// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "mojo/edk/embedder/embedder.h"

#include <utility>

#include "base/atomicops.h"
#include "base/bind.h"
#include "base/bind_helpers.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/task_runner.h"
#include "mojo/edk/embedder/embedder_internal.h"
#include "mojo/edk/embedder/master_process_delegate.h"
#include "mojo/edk/embedder/platform_support.h"
#include "mojo/edk/embedder/process_delegate.h"
#include "mojo/edk/embedder/slave_process_delegate.h"
#include "mojo/edk/system/channel.h"
#include "mojo/edk/system/channel_manager.h"
#include "mojo/edk/system/configuration.h"
#include "mojo/edk/system/core.h"
#include "mojo/edk/system/ipc_support.h"
#include "mojo/edk/system/message_pipe_dispatcher.h"
#include "mojo/edk/system/platform_handle_dispatcher.h"
#include "mojo/edk/system/raw_channel.h"
#include "mojo/edk/util/ref_ptr.h"

using mojo::util::RefPtr;

namespace mojo {
namespace embedder {

namespace internal {

// Declared in embedder_internal.h.
PlatformSupport* g_platform_support = nullptr;
system::Core* g_core = nullptr;
system::IPCSupport* g_ipc_support = nullptr;

}  // namespace internal

namespace {

// TODO(vtl): For now, we need this to be thread-safe (since theoretically we
// currently support multiple channel creation threads -- possibly one per
// channel). Eventually, we won't need it to be thread-safe (we'll require a
// single I/O thread), and eventually we won't need it at all. Remember to
// remove the base/atomicops.h include.
system::ChannelId MakeChannelId() {
  // Note that |AtomicWord| is signed.
  static base::subtle::AtomicWord counter = 0;

  base::subtle::AtomicWord new_counter_value =
      base::subtle::NoBarrier_AtomicIncrement(&counter, 1);
  // Don't allow the counter to wrap. Note that any (strictly) positive value is
  // a valid |ChannelId| (and |NoBarrier_AtomicIncrement()| returns the value
  // post-increment).
  CHECK_GT(new_counter_value, 0);
  // Use "negative" values for these IDs, so that we'll also be able to use
  // "positive" "process identifiers" (see connection_manager.h) as IDs (and
  // they won't conflict).
  return static_cast<system::ChannelId>(-new_counter_value);
}

// Note: Called on the I/O thread.
void ShutdownIPCSupportHelper() {
  // Save these before they get nuked by |ShutdownChannelOnIOThread()|.
  PlatformTaskRunnerRefPtr delegate_thread_task_runner(
      internal::g_ipc_support->delegate_thread_task_runner());
  ProcessDelegate* process_delegate =
      internal::g_ipc_support->process_delegate();

  ShutdownIPCSupportOnIOThread();

  PlatformPostTask(delegate_thread_task_runner.get(),
                   base::Bind(&ProcessDelegate::OnShutdownComplete,
                              base::Unretained(process_delegate)));
}

}  // namespace

Configuration* GetConfiguration() {
  return system::GetMutableConfiguration();
}

void Init(std::unique_ptr<PlatformSupport> platform_support) {
  DCHECK(platform_support);

  DCHECK(!internal::g_platform_support);
  internal::g_platform_support = platform_support.release();

  DCHECK(!internal::g_core);
  internal::g_core = new system::Core(internal::g_platform_support);
}

MojoResult AsyncWait(MojoHandle handle,
                     MojoHandleSignals signals,
                     const base::Callback<void(MojoResult)>& callback) {
  return internal::g_core->AsyncWait(handle, signals, callback);
}

MojoResult CreatePlatformHandleWrapper(
    ScopedPlatformHandle platform_handle,
    MojoHandle* platform_handle_wrapper_handle) {
  DCHECK(platform_handle_wrapper_handle);

  auto dispatcher =
      system::PlatformHandleDispatcher::Create(platform_handle.Pass());

