {
      return false;
    }
    for (const char* cp = value; *cp != '\0'; cp++) {
      if ((*cp < '0' || *cp > '9') && (*cp != '-')) {
        return false;
      }
    }
    return true;
  }

  static int64_t Parse(const char* value, int64_t default_value = -1) {
    if ((value == NULL) || (*value == '\0')) {
      return default_value;
    }
    char* end_ptr = NULL;
    int64_t result = strtoll(value, &end_ptr, 10);
    ASSERT(*end_ptr == '\0');  // Parsed full string
    return result;
  }
};

class IdParameter : public MethodParameter {
 public:
  IdParameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool Validate(const char* value) const { return (value != NULL); }
};

class StringParameter : public MethodParameter {
 public:
  StringParameter(const char* name, bool required)
      : MethodParameter(name, required) {}

  virtual bool Validate(const char* value) const { return (value != NULL); }
};

class RunnableIsolateParameter : public MethodParameter {
 public:
  explicit RunnableIsolateParameter(const char* name)
      : MethodParameter(name, true) {}

  virtual bool Validate(const char* value) const {
    Isolate* isolate = Isolate::Current();
    return (value != NULL) && (isolate != NULL) && (isolate->is_runnable());
  }

  virtual void PrintError(const char* name,
                          const char* value,
                          JSONStream* js) const {
    js->PrintError(kIsolateMustBeRunnable,
                   "Isolate must be runnable before this request is made.");
  }
};

#define ISOLATE_PARAMETER new IdParameter("isolateId", true)
#define NO_ISOLATE_PARAMETER new NoSuchParameter("isolateId")
#define RUNNABLE_ISOLATE_PARAMETER new RunnableIsolateParameter("isolateId")

class EnumParameter : public MethodParameter {
 public:
  EnumParameter(const char* name, bool required, const char* const* enums)
      : MethodParameter(name, required), enums_(enums) {}

  virtual bool Validate(const char* value) const {
    if (value == NULL) {
      return true;
    }
    for (intptr_t i = 0; enums_[i] != NULL; i++) {
      if (strcmp(value, enums_[i]) == 0) {
        return true;
      }
    }
    return false;
  }

 private:
  const char* const* enums_;
};

// If the key is not found, this function returns the last element in the
// values array. This can be used to encode the default value.
template <typename T>
T EnumMapper(const char* value, const char* const* enums, T* values) {
  ASSERT(value != NULL);
  intptr_t i = 0;
  for (i = 0; enums[i] != NULL; i++) {
    if (strcmp(value, enums[i]) == 0) {
      return values[i];
    }
  }
  // Default value.
  return values[i];
}

class EnumListParameter : public MethodParameter {
 public:
  EnumListParameter(const char* name, bool required, const char* const* enums)
      : MethodParameter(name, required), enums_(enums) {}

  virtual bool Validate(const char* value) const {
    return ElementCount(value) >= 0;
  }

  const char** Parse(Zone* zone, const char* value_in) const {
    const char* kJsonChars = " \t\r\n[,]";

    // Make a writeable copy of the value.
    char* value = zone->MakeCopyOfString(value_in);
    intptr_t element_count = ElementCount(value);
    intptr_t element_pos = 0;

    // Allocate our element array.  +1 for NULL terminator.
    char** elements = zone->Alloc<char*>(element_count + 1);
    elements[element_count] = NULL;

    // Parse the string destructively.  Build the list of elements.
    while (element_pos < element_count) {
      // Skip to the next element.
      value += strspn(value, kJsonChars);

      intptr_t len = strcspn(value, kJsonChars);
      ASSERT(len > 0);  // We rely on the parameter being validated already.
      value[len] = '\0';
      elements[element_pos++] = value;

      // Advance.  +1 for null terminator.
      value += (len + 1);
    }
    return const_cast<const char**>(elements);
  }

 private:
  // For now observatory enums are ascii letters plus underscore.
  static bool IsEnumChar(char c) {
    return (((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z')) ||
            (c == '_'));
  }

  // Returns number of elements in the list.  -1 on parse error.
  intptr_t ElementCount(const char* value) const {
    const char* kJsonWhitespaceChars = " \t\r\n";
    if (value == NULL) {
      return -1;
    }
    const char* cp = value;
    cp += strspn(cp, kJsonWhitespaceChars);
    if (*cp++ != '[') {
      // Missing initial [.
      return -1;
    }
    bool closed = false;
    bool element_allowed = true;
    intptr_t element_count = 0;
    while (true) {
      // Skip json whitespace.
      cp += strspn(cp, kJsonWhitespaceChars);
      switch (*cp) {
        case '\0':
          return closed ? element_count : -1;
        case ']':
          closed = true;
          cp++;
          break;
        case ',':
          if (element_allowed) {
            return -1;
          }
          element_allowed = true;
          cp++;
          break;
        default:
          if (!element_allowed) {
            return -1;
          }
          bool valid_enum = false;
          const char* id_start = cp;
          while (IsEnumChar(*cp)) {
            cp++;
          }
          if (cp == id_start) {
            // Empty identifier, something like this [,].
            return -1;
          }
          intptr_t id_len = cp - id_start;
          if (enums_ != NULL) {
            for (intptr_t i = 0; enums_[i] != NULL; i++) {
              intptr_t len = strlen(enums_[i]);
              if (len == id_len && strncmp(id_start, enums_[i], len) == 0) {
                element_count++;
                valid_enum = true;
                element_allowed = false;  // we need a comma first.
                break;
              }
            }
          }
          if (!valid_enum) {
            return -1;
          }
          break;
      }
    }
  }

  const char* const* enums_;
};

typedef bool (*ServiceMethodEntry)(Thread* thread, JSONStream* js);

struct ServiceMethodDescriptor {
  const char* name;
  const ServiceMethodEntry entry;
  const MethodParameter* const* parameters;
};

// TODO(johnmccutchan): Do we reject unexpected parameters?
static bool ValidateParameters(const MethodParameter* const* parameters,
                               JSONStream* js) {
  if (parameters == NULL) {
    return true;
  }
  if (js->NumObjectParameters() > 0) {
    Object& value = Object::Handle();
    for (intptr_t i = 0; parameters[i] != NULL; i++) {
      const MethodParameter* parameter = parameters[i];
      const char* name = parameter->name();
      const bool required = parameter->required();
      value = js->LookupObjectParam(name);
      const bool has_parameter = !value.IsNull();
      if (required && !has_parameter) {
        PrintMissingParamError(js, name);
        return false;
      }
      if (has_parameter && !parameter->ValidateObject(value)) {
        parameter->PrintErrorObject(name, value, js);
        return false;
      }
    }
  } else {
    for (intptr_t i = 0; parameters[i] != NULL; i++) {
      const MethodParameter* parameter = parameters[i];
      const char* name = parameter->name();
      const bool required = parameter->required();
      const char* value = js->LookupParam(name);
      const bool has_parameter = (value != NULL);
      if (required && !has_parameter) {
        PrintMissingParamError(js, name);
        return false;
      }
      if (has_parameter && !parameter->Validate(value)) {
        parameter->PrintError(name, value, js);
        return false;
      }
    }
  }
  return true;
}

void Service::PostError(const String& method_name,
                        const Array& parameter_keys,
                        const Array& parameter_values,
                        const Instance& reply_port,
                        const Instance& id,
                        const Error& error) {
  Thread* T = Thread::Current();
  StackZone zone(T);
  HANDLESCOPE(T);
  JSONStream js;
  js.Setup(zone.GetZone(), SendPort::Cast(reply_port).Id(), id, method_name,
           parameter_keys, parameter_values);
  js.PrintError(kExtensionError, "Error in extension `%s`: %s", js.method(),
                error.ToErrorCString());
  js.PostReply();
}

RawError* Service::InvokeMethod(Isolate* I,
                                const Array& msg,
                                bool parameters_are_dart_objects) {
  Thread* T = Thread::Current();
  ASSERT(I == T->isolate());
  ASSERT(I != NULL);
  ASSERT(T->execution_state() == Thread::kThreadInVM);
  ASSERT(!msg.IsNull());
  ASSERT(msg.Length() == 6);

  {
    StackZone zone(T);
    HANDLESCOPE(T);

    Instance& reply_port = Instance::Handle(Z);
    Instance& seq = String::Handle(Z);
    String& method_name = String::Handle(Z);
    Array& param_keys = Array::Handle(Z);
    Array& param_values = Array::Handle(Z);
    reply_port ^= msg.At(1);
    seq ^= msg.At(2);
    method_name ^= msg.At(3);
    param_keys ^= msg.At(4);
    param_values ^= msg.At(5);

    ASSERT(!method_name.IsNull());
    ASSERT(seq.IsNull() || seq.IsString() || seq.IsNumber());
    ASSERT(!param_keys.IsNull());
    ASSERT(!param_values.IsNull());
    ASSERT(param_keys.Length() == param_values.Length());

    // We expect a reply port unless there is a null sequence id,
    // which indicates that no reply should be sent.  We use this in
    // tests.
    if (!seq.IsNull() && !reply_port.IsSendPort()) {
      FATAL("SendPort expected.");
    }

    JSONStream js;
    Dart_Port reply_port_id =
        (reply_port.IsNull() ? ILLEGAL_PORT : SendPort::Cast(reply_port).Id());
    js.Setup(zone.GetZone(), reply_port_id, seq, method_name, param_keys,
             param_values, parameters_are_dart_objects);

    // RPC came in with a custom service id zone.
    const char* id_zone_param = js.LookupParam("_idZone");

    if (id_zone_param != NULL) {
      // Override id zone.
      if (strcmp("default", id_zone_param) == 0) {
        // Ring with eager id allocation. This is the default ring and default
        // policy.
        // Nothing to do.
      } else if (strcmp("default.reuse", id_zone_param) == 0) {
        // Change the default ring's policy.
        RingServiceIdZone* zone =
            reinterpret_cast<RingServiceIdZone*>(js.id_zone());
        zone->set_policy(ObjectIdRing::kReuseId);
      } else {
        // TODO(johnmccutchan): Support creating, deleting, and selecting
        // custom service id zones.
        // For now, always return an error.
        PrintInvalidParamError(&js, "_idZone");
        js.PostReply();
        return T->StealStickyError();
      }
    }
    const char* c_method_name = method_name.ToCString();

    const ServiceMethodDescriptor* method = FindMethod(c_method_name);
    if (method != NULL) {
      if (!ValidateParameters(method->parameters, &js)) {
        js.PostReply();
        return T->StealStickyError();
      }
      if (method->entry(T, &js)) {
        js.PostReply();
      } else {
        // NOTE(turnidge): All message handlers currently return true,
        // so this case shouldn't be reached, at present.
        UNIMPLEMENTED();
      }
      return T->StealStickyError();
    }

    EmbedderServiceHandler* handler = FindIsolateEmbedderHandler(c_method_name);
    if (handler == NULL) {
      handler = FindRootEmbedderHandler(c_method_name);
    }

    if (handler != NULL) {
      EmbedderHandleMessage(handler, &js);
      return T->StealStickyError();
    }

    const Instance& extension_handler =
        Instance::Handle(Z, I->LookupServiceExtensionHandler(method_name));
    if (!extension_handler.IsNull()) {
      ScheduleExtensionHandler(extension_handler, method_name, param_keys,
                               param_values, reply_port, seq);
      // Schedule was successful. Extension code will post a reply
      // asynchronously.
      return T->StealStickyError();
    }

    PrintUnrecognizedMethodError(&js);
    js.PostReply();
    return T->StealStickyError();
  }
}

RawError* Service::HandleRootMessage(const Array& msg_instance) {
  Isolate* isolate = Isolate::Current();
  return InvokeMethod(isolate, msg_instance);
}

RawError* Service::HandleObjectRootMessage(const Array& msg_instance) {
  Isolate* isolate = Isolate::Current();
  return InvokeMethod(isolate, msg_instance, true);
}

RawError* Service::HandleIsolateMessage(Isolate* isolate, const Array& msg) {
  ASSERT(isolate != NULL);
  const Error& error = Error::Handle(InvokeMethod(isolate, msg));
  return MaybePause(isolate, error);
}

static void Finalizer(void* isolate_callback_data,
                      Dart_WeakPersistentHandle handle,
                      void* buffer) {
  free(buffer);
}

void Service::SendEvent(const char* stream_id,
                        const char* event_type,
                        uint8_t* bytes,
                        intptr_t bytes_length) {
  Thread* thread = Thread::Current();
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  ASSERT(!Isolate::IsVMInternalIsolate(isolate));

  if (FLAG_trace_service) {
    OS::PrintErr(
        "vm-service: Pushing ServiceEvent(isolate='%s', "
        "isolateId='" ISOLATE_SERVICE_ID_FORMAT_STRING
        "', kind='%s',"
        " len=%" Pd ") to stream %s\n",
        isolate->name(), static_cast<int64_t>(isolate->main_port()), event_type,
        bytes_length, stream_id);
  }

  bool result;
  {
    TransitionVMToNative transition(thread);

    Dart_CObject cbytes;
    cbytes.type = Dart_CObject_kExternalTypedData;
    cbytes.value.as_external_typed_data.type = Dart_TypedData_kUint8;
    cbytes.value.as_external_typed_data.length = bytes_length;
    cbytes.value.as_external_typed_data.data = bytes;
    cbytes.value.as_external_typed_data.peer = bytes;
    cbytes.value.as_external_typed_data.callback = Finalizer;

    Dart_CObject cstream_id;
    cstream_id.type = Dart_CObject_kString;
    cstream_id.value.as_string = const_cast<char*>(stream_id);

    Dart_CObject* elements[2];
    elements[0] = &cstream_id;
    elements[1] = &cbytes;
    Dart_CObject message;
    message.type = Dart_CObject_kArray;
    message.value.as_array.length = 2;
    message.value.as_array.values = elements;

    result = Dart_PostCObject(ServiceIsolate::Port(), &message);
  }

  if (!result) {
    free(bytes);
  }
}

void Service::SendEventWithData(const char* stream_id,
                                const char* event_type,
                                const char* metadata,
                                intptr_t metadata_size,
                                const uint8_t* data,
                                intptr_t data_size) {
  // Bitstream: [metadata size (big-endian 64 bit)] [metadata (UTF-8)] [data]
  const intptr_t total_bytes = sizeof(uint64_t) + metadata_size + data_size;

  uint8_t* message = static_cast<uint8_t*>(malloc(total_bytes));
  if (message == NULL) {
    OUT_OF_MEMORY();
  }
  intptr_t offset = 0;

  // Metadata size.
  reinterpret_cast<uint64_t*>(message)[0] =
      Utils::HostToBigEndian64(metadata_size);
  offset += sizeof(uint64_t);

  // Metadata.
  memmove(&message[offset], metadata, metadata_size);
  offset += metadata_size;

  // Data.
  memmove(&message[offset], data, data_size);
  offset += data_size;

  ASSERT(offset == total_bytes);
  SendEvent(stream_id, event_type, message, total_bytes);
}

static void ReportPauseOnConsole(ServiceEvent* event) {
  const char* name = event->isolate()->name();
  const int64_t main_port = static_cast<int64_t>(event->isolate()->main_port());
  switch (event->kind()) {
    case ServiceEvent::kPauseStart:
      OS::PrintErr("vm-service: isolate(%" Pd64
                   ") '%s' has no debugger attached and is paused at start.",
                   main_port, name);
      break;
    case ServiceEvent::kPauseExit:
      OS::PrintErr("vm-service: isolate(%" Pd64
                   ")  '%s' has no debugger attached and is paused at exit.",
                   main_port, name);
      break;
    case ServiceEvent::kPauseException:
      OS::PrintErr(
          "vm-service: isolate (%" Pd64
          ") '%s' has no debugger attached and is paused due to exception.",
          main_port, name);
      break;
    case ServiceEvent::kPauseInterrupted:
      OS::PrintErr(
          "vm-service: isolate (%" Pd64
          ") '%s' has no debugger attached and is paused due to interrupt.",
          main_port, name);
      break;
    case ServiceEvent::kPauseBreakpoint:
      OS::PrintErr("vm-service: isolate (%" Pd64
                   ") '%s' has no debugger attached and is paused.",
                   main_port, name);
      break;
    case ServiceEvent::kPausePostRequest:
      OS::PrintErr("vm-service: isolate (%" Pd64
                   ") '%s' has no debugger attached and is paused post reload.",
                   main_port, name);
      break;
    default:
      UNREACHABLE();
      break;
  }
  if (!ServiceIsolate::IsRunning()) {
    OS::PrintErr("  Start the vm-service to debug.\n");
  } else if (ServiceIsolate::server_address() == NULL) {
    OS::PrintErr("  Connect to Observatory to debug.\n");
  } else {
    OS::PrintErr("  Connect to Observatory at %s to debug.\n",
                 ServiceIsolate::server_address());
  }
  const Error& err = Error::Handle(Thread::Current()->sticky_error());
  if (!err.IsNull()) {
    OS::PrintErr("%s\n", err.ToErrorCString());
  }
}

void Service::HandleEvent(ServiceEvent* event) {
  if (event->stream_info() != NULL && !event->stream_info()->enabled()) {
    if (FLAG_warn_on_pause_with_no_debugger && event->IsPause()) {
      // If we are about to pause a running program which has no
      // debugger connected, tell the user about it.
      ReportPauseOnConsole(event);
    }
    // Ignore events when no one is listening to the event stream.
    return;
  }
  if (!ServiceIsolate::IsRunning()) {
    return;
  }
  JSONStream js;
  const char* stream_id = event->stream_id();
  ASSERT(stream_id != NULL);
  {
    JSONObject jsobj(&js);
    jsobj.AddProperty("jsonrpc", "2.0");
    jsobj.AddProperty("method", "streamNotify");
    JSONObject params(&jsobj, "params");
    params.AddProperty("streamId", stream_id);
    params.AddProperty("event", event);
  }
  PostEvent(event->isolate(), stream_id, event->KindAsCString(), &js);

  // Post event to the native Service Stream handlers if set.
  if (event->stream_info() != nullptr &&
      event->stream_info()->consumer() != nullptr) {
    auto length = js.buffer()->length();
    event->stream_info()->consumer()(
        reinterpret_cast<uint8_t*>(js.buffer()->buf()), length);
  }
}

void Service::PostEvent(Isolate* isolate,
                        const char* stream_id,
                        const char* kind,
                        JSONStream* event) {
  ASSERT(stream_id != NULL);
  ASSERT(kind != NULL);
  ASSERT(event != NULL);

  if (FLAG_trace_service) {
    if (isolate != NULL) {
      OS::PrintErr(
          "vm-service: Pushing ServiceEvent(isolate='%s', "
          "isolateId='" ISOLATE_SERVICE_ID_FORMAT_STRING
          "', kind='%s') to stream %s\n",
          isolate->name(), static_cast<int64_t>(isolate->main_port()), kind,
          stream_id);
    } else {
      OS::PrintErr(
          "vm-service: Pushing ServiceEvent(isolate='<no current isolate>', "
          "kind='%s') to stream %s\n",
          kind, stream_id);
    }
  }

