/*
 * 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 AND ITS CONTRIBUTORS "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 OR ITS 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.
 */

#pragma once

#include <wtf/Platform.h>

#if ENABLE(WEBGL)

#include <atomic>
#include <wtf/RefCounted.h>

namespace WebCore {

class WebCoreOpaqueRoot;

// Manual variant discriminator for any WebGL extension. Used for downcasting the WebGLExtensionBase pointers
// to the concrete type.
enum class WebGLExtensionName {
    ANGLEInstancedArrays,
    EXTBlendMinMax,
    EXTClipControl,
    EXTColorBufferFloat,
    EXTColorBufferHalfFloat,
    EXTConservativeDepth,
    EXTDepthClamp,
    EXTDisjointTimerQuery,
    EXTDisjointTimerQueryWebGL2,
    EXTFloatBlend,
    EXTFragDepth,
    EXTPolygonOffsetClamp,
    EXTRenderSnorm,
    EXTShaderTextureLOD,
    EXTTextureCompressionBPTC,
    EXTTextureCompressionRGTC,
    EXTTextureFilterAnisotropic,
    EXTTextureMirrorClampToEdge,
    EXTTextureNorm16,
    EXTsRGB,
    KHRParallelShaderCompile,
    NVShaderNoperspectiveInterpolation,
    OESDrawBuffersIndexed,
    OESElementIndexUint,
    OESFBORenderMipmap,
    OESSampleVariables,
    OESShaderMultisampleInterpolation,
    OESStandardDerivatives,
    OESTextureFloat,
    OESTextureFloatLinear,
    OESTextureHalfFloat,
    OESTextureHalfFloatLinear,
    OESVertexArrayObject,
    WebGLBlendFuncExtended,
    WebGLClipCullDistance,
    WebGLColorBufferFloat,
    WebGLCompressedTextureASTC,
    WebGLCompressedTextureETC,
    WebGLCompressedTextureETC1,
    WebGLCompressedTexturePVRTC,
    WebGLCompressedTextureS3TC,
    WebGLCompressedTextureS3TCsRGB,
    WebGLDebugRendererInfo,
    WebGLDebugShaders,
    WebGLDepthTexture,
    WebGLDrawBuffers,
    WebGLDrawInstancedBaseVertexBaseInstance,
    WebGLLoseContext,
    WebGLMultiDraw,
    WebGLMultiDrawInstancedBaseVertexBaseInstance,
    WebGLPolygonMode,
    WebGLProvokingVertex,
    WebGLRenderSharedExponent,
    WebGLStencilTexturing
};

class WebGLExtensionBase : public RefCounted<WebGLExtensionBase> {
public:
    WebGLExtensionName name() const { return m_name; }

    virtual ~WebGLExtensionBase() = default;

protected:
    WebGLExtensionBase(WebGLExtensionName name)
        : m_name(name)
    {
    }
protected:
    const WebGLExtensionName m_name;
};

// Mixin class for WebGL extension implementations. All functions should start with preamble:
//
// if (isContextLost())
//     return;
//
// followed by `Ref context = this->context();` or `protectedContext()->drawSomething(...);`.
template<typename T>
class WebGLExtension : public WebGLExtensionBase {
public:
    void loseParentContext() { m_context = nullptr; }
    T& context() { ASSERT(!isContextLost()); return *m_context.load(std::memory_order::relaxed); }
    Ref<T> protectedContext() { return context(); }

    // Only to be used by friend WebCoreOpaqueRoot root(const WebGLExtension<T>*) that cannot be a friend
    // due to C++ warning on some compilers.
    T* opaqueRoot() const { return m_context.load(); }

protected:
    WebGLExtension(T& context, WebGLExtensionName name)
        : WebGLExtensionBase(name)
        , m_context(&context)
    {
    }
    bool isContextLost() const { return !m_context.load(std::memory_order::relaxed); }

private:
    std::atomic<T*> m_context;
};

} // namespace WebCore

#endif