  DCHECK(internal::g_core);
  MojoHandle h = internal::g_core->AddDispatcher(dispatcher.get());
  if (h == MOJO_HANDLE_INVALID) {
    LOG(ERROR) << "Handle table full";
    dispatcher->Close();
    return MOJO_RESULT_RESOURCE_EXHAUSTED;
  }

  *platform_handle_wrapper_handle = h;
  return MOJO_RESULT_OK;
}

MojoResult PassWrappedPlatformHandle(MojoHandle platform_handle_wrapper_handle,
                                     ScopedPlatformHandle* platform_handle) {
  DCHECK(platform_handle);

  DCHECK(internal::g_core);
  auto dispatcher =
      internal::g_core->GetDispatcher(platform_handle_wrapper_handle);
  if (!dispatcher)
    return MOJO_RESULT_INVALID_ARGUMENT;

  if (dispatcher->GetType() != system::Dispatcher::Type::PLATFORM_HANDLE)
    return MOJO_RESULT_INVALID_ARGUMENT;

  *platform_handle =
      static_cast<system::PlatformHandleDispatcher*>(dispatcher.get())
          ->PassPlatformHandle();
  return MOJO_RESULT_OK;
}

void InitIPCSupport(ProcessType process_type,
                    PlatformTaskRunnerRefPtr delegate_thread_task_runner,
                    ProcessDelegate* process_delegate,
                    PlatformTaskRunnerRefPtr io_thread_task_runner,
                    ScopedPlatformHandle platform_handle) {
  // |Init()| must have already been called.
  DCHECK(internal::g_core);
  // And not |InitIPCSupport()| (without |ShutdownIPCSupport()|).
  DCHECK(!internal::g_ipc_support);

  internal::g_ipc_support = new system::IPCSupport(
      internal::g_platform_support, process_type,
      std::move(delegate_thread_task_runner), process_delegate,
      std::move(io_thread_task_runner), platform_handle.Pass());
}

void ShutdownIPCSupportOnIOThread() {
  DCHECK(internal::g_ipc_support);

  internal::g_ipc_support->ShutdownOnIOThread();
  delete internal::g_ipc_support;
  internal::g_ipc_support = nullptr;
}

void ShutdownIPCSupport() {
  DCHECK(internal::g_ipc_support);

  PlatformPostTask(internal::g_ipc_support->io_thread_task_runner(),
                   base::Bind(&ShutdownIPCSupportHelper));
}

ScopedMessagePipeHandle ConnectToSlave(
    SlaveInfo slave_info,
    ScopedPlatformHandle platform_handle,
    const base::Closure& did_connect_to_slave_callback,
    PlatformTaskRunnerRefPtr did_connect_to_slave_runner,
    std::string* platform_connection_id,
    ChannelInfo** channel_info) {
  DCHECK(platform_connection_id);
  DCHECK(channel_info);
  DCHECK(internal::g_ipc_support);

  system::ConnectionIdentifier connection_id =
      internal::g_ipc_support->GenerateConnectionIdentifier();
  *platform_connection_id = connection_id.ToString();
  system::ChannelId channel_id = system::kInvalidChannelId;
  RefPtr<system::MessagePipeDispatcher> dispatcher =
      internal::g_ipc_support->ConnectToSlave(
          connection_id, slave_info, platform_handle.Pass(),
          did_connect_to_slave_callback, std::move(did_connect_to_slave_runner),
          &channel_id);
  *channel_info = new ChannelInfo(channel_id);

  ScopedMessagePipeHandle rv(
      MessagePipeHandle(internal::g_core->AddDispatcher(dispatcher.get())));
  CHECK(rv.is_valid());
  return rv;
}

ScopedMessagePipeHandle ConnectToMaster(
    const std::string& platform_connection_id,
    const base::Closure& did_connect_to_master_callback,
    PlatformTaskRunnerRefPtr did_connect_to_master_runner,
    ChannelInfo** channel_info) {
  DCHECK(channel_info);
  DCHECK(internal::g_ipc_support);

  bool ok = false;
  system::ConnectionIdentifier connection_id =
      system::ConnectionIdentifier::FromString(platform_connection_id, &ok);
  CHECK(ok);

  system::ChannelId channel_id = system::kInvalidChannelId;
  RefPtr<system::MessagePipeDispatcher> dispatcher =
      internal::g_ipc_support->ConnectToMaster(
          connection_id, did_connect_to_master_callback,
          std::move(did_connect_to_master_runner), &channel_id);
  *channel_info = new ChannelInfo(channel_id);