  // Message is of the format [<stream id>, <json string>].
  //
  // Build the event message in the C heap to avoid dart heap
  // allocation.  This method can be called while we have acquired a
  // direct pointer to typed data, so we can't allocate here.
  Dart_CObject list_cobj;
  Dart_CObject* list_values[2];
  list_cobj.type = Dart_CObject_kArray;
  list_cobj.value.as_array.length = 2;
  list_cobj.value.as_array.values = list_values;

  Dart_CObject stream_id_cobj;
  stream_id_cobj.type = Dart_CObject_kString;
  stream_id_cobj.value.as_string = const_cast<char*>(stream_id);
  list_values[0] = &stream_id_cobj;

  Dart_CObject json_cobj;
  json_cobj.type = Dart_CObject_kString;
  json_cobj.value.as_string = const_cast<char*>(event->ToCString());
  list_values[1] = &json_cobj;

  ApiMessageWriter writer;
  std::unique_ptr<Message> msg = writer.WriteCMessage(
      &list_cobj, ServiceIsolate::Port(), Message::kNormalPriority);
  if (msg != nullptr) {
    PortMap::PostMessage(std::move(msg));
  }
}

class EmbedderServiceHandler {
 public:
  explicit EmbedderServiceHandler(const char* name)
      : name_(NULL), callback_(NULL), user_data_(NULL), next_(NULL) {
    ASSERT(name != NULL);
    name_ = strdup(name);
  }

  ~EmbedderServiceHandler() { free(name_); }

  const char* name() const { return name_; }

  Dart_ServiceRequestCallback callback() const { return callback_; }
  void set_callback(Dart_ServiceRequestCallback callback) {
    callback_ = callback;
  }

  void* user_data() const { return user_data_; }
  void set_user_data(void* user_data) { user_data_ = user_data; }

  EmbedderServiceHandler* next() const { return next_; }
  void set_next(EmbedderServiceHandler* next) { next_ = next; }

 private:
  char* name_;
  Dart_ServiceRequestCallback callback_;
  void* user_data_;
  EmbedderServiceHandler* next_;
};

void Service::EmbedderHandleMessage(EmbedderServiceHandler* handler,
                                    JSONStream* js) {
  ASSERT(handler != NULL);
  Dart_ServiceRequestCallback callback = handler->callback();
  ASSERT(callback != NULL);
  const char* response = NULL;
  bool success;
  {
    TransitionVMToNative transition(Thread::Current());
    success = callback(js->method(), js->param_keys(), js->param_values(),
                       js->num_params(), handler->user_data(), &response);
  }
  ASSERT(response != NULL);
  if (!success) {
    js->SetupError();
  }
  js->buffer()->AddString(response);
  js->PostReply();
  free(const_cast<char*>(response));
}

void Service::RegisterIsolateEmbedderCallback(
    const char* name,
    Dart_ServiceRequestCallback callback,
    void* user_data) {
  if (name == NULL) {
    return;
  }
  EmbedderServiceHandler* handler = FindIsolateEmbedderHandler(name);
  if (handler != NULL) {
    // Update existing handler entry.
    handler->set_callback(callback);
    handler->set_user_data(user_data);
    return;
  }
  // Create a new handler.
  handler = new EmbedderServiceHandler(name);
  handler->set_callback(callback);
  handler->set_user_data(user_data);

  // Insert into isolate_service_handler_head_ list.
  handler->set_next(isolate_service_handler_head_);
  isolate_service_handler_head_ = handler;
}

EmbedderServiceHandler* Service::FindIsolateEmbedderHandler(const char* name) {
  EmbedderServiceHandler* current = isolate_service_handler_head_;
  while (current != NULL) {
    if (strcmp(name, current->name()) == 0) {
      return current;
    }
    current = current->next();
  }
  return NULL;
}

void Service::RegisterRootEmbedderCallback(const char* name,
                                           Dart_ServiceRequestCallback callback,
                                           void* user_data) {
  if (name == NULL) {
    return;
  }
  EmbedderServiceHandler* handler = FindRootEmbedderHandler(name);
  if (handler != NULL) {
    // Update existing handler entry.
    handler->set_callback(callback);
    handler->set_user_data(user_data);
    return;
  }
  // Create a new handler.
  handler = new EmbedderServiceHandler(name);
  handler->set_callback(callback);
  handler->set_user_data(user_data);

  // Insert into root_service_handler_head_ list.
  handler->set_next(root_service_handler_head_);
  root_service_handler_head_ = handler;
}

void Service::SetEmbedderStreamCallbacks(
    Dart_ServiceStreamListenCallback listen_callback,
    Dart_ServiceStreamCancelCallback cancel_callback) {
  stream_listen_callback_ = listen_callback;
  stream_cancel_callback_ = cancel_callback;
}

void Service::SetNativeServiceStreamCallback(Dart_NativeStreamConsumer consumer,
                                             const char* stream_id) {
  for (auto stream : streams_) {
    if (stream->id() == stream_id) {
      stream->set_consumer(consumer);
    }
  }
  // Enable stream.
  ListenStream(stream_id);
}

void Service::SetGetServiceAssetsCallback(
    Dart_GetVMServiceAssetsArchive get_service_assets) {
  get_service_assets_callback_ = get_service_assets;
}

void Service::SetEmbedderInformationCallback(
    Dart_EmbedderInformationCallback callback) {
  embedder_information_callback_ = callback;
}

int64_t Service::CurrentRSS() {
  if (embedder_information_callback_ == NULL) {
    return -1;
  }
  Dart_EmbedderInformation info = {
    0,  // version
    NULL,  // name
    0,  // max_rss
    0  // current_rss
  };
  embedder_information_callback_(&info);
  ASSERT(info.version == DART_EMBEDDER_INFORMATION_CURRENT_VERSION);
  return info.current_rss;
}

int64_t Service::MaxRSS() {
  if (embedder_information_callback_ == NULL) {
    return -1;
  }
  Dart_EmbedderInformation info = {
    0,  // version
    NULL,  // name
    0,  // max_rss
    0  // current_rss
  };
  embedder_information_callback_(&info);
  ASSERT(info.version == DART_EMBEDDER_INFORMATION_CURRENT_VERSION);
  return info.max_rss;
}

void Service::SetDartLibraryKernelForSources(const uint8_t* kernel_bytes,
                                             intptr_t kernel_length) {
  dart_library_kernel_ = kernel_bytes;
  dart_library_kernel_len_ = kernel_length;
}

EmbedderServiceHandler* Service::FindRootEmbedderHandler(const char* name) {
  EmbedderServiceHandler* current = root_service_handler_head_;
  while (current != NULL) {
    if (strcmp(name, current->name()) == 0) {
      return current;
    }
    current = current->next();
  }
  return NULL;
}

void Service::ScheduleExtensionHandler(const Instance& handler,
                                       const String& method_name,
                                       const Array& parameter_keys,
                                       const Array& parameter_values,
                                       const Instance& reply_port,
                                       const Instance& id) {
  ASSERT(!handler.IsNull());
  ASSERT(!method_name.IsNull());
  ASSERT(!parameter_keys.IsNull());
  ASSERT(!parameter_values.IsNull());
  ASSERT(!reply_port.IsNull());
  Isolate* isolate = Isolate::Current();
  ASSERT(isolate != NULL);
  isolate->AppendServiceExtensionCall(handler, method_name, parameter_keys,
                                      parameter_values, reply_port, id);
}

static const MethodParameter* get_isolate_params[] = {
    ISOLATE_PARAMETER, NULL,
};

static bool GetIsolate(Thread* thread, JSONStream* js) {
  thread->isolate()->PrintJSON(js, false);
  return true;
}

static const MethodParameter* get_memory_usage_params[] = {
    ISOLATE_PARAMETER,
    NULL,
};

static bool GetMemoryUsage(Thread* thread, JSONStream* js) {
  thread->isolate()->PrintMemoryUsageJSON(js);
  return true;
}

static const MethodParameter* get_scripts_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    NULL,
};

static bool GetScripts(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  Zone* zone = thread->zone();
  ASSERT(isolate != NULL);

  const GrowableObjectArray& libs =
      GrowableObjectArray::Handle(zone, isolate->object_store()->libraries());
  intptr_t num_libs = libs.Length();

  Library& lib = Library::Handle(zone);
  Array& scripts = Array::Handle(zone);
  Script& script = Script::Handle(zone);

  JSONObject jsobj(js);
  {
    jsobj.AddProperty("type", "ScriptList");
    JSONArray script_array(&jsobj, "scripts");
    for (intptr_t i = 0; i < num_libs; i++) {
      lib ^= libs.At(i);
      ASSERT(!lib.IsNull());
      scripts = lib.LoadedScripts();
      for (intptr_t j = 0; j < scripts.Length(); j++) {
        script ^= scripts.At(j);
        ASSERT(!script.IsNull());
        script_array.AddValue(script);
      }
    }
  }
  return true;
}

static const MethodParameter* get_unused_changes_in_last_reload_params[] = {
    ISOLATE_PARAMETER, NULL,
};

static bool GetUnusedChangesInLastReload(Thread* thread, JSONStream* js) {
  if (CheckCompilerDisabled(thread, js)) {
    return true;
  }

  const GrowableObjectArray& changed_in_last_reload =
      GrowableObjectArray::Handle(
          thread->isolate()->object_store()->changed_in_last_reload());
  if (changed_in_last_reload.IsNull()) {
    js->PrintError(kIsolateMustHaveReloaded, "No change to compare with.");
    return true;
  }
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "UnusedChangesInLastReload");
  JSONArray jsarr(&jsobj, "unused");
  Object& changed = Object::Handle();
  Function& function = Function::Handle();
  Field& field = Field::Handle();
  Class& cls = Class::Handle();
  Array& functions = Array::Handle();
  Array& fields = Array::Handle();
  for (intptr_t i = 0; i < changed_in_last_reload.Length(); i++) {
    changed = changed_in_last_reload.At(i);
    if (changed.IsFunction()) {
      function ^= changed.raw();
      if (!function.WasExecuted()) {
        jsarr.AddValue(function);
      }
    } else if (changed.IsField()) {
      field ^= changed.raw();
      if (field.IsUninitialized() ||
          field.initializer_changed_after_initialization()) {
        jsarr.AddValue(field);
      }
    } else if (changed.IsClass()) {
      cls ^= changed.raw();
      if (!cls.is_finalized()) {
        // Not used at all.
        jsarr.AddValue(cls);
      } else {
        functions = cls.functions();
        for (intptr_t j = 0; j < functions.Length(); j++) {
          function ^= functions.At(j);
          if (!function.WasExecuted()) {
            jsarr.AddValue(function);
          }
        }
        fields = cls.fields();
        for (intptr_t j = 0; j < fields.Length(); j++) {
          field ^= fields.At(j);
          if (field.IsUninitialized()) {
            jsarr.AddValue(field);
          }
        }
      }
    }
  }
  return true;
}

static const MethodParameter* get_stack_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    NULL,
};

static bool GetStack(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  Isolate* isolate = thread->isolate();
  DebuggerStackTrace* stack = isolate->debugger()->StackTrace();
  DebuggerStackTrace* async_causal_stack =
      isolate->debugger()->AsyncCausalStackTrace();
  DebuggerStackTrace* awaiter_stack = isolate->debugger()->AwaiterStackTrace();
  // Do we want the complete script object and complete local variable objects?
  // This is true for dump requests.
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "Stack");
  {
    JSONArray jsarr(&jsobj, "frames");

    intptr_t num_frames = stack->Length();
    for (intptr_t i = 0; i < num_frames; i++) {
      ActivationFrame* frame = stack->FrameAt(i);
      JSONObject jsobj(&jsarr);
      frame->PrintToJSONObject(&jsobj);
      jsobj.AddProperty("index", i);
    }
  }

  if (async_causal_stack != NULL) {
    JSONArray jsarr(&jsobj, "asyncCausalFrames");
    intptr_t num_frames = async_causal_stack->Length();
    for (intptr_t i = 0; i < num_frames; i++) {
      ActivationFrame* frame = async_causal_stack->FrameAt(i);
      JSONObject jsobj(&jsarr);
      frame->PrintToJSONObject(&jsobj);
      jsobj.AddProperty("index", i);
    }
  }

  if (awaiter_stack != NULL) {
    JSONArray jsarr(&jsobj, "awaiterFrames");
    intptr_t num_frames = awaiter_stack->Length();
    for (intptr_t i = 0; i < num_frames; i++) {
      ActivationFrame* frame = awaiter_stack->FrameAt(i);
      JSONObject jsobj(&jsarr);
      frame->PrintToJSONObject(&jsobj);
      jsobj.AddProperty("index", i);
    }
  }

  {
    MessageHandler::AcquiredQueues aq(isolate->message_handler());
    jsobj.AddProperty("messages", aq.queue());
  }

  return true;
}

static bool HandleCommonEcho(JSONObject* jsobj, JSONStream* js) {
  jsobj->AddProperty("type", "_EchoResponse");
  if (js->HasParam("text")) {
    jsobj->AddProperty("text", js->LookupParam("text"));
  }
  return true;
}

void Service::SendEchoEvent(Isolate* isolate, const char* text) {
  JSONStream js;
  {
    JSONObject jsobj(&js);
    jsobj.AddProperty("jsonrpc", "2.0");
    jsobj.AddProperty("method", "streamNotify");
    {
      JSONObject params(&jsobj, "params");
      params.AddProperty("streamId", echo_stream.id());
      {
        JSONObject event(&params, "event");
        event.AddProperty("type", "Event");
        event.AddProperty("kind", "_Echo");
        event.AddProperty("isolate", isolate);
        if (text != NULL) {
          event.AddProperty("text", text);
        }
        event.AddPropertyTimeMillis("timestamp", OS::GetCurrentTimeMillis());
      }
    }
  }
  uint8_t data[] = {0, 128, 255};
  SendEventWithData(echo_stream.id(), "_Echo", js.buffer()->buf(),
                    js.buffer()->length(), data, sizeof(data));
}

static bool TriggerEchoEvent(Thread* thread, JSONStream* js) {
  if (Service::echo_stream.enabled()) {
    Service::SendEchoEvent(thread->isolate(), js->LookupParam("text"));
  }
  JSONObject jsobj(js);
  return HandleCommonEcho(&jsobj, js);
}

static bool Echo(Thread* thread, JSONStream* js) {
  JSONObject jsobj(js);
  return HandleCommonEcho(&jsobj, js);
}

static bool ContainsNonInstance(const Object& obj) {
  if (obj.IsArray()) {
    const Array& array = Array::Cast(obj);
    Object& element = Object::Handle();
    for (intptr_t i = 0; i < array.Length(); ++i) {
      element = array.At(i);
      if (!(element.IsInstance() || element.IsNull())) {
        return true;
      }
    }
    return false;
  } else if (obj.IsGrowableObjectArray()) {
    const GrowableObjectArray& array = GrowableObjectArray::Cast(obj);
    Object& element = Object::Handle();
    for (intptr_t i = 0; i < array.Length(); ++i) {
      element = array.At(i);
      if (!(element.IsInstance() || element.IsNull())) {
        return true;
      }
    }
    return false;
  } else {
    return !(obj.IsInstance() || obj.IsNull());
  }
}

static RawObject* LookupObjectId(Thread* thread,
                                 const char* arg,
                                 ObjectIdRing::LookupResult* kind) {
  *kind = ObjectIdRing::kValid;
  if (strncmp(arg, "int-", 4) == 0) {
    arg += 4;
    int64_t value = 0;
    if (!OS::StringToInt64(arg, &value) || !Smi::IsValid(value)) {
      *kind = ObjectIdRing::kInvalid;
      return Object::null();
    }
    const Integer& obj =
        Integer::Handle(thread->zone(), Smi::New(static_cast<intptr_t>(value)));
    return obj.raw();
  } else if (strcmp(arg, "bool-true") == 0) {
    return Bool::True().raw();
  } else if (strcmp(arg, "bool-false") == 0) {
    return Bool::False().raw();
  } else if (strcmp(arg, "null") == 0) {
    return Object::null();
  }

  ObjectIdRing* ring = thread->isolate()->object_id_ring();
  ASSERT(ring != NULL);
  intptr_t id = -1;
  if (!GetIntegerId(arg, &id)) {
    *kind = ObjectIdRing::kInvalid;
    return Object::null();
  }
  return ring->GetObjectForId(id, kind);
}

static RawObject* LookupHeapObjectLibraries(Isolate* isolate,
                                            char** parts,
                                            int num_parts) {
  // Library ids look like "libraries/35"
  if (num_parts < 2) {
    return Object::sentinel().raw();
  }
  const GrowableObjectArray& libs =
      GrowableObjectArray::Handle(isolate->object_store()->libraries());
  ASSERT(!libs.IsNull());
  const String& id = String::Handle(String::New(parts[1]));
  // Scan for private key.
  String& private_key = String::Handle();
  Library& lib = Library::Handle();
  bool lib_found = false;
  for (intptr_t i = 0; i < libs.Length(); i++) {
    lib ^= libs.At(i);
    ASSERT(!lib.IsNull());
    private_key = lib.private_key();
    if (private_key.Equals(id)) {
      lib_found = true;
      break;
    }
  }
  if (!lib_found) {
    return Object::sentinel().raw();
  }
  if (num_parts == 2) {
    return lib.raw();
  }
  if (strcmp(parts[2], "scripts") == 0) {
    // Script ids look like "libraries/35/scripts/library%2Furl.dart/12345"
    if (num_parts != 5) {
      return Object::sentinel().raw();
    }
    const String& id = String::Handle(String::New(parts[3]));
    ASSERT(!id.IsNull());
    // The id is the url of the script % encoded, decode it.
    const String& requested_url = String::Handle(String::DecodeIRI(id));

    // Each script id is tagged with a load time.
    int64_t timestamp;
    if (!GetInteger64Id(parts[4], &timestamp, 16) || (timestamp < 0)) {
      return Object::sentinel().raw();
    }

