// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ppapi/proxy/ppb_message_loop_proxy.h"

#include <stddef.h>

#include <memory>
#include <vector>

#include "base/check.h"
#include "base/compiler_specific.h"
#include "base/functional/bind.h"
#include "base/functional/callback_helpers.h"
#include "base/task/single_thread_task_runner.h"
#include "ppapi/c/pp_errors.h"
#include "ppapi/c/ppb_message_loop.h"
#include "ppapi/proxy/plugin_dispatcher.h"
#include "ppapi/proxy/plugin_globals.h"
#include "ppapi/shared_impl/proxy_lock.h"
#include "ppapi/thunk/enter.h"

using ppapi::thunk::PPB_MessageLoop_API;

namespace ppapi {
namespace proxy {

namespace {
typedef thunk::EnterResource<PPB_MessageLoop_API> EnterMessageLoop;
}

MessageLoopResource::MessageLoopResource(PP_Instance instance)
    : MessageLoopShared(instance),
      nested_invocations_(0),
      destroyed_(false),
      should_destroy_(false),
      is_main_thread_loop_(false),
      currently_handling_blocking_message_(false) {
}

MessageLoopResource::MessageLoopResource(ForMainThread for_main_thread)
    : MessageLoopShared(for_main_thread),
      nested_invocations_(0),
      destroyed_(false),
      should_destroy_(false),
      is_main_thread_loop_(true),
      currently_handling_blocking_message_(false) {
  // We attach the main thread immediately. We can't use AttachToCurrentThread,
  // because the MessageLoop already exists.

  // This must be called only once, so the slot must be empty.
  CHECK(!PluginGlobals::Get()->msg_loop_slot());
  // We don't add a reference for TLS here, so we don't release it. Instead,
  // this loop is owned by PluginGlobals. Contrast with AttachToCurrentThread
  // where we register ReleaseMessageLoop with TLS and call AddRef.
  base::ThreadLocalStorage::Slot* slot = new base::ThreadLocalStorage::Slot();
  PluginGlobals::Get()->set_msg_loop_slot(slot);

  slot->Set(this);

  task_runner_ = base::SingleThreadTaskRunner::GetCurrentDefault();
}


MessageLoopResource::~MessageLoopResource() {
}

PPB_MessageLoop_API* MessageLoopResource::AsPPB_MessageLoop_API() {
  return this;
}

int32_t MessageLoopResource::AttachToCurrentThread() {
  if (is_main_thread_loop_)
    return PP_ERROR_INPROGRESS;

  PluginGlobals* globals = PluginGlobals::Get();

  base::ThreadLocalStorage::Slot* slot = globals->msg_loop_slot();
  if (!slot) {
    slot = new base::ThreadLocalStorage::Slot(&ReleaseMessageLoop);
    globals->set_msg_loop_slot(slot);
  } else {
    if (slot->Get())
      return PP_ERROR_INPROGRESS;
  }
  // TODO(dmichael) check that the current thread can support a task executor.

  // Take a ref to the MessageLoop on behalf of the TLS. Note that this is an
  // internal ref and not a plugin ref so the plugin can't accidentally
  // release it. This is released by ReleaseMessageLoop().
  AddRef();
  slot->Set(this);

  single_thread_task_executor_ =
      std::make_unique<base::SingleThreadTaskExecutor>();
  task_runner_ = base::SingleThreadTaskRunner::GetCurrentDefault();

  // Post all pending work to the task executor.
  for (auto& info : pending_tasks_) {
    PostClosure(info.from_here, std::move(info.closure), info.delay_ms);
  }
  pending_tasks_.clear();

  return PP_OK;
}

int32_t MessageLoopResource::Run() {
  if (!IsCurrent())
    return PP_ERROR_WRONG_THREAD;
  if (is_main_thread_loop_)
    return PP_ERROR_INPROGRESS;

  base::RunLoop* previous_run_loop = run_loop_;
  base::RunLoop run_loop;
  run_loop_ = &run_loop;

  nested_invocations_++;
  CallWhileUnlocked(base::BindOnce(&base::RunLoop::Run,
                                   base::Unretained(run_loop_), FROM_HERE));
  nested_invocations_--;

  run_loop_ = previous_run_loop;

  if (should_destroy_ && nested_invocations_ == 0) {
    task_runner_.reset();
    single_thread_task_executor_.reset();
    destroyed_ = true;
  }
  return PP_OK;
}

int32_t MessageLoopResource::PostWork(PP_CompletionCallback callback,
                                      int64_t delay_ms) {
  if (!callback.func)
    return PP_ERROR_BADARGUMENT;
  if (destroyed_)
    return PP_ERROR_FAILED;
  PostClosure(FROM_HERE,
              base::BindOnce(callback.func, callback.user_data,
                             static_cast<int32_t>(PP_OK)),
              delay_ms);
  return PP_OK;
}

int32_t MessageLoopResource::PostQuit(PP_Bool should_destroy) {
  if (is_main_thread_loop_)
    return PP_ERROR_WRONG_THREAD;

  if (PP_ToBool(should_destroy))
    should_destroy_ = true;

  if (IsCurrent() && nested_invocations_ > 0) {
    run_loop_->QuitWhenIdle();
  } else {
    PostClosure(FROM_HERE,
                base::BindOnce(&MessageLoopResource::QuitRunLoopWhenIdle,
                               Unretained(this)),
                0);
  }
  return PP_OK;
}

