// 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 "vm/port.h"

#include <utility>

#include "platform/utils.h"
#include "vm/dart_api_impl.h"
#include "vm/dart_entry.h"
#include "vm/isolate.h"
#include "vm/lockers.h"
#include "vm/message_handler.h"
#include "vm/os_thread.h"

namespace dart {

Mutex* PortMap::mutex_ = NULL;
PortMap::Entry* PortMap::map_ = NULL;
MessageHandler* PortMap::deleted_entry_ = reinterpret_cast<MessageHandler*>(1);
intptr_t PortMap::capacity_ = 0;
intptr_t PortMap::used_ = 0;
intptr_t PortMap::deleted_ = 0;
Random* PortMap::prng_ = NULL;

intptr_t PortMap::FindPort(Dart_Port port) {
  // ILLEGAL_PORT (0) is used as a sentinel value in Entry.port. The loop below
  // could return the index to a deleted port when we are searching for
  // port id ILLEGAL_PORT. Return -1 immediately to indicate the port
  // does not exist.
  if (port == ILLEGAL_PORT) {
    return -1;
  }
  ASSERT(port != ILLEGAL_PORT);
  intptr_t index = port % capacity_;
  intptr_t start_index = index;
  Entry entry = map_[index];
  while (entry.handler != NULL) {
    if (entry.port == port) {
      return index;
    }
    index = (index + 1) % capacity_;
    // Prevent endless loops.
    ASSERT(index != start_index);
    entry = map_[index];
  }
  return -1;
}

void PortMap::Rehash(intptr_t new_capacity) {
  Entry* new_ports = new Entry[new_capacity];
  memset(new_ports, 0, new_capacity * sizeof(Entry));

  for (intptr_t i = 0; i < capacity_; i++) {
    Entry entry = map_[i];
    // Skip free and deleted entries.
    if (entry.port != 0) {
      intptr_t new_index = entry.port % new_capacity;
      while (new_ports[new_index].port != 0) {
        new_index = (new_index + 1) % new_capacity;
      }
      new_ports[new_index] = entry;
    }
  }
  delete[] map_;
  map_ = new_ports;
  capacity_ = new_capacity;
  deleted_ = 0;
}

const char* PortMap::PortStateString(PortState kind) {
  switch (kind) {
    case kNewPort:
      return "new";
    case kLivePort:
      return "live";
    case kControlPort:
      return "control";
    default:
      UNREACHABLE();
      return "UNKNOWN";
  }
}

Dart_Port PortMap::AllocatePort() {
  Dart_Port result;

  // Keep getting new values while we have an illegal port number or the port
  // number is already in use.
  do {
    // Ensure port ids are representable in JavaScript for the benefit of
    // vm-service clients such as Observatory.
    const Dart_Port kMask1 = 0xFFFFFFFFFFFFF;
    // Ensure port ids are never valid object pointers so that reinterpreting
    // an object pointer as a port id never produces a used port id.
    const Dart_Port kMask2 = 0x3;
    result = (prng_->NextUInt64() & kMask1) | kMask2;
    ASSERT(!reinterpret_cast<RawObject*>(result)->IsWellFormed());
  } while (FindPort(result) >= 0);

  ASSERT(result != 0);
  ASSERT(FindPort(result) < 0);
  return result;
}

void PortMap::SetPortState(Dart_Port port, PortState state) {
  MutexLocker ml(mutex_);
  intptr_t index = FindPort(port);
  ASSERT(index >= 0);
  PortState old_state = map_[index].state;
  ASSERT(old_state == kNewPort);
  map_[index].state = state;
  if (state == kLivePort) {
    map_[index].handler->increment_live_ports();
  }
  if (FLAG_trace_isolates) {
    OS::PrintErr(
        "[^] Port (%s) -> (%s): \n"
        "\thandler:    %s\n"
        "\tport:       %" Pd64 "\n",
        PortStateString(old_state), PortStateString(state),
        map_[index].handler->name(), port);
  }
}

void PortMap::MaintainInvariants() {
  intptr_t empty = capacity_ - used_ - deleted_;
  if (used_ > ((capacity_ / 4) * 3)) {
    // Grow the port map.
    Rehash(capacity_ * 2);
  } else if (empty < deleted_) {
    // Rehash without growing the table to flush the deleted slots out of the
    // map.
    Rehash(capacity_);
  }
}

Dart_Port PortMap::CreatePort(MessageHandler* handler) {
  ASSERT(handler != NULL);
  MutexLocker ml(mutex_);
#if defined(DEBUG)
  handler->CheckAccess();
#endif

  Entry entry;
  entry.port = AllocatePort();
  entry.handler = handler;
  entry.state = kNewPort;

  // Search for the first unused slot. Make use of the knowledge that here is
  // currently no port with this id in the port map.
  ASSERT(FindPort(entry.port) < 0);
  intptr_t index = entry.port % capacity_;
  Entry cur = map_[index];
  // Stop the search at the first found unused (free or deleted) slot.
  while (cur.port != 0) {
    index = (index + 1) % capacity_;
    cur = map_[index];
  }

  // Insert the newly created port at the index.
  ASSERT(index >= 0);
  ASSERT(index < capacity_);
  ASSERT(map_[index].port == 0);
  ASSERT((map_[index].handler == NULL) ||
         (map_[index].handler == deleted_entry_));
  if (map_[index].handler == deleted_entry_) {
    // Consuming a deleted entry.
    deleted_--;
  }
  map_[index] = entry;

