// Copyright 2015 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 "modules/webgl/WebGLTimerQueryEXT.h"

#include "core/dom/TaskRunnerHelper.h"
#include "gpu/command_buffer/client/gles2_interface.h"
#include "modules/webgl/WebGLRenderingContextBase.h"
#include "public/platform/Platform.h"

namespace blink {

WebGLTimerQueryEXT* WebGLTimerQueryEXT::create(WebGLRenderingContextBase* ctx) {
  return new WebGLTimerQueryEXT(ctx);
}

WebGLTimerQueryEXT::~WebGLTimerQueryEXT() {
  // See the comment in WebGLObject::detachAndDeleteObject().
  detachAndDeleteObject();
}

WebGLTimerQueryEXT::WebGLTimerQueryEXT(WebGLRenderingContextBase* ctx)
    : WebGLContextObject(ctx),
      m_target(0),
      m_queryId(0),
      m_canUpdateAvailability(false),
      m_queryResultAvailable(false),
      m_queryResult(0),
      m_taskRunner(TaskRunnerHelper::get(TaskType::Unthrottled,
                                         &ctx->canvas()->document())
                       ->clone()) {
  context()->contextGL()->GenQueriesEXT(1, &m_queryId);
}

void WebGLTimerQueryEXT::resetCachedResult() {
  m_canUpdateAvailability = false;
  m_queryResultAvailable = false;
  m_queryResult = 0;
  // When this is called, the implication is that we should start
  // keeping track of whether we can update the cached availability
  // and result.
  scheduleAllowAvailabilityUpdate();
}

void WebGLTimerQueryEXT::updateCachedResult(gpu::gles2::GLES2Interface* gl) {
  if (m_queryResultAvailable)
    return;

  if (!m_canUpdateAvailability)
    return;

  if (!hasTarget())
    return;

  // If this is a timestamp query, set the result to 0 and make it available as
  // we don't support timestamps in WebGL due to very poor driver support for
  // them.
  if (m_target == GL_TIMESTAMP_EXT) {
    m_queryResult = 0;
    m_queryResultAvailable = true;
    return;
  }

  // We can only update the cached result when control returns to the browser.
  m_canUpdateAvailability = false;
  GLuint available = 0;
  gl->GetQueryObjectuivEXT(object(), GL_QUERY_RESULT_AVAILABLE_EXT, &available);
  m_queryResultAvailable = !!available;
  if (m_queryResultAvailable) {
    GLuint64 result = 0;
    gl->GetQueryObjectui64vEXT(object(), GL_QUERY_RESULT_EXT, &result);
    m_queryResult = result;
    m_taskHandle.cancel();
  } else {
    scheduleAllowAvailabilityUpdate();
  }
}

bool WebGLTimerQueryEXT::isQueryResultAvailable() {
  return m_queryResultAvailable;
}

GLuint64 WebGLTimerQueryEXT::getQueryResult() {
  return m_queryResult;
}

void WebGLTimerQueryEXT::deleteObjectImpl(gpu::gles2::GLES2Interface* gl) {
  gl->DeleteQueriesEXT(1, &m_queryId);
  m_queryId = 0;
}

void WebGLTimerQueryEXT::scheduleAllowAvailabilityUpdate() {
  if (m_taskHandle.isActive())
    return;
  m_taskHandle = m_taskRunner->postCancellableTask(
      BLINK_FROM_HERE, WTF::bind(&WebGLTimerQueryEXT::allowAvailabilityUpdate,
                                 wrapWeakPersistent(this)));
}

void WebGLTimerQueryEXT::allowAvailabilityUpdate() {
  m_canUpdateAvailability = true;
}

}  // namespace blink