    Script& script = Script::Handle();
    String& script_url = String::Handle();
    const Array& loaded_scripts = Array::Handle(lib.LoadedScripts());
    ASSERT(!loaded_scripts.IsNull());
    intptr_t i;
    for (i = 0; i < loaded_scripts.Length(); i++) {
      script ^= loaded_scripts.At(i);
      ASSERT(!script.IsNull());
      script_url = script.url();
      if (script_url.Equals(requested_url) &&
          (timestamp == script.load_timestamp())) {
        return script.raw();
      }
    }
  }

  // Not found.
  return Object::sentinel().raw();
}

static RawObject* LookupHeapObjectClasses(Thread* thread,
                                          char** parts,
                                          int num_parts) {
  // Class ids look like: "classes/17"
  if (num_parts < 2) {
    return Object::sentinel().raw();
  }
  Isolate* isolate = thread->isolate();
  Zone* zone = thread->zone();
  ClassTable* table = isolate->class_table();
  intptr_t id;
  if (!GetIntegerId(parts[1], &id) || !table->IsValidIndex(id)) {
    return Object::sentinel().raw();
  }
  Class& cls = Class::Handle(zone, table->At(id));
  if (num_parts == 2) {
    return cls.raw();
  }
  if (strcmp(parts[2], "closures") == 0) {
    // Closure ids look like: "classes/17/closures/11"
    if (num_parts != 4) {
      return Object::sentinel().raw();
    }
    intptr_t id;
    if (!GetIntegerId(parts[3], &id)) {
      return Object::sentinel().raw();
    }
    Function& func = Function::Handle(zone);
    func = isolate->ClosureFunctionFromIndex(id);
    if (func.IsNull()) {
      return Object::sentinel().raw();
    }
    return func.raw();

  } else if (strcmp(parts[2], "fields") == 0) {
    // Field ids look like: "classes/17/fields/name"
    if (num_parts != 4) {
      return Object::sentinel().raw();
    }
    const char* encoded_id = parts[3];
    String& id = String::Handle(zone, String::New(encoded_id));
    id = String::DecodeIRI(id);
    if (id.IsNull()) {
      return Object::sentinel().raw();
    }
    Field& field = Field::Handle(zone, cls.LookupField(id));
    if (field.IsNull()) {
      return Object::sentinel().raw();
    }
    return field.raw();

  } else if (strcmp(parts[2], "functions") == 0) {
    // Function ids look like: "classes/17/functions/name"
    if (num_parts != 4) {
      return Object::sentinel().raw();
    }
    const char* encoded_id = parts[3];
    String& id = String::Handle(zone, String::New(encoded_id));
    id = String::DecodeIRI(id);
    if (id.IsNull()) {
      return Object::sentinel().raw();
    }
    Function& func = Function::Handle(zone, cls.LookupFunction(id));
    if (func.IsNull()) {
      return Object::sentinel().raw();
    }
    return func.raw();

  } else if (strcmp(parts[2], "implicit_closures") == 0) {
    // Function ids look like: "classes/17/implicit_closures/11"
    if (num_parts != 4) {
      return Object::sentinel().raw();
    }
    intptr_t id;
    if (!GetIntegerId(parts[3], &id)) {
      return Object::sentinel().raw();
    }
    Function& func = Function::Handle(zone);
    func = cls.ImplicitClosureFunctionFromIndex(id);
    if (func.IsNull()) {
      return Object::sentinel().raw();
    }
    return func.raw();

  } else if (strcmp(parts[2], "dispatchers") == 0) {
    // Dispatcher Function ids look like: "classes/17/dispatchers/11"
    if (num_parts != 4) {
      return Object::sentinel().raw();
    }
    intptr_t id;
    if (!GetIntegerId(parts[3], &id)) {
      return Object::sentinel().raw();
    }
    Function& func = Function::Handle(zone);
    func = cls.InvocationDispatcherFunctionFromIndex(id);
    if (func.IsNull()) {
      return Object::sentinel().raw();
    }
    return func.raw();

  } else if (strcmp(parts[2], "types") == 0) {
    // Type ids look like: "classes/17/types/11"
    if (num_parts != 4) {
      return Object::sentinel().raw();
    }
    intptr_t id;
    if (!GetIntegerId(parts[3], &id)) {
      return Object::sentinel().raw();
    }
    if (id != 0) {
      return Object::sentinel().raw();
    }
    const Type& type = Type::Handle(zone, cls.DeclarationType());
    if (!type.IsNull()) {
      return type.raw();
    }
  }

  // Not found.
  return Object::sentinel().raw();
}

static RawObject* LookupHeapObjectTypeArguments(Thread* thread,
                                                char** parts,
                                                int num_parts) {
  Isolate* isolate = thread->isolate();
  // TypeArguments ids look like: "typearguments/17"
  if (num_parts < 2) {
    return Object::sentinel().raw();
  }
  intptr_t id;
  if (!GetIntegerId(parts[1], &id)) {
    return Object::sentinel().raw();
  }
  ObjectStore* object_store = isolate->object_store();
  const Array& table =
      Array::Handle(thread->zone(), object_store->canonical_type_arguments());
  ASSERT(table.Length() > 0);
  const intptr_t table_size = table.Length() - 1;
  if ((id < 0) || (id >= table_size) || (table.At(id) == Object::null())) {
    return Object::sentinel().raw();
  }
  return table.At(id);
}

static RawObject* LookupHeapObjectCode(Isolate* isolate,
                                       char** parts,
                                       int num_parts) {
  if (num_parts != 2) {
    return Object::sentinel().raw();
  }
  uword pc;
  static const char* const kCollectedPrefix = "collected-";
  static intptr_t kCollectedPrefixLen = strlen(kCollectedPrefix);
  static const char* const kNativePrefix = "native-";
  static const intptr_t kNativePrefixLen = strlen(kNativePrefix);
  static const char* const kReusedPrefix = "reused-";
  static const intptr_t kReusedPrefixLen = strlen(kReusedPrefix);
  const char* id = parts[1];
  if (strncmp(kCollectedPrefix, id, kCollectedPrefixLen) == 0) {
    if (!GetUnsignedIntegerId(&id[kCollectedPrefixLen], &pc, 16)) {
      return Object::sentinel().raw();
    }
    // TODO(turnidge): Return "collected" instead.
    return Object::null();
  }
  if (strncmp(kNativePrefix, id, kNativePrefixLen) == 0) {
    if (!GetUnsignedIntegerId(&id[kNativePrefixLen], &pc, 16)) {
      return Object::sentinel().raw();
    }
    // TODO(johnmccutchan): Support native Code.
    return Object::null();
  }
  if (strncmp(kReusedPrefix, id, kReusedPrefixLen) == 0) {
    if (!GetUnsignedIntegerId(&id[kReusedPrefixLen], &pc, 16)) {
      return Object::sentinel().raw();
    }
    // TODO(turnidge): Return "expired" instead.
    return Object::null();
  }
  int64_t timestamp = 0;
  if (!GetCodeId(id, &timestamp, &pc) || (timestamp < 0)) {
    return Object::sentinel().raw();
  }
  Code& code = Code::Handle(Code::FindCode(pc, timestamp));
  if (!code.IsNull()) {
    return code.raw();
  }
  Bytecode& bytecode = Bytecode::Handle(Bytecode::FindCode(pc));
  if (!bytecode.IsNull()) {
    return bytecode.raw();
  }

  // Not found.
  return Object::sentinel().raw();
}

static RawObject* LookupHeapObjectMessage(Thread* thread,
                                          char** parts,
                                          int num_parts) {
  if (num_parts != 2) {
    return Object::sentinel().raw();
  }
  uword message_id = 0;
  if (!GetUnsignedIntegerId(parts[1], &message_id, 16)) {
    return Object::sentinel().raw();
  }
  MessageHandler::AcquiredQueues aq(thread->isolate()->message_handler());
  Message* message = aq.queue()->FindMessageById(message_id);
  if (message == NULL) {
    // The user may try to load an expired message.
    return Object::sentinel().raw();
  }
  if (message->IsRaw()) {
    return message->raw_obj();
  } else {
    MessageSnapshotReader reader(message, thread);
    return reader.ReadObject();
  }
}

static RawObject* LookupHeapObject(Thread* thread,
                                   const char* id_original,
                                   ObjectIdRing::LookupResult* result) {
  char* id = thread->zone()->MakeCopyOfString(id_original);

  // Parse the id by splitting at each '/'.
  const int MAX_PARTS = 8;
  char* parts[MAX_PARTS];
  int num_parts = 0;
  int i = 0;
  int start_pos = 0;
  while (id[i] != '\0') {
    if (id[i] == '/') {
      id[i++] = '\0';
      parts[num_parts++] = &id[start_pos];
      if (num_parts == MAX_PARTS) {
        break;
      }
      start_pos = i;
    } else {
      i++;
    }
  }
  if (num_parts < MAX_PARTS) {
    parts[num_parts++] = &id[start_pos];
  }

  if (result != NULL) {
    *result = ObjectIdRing::kValid;
  }

  Isolate* isolate = thread->isolate();
  if (strcmp(parts[0], "objects") == 0) {
    // Object ids look like "objects/1123"
    Object& obj = Object::Handle(thread->zone());
    ObjectIdRing::LookupResult lookup_result;
    obj = LookupObjectId(thread, parts[1], &lookup_result);
    if (lookup_result != ObjectIdRing::kValid) {
      if (result != NULL) {
        *result = lookup_result;
      }
      return Object::sentinel().raw();
    }
    return obj.raw();

  } else if (strcmp(parts[0], "libraries") == 0) {
    return LookupHeapObjectLibraries(isolate, parts, num_parts);
  } else if (strcmp(parts[0], "classes") == 0) {
    return LookupHeapObjectClasses(thread, parts, num_parts);
  } else if (strcmp(parts[0], "typearguments") == 0) {
    return LookupHeapObjectTypeArguments(thread, parts, num_parts);
  } else if (strcmp(parts[0], "code") == 0) {
    return LookupHeapObjectCode(isolate, parts, num_parts);
  } else if (strcmp(parts[0], "messages") == 0) {
    return LookupHeapObjectMessage(thread, parts, num_parts);
  }

  // Not found.
  return Object::sentinel().raw();
}

enum SentinelType {
  kCollectedSentinel,
  kExpiredSentinel,
  kFreeSentinel,
};

static void PrintSentinel(JSONStream* js, SentinelType sentinel_type) {
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "Sentinel");
  switch (sentinel_type) {
    case kCollectedSentinel:
      jsobj.AddProperty("kind", "Collected");
      jsobj.AddProperty("valueAsString", "<collected>");
      break;
    case kExpiredSentinel:
      jsobj.AddProperty("kind", "Expired");
      jsobj.AddProperty("valueAsString", "<expired>");
      break;
    case kFreeSentinel:
      jsobj.AddProperty("kind", "Free");
      jsobj.AddProperty("valueAsString", "<free>");
      break;
    default:
      UNIMPLEMENTED();
      break;
  }
}

static Breakpoint* LookupBreakpoint(Isolate* isolate,
                                    const char* id,
                                    ObjectIdRing::LookupResult* result) {
  *result = ObjectIdRing::kInvalid;
  size_t end_pos = strcspn(id, "/");
  if (end_pos == strlen(id)) {
    return NULL;
  }
  const char* rest = id + end_pos + 1;  // +1 for '/'.
  if (strncmp("breakpoints", id, end_pos) == 0) {
    intptr_t bpt_id = 0;
    Breakpoint* bpt = NULL;
    if (GetIntegerId(rest, &bpt_id)) {
      bpt = isolate->debugger()->GetBreakpointById(bpt_id);
      if (bpt) {
        *result = ObjectIdRing::kValid;
        return bpt;
      }
      if (bpt_id < isolate->debugger()->limitBreakpointId()) {
        *result = ObjectIdRing::kCollected;
        return NULL;
      }
    }
  }
  return NULL;
}

static bool PrintInboundReferences(Thread* thread,
                                   Object* target,
                                   intptr_t limit,
                                   JSONStream* js) {
  ObjectGraph graph(thread);
  Array& path = Array::Handle(Array::New(limit * 2));
  intptr_t length = graph.InboundReferences(target, path);
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "InboundReferences");
  {
    JSONArray elements(&jsobj, "references");
    Object& source = Object::Handle();
    Smi& slot_offset = Smi::Handle();
    Class& source_class = Class::Handle();
    Field& field = Field::Handle();
    Array& parent_field_map = Array::Handle();
    limit = Utils::Minimum(limit, length);
    for (intptr_t i = 0; i < limit; ++i) {
      JSONObject jselement(&elements);
      source = path.At(i * 2);
      slot_offset ^= path.At((i * 2) + 1);

      jselement.AddProperty("source", source);
      if (source.IsArray()) {
        intptr_t element_index =
            slot_offset.Value() - (Array::element_offset(0) >> kWordSizeLog2);
        jselement.AddProperty("parentListIndex", element_index);
      } else if (source.IsInstance()) {
        source_class = source.clazz();
        parent_field_map = source_class.OffsetToFieldMap();
        intptr_t offset = slot_offset.Value();
        if (offset > 0 && offset < parent_field_map.Length()) {
          field ^= parent_field_map.At(offset);
          jselement.AddProperty("parentField", field);
        }
      } else {
        intptr_t element_index = slot_offset.Value();
        jselement.AddProperty("_parentWordOffset", element_index);
      }
    }
  }

  // We nil out the array after generating the response to prevent
  // reporting suprious references when repeatedly looking for the
  // references to an object.
  for (intptr_t i = 0; i < path.Length(); i++) {
    path.SetAt(i, Object::null_object());
  }

  return true;
}

static const MethodParameter* get_inbound_references_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetInboundReferences(Thread* thread, JSONStream* js) {
  const char* target_id = js->LookupParam("targetId");
  if (target_id == NULL) {
    PrintMissingParamError(js, "targetId");
    return true;
  }
  const char* limit_cstr = js->LookupParam("limit");
  if (limit_cstr == NULL) {
    PrintMissingParamError(js, "limit");
    return true;
  }
  intptr_t limit;
  if (!GetIntegerId(limit_cstr, &limit)) {
    PrintInvalidParamError(js, "limit");
    return true;
  }

  Object& obj = Object::Handle(thread->zone());
  ObjectIdRing::LookupResult lookup_result;
  {
    HANDLESCOPE(thread);
    obj = LookupHeapObject(thread, target_id, &lookup_result);
  }
  if (obj.raw() == Object::sentinel().raw()) {
    if (lookup_result == ObjectIdRing::kCollected) {
      PrintSentinel(js, kCollectedSentinel);
    } else if (lookup_result == ObjectIdRing::kExpired) {
      PrintSentinel(js, kExpiredSentinel);
    } else {
      PrintInvalidParamError(js, "targetId");
    }
    return true;
  }
  return PrintInboundReferences(thread, &obj, limit, js);
}

static bool PrintRetainingPath(Thread* thread,
                               Object* obj,
                               intptr_t limit,
                               JSONStream* js) {
  ObjectGraph graph(thread);
  Array& path = Array::Handle(Array::New(limit * 2));
  intptr_t length = graph.RetainingPath(obj, path);
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "RetainingPath");
  jsobj.AddProperty("length", length);
  JSONArray elements(&jsobj, "elements");
  Object& element = Object::Handle();
  Smi& slot_offset = Smi::Handle();
  Class& element_class = Class::Handle();
  Array& element_field_map = Array::Handle();
  LinkedHashMap& map = LinkedHashMap::Handle();
  Array& map_data = Array::Handle();
  Field& field = Field::Handle();
  limit = Utils::Minimum(limit, length);
  for (intptr_t i = 0; i < limit; ++i) {
    JSONObject jselement(&elements);
    element = path.At(i * 2);
    jselement.AddProperty("value", element);
    // Interpret the word offset from parent as list index, map key
    // or instance field.
    if (i > 0) {
      slot_offset ^= path.At((i * 2) - 1);
      jselement.AddProperty("offset", slot_offset.Value());
      if (element.IsArray() || element.IsGrowableObjectArray()) {
        intptr_t element_index =
            slot_offset.Value() - (Array::element_offset(0) >> kWordSizeLog2);
        jselement.AddProperty("parentListIndex", element_index);
      } else if (element.IsLinkedHashMap()) {
        map = static_cast<RawLinkedHashMap*>(path.At(i * 2));
        map_data = map.data();
        intptr_t element_index =
            slot_offset.Value() - (Array::element_offset(0) >> kWordSizeLog2);
        LinkedHashMap::Iterator iterator(map);
        while (iterator.MoveNext()) {
          if (iterator.CurrentKey() == map_data.At(element_index) ||
              iterator.CurrentValue() == map_data.At(element_index)) {
            element = iterator.CurrentKey();
            jselement.AddProperty("parentMapKey", element);
            break;
          }
        }
      } else if (element.IsInstance()) {
        element_class = element.clazz();
        element_field_map = element_class.OffsetToFieldMap();
        intptr_t offset = slot_offset.Value();
        if (offset > 0 && offset < element_field_map.Length()) {
          field ^= element_field_map.At(offset);
          jselement.AddProperty("parentField", field);
        }
      } else {
        intptr_t element_index = slot_offset.Value();
        jselement.AddProperty("_parentWordOffset", element_index);
      }
    }
  }

  // We nil out the array after generating the response to prevent
  // reporting spurious references when looking for inbound references
  // after looking for a retaining path.
  for (intptr_t i = 0; i < path.Length(); i++) {
    path.SetAt(i, Object::null_object());
  }

  return true;
}

static const MethodParameter* get_retaining_path_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetRetainingPath(Thread* thread, JSONStream* js) {
  const char* target_id = js->LookupParam("targetId");
  if (target_id == NULL) {
    PrintMissingParamError(js, "targetId");
    return true;
  }
  const char* limit_cstr = js->LookupParam("limit");
  if (limit_cstr == NULL) {
    PrintMissingParamError(js, "limit");
    return true;
  }
  intptr_t limit;
  if (!GetIntegerId(limit_cstr, &limit)) {
    PrintInvalidParamError(js, "limit");
    return true;
  }

