// Copyright (c) 2012, 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 <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "include/dart_api.h"
#include "include/dart_debugger_api.h"

#include "bin/builtin.h"
#include "bin/dartutils.h"
#include "bin/dbg_connection.h"
#include "bin/directory.h"
#include "bin/eventhandler.h"
#include "bin/extensions.h"
#include "bin/file.h"
#include "bin/isolate_data.h"
#include "bin/log.h"
#include "bin/platform.h"
#include "bin/process.h"
#include "bin/vmservice_impl.h"
#include "platform/globals.h"

namespace dart {
namespace bin {

// snapshot_buffer points to a snapshot if we link in a snapshot otherwise
// it is initialized to NULL.
extern const uint8_t* snapshot_buffer;

// Global state that stores a pointer to the application script snapshot.
static bool generate_script_snapshot = false;
static File* snapshot_file = NULL;


// Global state that indicates whether there is a debug breakpoint.
// This pointer points into an argv buffer and does not need to be
// free'd.
static const char* breakpoint_at = NULL;


// Global state that indicates whether we should open a connection
// and listen for a debugger to connect.
static bool start_debugger = false;
static const int DEFAULT_DEBUG_PORT = 5858;
static const char* DEFAULT_DEBUG_IP = "127.0.0.1";
static const char* debug_ip = DEFAULT_DEBUG_IP;
static int debug_port = -1;

// Value of the --package-root flag.
// (This pointer points into an argv buffer and does not need to be
// free'd.)
static const char* package_root = NULL;


// Global flag that is used to indicate that we want to compile all the
// dart functions and not run anything.
static bool has_compile_all = false;
// Global flag that is used to indicate that we want to check function
// fingerprints.
static bool has_check_function_fingerprints = false;

// Global flag that is used to indicate that we want to print the source code
// for script that is being run.
static bool has_print_script = false;


// VM Service options.
static bool start_vm_service = false;
static int vm_service_server_port = -1;
static const int DEFAULT_VM_SERVICE_SERVER_PORT = 8181;


static bool IsValidFlag(const char* name,
                        const char* prefix,
                        intptr_t prefix_length) {
  intptr_t name_length = strlen(name);
  return ((name_length > prefix_length) &&
          (strncmp(name, prefix, prefix_length) == 0));
}


static bool has_version_option = false;
static bool ProcessVersionOption(const char* arg) {
  if (*arg != '\0') {
    return false;
  }
  has_version_option = true;
  return true;
}


static bool has_help_option = false;
static bool ProcessHelpOption(const char* arg) {
  if (*arg != '\0') {
    return false;
  }
  has_help_option = true;
  return true;
}


static bool has_verbose_option = false;
static bool ProcessVerboseOption(const char* arg) {
  if (*arg != '\0') {
    return false;
  }
  has_verbose_option = true;
  return true;
}


static bool ProcessBreakpointOption(const char* funcname) {
  ASSERT(funcname != NULL);
  if (*funcname == '\0') {
    return false;
  }
  breakpoint_at = funcname;
  return true;
}


static bool ProcessPackageRootOption(const char* arg) {
  ASSERT(arg != NULL);
  if (*arg == '\0' || *arg == '-') {
    return false;
  }
  package_root = arg;
  return true;
}


static bool ProcessCompileAllOption(const char* arg) {
  ASSERT(arg != NULL);
  if (*arg != '\0') {
    return false;
  }
  has_compile_all = true;
  return true;
}


static bool ProcessFingerprintedFunctions(const char* arg) {
  ASSERT(arg != NULL);
  if (*arg != '\0') {
    return false;
  }
  has_check_function_fingerprints = true;
  return true;
}


static bool ProcessDebugOption(const char* port) {
  // TODO(hausner): Add support for specifying an IP address on which
  // the debugger should listen.
  ASSERT(port != NULL);
  debug_port = -1;
  if (*port == '\0') {
    debug_port = DEFAULT_DEBUG_PORT;
  } else {
    if ((*port == '=') || (*port == ':')) {
      debug_port = atoi(port + 1);
    }
  }
  if (debug_port < 0) {
    Log::PrintErr("unrecognized --debug option syntax. "
                    "Use --debug[:<port number>]\n");
    return false;
  }
  breakpoint_at = "main";
  start_debugger = true;
  return true;
}