  ScopedMessagePipeHandle rv(
      MessagePipeHandle(internal::g_core->AddDispatcher(dispatcher.get())));
  CHECK(rv.is_valid());
  return rv;
}

// TODO(vtl): Write tests for this.
ScopedMessagePipeHandle CreateChannelOnIOThread(
    ScopedPlatformHandle platform_handle,
    ChannelInfo** channel_info) {
  DCHECK(platform_handle.is_valid());
  DCHECK(channel_info);
  DCHECK(internal::g_ipc_support);

  system::ChannelManager* channel_manager =
      internal::g_ipc_support->channel_manager();

  *channel_info = new ChannelInfo(MakeChannelId());
  RefPtr<system::MessagePipeDispatcher> dispatcher =
      channel_manager->CreateChannelOnIOThread((*channel_info)->channel_id,
                                               platform_handle.Pass());

  ScopedMessagePipeHandle rv(
      MessagePipeHandle(internal::g_core->AddDispatcher(dispatcher.get())));
  CHECK(rv.is_valid());
  return rv;
}

ScopedMessagePipeHandle CreateChannel(
    ScopedPlatformHandle platform_handle,
    const base::Callback<void(ChannelInfo*)>& did_create_channel_callback,
    PlatformTaskRunnerRefPtr did_create_channel_runner) {
  DCHECK(platform_handle.is_valid());
  DCHECK(!did_create_channel_callback.is_null());
  DCHECK(internal::g_ipc_support);

  system::ChannelManager* channel_manager =
      internal::g_ipc_support->channel_manager();

  system::ChannelId channel_id = MakeChannelId();
  std::unique_ptr<ChannelInfo> channel_info(new ChannelInfo(channel_id));
  RefPtr<system::MessagePipeDispatcher> dispatcher =
      channel_manager->CreateChannel(
          channel_id, platform_handle.Pass(),
          base::Bind(did_create_channel_callback,
                     base::Unretained(channel_info.release())),
          did_create_channel_runner);

  ScopedMessagePipeHandle rv(
      MessagePipeHandle(internal::g_core->AddDispatcher(dispatcher.get())));
  CHECK(rv.is_valid());
  return rv;
}

// TODO(vtl): Write tests for this.
void DestroyChannelOnIOThread(ChannelInfo* channel_info) {
  DCHECK(channel_info);
  DCHECK(channel_info->channel_id);
  DCHECK(internal::g_ipc_support);

  system::ChannelManager* channel_manager =
      internal::g_ipc_support->channel_manager();
  channel_manager->ShutdownChannelOnIOThread(channel_info->channel_id);
  delete channel_info;
}

// TODO(vtl): Write tests for this.
void DestroyChannel(ChannelInfo* channel_info,
                    const base::Closure& did_destroy_channel_callback,
                    PlatformTaskRunnerRefPtr did_destroy_channel_runner) {
  DCHECK(channel_info);
  DCHECK(channel_info->channel_id);
  DCHECK(!did_destroy_channel_callback.is_null());
  DCHECK(internal::g_ipc_support);

  system::ChannelManager* channel_manager =
      internal::g_ipc_support->channel_manager();
  channel_manager->ShutdownChannel(channel_info->channel_id,
                                   did_destroy_channel_callback,
                                   did_destroy_channel_runner);
  delete channel_info;
}

void WillDestroyChannelSoon(ChannelInfo* channel_info) {
  DCHECK(channel_info);
  DCHECK(internal::g_ipc_support);

  system::ChannelManager* channel_manager =
      internal::g_ipc_support->channel_manager();
  channel_manager->WillShutdownChannel(channel_info->channel_id);
}

}  // namespace embedder
}  // namespace mojo