  Object& obj = Object::Handle(thread->zone());
  ObjectIdRing::LookupResult lookup_result;
  {
    HANDLESCOPE(thread);
    obj = LookupHeapObject(thread, target_id, &lookup_result);
  }
  if (obj.raw() == Object::sentinel().raw()) {
    if (lookup_result == ObjectIdRing::kCollected) {
      PrintSentinel(js, kCollectedSentinel);
    } else if (lookup_result == ObjectIdRing::kExpired) {
      PrintSentinel(js, kExpiredSentinel);
    } else {
      PrintInvalidParamError(js, "targetId");
    }
    return true;
  }
  return PrintRetainingPath(thread, &obj, limit, js);
}

static const MethodParameter* get_retained_size_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new IdParameter("targetId", true), NULL,
};

static bool GetRetainedSize(Thread* thread, JSONStream* js) {
  const char* target_id = js->LookupParam("targetId");
  ASSERT(target_id != NULL);
  ObjectIdRing::LookupResult lookup_result;
  Object& obj =
      Object::Handle(LookupHeapObject(thread, target_id, &lookup_result));
  if (obj.raw() == Object::sentinel().raw()) {
    if (lookup_result == ObjectIdRing::kCollected) {
      PrintSentinel(js, kCollectedSentinel);
    } else if (lookup_result == ObjectIdRing::kExpired) {
      PrintSentinel(js, kExpiredSentinel);
    } else {
      PrintInvalidParamError(js, "targetId");
    }
    return true;
  }
  // TODO(rmacnak): There is no way to get the size retained by a class object.
  // SizeRetainedByClass should be a separate RPC.
  if (obj.IsClass()) {
    const Class& cls = Class::Cast(obj);
    ObjectGraph graph(thread);
    intptr_t retained_size = graph.SizeRetainedByClass(cls.id());
    const Object& result = Object::Handle(Integer::New(retained_size));
    result.PrintJSON(js, true);
    return true;
  }

  ObjectGraph graph(thread);
  intptr_t retained_size = graph.SizeRetainedByInstance(obj);
  const Object& result = Object::Handle(Integer::New(retained_size));
  result.PrintJSON(js, true);
  return true;
}

static const MethodParameter* get_reachable_size_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new IdParameter("targetId", true), NULL,
};

static bool GetReachableSize(Thread* thread, JSONStream* js) {
  const char* target_id = js->LookupParam("targetId");
  ASSERT(target_id != NULL);
  ObjectIdRing::LookupResult lookup_result;
  Object& obj =
      Object::Handle(LookupHeapObject(thread, target_id, &lookup_result));
  if (obj.raw() == Object::sentinel().raw()) {
    if (lookup_result == ObjectIdRing::kCollected) {
      PrintSentinel(js, kCollectedSentinel);
    } else if (lookup_result == ObjectIdRing::kExpired) {
      PrintSentinel(js, kExpiredSentinel);
    } else {
      PrintInvalidParamError(js, "targetId");
    }
    return true;
  }
  // TODO(rmacnak): There is no way to get the size retained by a class object.
  // SizeRetainedByClass should be a separate RPC.
  if (obj.IsClass()) {
    const Class& cls = Class::Cast(obj);
    ObjectGraph graph(thread);
    intptr_t retained_size = graph.SizeReachableByClass(cls.id());
    const Object& result = Object::Handle(Integer::New(retained_size));
    result.PrintJSON(js, true);
    return true;
  }

  ObjectGraph graph(thread);
  intptr_t retained_size = graph.SizeReachableByInstance(obj);
  const Object& result = Object::Handle(Integer::New(retained_size));
  result.PrintJSON(js, true);
  return true;
}

static const MethodParameter* invoke_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    NULL,
};

static bool Invoke(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  const char* receiver_id = js->LookupParam("targetId");
  if (receiver_id == NULL) {
    PrintMissingParamError(js, "targetId");
    return true;
  }
  const char* selector_cstr = js->LookupParam("selector");
  if (selector_cstr == NULL) {
    PrintMissingParamError(js, "selector");
    return true;
  }
  const char* argument_ids = js->LookupParam("argumentIds");
  if (argument_ids == NULL) {
    PrintMissingParamError(js, "argumentIds");
    return true;
  }

  bool disable_breakpoints =
      BoolParameter::Parse(js->LookupParam("disableBreakpoints"), false);
  DisableBreakpointsScope db(thread->isolate()->debugger(),
                             disable_breakpoints);

  Zone* zone = thread->zone();
  ObjectIdRing::LookupResult lookup_result;
  Object& receiver = Object::Handle(
      zone, LookupHeapObject(thread, receiver_id, &lookup_result));
  if (receiver.raw() == Object::sentinel().raw()) {
    if (lookup_result == ObjectIdRing::kCollected) {
      PrintSentinel(js, kCollectedSentinel);
    } else if (lookup_result == ObjectIdRing::kExpired) {
      PrintSentinel(js, kExpiredSentinel);
    } else {
      PrintInvalidParamError(js, "targetId");
    }
    return true;
  }

  const GrowableObjectArray& growable_args =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());

  bool is_instance = (receiver.IsInstance() || receiver.IsNull()) &&
                     !ContainsNonInstance(receiver);
  if (is_instance) {
    growable_args.Add(receiver);
  }

  intptr_t n = strlen(argument_ids);
  if ((n < 2) || (argument_ids[0] != '[') || (argument_ids[n - 1] != ']')) {
    PrintInvalidParamError(js, "argumentIds");
    return true;
  }
  if (n > 2) {
    intptr_t start = 1;
    while (start < n) {
      intptr_t end = start;
      while ((argument_ids[end + 1] != ',') && (argument_ids[end + 1] != ']')) {
        end++;
      }
      if (end == start) {
        // Empty element.
        PrintInvalidParamError(js, "argumentIds");
        return true;
      }

      const char* argument_id =
          zone->MakeCopyOfStringN(&argument_ids[start], end - start + 1);

      ObjectIdRing::LookupResult lookup_result;
      Object& argument = Object::Handle(
          zone, LookupHeapObject(thread, argument_id, &lookup_result));
      if (argument.raw() == Object::sentinel().raw()) {
        if (lookup_result == ObjectIdRing::kCollected) {
          PrintSentinel(js, kCollectedSentinel);
        } else if (lookup_result == ObjectIdRing::kExpired) {
          PrintSentinel(js, kExpiredSentinel);
        } else {
          PrintInvalidParamError(js, "argumentIds");
        }
        return true;
      }
      growable_args.Add(argument);

      start = end + 3;
    }
  }

  const String& selector = String::Handle(zone, String::New(selector_cstr));
  const Array& args =
      Array::Handle(zone, Array::MakeFixedLength(growable_args));
  const Array& arg_names = Object::empty_array();

  if (receiver.IsLibrary()) {
    const Library& lib = Library::Cast(receiver);
    const Object& result =
        Object::Handle(zone, lib.Invoke(selector, args, arg_names));
    result.PrintJSON(js, true);
    return true;
  }
  if (receiver.IsClass()) {
    const Class& cls = Class::Cast(receiver);
    const Object& result =
        Object::Handle(zone, cls.Invoke(selector, args, arg_names));
    result.PrintJSON(js, true);
    return true;
  }
  if (is_instance) {
    // We don't use Instance::Cast here because it doesn't allow null.
    Instance& instance = Instance::Handle(zone);
    instance ^= receiver.raw();
    const Object& result =
        Object::Handle(zone, instance.Invoke(selector, args, arg_names));
    result.PrintJSON(js, true);
    return true;
  }
  js->PrintError(kInvalidParams,
                 "%s: invalid 'targetId' parameter: "
                 "Cannot invoke against a VM-internal object",
                 js->method());
  return true;
}

static const MethodParameter* evaluate_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool IsAlpha(char c) {
  return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}
static bool IsAlphaOrDollar(char c) {
  return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c == '$');
}
static bool IsAlphaNum(char c) {
  return (c >= '0' && c <= '9') || IsAlpha(c);
}
static bool IsAlphaNumOrDollar(char c) {
  return (c >= '0' && c <= '9') || IsAlphaOrDollar(c);
}
static bool IsWhitespace(char c) {
  return c <= ' ';
}
static bool IsObjectIdChar(char c) {
  return IsAlphaNum(c) || c == '/' || c == '-' || c == '@' || c == '%';
}

// TODO(vm-service): Consider whether we should pass structured objects in
// service messages instead of always flattening them to C strings.
static bool ParseScope(const char* scope,
                       GrowableArray<const char*>* names,
                       GrowableArray<const char*>* ids) {
  Zone* zone = Thread::Current()->zone();
  const char* c = scope;
  if (*c++ != '{') return false;

  for (;;) {
    while (IsWhitespace(*c)) {
      c++;
    }

    if (*c == '}') return true;

    const char* name = c;
    if (!IsAlphaOrDollar(*c)) return false;
    while (IsAlphaNumOrDollar(*c)) {
      c++;
    }
    names->Add(zone->MakeCopyOfStringN(name, c - name));

    while (IsWhitespace(*c)) {
      c++;
    }

    if (*c++ != ':') return false;

    while (IsWhitespace(*c)) {
      c++;
    }

    const char* id = c;
    if (!IsObjectIdChar(*c)) return false;
    while (IsObjectIdChar(*c)) {
      c++;
    }
    ids->Add(zone->MakeCopyOfStringN(id, c - id));

    while (IsWhitespace(*c)) {
      c++;
    }
    if (*c == ',') c++;
  }

  return false;
}

static bool BuildScope(Thread* thread,
                       JSONStream* js,
                       const GrowableObjectArray& names,
                       const GrowableObjectArray& values) {
  const char* scope = js->LookupParam("scope");
  GrowableArray<const char*> cnames;
  GrowableArray<const char*> cids;
  if (scope != NULL) {
    if (!ParseScope(scope, &cnames, &cids)) {
      PrintInvalidParamError(js, "scope");
      return true;
    }
    String& name = String::Handle();
    Object& obj = Object::Handle();
    for (intptr_t i = 0; i < cids.length(); i++) {
      ObjectIdRing::LookupResult lookup_result;
      obj = LookupHeapObject(thread, cids[i], &lookup_result);
      if (obj.raw() == Object::sentinel().raw()) {
        if (lookup_result == ObjectIdRing::kCollected) {
          PrintSentinel(js, kCollectedSentinel);
        } else if (lookup_result == ObjectIdRing::kExpired) {
          PrintSentinel(js, kExpiredSentinel);
        } else {
          PrintInvalidParamError(js, "targetId");
        }
        return true;
      }
      if ((!obj.IsInstance() && !obj.IsNull()) || ContainsNonInstance(obj)) {
        js->PrintError(kInvalidParams,
                       "%s: invalid scope 'targetId' parameter: "
                       "Cannot evaluate against a VM-internal object",
                       js->method());
        return true;
      }
      name = String::New(cnames[i]);
      names.Add(name);
      values.Add(obj);
    }
  }
  return false;
}

static bool Evaluate(Thread* thread, JSONStream* js) {
  // If a compilation service is available, this RPC invocation will have been
  // intercepted by RunningIsolates.routeRequest.
  js->PrintError(
      kExpressionCompilationError,
      "%s: No compilation service available; cannot evaluate from source.",
      js->method());
  return true;
}

static const MethodParameter* build_expression_evaluation_scope_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new IdParameter("frameIndex", false),
    new IdParameter("targetId", false),
    NULL,
};

static bool BuildExpressionEvaluationScope(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  Isolate* isolate = thread->isolate();
  DebuggerStackTrace* stack = isolate->debugger()->StackTrace();
  intptr_t framePos = UIntParameter::Parse(js->LookupParam("frameIndex"));
  if (framePos >= stack->Length()) {
    PrintInvalidParamError(js, "frameIndex");
    return true;
  }

  Zone* zone = thread->zone();
  const GrowableObjectArray& param_names =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());
  const GrowableObjectArray& param_values =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());
  const GrowableObjectArray& type_params_names =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());
  String& klass_name = String::Handle(zone);
  String& library_uri = String::Handle(zone);
  bool isStatic = false;

  if (BuildScope(thread, js, param_names, param_values)) {
    return true;
  }

  if (js->HasParam("frameIndex")) {
    // building scope in the context of a given frame
    DebuggerStackTrace* stack = isolate->debugger()->StackTrace();
    intptr_t framePos = UIntParameter::Parse(js->LookupParam("frameIndex"));
    if (framePos >= stack->Length()) {
      PrintInvalidParamError(js, "frameIndex");
      return true;
    }

    ActivationFrame* frame = stack->FrameAt(framePos);
    frame->BuildParameters(param_names, param_values, type_params_names);

    if (frame->function().is_static()) {
      const Class& cls = Class::Handle(zone, frame->function().Owner());
      if (!cls.IsTopLevel()) {
        klass_name = cls.UserVisibleName();
      }
      library_uri = Library::Handle(zone, cls.library()).url();
      isStatic = !cls.IsTopLevel();
    } else {
      const Class& method_cls = Class::Handle(zone, frame->function().origin());
      library_uri = Library::Handle(zone, method_cls.library()).url();
      klass_name = method_cls.UserVisibleName();
    }
  } else {
    // building scope in the context of a given object
    if (!js->HasParam("targetId")) {
      js->PrintError(kInvalidParams,
                     "Either targetId or frameIndex has to be provided.");
      return true;
    }
    const char* target_id = js->LookupParam("targetId");

    ObjectIdRing::LookupResult lookup_result;
    Object& obj = Object::Handle(
        zone, LookupHeapObject(thread, target_id, &lookup_result));
    if (obj.raw() == Object::sentinel().raw()) {
      PrintInvalidParamError(js, "targetId");
      return true;
    }
    if (obj.IsLibrary()) {
      const Library& lib = Library::Cast(obj);
      library_uri = lib.url();
    } else if (obj.IsClass() || ((obj.IsInstance() || obj.IsNull()) &&
                                 !ContainsNonInstance(obj))) {
      Class& cls = Class::Handle(zone);
      if (obj.IsClass()) {
        cls ^= obj.raw();
      } else {
        Instance& instance = Instance::Handle(zone);
        instance ^= obj.raw();
        cls = instance.clazz();
      }
      if (cls.id() < kInstanceCid || cls.id() == kTypeArgumentsCid) {
        js->PrintError(
            kInvalidParams,
            "Expressions can be evaluated only with regular Dart instances");
        return true;
      }

      if (!cls.IsTopLevel()) {
        klass_name = cls.UserVisibleName();
      }
      library_uri = Library::Handle(zone, cls.library()).url();
    } else {
      js->PrintError(kInvalidParams,
                     "%s: invalid 'targetId' parameter: "
                     "Cannot evaluate against a VM-internal object",
                     js->method());
    }
  }

  JSONObject report(js);
  {
    JSONArray jsonParamNames(&report, "param_names");

    String& param_name = String::Handle(zone);
    for (intptr_t i = 0; i < param_names.Length(); i++) {
      param_name ^= param_names.At(i);
      jsonParamNames.AddValue(param_name.ToCString());
    }
  }

  {
    JSONArray jsonTypeParamsNames(&report, "type_params_names");
    String& type_param_name = String::Handle(zone);
    for (intptr_t i = 0; i < type_params_names.Length(); i++) {
      type_param_name ^= type_params_names.At(i);
      jsonTypeParamsNames.AddValue(type_param_name.ToCString());
    }
  }
  report.AddProperty("libraryUri", library_uri.ToCString());
  if (!klass_name.IsNull()) {
    report.AddProperty("klass", klass_name.ToCString());
  }
  report.AddProperty("isStatic", isStatic);

  return true;
}

#if !defined(DART_PRECOMPILED_RUNTIME)
// Parse comma-separated list of values, put them into values
static bool ParseCSVList(const char* csv_list,
                         const GrowableObjectArray& values) {
  Zone* zone = Thread::Current()->zone();
  String& s = String::Handle(zone);
  const char* c = csv_list;
  if (*c++ != '[') return false;
  while (IsWhitespace(*c) && *c != '\0') {
    c++;
  }
  while (*c != '\0') {
    const char* value = c;
    while (*c != '\0' && *c != ']' && *c != ',' && !IsWhitespace(*c)) {
      c++;
    }
    if (c > value) {
      s = String::New(zone->MakeCopyOfStringN(value, c - value));
      values.Add(s);
    }
    switch (*c) {
      case '\0':
        return false;
      case ',':
        c++;
        break;
      case ']':
        return true;
    }
    while (IsWhitespace(*c) && *c != '\0') {
      c++;
    }
  }
  return false;
}
#endif

static const MethodParameter* compile_expression_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new StringParameter("expression", true),
    new StringParameter("definitions", false),
    new StringParameter("typeDefinitions", false),
    new StringParameter("libraryUri", true),
    new StringParameter("klass", false),
    new BoolParameter("isStatic", false),
    NULL,
};

static bool CompileExpression(Thread* thread, JSONStream* js) {
#if defined(DART_PRECOMPILED_RUNTIME)
  js->PrintError(kFeatureDisabled, "Debugger is disabled in AOT mode.");
  return true;
#else
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  if (!KernelIsolate::IsRunning()) {
    // Assume we are in dart1 mode where separate compilation is not required.
    // 0-length kernelBytes signals that we should evaluate expression in dart1
    // mode.
    // TODO(aam): When dart1 is no longer supported we need to return error
    // here.
    JSONObject report(js);
    const uint8_t kernel_bytes[] = {0};
    report.AddPropertyBase64("kernelBytes", kernel_bytes, 0);
    return true;
  }

  bool is_static = BoolParameter::Parse(js->LookupParam("isStatic"), false);

  const GrowableObjectArray& params =
      GrowableObjectArray::Handle(thread->zone(), GrowableObjectArray::New());
  if (!ParseCSVList(js->LookupParam("definitions"), params)) {
    PrintInvalidParamError(js, "definitions");
    return true;
  }

  const GrowableObjectArray& type_params =
      GrowableObjectArray::Handle(thread->zone(), GrowableObjectArray::New());
  if (!ParseCSVList(js->LookupParam("typeDefinitions"), type_params)) {
    PrintInvalidParamError(js, "typedDefinitions");
    return true;
  }

  Dart_KernelCompilationResult compilation_result =
      KernelIsolate::CompileExpressionToKernel(
          js->LookupParam("expression"),
          Array::Handle(Array::MakeFixedLength(params)),
          Array::Handle(Array::MakeFixedLength(type_params)),
          js->LookupParam("libraryUri"), js->LookupParam("klass"), is_static);

  if (compilation_result.status != Dart_KernelCompilationStatus_Ok) {
    js->PrintError(kExpressionCompilationError, "%s", compilation_result.error);
    free(compilation_result.error);
    return true;
  }

  const uint8_t* kernel_bytes = compilation_result.kernel;
  intptr_t kernel_length = compilation_result.kernel_size;
  ASSERT(kernel_bytes != NULL);

  JSONObject report(js);
  report.AddPropertyBase64("kernelBytes", kernel_bytes, kernel_length);
  return true;
#endif
}

static const MethodParameter* evaluate_compiled_expression_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new UIntParameter("frameIndex", false),
    new IdParameter("targetId", false),
    new StringParameter("kernelBytes", true),
    NULL,
};

static bool EvaluateCompiledExpression(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  Isolate* isolate = thread->isolate();

  bool disable_breakpoints =
      BoolParameter::Parse(js->LookupParam("disableBreakpoints"), false);
  DisableBreakpointsScope db(isolate->debugger(), disable_breakpoints);