static bool ProcessPrintScriptOption(const char* arg) {
  ASSERT(arg != NULL);
  if (*arg != '\0') {
    return false;
  }
  has_print_script = true;
  return true;
}


static bool ProcessGenScriptSnapshotOption(const char* filename) {
  if (filename != NULL && strlen(filename) != 0) {
    // Ensure that are already running using a full snapshot.
    if (snapshot_buffer == NULL) {
      Log::PrintErr("Script snapshots cannot be generated in this version of"
                    " dart\n");
      return false;
    }
    snapshot_file = File::Open(filename, File::kWriteTruncate);
    if (snapshot_file == NULL) {
      Log::PrintErr("Unable to open file %s for writing the snapshot\n",
                    filename);
      return false;
    }
    generate_script_snapshot = true;
    return true;
  }
  return false;
}


static bool ProcessEnableVmServiceOption(const char* port) {
  ASSERT(port != NULL);
  vm_service_server_port = -1;
  if (*port == '\0') {
    vm_service_server_port = DEFAULT_VM_SERVICE_SERVER_PORT;
  } else {
    if ((*port == '=') || (*port == ':')) {
      vm_service_server_port = atoi(port + 1);
    }
  }
  if (vm_service_server_port < 0) {
    Log::PrintErr("unrecognized --enable-vm-service option syntax. "
                    "Use --enable-vm-service[:<port number>]\n");
    return false;
  }
  start_vm_service = true;
  return true;
}

static struct {
  const char* option_name;
  bool (*process)(const char* option);
} main_options[] = {
  // Standard options shared with dart2js.
  { "--version", ProcessVersionOption },
  { "--help", ProcessHelpOption },
  { "-h", ProcessHelpOption },
  { "--verbose", ProcessVerboseOption },
  { "-v", ProcessVerboseOption },
  { "--package-root=", ProcessPackageRootOption },
  // VM specific options to the standalone dart program.
  { "--break-at=", ProcessBreakpointOption },
  { "--compile_all", ProcessCompileAllOption },
  { "--debug", ProcessDebugOption },
  { "--snapshot=", ProcessGenScriptSnapshotOption },
  { "--print-script", ProcessPrintScriptOption },
  { "--check-function-fingerprints", ProcessFingerprintedFunctions },
  { "--enable-vm-service", ProcessEnableVmServiceOption },
  { NULL, NULL }
};


static bool ProcessMainOptions(const char* option) {
  int i = 0;
  const char* name = main_options[0].option_name;
  int option_length = strlen(option);
  while (name != NULL) {
    int length = strlen(name);
    if ((option_length >= length) && (strncmp(option, name, length) == 0)) {
      if (main_options[i].process(option + length)) {
        return true;
      }
    }
    i += 1;
    name = main_options[i].option_name;
  }
  return false;
}


// Convert all the arguments to UTF8. On Windows, the arguments are
// encoded in the current code page and not UTF8.
//
// Returns true if the arguments are converted. In that case
// each of the arguments need to be deallocated using free.
static bool Utf8ConvertArgv(int argc, char** argv) {
  int unicode_argc = 0;
  wchar_t** unicode_argv = ShellUtils::GetUnicodeArgv(&unicode_argc);
  if (unicode_argv == NULL) return false;
  for (int i = 0; i < unicode_argc; i++) {
    wchar_t* arg = unicode_argv[i];
    argv[i] = StringUtils::WideToUtf8(arg);
  }
  ShellUtils::FreeUnicodeArgv(unicode_argv);
  return true;
}


// Parse out the command line arguments. Returns -1 if the arguments
// are incorrect, 0 otherwise.
static int ParseArguments(int argc,
                          char** argv,
                          CommandLineOptions* vm_options,
                          char** script_name,
                          CommandLineOptions* dart_options,
                          bool* print_flags_seen,
                          bool* verbose_debug_seen) {
  const char* kPrefix = "--";
  const intptr_t kPrefixLen = strlen(kPrefix);

