// 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/WebGLQuery.h"

#include "gpu/command_buffer/client/gles2_interface.h"
#include "modules/webgl/WebGL2RenderingContextBase.h"
#include "public/platform/Platform.h"

namespace blink {

WebGLQuery* WebGLQuery::create(WebGL2RenderingContextBase* ctx)
{
    return new WebGLQuery(ctx);
}

WebGLQuery::~WebGLQuery()
{
    unregisterTaskObserver();

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

WebGLQuery::WebGLQuery(WebGL2RenderingContextBase* ctx)
    : WebGLSharedPlatform3DObject(ctx)
    , m_target(0)
    , m_taskObserverRegistered(false)
    , m_canUpdateAvailability(false)
    , m_queryResultAvailable(false)
    , m_queryResult(0)
{
    GLuint query;
    ctx->contextGL()->GenQueriesEXT(1, &query);
    setObject(query);
}

void WebGLQuery::setTarget(GLenum target)
{
    ASSERT(object());
    ASSERT(!m_target);
    m_target = target;
}

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

void WebGLQuery::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.
    registerTaskObserver();
}

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

    if (!m_canUpdateAvailability)
        return;

    if (!hasTarget())
        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) {
        GLuint result = 0;
        gl->GetQueryObjectuivEXT(object(), GL_QUERY_RESULT_EXT, &result);
        m_queryResult = result;
        unregisterTaskObserver();
    }
}

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

GLuint WebGLQuery::getQueryResult()
{
    return m_queryResult;
}

void WebGLQuery::registerTaskObserver()
{
    if (!m_taskObserverRegistered) {
        m_taskObserverRegistered = true;
        Platform::current()->currentThread()->addTaskObserver(this);
    }
}

void WebGLQuery::unregisterTaskObserver()
{
    if (m_taskObserverRegistered) {
        m_taskObserverRegistered = false;
        Platform::current()->currentThread()->removeTaskObserver(this);
    }
}

void WebGLQuery::didProcessTask()
{
    m_canUpdateAvailability = true;
}

} // namespace blink