  DebuggerStackTrace* stack = isolate->debugger()->StackTrace();
  intptr_t frame_pos = UIntParameter::Parse(js->LookupParam("frameIndex"));
  if (frame_pos >= stack->Length()) {
    PrintInvalidParamError(js, "frameIndex");
    return true;
  }
  Zone* zone = thread->zone();
  const GrowableObjectArray& param_names =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());
  const GrowableObjectArray& param_values =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());
  if (BuildScope(thread, js, param_names, param_values)) {
    return true;
  }
  const GrowableObjectArray& type_params_names =
      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());

  intptr_t kernel_length;
  const char* kernel_bytes_str = js->LookupParam("kernelBytes");
  uint8_t* kernel_bytes = DecodeBase64(zone, kernel_bytes_str, &kernel_length);

  if (js->HasParam("frameIndex")) {
    DebuggerStackTrace* stack = isolate->debugger()->StackTrace();
    intptr_t frame_pos = UIntParameter::Parse(js->LookupParam("frameIndex"));
    if (frame_pos >= stack->Length()) {
      PrintInvalidParamError(js, "frameIndex");
      return true;
    }

    ActivationFrame* frame = stack->FrameAt(frame_pos);
    TypeArguments& type_arguments = TypeArguments::Handle(
        zone,
        frame->BuildParameters(param_names, param_values, type_params_names));

    const Object& result = Object::Handle(
        zone,
        frame->EvaluateCompiledExpression(
            kernel_bytes, kernel_length,
            Array::Handle(zone, Array::MakeFixedLength(type_params_names)),
            Array::Handle(zone, Array::MakeFixedLength(param_values)),
            type_arguments));
    result.PrintJSON(js, true);
    return true;
  } else {
    // evaluating expression in the context of a given object
    if (!js->HasParam("targetId")) {
      js->PrintError(kInvalidParams,
                     "Either targetId or frameIndex has to be provided.");
      return true;
    }
    const char* target_id = js->LookupParam("targetId");
    ObjectIdRing::LookupResult lookup_result;
    Object& obj = Object::Handle(
        zone, LookupHeapObject(thread, target_id, &lookup_result));
    if (obj.raw() == Object::sentinel().raw()) {
      if (lookup_result == ObjectIdRing::kCollected) {
        PrintSentinel(js, kCollectedSentinel);
      } else if (lookup_result == ObjectIdRing::kExpired) {
        PrintSentinel(js, kExpiredSentinel);
      } else {
        PrintInvalidParamError(js, "targetId");
      }
      return true;
    }
    TypeArguments& type_arguments = TypeArguments::Handle(zone);
    if (obj.IsLibrary()) {
      const Library& lib = Library::Cast(obj);
      const Object& result = Object::Handle(
          zone,
          lib.EvaluateCompiledExpression(
              kernel_bytes, kernel_length,
              Array::Handle(zone, Array::MakeFixedLength(type_params_names)),
              Array::Handle(zone, Array::MakeFixedLength(param_values)),
              type_arguments));
      result.PrintJSON(js, true);
      return true;
    }
    if (obj.IsClass()) {
      const Class& cls = Class::Cast(obj);
      const Object& result = Object::Handle(
          zone,
          cls.EvaluateCompiledExpression(
              kernel_bytes, kernel_length,
              Array::Handle(zone, Array::MakeFixedLength(type_params_names)),
              Array::Handle(zone, Array::MakeFixedLength(param_values)),
              type_arguments));
      result.PrintJSON(js, true);
      return true;
    }
    if ((obj.IsInstance() || obj.IsNull()) && !ContainsNonInstance(obj)) {
      // We don't use Instance::Cast here because it doesn't allow null.
      Instance& instance = Instance::Handle(zone);
      instance ^= obj.raw();
      const Class& receiver_cls = Class::Handle(zone, instance.clazz());
      const Object& result = Object::Handle(
          zone,
          instance.EvaluateCompiledExpression(
              receiver_cls, kernel_bytes, kernel_length,
              Array::Handle(zone, Array::MakeFixedLength(type_params_names)),
              Array::Handle(zone, Array::MakeFixedLength(param_values)),
              type_arguments));
      result.PrintJSON(js, true);
      return true;
    }
    js->PrintError(kInvalidParams,
                   "%s: invalid 'targetId' parameter: "
                   "Cannot evaluate against a VM-internal object",
                   js->method());
    return true;
  }
}

static const MethodParameter* evaluate_in_frame_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new UIntParameter("frameIndex", true),
    new MethodParameter("expression", true), NULL,
};

static bool EvaluateInFrame(Thread* thread, JSONStream* js) {
  // If a compilation service is available, this RPC invocation will have been
  // intercepted by RunningIsolates.routeRequest.
  js->PrintError(
      kExpressionCompilationError,
      "%s: No compilation service available; cannot evaluate from source.",
      js->method());
  return true;
}

class GetInstancesVisitor : public ObjectGraph::Visitor {
 public:
  GetInstancesVisitor(const Class& cls, const Array& storage)
      : cls_(cls), storage_(storage), count_(0) {}

  virtual Direction VisitObject(ObjectGraph::StackIterator* it) {
    RawObject* raw_obj = it->Get();
    if (raw_obj->IsPseudoObject()) {
      return kProceed;
    }
    Thread* thread = Thread::Current();
    REUSABLE_OBJECT_HANDLESCOPE(thread);
    Object& obj = thread->ObjectHandle();
    obj = raw_obj;
    if (obj.GetClassId() == cls_.id()) {
      if (!storage_.IsNull() && count_ < storage_.Length()) {
        storage_.SetAt(count_, obj);
      }
      ++count_;
    }
    return kProceed;
  }

  intptr_t count() const { return count_; }

 private:
  const Class& cls_;
  const Array& storage_;
  intptr_t count_;
};

static const MethodParameter* get_instances_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetInstances(Thread* thread, JSONStream* js) {
  const char* target_id = js->LookupParam("classId");
  if (target_id == NULL) {
    PrintMissingParamError(js, "classId");
    return true;
  }
  const char* limit_cstr = js->LookupParam("limit");
  if (limit_cstr == NULL) {
    PrintMissingParamError(js, "limit");
    return true;
  }
  intptr_t limit;
  if (!GetIntegerId(limit_cstr, &limit)) {
    PrintInvalidParamError(js, "limit");
    return true;
  }
  const Object& obj = Object::Handle(LookupHeapObject(thread, target_id, NULL));
  if (obj.raw() == Object::sentinel().raw() || !obj.IsClass()) {
    PrintInvalidParamError(js, "classId");
    return true;
  }
  const Class& cls = Class::Cast(obj);
  Array& storage = Array::Handle(Array::New(limit));
  GetInstancesVisitor visitor(cls, storage);
  ObjectGraph graph(thread);
  HeapIterationScope iteration_scope(Thread::Current(), true);
  graph.IterateObjects(&visitor);
  intptr_t count = visitor.count();
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "InstanceSet");
  jsobj.AddProperty("totalCount", count);
  {
    JSONArray samples(&jsobj, "samples");
    for (int i = 0; (i < storage.Length()) && (i < count); i++) {
      const Object& sample = Object::Handle(storage.At(i));
      samples.AddValue(sample);
    }
  }

  // We nil out the array after generating the response to prevent
  // reporting spurious references when looking for inbound references
  // after looking at allInstances.
  for (intptr_t i = 0; i < storage.Length(); i++) {
    storage.SetAt(i, Object::null_object());
  }

  return true;
}

#if !defined(DART_PRECOMPILED_RUNTIME)
static const char* const report_enum_names[] = {
    SourceReport::kCallSitesStr,
    SourceReport::kCoverageStr,
    SourceReport::kPossibleBreakpointsStr,
    SourceReport::kProfileStr,
    NULL,
};
#endif

static const MethodParameter* get_source_report_params[] = {
#if !defined(DART_PRECOMPILED_RUNTIME)
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumListParameter("reports", true, report_enum_names),
    new IdParameter("scriptId", false),
    new UIntParameter("tokenPos", false),
    new UIntParameter("endTokenPos", false),
    new BoolParameter("forceCompile", false),
#endif
    NULL,
};

static bool GetSourceReport(Thread* thread, JSONStream* js) {
#if defined(DART_PRECOMPILED_RUNTIME)
  js->PrintError(kFeatureDisabled, "disabled in AOT mode and PRODUCT.");
  return false;
#else
  if (CheckCompilerDisabled(thread, js)) {
    return true;
  }

  const char* reports_str = js->LookupParam("reports");
  const EnumListParameter* reports_parameter =
      static_cast<const EnumListParameter*>(get_source_report_params[1]);
  const char** reports = reports_parameter->Parse(thread->zone(), reports_str);
  intptr_t report_set = 0;
  while (*reports != NULL) {
    if (strcmp(*reports, SourceReport::kCallSitesStr) == 0) {
      report_set |= SourceReport::kCallSites;
    } else if (strcmp(*reports, SourceReport::kCoverageStr) == 0) {
      report_set |= SourceReport::kCoverage;
    } else if (strcmp(*reports, SourceReport::kPossibleBreakpointsStr) == 0) {
      report_set |= SourceReport::kPossibleBreakpoints;
    } else if (strcmp(*reports, SourceReport::kProfileStr) == 0) {
      report_set |= SourceReport::kProfile;
    }
    reports++;
  }

  SourceReport::CompileMode compile_mode = SourceReport::kNoCompile;
  if (BoolParameter::Parse(js->LookupParam("forceCompile"), false)) {
    compile_mode = SourceReport::kForceCompile;
  }

  Script& script = Script::Handle();
  intptr_t start_pos = UIntParameter::Parse(js->LookupParam("tokenPos"));
  intptr_t end_pos = UIntParameter::Parse(js->LookupParam("endTokenPos"));

  if (js->HasParam("scriptId")) {
    // Get the target script.
    const char* script_id_param = js->LookupParam("scriptId");
    const Object& obj =
        Object::Handle(LookupHeapObject(thread, script_id_param, NULL));
    if (obj.raw() == Object::sentinel().raw() || !obj.IsScript()) {
      PrintInvalidParamError(js, "scriptId");
      return true;
    }
    script ^= obj.raw();
  } else {
    if (js->HasParam("tokenPos")) {
      js->PrintError(
          kInvalidParams,
          "%s: the 'tokenPos' parameter requires the 'scriptId' parameter",
          js->method());
      return true;
    }
    if (js->HasParam("endTokenPos")) {
      js->PrintError(
          kInvalidParams,
          "%s: the 'endTokenPos' parameter requires the 'scriptId' parameter",
          js->method());
      return true;
    }
  }
  SourceReport report(report_set, compile_mode);
  report.PrintJSON(js, script, TokenPosition(start_pos),
                   TokenPosition(end_pos));
  return true;
#endif  // !DART_PRECOMPILED_RUNTIME
}

static const MethodParameter* reload_sources_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new BoolParameter("force", false),
    new BoolParameter("pause", false),
    new StringParameter("rootLibUri", false),
    new StringParameter("packagesUri", false),
    NULL,
};

static bool ReloadSources(Thread* thread, JSONStream* js) {
#if defined(DART_PRECOMPILED_RUNTIME)
  js->PrintError(kFeatureDisabled, "Compiler is disabled in AOT mode.");
  return true;
#else
  if (CheckCompilerDisabled(thread, js)) {
    return true;
  }

  Isolate* isolate = thread->isolate();
  if (!isolate->HasTagHandler()) {
    js->PrintError(kFeatureDisabled,
                   "A library tag handler must be installed.");
    return true;
  }
  if ((isolate->sticky_error() != Error::null()) ||
      (Thread::Current()->sticky_error() != Error::null())) {
    js->PrintError(kIsolateReloadBarred,
                   "This isolate cannot reload sources anymore because there "
                   "was an unhandled exception error. Restart the isolate.");
    return true;
  }
  if (isolate->IsReloading()) {
    js->PrintError(kIsolateIsReloading, "This isolate is being reloaded.");
    return true;
  }
  if (!isolate->CanReload()) {
    js->PrintError(kFeatureDisabled,
                   "This isolate cannot reload sources right now.");
    return true;
  }
  const bool force_reload =
      BoolParameter::Parse(js->LookupParam("force"), false);

  isolate->ReloadSources(js, force_reload, js->LookupParam("rootLibUri"),
                         js->LookupParam("packagesUri"));

  Service::CheckForPause(isolate, js);

  return true;
#endif
}

void Service::CheckForPause(Isolate* isolate, JSONStream* stream) {
  // Should we pause?
  isolate->set_should_pause_post_service_request(
      BoolParameter::Parse(stream->LookupParam("pause"), false));
}

RawError* Service::MaybePause(Isolate* isolate, const Error& error) {
  // Don't pause twice.
  if (!isolate->IsPaused()) {
    if (isolate->should_pause_post_service_request()) {
      isolate->set_should_pause_post_service_request(false);
      if (!error.IsNull()) {
        // Before pausing, restore the sticky error. The debugger will return it
        // from PausePostRequest.
        Thread::Current()->set_sticky_error(error);
      }
      return isolate->PausePostRequest();
    }
  }
  return error.raw();
}

static bool AddBreakpointCommon(Thread* thread,
                                JSONStream* js,
                                const String& script_uri) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  const char* line_param = js->LookupParam("line");
  intptr_t line = UIntParameter::Parse(line_param);
  const char* col_param = js->LookupParam("column");
  intptr_t col = -1;
  if (col_param != NULL) {
    col = UIntParameter::Parse(col_param);
    if (col == 0) {
      // Column number is 1-based.
      PrintInvalidParamError(js, "column");
      return true;
    }
  }
  ASSERT(!script_uri.IsNull());
  Breakpoint* bpt = NULL;
  bpt = thread->isolate()->debugger()->SetBreakpointAtLineCol(script_uri, line,
                                                              col);
  if (bpt == NULL) {
    js->PrintError(kCannotAddBreakpoint,
                   "%s: Cannot add breakpoint at line '%s'", js->method(),
                   line_param);
    return true;
  }
  bpt->PrintJSON(js);
  return true;
}

static const MethodParameter* add_breakpoint_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new IdParameter("scriptId", true),
    new UIntParameter("line", true),
    new UIntParameter("column", false),
    NULL,
};

static bool AddBreakpoint(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  const char* script_id_param = js->LookupParam("scriptId");
  Object& obj = Object::Handle(LookupHeapObject(thread, script_id_param, NULL));
  if (obj.raw() == Object::sentinel().raw() || !obj.IsScript()) {
    PrintInvalidParamError(js, "scriptId");
    return true;
  }
  const Script& script = Script::Cast(obj);
  const String& script_uri = String::Handle(script.url());
  ASSERT(!script_uri.IsNull());
  return AddBreakpointCommon(thread, js, script_uri);
}

static const MethodParameter* add_breakpoint_with_script_uri_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new IdParameter("scriptUri", true),
    new UIntParameter("line", true),
    new UIntParameter("column", false),
    NULL,
};

static bool AddBreakpointWithScriptUri(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  const char* script_uri_param = js->LookupParam("scriptUri");
  const String& script_uri = String::Handle(String::New(script_uri_param));
  return AddBreakpointCommon(thread, js, script_uri);
}

static const MethodParameter* add_breakpoint_at_entry_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new IdParameter("functionId", true), NULL,
};

static bool AddBreakpointAtEntry(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  const char* function_id = js->LookupParam("functionId");
  Object& obj = Object::Handle(LookupHeapObject(thread, function_id, NULL));
  if (obj.raw() == Object::sentinel().raw() || !obj.IsFunction()) {
    PrintInvalidParamError(js, "functionId");
    return true;
  }
  const Function& function = Function::Cast(obj);
  Breakpoint* bpt =
      thread->isolate()->debugger()->SetBreakpointAtEntry(function, false);
  if (bpt == NULL) {
    js->PrintError(kCannotAddBreakpoint,
                   "%s: Cannot add breakpoint at function '%s'", js->method(),
                   function.ToCString());
    return true;
  }
  bpt->PrintJSON(js);
  return true;
}

static const MethodParameter* add_breakpoint_at_activation_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new IdParameter("objectId", true), NULL,
};

static bool AddBreakpointAtActivation(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  const char* object_id = js->LookupParam("objectId");
  Object& obj = Object::Handle(LookupHeapObject(thread, object_id, NULL));
  if (obj.raw() == Object::sentinel().raw() || !obj.IsInstance()) {
    PrintInvalidParamError(js, "objectId");
    return true;
  }
  const Instance& closure = Instance::Cast(obj);
  Breakpoint* bpt =
      thread->isolate()->debugger()->SetBreakpointAtActivation(closure, false);
  if (bpt == NULL) {
    js->PrintError(kCannotAddBreakpoint,
                   "%s: Cannot add breakpoint at activation", js->method());
    return true;
  }
  bpt->PrintJSON(js);
  return true;
}

static const MethodParameter* remove_breakpoint_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool RemoveBreakpoint(Thread* thread, JSONStream* js) {
  if (CheckDebuggerDisabled(thread, js)) {
    return true;
  }

  if (!js->HasParam("breakpointId")) {
    PrintMissingParamError(js, "breakpointId");
    return true;
  }
  const char* bpt_id = js->LookupParam("breakpointId");
  ObjectIdRing::LookupResult lookup_result;
  Isolate* isolate = thread->isolate();
  Breakpoint* bpt = LookupBreakpoint(isolate, bpt_id, &lookup_result);
  // TODO(turnidge): Should we return a different error for bpts whic
  // have been already removed?
  if (bpt == NULL) {
    PrintInvalidParamError(js, "breakpointId");
    return true;
  }
  isolate->debugger()->RemoveBreakpoint(bpt->id());
  PrintSuccess(js);
  return true;
}

static RawClass* GetMetricsClass(Thread* thread) {
  Zone* zone = thread->zone();
  const Library& prof_lib = Library::Handle(zone, Library::DeveloperLibrary());
  ASSERT(!prof_lib.IsNull());
  const String& metrics_cls_name = String::Handle(zone, String::New("Metrics"));
  ASSERT(!metrics_cls_name.IsNull());
  const Class& metrics_cls =
      Class::Handle(zone, prof_lib.LookupClass(metrics_cls_name));
  ASSERT(!metrics_cls.IsNull());
  return metrics_cls.raw();
}