  // Store the executable name.
  Platform::SetExecutableName(argv[0]);

  // Start the rest after the executable name.
  int i = 1;

  // Parse out the vm options.
  while (i < argc) {
    if (ProcessMainOptions(argv[i])) {
      i++;
    } else {
      // Check if this flag is a potentially valid VM flag.
      const char* kChecked = "-c";
      const char* kPackageRoot = "-p";
      if (strncmp(argv[i], kPackageRoot, strlen(kPackageRoot)) == 0) {
        if (!ProcessPackageRootOption(argv[i] + strlen(kPackageRoot))) {
          i++;
          if (!ProcessPackageRootOption(argv[i])) {
            Log::PrintErr("Invalid option specification : '%s'\n", argv[i - 1]);
            i++;
            break;
          }
        }
      } else if (strncmp(argv[i], kChecked, strlen(kChecked)) == 0) {
        vm_options->AddArgument("--checked");
      } else if (!IsValidFlag(argv[i], kPrefix, kPrefixLen)) {
        break;
      }
      const char* kPrintFlags1 = "--print-flags";
      const char* kPrintFlags2 = "--print_flags";
      if ((strncmp(argv[i], kPrintFlags1, strlen(kPrintFlags1)) == 0) ||
          (strncmp(argv[i], kPrintFlags2, strlen(kPrintFlags2)) == 0)) {
        *print_flags_seen = true;
      }
      const char* kVerboseDebug = "--verbose_debug";
      if (strncmp(argv[i], kVerboseDebug, strlen(kVerboseDebug)) == 0) {
        *verbose_debug_seen = true;
      }
      vm_options->AddArgument(argv[i]);
      i++;
    }
  }

  // The arguments to the VM are at positions 1 through i-1 in argv.
  Platform::SetExecutableArguments(i, argv);

  // Get the script name.
  if (i < argc) {
    *script_name = argv[i];
    i++;
  } else {
    return -1;
  }

  // Parse out options to be passed to dart main.
  while (i < argc) {
    dart_options->AddArgument(argv[i]);
    i++;
  }

  return 0;
}


static Dart_Handle CreateRuntimeOptions(CommandLineOptions* options) {
  int options_count = options->count();
  Dart_Handle dart_arguments = Dart_NewList(options_count);
  if (Dart_IsError(dart_arguments)) {
    return dart_arguments;
  }
  for (int i = 0; i < options_count; i++) {
    Dart_Handle argument_value =
        DartUtils::NewString(options->GetArgument(i));
    if (Dart_IsError(argument_value)) {
      return argument_value;
    }
    Dart_Handle result = Dart_ListSetAt(dart_arguments, i, argument_value);
    if (Dart_IsError(result)) {
      return result;
    }
  }
  return dart_arguments;
}


static Dart_Handle SetupRuntimeOptions(CommandLineOptions* options) {
  Dart_Handle dart_arguments = CreateRuntimeOptions(options);
  if (Dart_IsError(dart_arguments)) {
    return dart_arguments;
  }
  Dart_Handle io_lib_url = DartUtils::NewString("dart:io");
  if (Dart_IsError(io_lib_url)) {
    return io_lib_url;
  }
  Dart_Handle io_lib = Dart_LookupLibrary(io_lib_url);
  if (Dart_IsError(io_lib)) {
    return io_lib;
  }
  Dart_Handle runtime_options_class_name = DartUtils::NewString("_OptionsImpl");
  if (Dart_IsError(runtime_options_class_name)) {
    return runtime_options_class_name;
  }
  Dart_Handle runtime_options_type = Dart_GetType(
      io_lib, runtime_options_class_name, 0, NULL);
  if (Dart_IsError(runtime_options_type)) {
    return runtime_options_type;
  }
  Dart_Handle native_name = DartUtils::NewString("_nativeArguments");
  if (Dart_IsError(native_name)) {
    return native_name;
  }

  return Dart_SetField(runtime_options_type, native_name, dart_arguments);
}


#define CHECK_RESULT(result)                                                   \
  if (Dart_IsError(result)) {                                                  \
    *error = strdup(Dart_GetError(result));                                    \
    *is_compile_error = Dart_IsCompilationError(result);                       \
    Dart_ExitScope();                                                          \
    Dart_ShutdownIsolate();                                                    \
    return NULL;                                                               \
  }                                                                            \