  // Increment number of used slots and grow if necessary.
  used_++;
  MaintainInvariants();

  if (FLAG_trace_isolates) {
    OS::PrintErr(
        "[+] Opening port: \n"
        "\thandler:    %s\n"
        "\tport:       %" Pd64 "\n",
        handler->name(), entry.port);
  }

  return entry.port;
}

bool PortMap::ClosePort(Dart_Port port) {
  MessageHandler* handler = NULL;
  {
    MutexLocker ml(mutex_);
    intptr_t index = FindPort(port);
    if (index < 0) {
      return false;
    }
    ASSERT(index < capacity_);
    ASSERT(map_[index].port != 0);
    ASSERT(map_[index].handler != deleted_entry_);
    ASSERT(map_[index].handler != NULL);

    handler = map_[index].handler;
#if defined(DEBUG)
    handler->CheckAccess();
#endif
    // Before releasing the lock mark the slot in the map as deleted. This makes
    // it possible to release the port map lock before flushing all of its
    // pending messages below.
    map_[index].port = 0;
    map_[index].handler = deleted_entry_;
    if (map_[index].state == kLivePort) {
      handler->decrement_live_ports();
    }

    used_--;
    deleted_++;
    MaintainInvariants();
  }
  handler->ClosePort(port);
  if (!handler->HasLivePorts() && handler->OwnedByPortMap()) {
    // Delete handler as soon as it isn't busy with a task.
    handler->RequestDeletion();
  }
  return true;
}

void PortMap::ClosePorts(MessageHandler* handler) {
  {
    MutexLocker ml(mutex_);
    for (intptr_t i = 0; i < capacity_; i++) {
      if (map_[i].handler == handler) {
        // Mark the slot as deleted.
        map_[i].port = 0;
        map_[i].handler = deleted_entry_;
        if (map_[i].state == kLivePort) {
          handler->decrement_live_ports();
        }
        used_--;
        deleted_++;
      }
    }
    MaintainInvariants();
  }
  handler->CloseAllPorts();
}

bool PortMap::PostMessage(std::unique_ptr<Message> message,
                          bool before_events) {
  MutexLocker ml(mutex_);
  intptr_t index = FindPort(message->dest_port());
  if (index < 0) {
    // Ownership of external data remains with the poster.
    message->DropFinalizers();
    return false;
  }
  ASSERT(index >= 0);
  ASSERT(index < capacity_);
  MessageHandler* handler = map_[index].handler;
  ASSERT(map_[index].port != 0);
  ASSERT((handler != NULL) && (handler != deleted_entry_));
  handler->PostMessage(std::move(message), before_events);
  return true;
}

bool PortMap::IsLocalPort(Dart_Port id) {
  MutexLocker ml(mutex_);
  intptr_t index = FindPort(id);
  if (index < 0) {
    // Port does not exist.
    return false;
  }

  MessageHandler* handler = map_[index].handler;
  return handler->IsCurrentIsolate();
}

Isolate* PortMap::GetIsolate(Dart_Port id) {
  MutexLocker ml(mutex_);
  intptr_t index = FindPort(id);
  if (index < 0) {
    // Port does not exist.
    return NULL;
  }

  MessageHandler* handler = map_[index].handler;
  return handler->isolate();
}

void PortMap::Init() {
  if (mutex_ == NULL) {
    mutex_ = new Mutex();
  }
  ASSERT(mutex_ != NULL);
  prng_ = new Random();

  static const intptr_t kInitialCapacity = 8;
  // TODO(iposva): Verify whether we want to keep exponentially growing.
  ASSERT(Utils::IsPowerOfTwo(kInitialCapacity));
  if (map_ == NULL) {
    // TODO(bkonyi): don't keep map_ after Dart_Cleanup.
    map_ = new Entry[kInitialCapacity];
    capacity_ = kInitialCapacity;
  }
  memset(map_, 0, capacity_ * sizeof(Entry));
  used_ = 0;
  deleted_ = 0;
}

void PortMap::Cleanup() {
  ASSERT(map_ != NULL);
  ASSERT(prng_ != NULL);
  for (intptr_t i = 0; i < capacity_; ++i) {
    auto handler = map_[i].handler;
    if (handler != NULL && handler != deleted_entry_) {
      ClosePorts(handler);
      delete handler;
    }
  }
  delete prng_;
  prng_ = NULL;
  // TODO(bkonyi): find out why deleting map_ sometimes causes crashes.
  // delete[] map_;
  // map_ = NULL;
}

void PortMap::PrintPortsForMessageHandler(MessageHandler* handler,
                                          JSONStream* stream) {
#ifndef PRODUCT
  JSONObject jsobj(stream);
  jsobj.AddProperty("type", "_Ports");
  Object& msg_handler = Object::Handle();
  {
    JSONArray ports(&jsobj, "ports");
    SafepointMutexLocker ml(mutex_);
    for (intptr_t i = 0; i < capacity_; i++) {
      if (map_[i].handler == handler) {
        if (map_[i].state == kLivePort) {
          JSONObject port(&ports);
          port.AddProperty("type", "_Port");
          port.AddPropertyF("name", "Isolate Port (%" Pd64 ")", map_[i].port);
          msg_handler = DartLibraryCalls::LookupHandler(map_[i].port);
          port.AddProperty("handler", msg_handler);
        }
      }
    }
  }
#endif
}

void PortMap::DebugDumpForMessageHandler(MessageHandler* handler) {
  SafepointMutexLocker ml(mutex_);
  Object& msg_handler = Object::Handle();
  for (intptr_t i = 0; i < capacity_; i++) {
    if (map_[i].handler == handler) {
      if (map_[i].state == kLivePort) {
        OS::PrintErr("Live Port = %" Pd64 "\n", map_[i].port);
        msg_handler = DartLibraryCalls::LookupHandler(map_[i].port);
        OS::PrintErr("Handler = %s\n", msg_handler.ToCString());
      }
    }
  }
}

}  // namespace dart