static bool HandleNativeMetricsList(Thread* thread, JSONStream* js) {
  JSONObject obj(js);
  obj.AddProperty("type", "MetricList");
  {
    JSONArray metrics(&obj, "metrics");
    Metric* current = thread->isolate()->metrics_list_head();
    while (current != NULL) {
      metrics.AddValue(current);
      current = current->next();
    }
  }
  return true;
}

static bool HandleNativeMetric(Thread* thread, JSONStream* js, const char* id) {
  Metric* current = thread->isolate()->metrics_list_head();
  while (current != NULL) {
    const char* name = current->name();
    ASSERT(name != NULL);
    if (strcmp(name, id) == 0) {
      current->PrintJSON(js);
      return true;
    }
    current = current->next();
  }
  PrintInvalidParamError(js, "metricId");
  return true;
}

static bool HandleDartMetricsList(Thread* thread, JSONStream* js) {
  Zone* zone = thread->zone();
  const Class& metrics_cls = Class::Handle(zone, GetMetricsClass(thread));
  const String& print_metrics_name =
      String::Handle(String::New("_printMetrics"));
  ASSERT(!print_metrics_name.IsNull());
  const Function& print_metrics = Function::Handle(
      zone, metrics_cls.LookupStaticFunctionAllowPrivate(print_metrics_name));
  ASSERT(!print_metrics.IsNull());
  const Array& args = Object::empty_array();
  const Object& result =
      Object::Handle(zone, DartEntry::InvokeFunction(print_metrics, args));
  ASSERT(!result.IsNull());
  ASSERT(result.IsString());
  TextBuffer* buffer = js->buffer();
  buffer->AddString(String::Cast(result).ToCString());
  return true;
}

static bool HandleDartMetric(Thread* thread, JSONStream* js, const char* id) {
  Zone* zone = thread->zone();
  const Class& metrics_cls = Class::Handle(zone, GetMetricsClass(thread));
  const String& print_metric_name = String::Handle(String::New("_printMetric"));
  ASSERT(!print_metric_name.IsNull());
  const Function& print_metric = Function::Handle(
      zone, metrics_cls.LookupStaticFunctionAllowPrivate(print_metric_name));
  ASSERT(!print_metric.IsNull());
  const String& arg0 = String::Handle(String::New(id));
  ASSERT(!arg0.IsNull());
  const Array& args = Array::Handle(Array::New(1));
  ASSERT(!args.IsNull());
  args.SetAt(0, arg0);
  const Object& result =
      Object::Handle(zone, DartEntry::InvokeFunction(print_metric, args));
  if (!result.IsNull()) {
    ASSERT(result.IsString());
    TextBuffer* buffer = js->buffer();
    buffer->AddString(String::Cast(result).ToCString());
    return true;
  }
  PrintInvalidParamError(js, "metricId");
  return true;
}

static const MethodParameter* get_isolate_metric_list_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetIsolateMetricList(Thread* thread, JSONStream* js) {
  bool native_metrics = false;
  if (js->HasParam("type")) {
    if (js->ParamIs("type", "Native")) {
      native_metrics = true;
    } else if (js->ParamIs("type", "Dart")) {
      native_metrics = false;
    } else {
      PrintInvalidParamError(js, "type");
      return true;
    }
  } else {
    PrintMissingParamError(js, "type");
    return true;
  }
  if (native_metrics) {
    return HandleNativeMetricsList(thread, js);
  }
  return HandleDartMetricsList(thread, js);
}

static const MethodParameter* get_isolate_metric_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetIsolateMetric(Thread* thread, JSONStream* js) {
  const char* metric_id = js->LookupParam("metricId");
  if (metric_id == NULL) {
    PrintMissingParamError(js, "metricId");
    return true;
  }
  // Verify id begins with "metrics/".
  static const char* const kMetricIdPrefix = "metrics/";
  static intptr_t kMetricIdPrefixLen = strlen(kMetricIdPrefix);
  if (strncmp(metric_id, kMetricIdPrefix, kMetricIdPrefixLen) != 0) {
    PrintInvalidParamError(js, "metricId");
    return true;
  }
  // Check if id begins with "metrics/native/".
  static const char* const kNativeMetricIdPrefix = "metrics/native/";
  static intptr_t kNativeMetricIdPrefixLen = strlen(kNativeMetricIdPrefix);
  const bool native_metric =
      strncmp(metric_id, kNativeMetricIdPrefix, kNativeMetricIdPrefixLen) == 0;
  if (native_metric) {
    const char* id = metric_id + kNativeMetricIdPrefixLen;
    return HandleNativeMetric(thread, js, id);
  }
  const char* id = metric_id + kMetricIdPrefixLen;
  return HandleDartMetric(thread, js, id);
}

static const MethodParameter* get_vm_metric_list_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool GetVMMetricList(Thread* thread, JSONStream* js) {
  return false;
}

static const MethodParameter* get_vm_metric_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool GetVMMetric(Thread* thread, JSONStream* js) {
  const char* metric_id = js->LookupParam("metricId");
  if (metric_id == NULL) {
    PrintMissingParamError(js, "metricId");
  }
  return false;
}

static const char* const timeline_streams_enum_names[] = {
    "all",
#define DEFINE_NAME(name, unused) #name,
    TIMELINE_STREAM_LIST(DEFINE_NAME)
#undef DEFINE_NAME
        NULL};

static const MethodParameter* set_vm_timeline_flags_params[] = {
    NO_ISOLATE_PARAMETER,
    new EnumListParameter("recordedStreams",
                          false,
                          timeline_streams_enum_names),
    NULL,
};

#if defined(SUPPORT_TIMELINE)
static bool HasStream(const char** recorded_streams, const char* stream) {
  while (*recorded_streams != NULL) {
    if ((strstr(*recorded_streams, "all") != NULL) ||
        (strstr(*recorded_streams, stream) != NULL)) {
      return true;
    }
    recorded_streams++;
  }
  return false;
}
#endif

static bool SetVMTimelineFlags(Thread* thread, JSONStream* js) {
#if !defined(SUPPORT_TIMELINE)
  PrintSuccess(js);
  return true;
#else
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  StackZone zone(thread);

  const EnumListParameter* recorded_streams_param =
      static_cast<const EnumListParameter*>(set_vm_timeline_flags_params[1]);

  const char* recorded_streams_str = js->LookupParam("recordedStreams");
  const char** recorded_streams =
      recorded_streams_param->Parse(thread->zone(), recorded_streams_str);

#define SET_ENABLE_STREAM(name, unused)                                        \
  Timeline::SetStream##name##Enabled(HasStream(recorded_streams, #name));
  TIMELINE_STREAM_LIST(SET_ENABLE_STREAM);
#undef SET_ENABLE_STREAM

  PrintSuccess(js);

  return true;
#endif
}

static const MethodParameter* get_vm_timeline_flags_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool GetVMTimelineFlags(Thread* thread, JSONStream* js) {
#if !defined(SUPPORT_TIMELINE)
  JSONObject obj(js);
  obj.AddProperty("type", "TimelineFlags");
  return true;
#else
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  StackZone zone(thread);
  Timeline::PrintFlagsToJSON(js);
  return true;
#endif
}

static const MethodParameter* clear_vm_timeline_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool ClearVMTimeline(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  StackZone zone(thread);

  Timeline::Clear();

  PrintSuccess(js);

  return true;
}

static const MethodParameter* get_vm_timeline_params[] = {
    NO_ISOLATE_PARAMETER, new Int64Parameter("timeOriginMicros", false),
    new Int64Parameter("timeExtentMicros", false), NULL,
};

static bool GetVMTimeline(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);
  StackZone zone(thread);
  Timeline::ReclaimCachedBlocksFromThreads();
  TimelineEventRecorder* timeline_recorder = Timeline::recorder();
  // TODO(johnmccutchan): Return an error.
  ASSERT(timeline_recorder != NULL);
  const char* name = timeline_recorder->name();
  if ((strcmp(name, FUCHSIA_RECORDER_NAME) == 0) ||
      (strcmp(name, SYSTRACE_RECORDER_NAME) == 0)) {
    js->PrintError(kInvalidTimelineRequest,
                   "A recorder of type \"%s\" is "
                   "currently in use. As a result, timeline events are handled "
                   "by the OS rather than the VM. See the VM service "
                   "documentation for more details on where timeline events "
                   "can be found for this recorder type.",
                   timeline_recorder->name());
    return true;
  }
  int64_t time_origin_micros =
      Int64Parameter::Parse(js->LookupParam("timeOriginMicros"));
  int64_t time_extent_micros =
      Int64Parameter::Parse(js->LookupParam("timeExtentMicros"));
  TimelineEventFilter filter(time_origin_micros, time_extent_micros);
  timeline_recorder->PrintJSON(js, &filter);
  return true;
}

static const char* const step_enum_names[] = {
    "None", "Into", "Over", "Out", "Rewind", "OverAsyncSuspension", NULL,
};

static const Debugger::ResumeAction step_enum_values[] = {
    Debugger::kContinue,   Debugger::kStepInto,
    Debugger::kStepOver,   Debugger::kStepOut,
    Debugger::kStepRewind, Debugger::kStepOverAsyncSuspension,
    Debugger::kContinue,  // Default value
};

static const MethodParameter* resume_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumParameter("step", false, step_enum_names),
    new UIntParameter("frameIndex", false), NULL,
};

static bool Resume(Thread* thread, JSONStream* js) {
  const char* step_param = js->LookupParam("step");
  Debugger::ResumeAction step = Debugger::kContinue;
  if (step_param != NULL) {
    step = EnumMapper(step_param, step_enum_names, step_enum_values);
  }
  intptr_t frame_index = 1;
  const char* frame_index_param = js->LookupParam("frameIndex");
  if (frame_index_param != NULL) {
    if (step != Debugger::kStepRewind) {
      // Only rewind supports the frameIndex parameter.
      js->PrintError(
          kInvalidParams,
          "%s: the 'frameIndex' parameter can only be used when rewinding",
          js->method());
      return true;
    }
    frame_index = UIntParameter::Parse(js->LookupParam("frameIndex"));
  }
  Isolate* isolate = thread->isolate();
  if (isolate->message_handler()->is_paused_on_start()) {
    // If the user is issuing a 'Over' or an 'Out' step, that is the
    // same as a regular resume request.
    if (step == Debugger::kStepInto) {
      isolate->debugger()->EnterSingleStepMode();
    }
    isolate->message_handler()->set_should_pause_on_start(false);
    isolate->SetResumeRequest();
    if (Service::debug_stream.enabled()) {
      ServiceEvent event(isolate, ServiceEvent::kResume);
      Service::HandleEvent(&event);
    }
    PrintSuccess(js);
    return true;
  }
  if (isolate->message_handler()->should_pause_on_start()) {
    isolate->message_handler()->set_should_pause_on_start(false);
    isolate->SetResumeRequest();
    if (Service::debug_stream.enabled()) {
      ServiceEvent event(isolate, ServiceEvent::kResume);
      Service::HandleEvent(&event);
    }
    PrintSuccess(js);
    return true;
  }
  if (isolate->message_handler()->is_paused_on_exit()) {
    isolate->message_handler()->set_should_pause_on_exit(false);
    isolate->SetResumeRequest();
    // We don't send a resume event because we will be exiting.
    PrintSuccess(js);
    return true;
  }
  if (isolate->debugger()->PauseEvent() == NULL) {
    js->PrintError(kIsolateMustBePaused, NULL);
    return true;
  }

  const char* error = NULL;
  if (!isolate->debugger()->SetResumeAction(step, frame_index, &error)) {
    js->PrintError(kCannotResume, "%s", error);
    return true;
  }
  isolate->SetResumeRequest();
  PrintSuccess(js);
  return true;
}

static const MethodParameter* kill_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    NULL,
};

static bool Kill(Thread* thread, JSONStream* js) {
  const String& msg =
      String::Handle(String::New("isolate terminated by Kill service request"));
  const UnwindError& error = UnwindError::Handle(UnwindError::New(msg));
  error.set_is_user_initiated(true);
  Thread::Current()->set_sticky_error(error);
  PrintSuccess(js);
  return true;
}

static const MethodParameter* pause_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool Pause(Thread* thread, JSONStream* js) {
  // TODO(turnidge): This interrupt message could have been sent from
  // the service isolate directly, but would require some special case
  // code.  That would prevent this isolate getting double-interrupted
  // with OOB messages.
  Isolate* isolate = thread->isolate();
  isolate->SendInternalLibMessage(Isolate::kInterruptMsg,
                                  isolate->pause_capability());
  PrintSuccess(js);
  return true;
}

static const MethodParameter* enable_profiler_params[] = {
    NULL,
};

static bool EnableProfiler(Thread* thread, JSONStream* js) {
  if (!FLAG_profiler) {
    FLAG_profiler = true;
    Profiler::Init();
  }
  PrintSuccess(js);
  return true;
}

static const MethodParameter* get_tag_profile_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetTagProfile(Thread* thread, JSONStream* js) {
  JSONObject miniProfile(js);
  miniProfile.AddProperty("type", "TagProfile");
  thread->isolate()->vm_tag_counters()->PrintToJSONObject(&miniProfile);
  return true;
}

static const char* const tags_enum_names[] = {
    "None", "UserVM", "UserOnly", "VMUser", "VMOnly", NULL,
};

static const Profile::TagOrder tags_enum_values[] = {
    Profile::kNoTags, Profile::kUserVM, Profile::kUser,
    Profile::kVMUser, Profile::kVM,
    Profile::kNoTags,  // Default value.
};

static const MethodParameter* get_cpu_profile_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumParameter("tags", true, tags_enum_names),
    new BoolParameter("_codeTransitionTags", false),
    new Int64Parameter("timeOriginMicros", false),
    new Int64Parameter("timeExtentMicros", false),
    NULL,
};

// TODO(johnmccutchan): Rename this to GetCpuSamples.
static bool GetCpuProfile(Thread* thread, JSONStream* js) {
  if (CheckProfilerDisabled(thread, js)) {
    return true;
  }

  Profile::TagOrder tag_order =
      EnumMapper(js->LookupParam("tags"), tags_enum_names, tags_enum_values);
  intptr_t extra_tags = 0;
  if (BoolParameter::Parse(js->LookupParam("_codeTransitionTags"))) {
    extra_tags |= ProfilerService::kCodeTransitionTagsBit;
  }
  int64_t time_origin_micros =
      Int64Parameter::Parse(js->LookupParam("timeOriginMicros"));
  int64_t time_extent_micros =
      Int64Parameter::Parse(js->LookupParam("timeExtentMicros"));
  ProfilerService::PrintJSON(js, tag_order, extra_tags, time_origin_micros,
                             time_extent_micros);
  return true;
}

static const MethodParameter* get_cpu_profile_timeline_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumParameter("tags", true, tags_enum_names),
    new Int64Parameter("timeOriginMicros", false),
    new Int64Parameter("timeExtentMicros", false),
    NULL,
};

static bool GetCpuProfileTimeline(Thread* thread, JSONStream* js) {
  if (CheckProfilerDisabled(thread, js)) {
    return true;
  }

  Profile::TagOrder tag_order =
      EnumMapper(js->LookupParam("tags"), tags_enum_names, tags_enum_values);
  int64_t time_origin_micros =
      Int64Parameter::Parse(js->LookupParam("timeOriginMicros"));
  int64_t time_extent_micros =
      Int64Parameter::Parse(js->LookupParam("timeExtentMicros"));
  bool code_trie = BoolParameter::Parse(js->LookupParam("code"), false);
  ProfilerService::PrintTimelineJSON(js, tag_order, time_origin_micros,
                                     time_extent_micros, code_trie);
  return true;
}

static const MethodParameter* write_cpu_profile_timeline_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumParameter("tags", true, tags_enum_names),
    new Int64Parameter("timeOriginMicros", false),
    new Int64Parameter("timeExtentMicros", false),
    NULL,
};

static bool WriteCpuProfileTimeline(Thread* thread, JSONStream* js) {
  if (CheckProfilerDisabled(thread, js)) {
    return true;
  }