// Returns true on success, false on failure.
static Dart_Isolate CreateIsolateAndSetupHelper(const char* script_uri,
                                                const char* main,
                                                void* data,
                                                char** error,
                                                bool* is_compile_error) {
  Dart_Isolate isolate =
      Dart_CreateIsolate(script_uri, main, snapshot_buffer, data, error);
  if (isolate == NULL) {
    return NULL;
  }

  Dart_EnterScope();

  if (snapshot_buffer != NULL) {
    // Setup the native resolver as the snapshot does not carry it.
    Builtin::SetNativeResolver(Builtin::kBuiltinLibrary);
    Builtin::SetNativeResolver(Builtin::kIOLibrary);
  }

  // Set up the library tag handler for this isolate.
  Dart_Handle result = Dart_SetLibraryTagHandler(DartUtils::LibraryTagHandler);
  CHECK_RESULT(result);

  // Load the specified application script into the newly created isolate.

  // Prepare builtin and its dependent libraries for use to resolve URIs.
  // The builtin library is part of the core snapshot and would already be
  // available here in the case of script snapshot loading.
  Dart_Handle builtin_lib =
      Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
  CHECK_RESULT(builtin_lib);

  // Prepare for script loading by setting up the 'print' and 'timer'
  // closures and setting up 'package root' for URI resolution.
  result = DartUtils::PrepareForScriptLoading(package_root, builtin_lib);
  CHECK_RESULT(result);

  Dart_Handle library = DartUtils::LoadScript(script_uri, builtin_lib);
  CHECK_RESULT(library);
  if (!Dart_IsLibrary(library)) {
    char errbuf[256];
    snprintf(errbuf, sizeof(errbuf),
             "Expected a library when loading script: %s",
             script_uri);
    *error = strdup(errbuf);
    Dart_ExitScope();
    Dart_ShutdownIsolate();
    return NULL;
  }

  Platform::SetPackageRoot(package_root);
  Dart_Handle io_lib_url = DartUtils::NewString("dart:io");
  CHECK_RESULT(io_lib_url);
  Dart_Handle io_lib = Dart_LookupLibrary(io_lib_url);
  CHECK_RESULT(io_lib);
  Dart_Handle platform_class_name = DartUtils::NewString("Platform");
  CHECK_RESULT(platform_class_name);
  Dart_Handle platform_type =
      Dart_GetType(io_lib, platform_class_name, 0, NULL);
  CHECK_RESULT(platform_type);
  Dart_Handle script_name_name = DartUtils::NewString("_nativeScript");
  CHECK_RESULT(script_name_name);
  Dart_Handle dart_script = DartUtils::NewString(script_uri);
  CHECK_RESULT(dart_script);
  Dart_Handle set_script_name =
      Dart_SetField(platform_type, script_name_name, dart_script);
  CHECK_RESULT(set_script_name);

  Dart_Handle debug_name = Dart_DebugName();
  CHECK_RESULT(debug_name);
  VmService::SendIsolateStartupMessage(Dart_GetMainPortId(), debug_name);

  // Make the isolate runnable so that it is ready to handle messages.
  Dart_ExitScope();
  Dart_ExitIsolate();
  bool retval = Dart_IsolateMakeRunnable(isolate);
  if (!retval) {
    *error = strdup("Invalid isolate state - Unable to make it runnable");
    Dart_EnterIsolate(isolate);
    Dart_ShutdownIsolate();
    return NULL;
  }

  return isolate;
}


static Dart_Isolate CreateIsolateAndSetup(const char* script_uri,
                                          const char* main,
                                          void* data, char** error) {
  bool is_compile_error = false;
  return CreateIsolateAndSetupHelper(script_uri,
                                     main,
                                     new IsolateData(),
                                     error,
                                     &is_compile_error);
}


static void PrintVersion() {
  Log::PrintErr("Dart VM version: %s\n", Dart_VersionString());
}