// static
MessageLoopResource* MessageLoopResource::GetCurrent() {
  PluginGlobals* globals = PluginGlobals::Get();
  if (!globals->msg_loop_slot())
    return NULL;
  return reinterpret_cast<MessageLoopResource*>(
      globals->msg_loop_slot()->Get());
}

void MessageLoopResource::DetachFromThread() {
  // Note that the task executor must be destroyed on the thread it was created
  // on.
  task_runner_.reset();
  single_thread_task_executor_.reset();

  // Cancel out the AddRef in AttachToCurrentThread().
  Release();
  // DANGER: may delete this.
}

bool MessageLoopResource::IsCurrent() const {
  PluginGlobals* globals = PluginGlobals::Get();
  if (!globals->msg_loop_slot())
    return false;  // Can't be current if there's nothing in the slot.
  return static_cast<const void*>(globals->msg_loop_slot()->Get()) ==
         static_cast<const void*>(this);
}

void MessageLoopResource::PostClosure(const base::Location& from_here,
                                      base::OnceClosure closure,
                                      int64_t delay_ms) {
  if (task_runner_.get()) {
    task_runner_->PostDelayedTask(from_here, std::move(closure),
                                  base::Milliseconds(delay_ms));
  } else {
    TaskInfo info;
    info.from_here = FROM_HERE;
    info.closure = std::move(closure);
    info.delay_ms = delay_ms;
    pending_tasks_.push_back(std::move(info));
  }
}

base::SingleThreadTaskRunner* MessageLoopResource::GetTaskRunner() {
  return task_runner_.get();
}

bool MessageLoopResource::CurrentlyHandlingBlockingMessage() {
  return currently_handling_blocking_message_;
}

void MessageLoopResource::QuitRunLoopWhenIdle() {
  DCHECK(IsCurrent());
  DCHECK(run_loop_);
  run_loop_->QuitWhenIdle();
}

// static
void MessageLoopResource::ReleaseMessageLoop(void* value) {
  static_cast<MessageLoopResource*>(value)->DetachFromThread();
}

// -----------------------------------------------------------------------------

PP_Resource Create(PP_Instance instance) {
  ProxyAutoLock lock;
  // Validate the instance.
  PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
  if (!dispatcher)
    return 0;
  return (new MessageLoopResource(instance))->GetReference();
}

PP_Resource GetForMainThread() {
  ProxyAutoLock lock;
  return PluginGlobals::Get()->loop_for_main_thread()->GetReference();
}

PP_Resource GetCurrent() {
  ProxyAutoLock lock;
  Resource* resource = MessageLoopResource::GetCurrent();
  if (resource)
    return resource->GetReference();
  return 0;
}

int32_t AttachToCurrentThread(PP_Resource message_loop) {
  EnterMessageLoop enter(message_loop, true);
  if (enter.succeeded())
    return enter.object()->AttachToCurrentThread();
  return PP_ERROR_BADRESOURCE;
}

int32_t Run(PP_Resource message_loop) {
  EnterMessageLoop enter(message_loop, true);
  if (enter.succeeded())
    return enter.object()->Run();
  return PP_ERROR_BADRESOURCE;
}

int32_t PostWork(PP_Resource message_loop,
                 PP_CompletionCallback callback,
                 int64_t delay_ms) {
  EnterMessageLoop enter(message_loop, true);
  if (enter.succeeded())
    return enter.object()->PostWork(callback, delay_ms);
  return PP_ERROR_BADRESOURCE;
}

int32_t PostQuit(PP_Resource message_loop, PP_Bool should_destroy) {
  EnterMessageLoop enter(message_loop, true);
  if (enter.succeeded())
    return enter.object()->PostQuit(should_destroy);
  return PP_ERROR_BADRESOURCE;
}

const PPB_MessageLoop_1_0 ppb_message_loop_interface = {
  &Create,
  &GetForMainThread,
  &GetCurrent,
  &AttachToCurrentThread,
  &Run,
  &PostWork,
  &PostQuit
};

PPB_MessageLoop_Proxy::PPB_MessageLoop_Proxy(Dispatcher* dispatcher)
    : InterfaceProxy(dispatcher) {
}

PPB_MessageLoop_Proxy::~PPB_MessageLoop_Proxy() {
}

// static
const PPB_MessageLoop_1_0* PPB_MessageLoop_Proxy::GetInterface() {
  return &ppb_message_loop_interface;
}

}  // namespace proxy
}  // namespace ppapi