  Profile::TagOrder tag_order =
      EnumMapper(js->LookupParam("tags"), tags_enum_names, tags_enum_values);
  int64_t time_origin_micros =
      Int64Parameter::Parse(js->LookupParam("timeOriginMicros"));
  int64_t time_extent_micros =
      Int64Parameter::Parse(js->LookupParam("timeExtentMicros"));
  bool code_trie = BoolParameter::Parse(js->LookupParam("code"), true);
  ProfilerService::AddToTimeline(tag_order, time_origin_micros,
                                 time_extent_micros, code_trie);
  PrintSuccess(js);  // The "result" is a side-effect in the timeline.
  return true;
}

static const MethodParameter* get_allocation_samples_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumParameter("tags", true, tags_enum_names),
    new IdParameter("classId", false),
    new Int64Parameter("timeOriginMicros", false),
    new Int64Parameter("timeExtentMicros", false),
    NULL,
};

static bool GetAllocationSamples(Thread* thread, JSONStream* js) {
  Profile::TagOrder tag_order =
      EnumMapper(js->LookupParam("tags"), tags_enum_names, tags_enum_values);
  int64_t time_origin_micros =
      Int64Parameter::Parse(js->LookupParam("timeOriginMicros"));
  int64_t time_extent_micros =
      Int64Parameter::Parse(js->LookupParam("timeExtentMicros"));
  const char* class_id = js->LookupParam("classId");
  intptr_t cid = -1;
  GetPrefixedIntegerId(class_id, "classes/", &cid);
  Isolate* isolate = thread->isolate();
  if (IsValidClassId(isolate, cid)) {
    const Class& cls = Class::Handle(GetClassForId(isolate, cid));
    ProfilerService::PrintAllocationJSON(js, tag_order, cls, time_origin_micros,
                                         time_extent_micros);
  } else {
    PrintInvalidParamError(js, "classId");
  }
  return true;
}

static const MethodParameter* get_native_allocation_samples_params[] = {
    NO_ISOLATE_PARAMETER,
    new EnumParameter("tags", true, tags_enum_names),
    new Int64Parameter("timeOriginMicros", false),
    new Int64Parameter("timeExtentMicros", false),
    NULL,
};

static bool GetNativeAllocationSamples(Thread* thread, JSONStream* js) {
  Profile::TagOrder tag_order =
      EnumMapper(js->LookupParam("tags"), tags_enum_names, tags_enum_values);
  int64_t time_origin_micros =
      Int64Parameter::Parse(js->LookupParam("timeOriginMicros"));
  int64_t time_extent_micros =
      Int64Parameter::Parse(js->LookupParam("timeExtentMicros"));
#if defined(DEBUG)
  Isolate::Current()->heap()->CollectAllGarbage();
#endif
  ProfilerService::PrintNativeAllocationJSON(js, tag_order, time_origin_micros,
                                             time_extent_micros);
  return true;
}

static const MethodParameter* clear_cpu_profile_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool ClearCpuProfile(Thread* thread, JSONStream* js) {
  ProfilerService::ClearSamples();
  PrintSuccess(js);
  return true;
}

static bool GetAllocationProfileImpl(Thread* thread,
                                     JSONStream* js,
                                     bool internal) {
  bool should_reset_accumulator = false;
  bool should_collect = false;
  if (js->HasParam("reset")) {
    if (js->ParamIs("reset", "true")) {
      should_reset_accumulator = true;
    } else {
      PrintInvalidParamError(js, "reset");
      return true;
    }
  }
  if (js->HasParam("gc")) {
    if (js->ParamIs("gc", "true")) {
      should_collect = true;
    } else {
      PrintInvalidParamError(js, "gc");
      return true;
    }
  }
  Isolate* isolate = thread->isolate();
  if (should_reset_accumulator) {
    isolate->UpdateLastAllocationProfileAccumulatorResetTimestamp();
    isolate->class_table()->ResetAllocationAccumulators();
  }
  if (should_collect) {
    isolate->UpdateLastAllocationProfileGCTimestamp();
    isolate->heap()->CollectAllGarbage();
  }
  isolate->class_table()->AllocationProfilePrintJSON(js, internal);
  return true;
}

static const MethodParameter* get_allocation_profile_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    NULL,
};

static bool GetAllocationProfilePublic(Thread* thread, JSONStream* js) {
  return GetAllocationProfileImpl(thread, js, false);
}

static bool GetAllocationProfile(Thread* thread, JSONStream* js) {
  return GetAllocationProfileImpl(thread, js, true);
}

static const MethodParameter* collect_all_garbage_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool CollectAllGarbage(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  isolate->heap()->CollectAllGarbage(Heap::kDebugging);
  PrintSuccess(js);
  return true;
}

static const MethodParameter* get_heap_map_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetHeapMap(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  if (js->HasParam("gc")) {
    if (js->ParamIs("gc", "scavenge")) {
      isolate->heap()->CollectGarbage(Heap::kScavenge, Heap::kDebugging);
    } else if (js->ParamIs("gc", "mark-sweep")) {
      isolate->heap()->CollectGarbage(Heap::kMarkSweep, Heap::kDebugging);
    } else if (js->ParamIs("gc", "mark-compact")) {
      isolate->heap()->CollectGarbage(Heap::kMarkCompact, Heap::kDebugging);
    } else {
      PrintInvalidParamError(js, "gc");
      return true;
    }
  }
  isolate->heap()->PrintHeapMapToJSONStream(isolate, js);
  return true;
}

static const char* snapshot_roots_names[] = {
    "User", "VM", NULL,
};

static ObjectGraph::SnapshotRoots snapshot_roots_values[] = {
    ObjectGraph::kUser, ObjectGraph::kVM,
};

static const MethodParameter* request_heap_snapshot_params[] = {
    RUNNABLE_ISOLATE_PARAMETER,
    new EnumParameter("roots", false /* not required */, snapshot_roots_names),
    new BoolParameter("collectGarbage", false /* not required */), NULL,
};

static bool RequestHeapSnapshot(Thread* thread, JSONStream* js) {
  ObjectGraph::SnapshotRoots roots = ObjectGraph::kVM;
  const char* roots_arg = js->LookupParam("roots");
  if (roots_arg != NULL) {
    roots = EnumMapper(roots_arg, snapshot_roots_names, snapshot_roots_values);
  }
  const bool collect_garbage =
      BoolParameter::Parse(js->LookupParam("collectGarbage"), true);
  if (Service::graph_stream.enabled()) {
    Service::SendGraphEvent(thread, roots, collect_garbage);
  }
  // TODO(koda): Provide some id that ties this request to async response(s).
  PrintSuccess(js);
  return true;
}

void Service::SendGraphEvent(Thread* thread,
                             ObjectGraph::SnapshotRoots roots,
                             bool collect_garbage) {
  uint8_t* buffer = NULL;
  WriteStream stream(&buffer, &allocator, 1 * MB);
  ObjectGraph graph(thread);
  intptr_t node_count = graph.Serialize(&stream, roots, collect_garbage);

  // Chrome crashes receiving a single tens-of-megabytes blob, so send the
  // snapshot in megabyte-sized chunks instead.
  const intptr_t kChunkSize = 1 * MB;
  intptr_t num_chunks =
      (stream.bytes_written() + (kChunkSize - 1)) / kChunkSize;
  for (intptr_t i = 0; i < num_chunks; i++) {
    JSONStream js;
    {
      JSONObject jsobj(&js);
      jsobj.AddProperty("jsonrpc", "2.0");
      jsobj.AddProperty("method", "streamNotify");
      {
        JSONObject params(&jsobj, "params");
        params.AddProperty("streamId", graph_stream.id());
        {
          JSONObject event(&params, "event");
          event.AddProperty("type", "Event");
          event.AddProperty("kind", "_Graph");
          event.AddProperty("isolate", thread->isolate());
          event.AddPropertyTimeMillis("timestamp", OS::GetCurrentTimeMillis());

          event.AddProperty("chunkIndex", i);
          event.AddProperty("chunkCount", num_chunks);
          event.AddProperty("nodeCount", node_count);
        }
      }
    }

    uint8_t* chunk_start = buffer + (i * kChunkSize);
    intptr_t chunk_size = (i + 1 == num_chunks)
                              ? stream.bytes_written() - (i * kChunkSize)
                              : kChunkSize;

    SendEventWithData(graph_stream.id(), "_Graph", js.buffer()->buf(),
                      js.buffer()->length(), chunk_start, chunk_size);
  }
}

void Service::SendInspectEvent(Isolate* isolate, const Object& inspectee) {
  if (!Service::debug_stream.enabled()) {
    return;
  }
  ServiceEvent event(isolate, ServiceEvent::kInspect);
  event.set_inspectee(&inspectee);
  Service::HandleEvent(&event);
}

void Service::SendEmbedderEvent(Isolate* isolate,
                                const char* stream_id,
                                const char* event_kind,
                                const uint8_t* bytes,
                                intptr_t bytes_len) {
  if (!Service::debug_stream.enabled()) {
    return;
  }
  ServiceEvent event(isolate, ServiceEvent::kEmbedder);
  event.set_embedder_kind(event_kind);
  event.set_embedder_stream_id(stream_id);
  event.set_bytes(bytes, bytes_len);
  Service::HandleEvent(&event);
}

void Service::SendLogEvent(Isolate* isolate,
                           int64_t sequence_number,
                           int64_t timestamp,
                           intptr_t level,
                           const String& name,
                           const String& message,
                           const Instance& zone,
                           const Object& error,
                           const Instance& stack_trace) {
  if (!Service::logging_stream.enabled()) {
    return;
  }
  ServiceEvent::LogRecord log_record;
  log_record.sequence_number = sequence_number;
  log_record.timestamp = timestamp;
  log_record.level = level;
  log_record.name = &name;
  log_record.message = &message;
  log_record.zone = &zone;
  log_record.error = &error;
  log_record.stack_trace = &stack_trace;
  ServiceEvent event(isolate, ServiceEvent::kLogging);
  event.set_log_record(log_record);
  Service::HandleEvent(&event);
}

void Service::SendExtensionEvent(Isolate* isolate,
                                 const String& event_kind,
                                 const String& event_data) {
  if (!Service::extension_stream.enabled()) {
    return;
  }
  ServiceEvent::ExtensionEvent extension_event;
  extension_event.event_kind = &event_kind;
  extension_event.event_data = &event_data;
  ServiceEvent event(isolate, ServiceEvent::kExtension);
  event.set_extension_event(extension_event);
  Service::HandleEvent(&event);
}

class ContainsAddressVisitor : public FindObjectVisitor {
 public:
  explicit ContainsAddressVisitor(uword addr) : addr_(addr) {}
  virtual ~ContainsAddressVisitor() {}

  virtual uword filter_addr() const { return addr_; }

  virtual bool FindObject(RawObject* obj) const {
    if (obj->IsPseudoObject()) {
      return false;
    }
    uword obj_begin = RawObject::ToAddr(obj);
    uword obj_end = obj_begin + obj->HeapSize();
    return obj_begin <= addr_ && addr_ < obj_end;
  }

 private:
  uword addr_;
};

static const MethodParameter* get_object_by_address_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static RawObject* GetObjectHelper(Thread* thread, uword addr) {
  HeapIterationScope iteration(thread);
  Object& object = Object::Handle(thread->zone());

  {
    NoSafepointScope no_safepoint;
    Isolate* isolate = thread->isolate();
    ContainsAddressVisitor visitor(addr);
    object = isolate->heap()->FindObject(&visitor);
  }

  if (!object.IsNull()) {
    return object.raw();
  }

  {
    NoSafepointScope no_safepoint;
    ContainsAddressVisitor visitor(addr);
    object = Dart::vm_isolate()->heap()->FindObject(&visitor);
  }

  return object.raw();
}

static bool GetObjectByAddress(Thread* thread, JSONStream* js) {
  const char* addr_str = js->LookupParam("address");
  if (addr_str == NULL) {
    PrintMissingParamError(js, "address");
    return true;
  }

  // Handle heap objects.
  uword addr = 0;
  if (!GetUnsignedIntegerId(addr_str, &addr, 16)) {
    PrintInvalidParamError(js, "address");
    return true;
  }
  bool ref = js->HasParam("ref") && js->ParamIs("ref", "true");
  const Object& obj =
      Object::Handle(thread->zone(), GetObjectHelper(thread, addr));
  if (obj.IsNull()) {
    PrintSentinel(js, kFreeSentinel);
  } else {
    obj.PrintJSON(js, ref);
  }
  return true;
}

static const MethodParameter* get_persistent_handles_params[] = {
    ISOLATE_PARAMETER, NULL,
};

template <typename T>
class PersistentHandleVisitor : public HandleVisitor {
 public:
  PersistentHandleVisitor(Thread* thread, JSONArray* handles)
      : HandleVisitor(thread), handles_(handles) {
    ASSERT(handles_ != NULL);
  }

  void Append(PersistentHandle* persistent_handle) {
    JSONObject obj(handles_);
    obj.AddProperty("type", "_PersistentHandle");
    const Object& object = Object::Handle(persistent_handle->raw());
    obj.AddProperty("object", object);
  }

  void Append(FinalizablePersistentHandle* weak_persistent_handle) {
    if (!weak_persistent_handle->raw()->IsHeapObject()) {
      return;  // Free handle.
    }

    JSONObject obj(handles_);
    obj.AddProperty("type", "_WeakPersistentHandle");
    const Object& object = Object::Handle(weak_persistent_handle->raw());
    obj.AddProperty("object", object);
    obj.AddPropertyF(
        "peer", "0x%" Px "",
        reinterpret_cast<uintptr_t>(weak_persistent_handle->peer()));
    obj.AddPropertyF(
        "callbackAddress", "0x%" Px "",
        reinterpret_cast<uintptr_t>(weak_persistent_handle->callback()));
    // Attempt to include a native symbol name.
    char* name = NativeSymbolResolver::LookupSymbolName(
        reinterpret_cast<uintptr_t>(weak_persistent_handle->callback()), NULL);
    obj.AddProperty("callbackSymbolName", (name == NULL) ? "" : name);
    if (name != NULL) {
      NativeSymbolResolver::FreeSymbolName(name);
    }
    obj.AddPropertyF("externalSize", "%" Pd "",
                     weak_persistent_handle->external_size());
  }

 protected:
  virtual void VisitHandle(uword addr) {
    T* handle = reinterpret_cast<T*>(addr);
    Append(handle);
  }

  JSONArray* handles_;
};

static bool GetPersistentHandles(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  ASSERT(isolate != NULL);

  ApiState* api_state = isolate->api_state();
  ASSERT(api_state != NULL);

  {
    JSONObject obj(js);
    obj.AddProperty("type", "_PersistentHandles");
    // Persistent handles.
    {
      JSONArray persistent_handles(&obj, "persistentHandles");
      PersistentHandles& handles = api_state->persistent_handles();
      PersistentHandleVisitor<PersistentHandle> visitor(thread,
                                                        &persistent_handles);
      handles.Visit(&visitor);
    }
    // Weak persistent handles.
    {
      JSONArray weak_persistent_handles(&obj, "weakPersistentHandles");
      FinalizablePersistentHandles& handles =
          api_state->weak_persistent_handles();
      PersistentHandleVisitor<FinalizablePersistentHandle> visitor(
          thread, &weak_persistent_handles);
      handles.VisitHandles(&visitor);
    }
  }

  return true;
}

static const MethodParameter* get_ports_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetPorts(Thread* thread, JSONStream* js) {
  MessageHandler* message_handler = thread->isolate()->message_handler();
  PortMap::PrintPortsForMessageHandler(message_handler, js);
  return true;
}

static bool RespondWithMalformedJson(Thread* thread, JSONStream* js) {
  JSONObject jsobj(js);
  jsobj.AddProperty("a", "a");
  JSONObject jsobj1(js);
  jsobj1.AddProperty("a", "a");
  JSONObject jsobj2(js);
  jsobj2.AddProperty("a", "a");
  JSONObject jsobj3(js);
  jsobj3.AddProperty("a", "a");
  return true;
}

static bool RespondWithMalformedObject(Thread* thread, JSONStream* js) {
  JSONObject jsobj(js);
  jsobj.AddProperty("bart", "simpson");
  return true;
}

static const MethodParameter* get_object_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new UIntParameter("offset", false),
    new UIntParameter("count", false), NULL,
};

static bool GetObject(Thread* thread, JSONStream* js) {
  const char* id = js->LookupParam("objectId");
  if (id == NULL) {
    PrintMissingParamError(js, "objectId");
    return true;
  }
  if (js->HasParam("offset")) {
    intptr_t value = UIntParameter::Parse(js->LookupParam("offset"));
    if (value < 0) {
      PrintInvalidParamError(js, "offset");
      return true;
    }
    js->set_offset(value);
  }
  if (js->HasParam("count")) {
    intptr_t value = UIntParameter::Parse(js->LookupParam("count"));
    if (value < 0) {
      PrintInvalidParamError(js, "count");
      return true;
    }
    js->set_count(value);
  }

  // Handle heap objects.
  ObjectIdRing::LookupResult lookup_result;
  Object& obj = Object::Handle(LookupHeapObject(thread, id, &lookup_result));
  if (obj.raw() != Object::sentinel().raw()) {
#if !defined(DART_PRECOMPILED_RUNTIME)
    // If obj is a script from dart:* and doesn't have source loaded, try and
    // load the source before sending the response.
    if (obj.IsScript()) {
      const Script& script = Script::Cast(obj);
      if (!script.HasSource() && script.IsPartOfDartColonLibrary() &&
          Service::HasDartLibraryKernelForSources()) {
        const uint8_t* kernel_buffer = Service::dart_library_kernel();
        const intptr_t kernel_buffer_len =
            Service::dart_library_kernel_length();
        script.LoadSourceFromKernel(kernel_buffer, kernel_buffer_len);
      }
    }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)
    // We found a heap object for this id.  Return it.
    obj.PrintJSON(js, false);
    return true;
  } else if (lookup_result == ObjectIdRing::kCollected) {
    PrintSentinel(js, kCollectedSentinel);
    return true;
  } else if (lookup_result == ObjectIdRing::kExpired) {
    PrintSentinel(js, kExpiredSentinel);
    return true;
  }

  // Handle non-heap objects.
  Breakpoint* bpt = LookupBreakpoint(thread->isolate(), id, &lookup_result);
  if (bpt != NULL) {
    bpt->PrintJSON(js);
    return true;
  } else if (lookup_result == ObjectIdRing::kCollected) {
    PrintSentinel(js, kCollectedSentinel);
    return true;
  }

