/****************************************************************************
 Copyright (c) 2018-2019 Xiamen Yaji Software Co., Ltd.

 http://www.cocos2d-x.org

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
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 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 ****************************************************************************/
 
#pragma once

#include "../CommandBuffer.h"
#include "DeviceMTL.h"
#include <unordered_map>

CC_BACKEND_BEGIN

class RenderPipelineMTL;
class DepthStencilStateMTL;

/**
 * @addtogroup _metal
 * @{
 */

/**
 * @brief Store encoded commands for the GPU to execute.
 * A command buffer stores encoded commands until the buffer is committed for execution by the GPU
 */
class CommandBufferMTL : public CommandBuffer
{
public:
    /// @name Constructor, Destructor and Initializers
    /**
     * @param deviceMTL The device for which MTLCommandQueue object was created.
     */
    CommandBufferMTL(DeviceMTL* deviceMTL);
    ~CommandBufferMTL();
    
    /**
     * Set depthStencil status
     * @param depthStencilState Specifies the depth and stencil status
     */
    virtual void setDepthStencilState(DepthStencilState* depthStencilState) override;
    
    /**
     * Sets the current render pipeline state object once
     * @param renderPipeline An object that contains the graphics functions and configuration state used in a render pass.
     */
    virtual void setRenderPipeline(RenderPipeline* renderPipeline) override;
    
    
    /// @name Setters & Getters
    /**
     * @brief Indicate the begining of a frame
     * Wait until the inflight command buffer has completed its work.
     * Then create MTLCommandBuffer and enqueue it to MTLCommandQueue.
     * Then start schedule available MTLBuffer
     */
    virtual void beginFrame() override;
    
    /**
     * Create a MTLRenderCommandEncoder object for graphics rendering to an attachment in a RenderPassParams.
     * MTLRenderCommandEncoder is cached if current RenderPassParams is identical to previous one.
     * @param descriptor Specifies a group of render targets that hold the results of a render pass.
     */
    virtual void beginRenderPass(const RenderTarget* renderTarget, const RenderPassParams& descriptor) override;

    /**
     * Update depthStencil status, improvment: for metal backend cache it
     * @param depthStencilState Specifies the depth and stencil status
     */
    virtual void updateDepthStencilState(const DepthStencilDescriptor& descriptor) override;

    /**
     * Update render pipeline status
     * Building a programmable pipeline involves an expensive evaluation of GPU state.
     * So a new render pipeline object will be created only if it hasn't been created before.
     * @param rt Specifies the render target.
     * @param pipelineDescriptor Specifies the pipeline descriptor.
     */
    virtual void updatePipelineState(const RenderTarget* rt, const PipelineDescriptor& descriptor) override;
    
    /**
     * Fixed-function state
     * @param x The x coordinate of the upper-left corner of the viewport.
     * @param y The y coordinate of the upper-left corner of the viewport.
     * @param w The width of the viewport, in pixels.
     * @param h The height of the viewport, in pixels.
     */
    virtual void setViewport(int x, int y, unsigned int w, unsigned int h) override;
    
    /**
     * Fixed-function state
     * @param mode Controls if primitives are culled when front facing, back facing, or not culled at all.
     */
    virtual void setCullMode(CullMode mode) override;
    
    /**
     * Fixed-function state
     * @param winding The winding order of front-facing primitives.
     */
    virtual void setWinding(Winding winding) override;
    
    /**
     * Set a global buffer for all vertex shaders at the given bind point index 0.
     * @param buffer The buffer to set in the buffer argument table.
     */
    virtual void setVertexBuffer(Buffer* buffer) override;
    
    /**
     * Set the uniform data at a given vertex and fragment buffer binding point 1
     * Set a global texture for all vertex and fragment shaders at the given bind location.
     * @param programState A programState object that hold the uniform and texture data.
     */
    virtual void setProgramState(ProgramState* programState) override;
    
    /**
     * Set indexes when drawing primitives with index list
     * @ buffer A buffer object that the device will read indexes from.
     * @ see `drawElements(PrimitiveType primitiveType, IndexFormat indexType, unsigned int count, unsigned int offset)`
     */
    virtual void setIndexBuffer(Buffer* buffer) override;
    