static void PrintUsage() {
  Log::PrintErr(
      "Usage: dart [<vm-flags>] <dart-script-file> [<dart-options>]\n"
      "\n"
      "Executes the Dart script passed as <dart-script-file>.\n"
      "\n");
  if (!has_verbose_option) {
    Log::PrintErr(
"Common options:\n"
"--checked or -c\n"
"  Insert runtime type checks and enable assertions (checked mode).\n"
"--help or -h\n"
"  Display this message (add -v or --verbose for information about\n"
"  all VM options).\n"
"--package-root=<path> or -p<path>\n"
"  Where to find packages, that is, \"package:...\" imports.\n"
"--version\n"
"  Print the VM version.\n");
  } else {
    Log::PrintErr(
"Supported options:\n"
"--checked or -c\n"
"  Insert runtime type checks and enable assertions (checked mode).\n"
"--help or -h\n"
"  Display this message (add -v or --verbose for information about\n"
"  all VM options).\n"
"--package-root=<path> or -p<path>\n"
"  Where to find packages, that is, \"package:...\" imports.\n"
"--version\n"
"  Print the VM version.\n"
"\n"
"--debug[:<port number>]\n"
"  enables debugging and listens on specified port for debugger connections\n"
"  (default port number is 5858)\n"
"\n"
"--break-at=<location>\n"
"  sets a breakpoint at specified location where <location> is one of :\n"
"  url:<line_num> e.g. test.dart:10\n"
"  [<class_name>.]<function_name> e.g. B.foo\n"
"\n"
"--snapshot=<file_name>\n"
"  loads Dart script and generates a snapshot in the specified file\n"
"\n"
"--print-script\n"
"  generates Dart source code back and prints it after parsing a Dart script\n"
"\n"
"--enable-vm-service[:<port number>]\n"
"  enables the VM service and listens on specified port for connections\n"
"  (default port number is 8181)\n"
"\n"
"The following options are only used for VM development and may\n"
"be changed in any future version:\n");
    const char* print_flags = "--print_flags";
    Dart_SetVMFlags(1, &print_flags);
  }
}


static Dart_Handle SetBreakpoint(const char* breakpoint_at,
                                 Dart_Handle library) {
  char* bpt_function = strdup(breakpoint_at);
  Dart_Handle class_name;
  Dart_Handle function_name;
  char* dot = strchr(bpt_function, '.');
  if (dot == NULL) {
    class_name = DartUtils::NewString("");
    function_name = DartUtils::NewString(breakpoint_at);
  } else {
    *dot = '\0';
    class_name = DartUtils::NewString(bpt_function);
    function_name = DartUtils::NewString(dot + 1);
  }
  free(bpt_function);
  return Dart_OneTimeBreakAtEntry(library, class_name, function_name);
}


char* BuildIsolateName(const char* script_name,
                       const char* func_name) {
  // Skip past any slashes in the script name.
  const char* last_slash = strrchr(script_name, '/');
  if (last_slash != NULL) {
    script_name = last_slash + 1;
  }

  const char* kFormat = "%s/%s";
  intptr_t len = strlen(script_name) + strlen(func_name) + 2;
  char* buffer = new char[len];
  ASSERT(buffer != NULL);
  snprintf(buffer, len, kFormat, script_name, func_name);
  return buffer;
}


// Exit code indicating a compilation error.
static const int kCompilationErrorExitCode = 254;

// Exit code indicating an unhandled error that is not a compilation error.
static const int kErrorExitCode = 255;


static int ErrorExit(int exit_code, const char* format, ...) {
  va_list arguments;
  va_start(arguments, format);
  Log::VPrintErr(format, arguments);
  va_end(arguments);
  fflush(stderr);

  Dart_ExitScope();
  Dart_ShutdownIsolate();