  PrintInvalidParamError(js, "objectId");
  return true;
}

static const MethodParameter* get_object_store_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetObjectStore(Thread* thread, JSONStream* js) {
  JSONObject jsobj(js);
  thread->isolate()->object_store()->PrintToJSONObject(&jsobj);
  return true;
}

static const MethodParameter* get_class_list_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetClassList(Thread* thread, JSONStream* js) {
  ClassTable* table = thread->isolate()->class_table();
  JSONObject jsobj(js);
  table->PrintToJSONObject(&jsobj);
  return true;
}

static const MethodParameter* get_type_arguments_list_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, NULL,
};

static bool GetTypeArgumentsList(Thread* thread, JSONStream* js) {
  bool only_with_instantiations = false;
  if (js->ParamIs("onlyWithInstantiations", "true")) {
    only_with_instantiations = true;
  }
  Zone* zone = thread->zone();
  ObjectStore* object_store = thread->isolate()->object_store();
  CanonicalTypeArgumentsSet typeargs_table(
      zone, object_store->canonical_type_arguments());
  const intptr_t table_size = typeargs_table.NumEntries();
  const intptr_t table_used = typeargs_table.NumOccupied();
  const Array& typeargs_array =
      Array::Handle(zone, HashTables::ToArray(typeargs_table, false));
  ASSERT(typeargs_array.Length() == table_used);
  TypeArguments& typeargs = TypeArguments::Handle(zone);
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "TypeArgumentsList");
  jsobj.AddProperty("canonicalTypeArgumentsTableSize", table_size);
  jsobj.AddProperty("canonicalTypeArgumentsTableUsed", table_used);
  JSONArray members(&jsobj, "typeArguments");
  for (intptr_t i = 0; i < table_used; i++) {
    typeargs ^= typeargs_array.At(i);
    if (!typeargs.IsNull()) {
      if (!only_with_instantiations || typeargs.HasInstantiations()) {
        members.AddValue(typeargs);
      }
    }
  }
  typeargs_table.Release();
  return true;
}

static const MethodParameter* get_version_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool GetVersion(Thread* thread, JSONStream* js) {
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "Version");
  jsobj.AddProperty("major",
                    static_cast<intptr_t>(SERVICE_PROTOCOL_MAJOR_VERSION));
  jsobj.AddProperty("minor",
                    static_cast<intptr_t>(SERVICE_PROTOCOL_MINOR_VERSION));
  jsobj.AddProperty("_privateMajor", static_cast<intptr_t>(0));
  jsobj.AddProperty("_privateMinor", static_cast<intptr_t>(0));
  return true;
}

class ServiceIsolateVisitor : public IsolateVisitor {
 public:
  explicit ServiceIsolateVisitor(JSONArray* jsarr) : jsarr_(jsarr) {}
  virtual ~ServiceIsolateVisitor() {}

  void VisitIsolate(Isolate* isolate) {
    if (!IsVMInternalIsolate(isolate)) {
      jsarr_->AddValue(isolate);
    }
  }

 private:
  JSONArray* jsarr_;
};

static const MethodParameter* get_vm_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

void Service::PrintJSONForEmbedderInformation(JSONObject *jsobj) {
  if (embedder_information_callback_ != NULL) {
    Dart_EmbedderInformation info = {
      0,  // version
      NULL,  // name
      -1,  // max_rss
      -1  // current_rss
    };
    embedder_information_callback_(&info);
    ASSERT(info.version == DART_EMBEDDER_INFORMATION_CURRENT_VERSION);
    if (info.name != NULL) {
      jsobj->AddProperty("_embedder", info.name);
    }
    if (info.max_rss >= 0) {
      jsobj->AddProperty64("_maxRSS", info.max_rss);
    }
    if (info.current_rss >= 0) {
      jsobj->AddProperty64("_currentRSS", info.current_rss);
    }
  }
}

void Service::PrintJSONForVM(JSONStream* js, bool ref) {
  JSONObject jsobj(js);
  jsobj.AddProperty("type", (ref ? "@VM" : "VM"));
  jsobj.AddProperty("name", GetVMName());
  if (ref) {
    return;
  }
  jsobj.AddProperty("architectureBits", static_cast<intptr_t>(kBitsPerWord));
  jsobj.AddProperty("targetCPU", CPU::Id());
  jsobj.AddProperty("hostCPU", HostCPUFeatures::hardware());
  jsobj.AddProperty("version", Version::String());
  jsobj.AddProperty("_profilerMode", FLAG_profile_vm ? "VM" : "Dart");
  jsobj.AddProperty64("_nativeZoneMemoryUsage",
                      ApiNativeScope::current_memory_usage());
  jsobj.AddProperty64("pid", OS::ProcessId());
  jsobj.AddPropertyTimeMillis(
      "startTime", OS::GetCurrentTimeMillis() - Dart::UptimeMillis());
  MallocHooks::PrintToJSONObject(&jsobj);
  PrintJSONForEmbedderInformation(&jsobj);
  // Construct the isolate list.
  {
    JSONArray jsarr(&jsobj, "isolates");
    ServiceIsolateVisitor visitor(&jsarr);
    Isolate::VisitIsolates(&visitor);
  }
}

static bool GetVM(Thread* thread, JSONStream* js) {
  Service::PrintJSONForVM(js, false);
  return true;
}

static const char* exception_pause_mode_names[] = {
    "All", "None", "Unhandled", NULL,
};

static Dart_ExceptionPauseInfo exception_pause_mode_values[] = {
    kPauseOnAllExceptions, kNoPauseOnExceptions, kPauseOnUnhandledExceptions,
    kInvalidExceptionPauseInfo,
};

static const MethodParameter* set_exception_pause_mode_params[] = {
    ISOLATE_PARAMETER,
    new EnumParameter("mode", true, exception_pause_mode_names), NULL,
};

static bool SetExceptionPauseMode(Thread* thread, JSONStream* js) {
  const char* mode = js->LookupParam("mode");
  if (mode == NULL) {
    PrintMissingParamError(js, "mode");
    return true;
  }
  Dart_ExceptionPauseInfo info =
      EnumMapper(mode, exception_pause_mode_names, exception_pause_mode_values);
  if (info == kInvalidExceptionPauseInfo) {
    PrintInvalidParamError(js, "mode");
    return true;
  }
  Isolate* isolate = thread->isolate();
  isolate->debugger()->SetExceptionPauseInfo(info);
  if (Service::debug_stream.enabled()) {
    ServiceEvent event(isolate, ServiceEvent::kDebuggerSettingsUpdate);
    Service::HandleEvent(&event);
  }
  PrintSuccess(js);
  return true;
}

static const MethodParameter* get_flag_list_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool GetFlagList(Thread* thread, JSONStream* js) {
  Flags::PrintJSON(js);
  return true;
}

static const MethodParameter* set_flags_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool SetFlag(Thread* thread, JSONStream* js) {
  const char* flag_name = js->LookupParam("name");
  if (flag_name == NULL) {
    PrintMissingParamError(js, "name");
    return true;
  }
  const char* flag_value = js->LookupParam("value");
  if (flag_value == NULL) {
    PrintMissingParamError(js, "value");
    return true;
  }

  if (Flags::Lookup(flag_name) == NULL) {
    JSONObject jsobj(js);
    jsobj.AddProperty("type", "Error");
    jsobj.AddProperty("message", "Cannot set flag: flag not found");
    return true;
  }

  // Changing most flags at runtime is dangerous because e.g., it may leave the
  // behavior generated code and the runtime out of sync.
  const uintptr_t kProfilePeriodIndex = 3;
  const char* kAllowedFlags[] = {
      "pause_isolates_on_start",
      "pause_isolates_on_exit",
      "pause_isolates_on_unhandled_exceptions",
      "profile_period",
  };

  bool allowed = false;
  bool profile_period = false;
  for (size_t i = 0; i < ARRAY_SIZE(kAllowedFlags); i++) {
    if (strcmp(flag_name, kAllowedFlags[i]) == 0) {
      allowed = true;
      profile_period = (i == kProfilePeriodIndex);
      break;
    }
  }

  if (!allowed) {
    JSONObject jsobj(js);
    jsobj.AddProperty("type", "Error");
    jsobj.AddProperty("message", "Cannot set flag: cannot change at runtime");
    return true;
  }

  const char* error = NULL;
  if (Flags::SetFlag(flag_name, flag_value, &error)) {
    PrintSuccess(js);
    if (profile_period) {
      // FLAG_profile_period has already been set to the new value. Now we need
      // to notify the ThreadInterrupter to pick up the change.
      Profiler::UpdateSamplePeriod();
    }
    return true;
  } else {
    JSONObject jsobj(js);
    jsobj.AddProperty("type", "Error");
    jsobj.AddProperty("message", error);
    return true;
  }
}

static const MethodParameter* set_library_debuggable_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new IdParameter("libraryId", true),
    new BoolParameter("isDebuggable", true), NULL,
};

static bool SetLibraryDebuggable(Thread* thread, JSONStream* js) {
  const char* lib_id = js->LookupParam("libraryId");
  ObjectIdRing::LookupResult lookup_result;
  Object& obj =
      Object::Handle(LookupHeapObject(thread, lib_id, &lookup_result));
  const bool is_debuggable =
      BoolParameter::Parse(js->LookupParam("isDebuggable"), false);
  if (obj.IsLibrary()) {
    const Library& lib = Library::Cast(obj);
    if (lib.is_dart_scheme()) {
      const String& url = String::Handle(lib.url());
      if (url.StartsWith(Symbols::DartSchemePrivate())) {
        PrintIllegalParamError(js, "libraryId");
        return true;
      }
    }
    lib.set_debuggable(is_debuggable);
    PrintSuccess(js);
    return true;
  }
  PrintInvalidParamError(js, "libraryId");
  return true;
}

static const MethodParameter* set_name_params[] = {
    ISOLATE_PARAMETER, new MethodParameter("name", true), NULL,
};

static bool SetName(Thread* thread, JSONStream* js) {
  Isolate* isolate = thread->isolate();
  isolate->set_name(js->LookupParam("name"));
  if (Service::isolate_stream.enabled()) {
    ServiceEvent event(isolate, ServiceEvent::kIsolateUpdate);
    Service::HandleEvent(&event);
  }
  PrintSuccess(js);
  return true;
}

static const MethodParameter* set_vm_name_params[] = {
    NO_ISOLATE_PARAMETER, new MethodParameter("name", true), NULL,
};

static bool SetVMName(Thread* thread, JSONStream* js) {
  const char* name_param = js->LookupParam("name");
  free(vm_name);
  vm_name = strdup(name_param);
  if (Service::vm_stream.enabled()) {
    ServiceEvent event(NULL, ServiceEvent::kVMUpdate);
    Service::HandleEvent(&event);
  }
  PrintSuccess(js);
  return true;
}

static const MethodParameter* set_trace_class_allocation_params[] = {
    RUNNABLE_ISOLATE_PARAMETER, new IdParameter("classId", true),
    new BoolParameter("enable", true), NULL,
};

static bool SetTraceClassAllocation(Thread* thread, JSONStream* js) {
  if (CheckCompilerDisabled(thread, js)) {
    return true;
  }

  const char* class_id = js->LookupParam("classId");
  const bool enable = BoolParameter::Parse(js->LookupParam("enable"));
  intptr_t cid = -1;
  GetPrefixedIntegerId(class_id, "classes/", &cid);
  Isolate* isolate = thread->isolate();
  if (!IsValidClassId(isolate, cid)) {
    PrintInvalidParamError(js, "classId");
    return true;
  }
  const Class& cls = Class::Handle(GetClassForId(isolate, cid));
  ASSERT(!cls.IsNull());
  cls.SetTraceAllocation(enable);
  PrintSuccess(js);
  return true;
}

static const MethodParameter* get_default_classes_aliases_params[] = {
    NO_ISOLATE_PARAMETER, NULL,
};

static bool GetDefaultClassesAliases(Thread* thread, JSONStream* js) {
  JSONObject jsobj(js);
  jsobj.AddProperty("type", "ClassesAliasesMap");

  JSONObject map(&jsobj, "map");

#define DEFINE_ADD_VALUE_F(id)                                                 \
  internals.AddValueF("classes/%" Pd, static_cast<intptr_t>(id));
#define DEFINE_ADD_VALUE_F_CID(clazz) DEFINE_ADD_VALUE_F(k##clazz##Cid)
  {
    JSONArray internals(&map, "<VM Internals>");
    for (intptr_t id = kClassCid; id < kInstanceCid; ++id) {
      DEFINE_ADD_VALUE_F(id);
    }
    DEFINE_ADD_VALUE_F_CID(LibraryPrefix);
  }
  {
    JSONArray internals(&map, "Type");
    for (intptr_t id = kAbstractTypeCid; id <= kTypeParameterCid; ++id) {
      DEFINE_ADD_VALUE_F(id);
    }
  }
  {
    JSONArray internals(&map, "Object");
    DEFINE_ADD_VALUE_F_CID(Instance);
  }
  {
    JSONArray internals(&map, "Closure");
    DEFINE_ADD_VALUE_F_CID(Closure);
    DEFINE_ADD_VALUE_F_CID(Context);
  }
  {
    JSONArray internals(&map, "Int");
    for (intptr_t id = kIntegerCid; id <= kMintCid; ++id) {
      DEFINE_ADD_VALUE_F(id);
    }
  }
  {
    JSONArray internals(&map, "Double");
    DEFINE_ADD_VALUE_F_CID(Double);
  }
  {
    JSONArray internals(&map, "String");
    CLASS_LIST_STRINGS(DEFINE_ADD_VALUE_F_CID)
  }
  {
    JSONArray internals(&map, "List");
    CLASS_LIST_ARRAYS(DEFINE_ADD_VALUE_F_CID)
    DEFINE_ADD_VALUE_F_CID(GrowableObjectArray)
    DEFINE_ADD_VALUE_F_CID(ByteBuffer)
  }
  {
    JSONArray internals(&map, "Map");
    DEFINE_ADD_VALUE_F_CID(LinkedHashMap)
  }
#define DEFINE_ADD_MAP_KEY(clazz)                                              \
  {                                                                            \
    JSONArray internals(&map, #clazz);                                         \
    DEFINE_ADD_VALUE_F_CID(TypedData##clazz)                                   \
    DEFINE_ADD_VALUE_F_CID(TypedData##clazz)                                   \
    DEFINE_ADD_VALUE_F_CID(ExternalTypedData##clazz)                           \
  }
  CLASS_LIST_TYPED_DATA(DEFINE_ADD_MAP_KEY)
#undef DEFINE_ADD_MAP_KEY
#define DEFINE_ADD_MAP_KEY(clazz)                                              \
  {                                                                            \
    JSONArray internals(&map, #clazz);                                         \
    DEFINE_ADD_VALUE_F_CID(Ffi##clazz)                                         \
  }
  CLASS_LIST_FFI(DEFINE_ADD_MAP_KEY)
#undef DEFINE_ADD_MAP_KEY
#undef DEFINE_ADD_VALUE_F_CID
#undef DEFINE_ADD_VALUE_F

  return true;
}

// clang-format off
static const ServiceMethodDescriptor service_methods_[] = {
  { "_echo", Echo,
    NULL },
  { "_respondWithMalformedJson", RespondWithMalformedJson,
    NULL },
  { "_respondWithMalformedObject", RespondWithMalformedObject,
    NULL },
  { "_triggerEchoEvent", TriggerEchoEvent,
    NULL },
  { "addBreakpoint", AddBreakpoint,
    add_breakpoint_params },
  { "addBreakpointWithScriptUri", AddBreakpointWithScriptUri,
    add_breakpoint_with_script_uri_params },
  { "addBreakpointAtEntry", AddBreakpointAtEntry,
    add_breakpoint_at_entry_params },
  { "_addBreakpointAtActivation", AddBreakpointAtActivation,
    add_breakpoint_at_activation_params },
  { "_buildExpressionEvaluationScope", BuildExpressionEvaluationScope,
    build_expression_evaluation_scope_params },
  { "_clearCpuProfile", ClearCpuProfile,
    clear_cpu_profile_params },
  { "clearVMTimeline", ClearVMTimeline,
    clear_vm_timeline_params, },
  { "_compileExpression", CompileExpression, compile_expression_params },
  { "_enableProfiler", EnableProfiler,
    enable_profiler_params, },
  { "evaluate", Evaluate,
    evaluate_params },
  { "evaluateInFrame", EvaluateInFrame,
    evaluate_in_frame_params },
  { "_getAllocationProfile", GetAllocationProfile,
    get_allocation_profile_params },
  { "getAllocationProfile", GetAllocationProfilePublic,
    get_allocation_profile_params },
  { "_getAllocationSamples", GetAllocationSamples,
      get_allocation_samples_params },
  { "_getNativeAllocationSamples", GetNativeAllocationSamples,
      get_native_allocation_samples_params },
  { "getClassList", GetClassList,
    get_class_list_params },
  { "_getCpuProfile", GetCpuProfile,
    get_cpu_profile_params },
  { "_getCpuProfileTimeline", GetCpuProfileTimeline,
    get_cpu_profile_timeline_params },
  { "_writeCpuProfileTimeline", WriteCpuProfileTimeline,
    write_cpu_profile_timeline_params },
  { "getFlagList", GetFlagList,
    get_flag_list_params },
  { "_getHeapMap", GetHeapMap,
    get_heap_map_params },
  { "_getInboundReferences", GetInboundReferences,
    get_inbound_references_params },
  { "_getInstances", GetInstances,
    get_instances_params },
  { "getIsolate", GetIsolate,
    get_isolate_params },
  { "getMemoryUsage", GetMemoryUsage,
    get_memory_usage_params },
  { "_getIsolateMetric", GetIsolateMetric,
    get_isolate_metric_params },
  { "_getIsolateMetricList", GetIsolateMetricList,
    get_isolate_metric_list_params },
  { "getObject", GetObject,
    get_object_params },
  { "_getObjectStore", GetObjectStore,
    get_object_store_params },
  { "_getObjectByAddress", GetObjectByAddress,
    get_object_by_address_params },
  { "_getPersistentHandles", GetPersistentHandles,
      get_persistent_handles_params, },
  { "_getPorts", GetPorts,
    get_ports_params },
  { "_getReachableSize", GetReachableSize,
    get_reachable_size_params },
  { "_getRetainedSize", GetRetainedSize,
    get_retained_size_params },
  { "_getRetainingPath", GetRetainingPath,
    get_retaining_path_params },
  { "getScripts", GetScripts,
    get_scripts_params },
  { "getSourceReport", GetSourceReport,
    get_source_report_params },
  { "getStack", GetStack,
    get_stack_params },
  { "_getUnusedChangesInLastReload", GetUnusedChangesInLastReload,
    get_unused_changes_in_last_reload_params },
  { "_getTagProfile", GetTagProfile,
    get_tag_profile_params },
  { "_getTypeArgumentsList", GetTypeArgumentsList,
    get_type_arguments_list_params },
  { "getVersion", GetVersion,
    get_version_params },
  { "getVM", GetVM,
    get_vm_params },
  { "_getVMMetric", GetVMMetric,
    get_vm_metric_params },
  { "_getVMMetricList", GetVMMetricList,
    get_vm_metric_list_params },
  { "getVMTimeline", GetVMTimeline,
    get_vm_timeline_params },
  { "getVMTimelineFlags", GetVMTimelineFlags,
    get_vm_timeline_flags_params },
  { "invoke", Invoke, invoke_params },
  { "kill", Kill, kill_params },
  { "pause", Pause,
    pause_params },
  { "removeBreakpoint", RemoveBreakpoint,
    remove_breakpoint_params },
  { "reloadSources", ReloadSources,
    reload_sources_params },
  { "_reloadSources", ReloadSources,
    reload_sources_params },
  { "resume", Resume,
    resume_params },
  { "_requestHeapSnapshot", RequestHeapSnapshot,
    request_heap_snapshot_params },
  { "_evaluateCompiledExpression", EvaluateCompiledExpression,
    evaluate_compiled_expression_params },
  { "setExceptionPauseMode", SetExceptionPauseMode,
    set_exception_pause_mode_params },
  { "setFlag", SetFlag,
    set_flags_params },
  { "setLibraryDebuggable", SetLibraryDebuggable,
    set_library_debuggable_params },
  { "setName", SetName,
    set_name_params },
  { "_setTraceClassAllocation", SetTraceClassAllocation,
    set_trace_class_allocation_params },
  { "setVMName", SetVMName,
    set_vm_name_params },
  { "setVMTimelineFlags", SetVMTimelineFlags,
    set_vm_timeline_flags_params },
  { "_collectAllGarbage", CollectAllGarbage,
    collect_all_garbage_params },
  { "_getDefaultClassesAliases", GetDefaultClassesAliases,
    get_default_classes_aliases_params },
};
// clang-format on

const ServiceMethodDescriptor* FindMethod(const char* method_name) {
  intptr_t num_methods = sizeof(service_methods_) / sizeof(service_methods_[0]);
  for (intptr_t i = 0; i < num_methods; i++) {
    const ServiceMethodDescriptor& method = service_methods_[i];
    if (strcmp(method_name, method.name) == 0) {
      return &method;
    }
  }
  return NULL;
}

#endif  // !PRODUCT

}  // namespace dart