    /**
     * Draw primitives without an index list.
     * @param primitiveType The type of primitives that elements are assembled into.
     * @param start For each instance, the first index to draw
     * @param count For each instance, the number of indexes to draw
     * @see `drawElements(PrimitiveType primitiveType, IndexFormat indexType, unsigned int count, unsigned int offset)`
     */
    virtual void drawArrays(PrimitiveType primitiveType, std::size_t start,  std::size_t count) override;
    
    /**
     * Draw primitives with an index list.
     * @param primitiveType The type of primitives that elements are assembled into.
     * @param indexType The type if indexes, either 16 bit integer or 32 bit integer.
     * @param count The number of indexes to read from the index buffer for each instance.
     * @param offset Byte offset within indexBuffer to start reading indexes from.
     * @see `setIndexBuffer(Buffer* buffer)`
     * @see `drawArrays(PrimitiveType primitiveType, unsigned int start,  unsigned int count)`
    */
    virtual void drawElements(PrimitiveType primitiveType, IndexFormat indexType, std::size_t count, std::size_t offset) override;
    
    /**
     * Do some resources release.
     */
    virtual void endRenderPass() override;
    
    /**
     * Present a drawable and commit a command buffer so it can be executed as soon as possible.
     */
    virtual void endFrame() override;
    
    /**
     * Fixed-function state
     * @param lineWidth Specifies the width of rasterized lines.
     * @todo Currently metal do not support setting line with. A Corresponding issue had create here:https://github.com/cocos2d/cocos2d-x/issues/19772
     */
    virtual void setLineWidth(float lineWidth) override;
    
    /**
     * Fixed-function state
     * @param x, y Specifies the lower left corner of the scissor box
     * @param wdith Specifies the width of the scissor box
     * @param height Specifies the height of the scissor box
     */
    virtual void setScissorRect(bool isEnabled, float x, float y, float width, float height) override;
    
    /**
     * Read pixels from RenderTarget
     * @param callback A callback to deal with pixel data read.
     */
    virtual void readPixels(RenderTarget* rt, std::function<void(const PixelBufferDescriptor&)> callback) override;
    
protected:  
    /**
     * Read a block of pixels from the given texture
     * @param texture Specifies the texture to get the image.
     * @param origX,origY Specify the window coordinates of the first pixel that is read from the given texture. This location is the lower left corner of a rectangular block of pixels.
     * @param rectWidth,rectHeight Specify the dimensions of the pixel rectangle. rectWidth and rectHeight of one correspond to a single pixel.
     * @param pbd, the output buffer for fill texels data
     * @remark: !!!this function only can call after endFrame, then it's could be works well.
    */
    static void readPixels(TextureBackend* texture, std::size_t origX, std::size_t origY, std::size_t rectWidth, std::size_t rectHeight, PixelBufferDescriptor& pbd);
    static void readPixels(id<MTLTexture> texture, std::size_t origX, std::size_t origY, std::size_t rectWidth, std::size_t rectHeight, PixelBufferDescriptor& pbd);
    
private:
    void prepareDrawing() const;
    void setTextures() const;
    void doSetTextures(bool isVertex) const;
    void setUniformBuffer() const;
    void afterDraw();
    void flush();
    void flushCaptureCommands();
    id<MTLRenderCommandEncoder> getRenderCommandEncoder(const RenderTarget* renderTarget, const RenderPassParams& renderPassParams);

    id<MTLCommandBuffer> _mtlCommandBuffer = nil;
    id<MTLCommandQueue> _mtlCommandQueue = nil;
    id<MTLRenderCommandEncoder> _mtlRenderEncoder = nil;
    id<MTLBuffer> _mtlIndexBuffer = nil;
    id<MTLTexture> _drawableTexture = nil;
    
    DepthStencilStateMTL* _depthStencilStateMTL = nullptr;
    RenderPipelineMTL* _renderPipelineMTL = nullptr;
    ProgramState* _programState = nullptr;
    
    unsigned int _renderTargetWidth = 0;
    unsigned int _renderTargetHeight = 0;
    
    dispatch_semaphore_t _frameBoundarySemaphore;
    const RenderTarget* _currentRenderTarget = nil; // weak ref
    RenderPassParams _currentRenderPassParams;
    NSAutoreleasePool* _autoReleasePool = nil;
    
    std::vector<std::pair<TextureBackend*,std::function<void(const PixelBufferDescriptor&)>>> _captureCallbacks;
};

// end of _metal group
/// @}
CC_BACKEND_END