  Dart_Cleanup();

  return exit_code;
}


static int DartErrorExit(Dart_Handle error) {
  const int exit_code = Dart_IsCompilationError(error) ?
      kCompilationErrorExitCode : kErrorExitCode;
  return ErrorExit(exit_code, "%s\n", Dart_GetError(error));
}


static void ShutdownIsolate(void* callback_data) {
  VmService::VmServiceShutdownCallback(callback_data);
  IsolateData* isolate_data = reinterpret_cast<IsolateData*>(callback_data);
  delete isolate_data;
}


static Dart_Handle GenerateScriptSource() {
  Dart_Handle library_url = Dart_LibraryUrl(Dart_RootLibrary());
  if (Dart_IsError(library_url)) {
    return library_url;
  }
  Dart_Handle script_urls = Dart_GetScriptURLs(library_url);
  if (Dart_IsError(script_urls)) {
    return script_urls;
  }
  intptr_t length;
  Dart_Handle result = Dart_ListLength(script_urls, &length);
  if (Dart_IsError(result)) {
    return result;
  }
  for (intptr_t i = 0; i < length; i++) {
    Dart_Handle script_url = Dart_ListGetAt(script_urls, i);
    if (Dart_IsError(script_url)) {
      return script_url;
    }
    result = Dart_GenerateScriptSource(library_url, script_url);
    if (Dart_IsError(result)) {
      return result;
    }
    const char* script_source = NULL;
    result = Dart_StringToCString(result, &script_source);
    if (Dart_IsError(result)) {
      return result;
    }
    Log::Print("%s\n", script_source);
  }
  return Dart_True();
}


int main(int argc, char** argv) {
  char* script_name;
  CommandLineOptions vm_options(argc);
  CommandLineOptions dart_options(argc);
  bool print_flags_seen = false;
  bool verbose_debug_seen = false;

  // Perform platform specific initialization.
  if (!Platform::Initialize()) {
    Log::PrintErr("Initialization failed\n");
  }

  // On Windows, the argv strings are code page encoded and not
  // utf8. We need to convert them to utf8.
  bool argv_converted = Utf8ConvertArgv(argc, argv);

  // Parse command line arguments.
  if (ParseArguments(argc,
                     argv,
                     &vm_options,
                     &script_name,
                     &dart_options,
                     &print_flags_seen,
                     &verbose_debug_seen) < 0) {
    if (has_help_option) {
      PrintUsage();
      return 0;
    } else if (has_version_option) {
      PrintVersion();
      return 0;
    } else if (print_flags_seen) {
      // Will set the VM flags, print them out and then we exit as no
      // script was specified on the command line.
      Dart_SetVMFlags(vm_options.count(), vm_options.arguments());
      return 0;
    } else {
      PrintUsage();
      return kErrorExitCode;
    }
  }

  if (!DartUtils::SetOriginalWorkingDirectory()) {
    OSError err;
    fprintf(stderr, "Error determinig current directory: %s\n", err.message());
    fflush(stderr);
    return kErrorExitCode;
  }

  Dart_SetVMFlags(vm_options.count(), vm_options.arguments());

  // Initialize the Dart VM.
  if (!Dart_Initialize(CreateIsolateAndSetup, NULL, NULL, ShutdownIsolate,
                       DartUtils::OpenFile,
                       DartUtils::ReadFile,
                       DartUtils::WriteFile,
                       DartUtils::CloseFile)) {
    fprintf(stderr, "%s", "VM initialization failed\n");
    fflush(stderr);
    return kErrorExitCode;
  }

  // Start the debugger wire protocol handler if necessary.
  if (start_debugger) {
    ASSERT(debug_port >= 0);
    bool print_msg = verbose_debug_seen || (debug_port == 0);
    debug_port = DebuggerConnectionHandler::StartHandler(debug_ip, debug_port);
    if (print_msg) {
      Log::Print("Debugger listening on port %d\n", debug_port);
    }
  }

  // Start event handler.
  EventHandler::Start();

  // Start the VM service isolate, if necessary.
  if (start_vm_service) {
    ASSERT(vm_service_server_port >= 0);
    bool r = VmService::Start(vm_service_server_port);
    if (!r) {
      Log::PrintErr("Could not start VM Service isolate %s\n",
                    VmService::GetErrorMessage());
    }
  }

