/*
 * Copyright (C) 2010 Google Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include "third_party/blink/renderer/core/dom/events/event_queue.h"

#include "base/task/single_thread_task_runner.h"
#include "third_party/blink/public/platform/task_type.h"
#include "third_party/blink/renderer/core/dom/events/event.h"
#include "third_party/blink/renderer/core/frame/local_dom_window.h"
#include "third_party/blink/renderer/core/probe/core_probes.h"
#include "third_party/blink/renderer/platform/wtf/functional.h"

namespace blink {

EventQueue::EventQueue(ExecutionContext* context, TaskType task_type)
    : ExecutionContextLifecycleObserver(context),
      task_type_(task_type),
      is_closed_(false) {
  if (!GetExecutionContext() || GetExecutionContext()->IsContextDestroyed())
    Close(nullptr);
}

EventQueue::~EventQueue() = default;

void EventQueue::Trace(Visitor* visitor) const {
  visitor->Trace(queued_events_);
  ExecutionContextLifecycleObserver::Trace(visitor);
}

bool EventQueue::EnqueueEvent(const base::Location& from_here, Event& event) {
  if (is_closed_)
    return false;

  DCHECK(event.RawTarget());
  DCHECK(GetExecutionContext());

  event.async_task_context()->Schedule(GetExecutionContext(), event.type());

  bool was_added = queued_events_.insert(&event).is_new_entry;
  DCHECK(was_added);  // It should not have already been in the list.

  scoped_refptr<base::SingleThreadTaskRunner> task_runner =
      GetExecutionContext()->GetTaskRunner(task_type_);

  // Pass the event as a weak persistent so that GC can collect an event-related
  // object like IDBTransaction as soon as possible.
  task_runner->PostTask(
      from_here, BindOnce(&EventQueue::DispatchEvent, WrapPersistent(this),
                          WrapWeakPersistent(&event)));

  return true;
}

void EventQueue::CancelAllEvents() {
  if (!GetExecutionContext()) {
    DCHECK(!queued_events_.size());
    return;
  }
  DoCancelAllEvents(GetExecutionContext());
}

bool EventQueue::RemoveEvent(Event& event) {
  auto found = queued_events_.find(&event);
  if (found == queued_events_.end())
    return false;
  queued_events_.erase(found);
  return true;
}

void EventQueue::DispatchEvent(Event* event) {
  if (!event || !RemoveEvent(*event))
    return;

  DCHECK(GetExecutionContext());

  probe::AsyncTask async_task(GetExecutionContext(),
                              event->async_task_context());
  EventTarget* target = event->RawTarget();
  if (LocalDOMWindow* window = target->ToLocalDOMWindow())
    window->DispatchEvent(*event, nullptr);
  else
    target->DispatchEvent(*event);
}

void EventQueue::ContextDestroyed() {
  Close(GetExecutionContext());
}

void EventQueue::Close(ExecutionContext* context) {
  is_closed_ = true;
  DoCancelAllEvents(context);
}

void EventQueue::DoCancelAllEvents(ExecutionContext* context) {
  for (const auto& queued_event : queued_events_)
    queued_event->async_task_context()->Cancel();
  queued_events_.clear();
}

bool EventQueue::HasPendingEvents() const {
  return queued_events_.size() > 0;
}

}  // namespace blink