  // Call CreateIsolateAndSetup which creates an isolate and loads up
  // the specified application script.
  char* error = NULL;
  bool is_compile_error = false;
  char* isolate_name = BuildIsolateName(script_name, "main");
  Dart_Isolate isolate = CreateIsolateAndSetupHelper(script_name,
                                                     "main",
                                                     new IsolateData(),
                                                     &error,
                                                     &is_compile_error);
  if (isolate == NULL) {
    Log::PrintErr("%s\n", error);
    free(error);
    delete [] isolate_name;
    return is_compile_error ? kCompilationErrorExitCode : kErrorExitCode;
  }
  delete [] isolate_name;

  Dart_EnterIsolate(isolate);
  ASSERT(isolate == Dart_CurrentIsolate());
  ASSERT(isolate != NULL);
  Dart_Handle result;

  Dart_EnterScope();

  if (generate_script_snapshot) {
    // First create a snapshot.
    Dart_Handle result;
    uint8_t* buffer = NULL;
    intptr_t size = 0;
    result = Dart_CreateScriptSnapshot(&buffer, &size);
    if (Dart_IsError(result)) {
      Log::PrintErr("%s\n", Dart_GetError(result));
      return DartErrorExit(result);
    }

    // Write the magic number to indicate file is a script snapshot.
    DartUtils::WriteMagicNumber(snapshot_file);

    // Now write the snapshot out to specified file.
    bool bytes_written = snapshot_file->WriteFully(buffer, size);
    ASSERT(bytes_written);
    delete snapshot_file;
  } else {
    if (has_compile_all) {
      result = Dart_CompileAll();
      if (Dart_IsError(result)) {
        return DartErrorExit(result);
      }
    }

    if (has_check_function_fingerprints) {
      result = Dart_CheckFunctionFingerprints();
      if (Dart_IsError(result)) {
        return DartErrorExit(result);
      }
    }

    // Create a dart options object that can be accessed from dart code.
    Dart_Handle options_result = SetupRuntimeOptions(&dart_options);
    if (Dart_IsError(options_result)) {
      return DartErrorExit(options_result);
    }
    // Lookup the library of the root script.
    Dart_Handle library = Dart_RootLibrary();
    if (Dart_IsNull(library)) {
      return ErrorExit(kErrorExitCode,
                       "Unable to find root library for '%s'\n",
                       script_name);
    }
    // Set debug breakpoint if specified on the command line.
    if (breakpoint_at != NULL) {
      result = SetBreakpoint(breakpoint_at, library);
      if (Dart_IsError(result)) {
        return ErrorExit(kErrorExitCode,
                         "Error setting breakpoint at '%s': %s\n",
                         breakpoint_at,
                         Dart_GetError(result));
      }
    }
    if (has_print_script) {
      result = GenerateScriptSource();
      if (Dart_IsError(result)) {
        return DartErrorExit(result);
      }
    } else {
      // Lookup and invoke the top level main function.
      Dart_Handle main_args[1];
      main_args[0] = CreateRuntimeOptions(&dart_options);
      result = Dart_Invoke(library, DartUtils::NewString("main"), 1, main_args);
      // TODO(iposva): Return a special error type for mismatched argument
      // counts from Dart_Invoke to avoid the string comparison.
      const char* expected_error = "Dart_Invoke: wrong argument count for "
          "function 'main': 1 passed, 0 expected.";
      if (Dart_IsError(result) &&
          strcmp(expected_error, Dart_GetError(result)) == 0) {
        result = Dart_Invoke(library, DartUtils::NewString("main"), 0, NULL);
      }
      if (Dart_IsError(result)) {
        return DartErrorExit(result);
      }

      // Keep handling messages until the last active receive port is closed.
      result = Dart_RunLoop();
      if (Dart_IsError(result)) {
        return DartErrorExit(result);
      }
    }
  }

  Dart_ExitScope();
  // Shutdown the isolate.
  Dart_ShutdownIsolate();
  // Terminate process exit-code handler.
  Process::TerminateExitCodeHandler();

  Dart_Cleanup();

  // Free copied argument strings if converted.
  if (argv_converted) {
    for (int i = 0; i < argc; i++) free(argv[i]);
  }

  return Process::GlobalExitCode();
}

}  // namespace bin
}  // namespace dart

int main(int argc, char** argv) {
  return dart::bin::main(argc, argv);
}