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

 https://axmolengine.github.io/

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 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,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ****************************************************************************/

#pragma once

#include "../Macros.h"
#include "../Types.h"
#include "base/Ref.h"
#include "base/EventListenerCustom.h"
#include "platform/GL.h"
#include "../Program.h"
#include "renderer/backend/Device.h"
#include "renderer/backend/opengl/BufferGL.h"

#include <string>
#include <vector>
#include <unordered_map>

NS_AX_BACKEND_BEGIN

class ShaderModuleGL;

/**
 * Store attribute information.
 */
struct AttributeInfo
{
    unsigned int location         = 0;
    unsigned int size             = 0;
    GLenum type                   = GL_BYTE;
    GLsizei stride                = 0;
    unsigned int offset           = 0;
    GLboolean needToBeNormallized = GL_FALSE;
    std::string name;
};

/**
 * @addtogroup _opengl
 * @{
 */

#define MAX_UNIFORM_NAME_LENGTH 256
#define UNIFORM_BLOCK_IDENTIFIER UINT16_MAX

struct UniformBlockDescriptor
{
    void bindUniformBlock(GLint _program, UniformBlockStage _stage);

    UniformBlockStage stage = UniformBlockStage::UBO_NOT_FOUND;

    GLuint blockIndex = -1;
    GLuint bindingPoint = -1;
    GLint blockSize = -1;
    GLint numUniforms = -1;
    GLint* uniformIndices = nullptr;
    GLint* uniformOffsets = nullptr;

    ~UniformBlockDescriptor();
};

class UniformBlockHandler
{
public:
    void setProgram(GLint _program) { this->_program = _program; };

    void bindUniformBlock(UniformBlockStage _stage);
    void bindUniformBlocks();
    void generateUniformOffsets(UniformBlockStage _stage);
    void allocateUBOBuffer();

    UniformLocation getUniformLocationByName(std::string name) const;

    std::unordered_map<std::string, UniformLocation> uniformOffsetsByName;

    BufferGL* getVertexBuffer() const { return _UBOVertBuffer; };
    BufferGL* getFragmentBuffer() const { return _UBOFragBuffer; };

    ~UniformBlockHandler();

    GLint vertBlockSize = 0;
    GLint fragBlockSize = 0;

private:
    ax::backend::BufferGL* _UBOVertBuffer = nullptr;
    ax::backend::BufferGL* _UBOFragBuffer = nullptr;
    UniformBlockDescriptor _vertexUBO;
    UniformBlockDescriptor _fragmentUBO;

    GLint _program;
};

/**
 * An OpenGL program.
 */
class ProgramGL : public Program
{
public:
    /**
     * @param vertexShader Specifes the vertex shader source.
     * @param fragmentShader Specifes the fragment shader source.
     */
    ProgramGL(std::string_view vertexShader, std::string_view fragmentShader);

    ~ProgramGL();

    /**
     * Get attribute informations.
     * @return Attribute informations.
     */
    inline const std::vector<AttributeInfo>& getAttributeInfos() const { return _attributeInfos; }

    /**
     * Get program object.
     * @return Program object.
     */
    inline GLuint getHandler() const { return _program; }

    /**
     * Get uniform location by name.
     * @param uniform Specifies the uniform name.
     * @return The uniform location.
     */
    virtual UniformLocation getUniformLocation(std::string_view uniform) const override;

    /**
     * Get uniform location by engine built-in uniform enum name.
     * @param name Specifies the engine built-in uniform enum name.
     * @return The uniform location.
     */
    virtual UniformLocation getUniformLocation(backend::Uniform name) const override;

    /**
     * Get attribute location by attribute name.
     * @param name Specifies the attribute name.
     * @return The attribute location.
     */
    virtual int getAttributeLocation(std::string_view name) const override;

    /**
     * Get attribute location by engine built-in attribute enum name.
     * @param name Specifies the engine built-in attribute enum name.
     * @return The attribute location.
     */
    virtual int getAttributeLocation(Attribute name) const override;

    /**
     * Get maximum vertex location.
     * @return Maximum vertex locaiton.
     */
    virtual int getMaxVertexLocation() const override;

    /**
     * Get maximum fragment location.
     * @return Maximum fragment location.
     */
    virtual int getMaxFragmentLocation() const override;

    /**
     * Get active vertex attributes.
     * @return Active vertex attributes. key is active attribute name, Value is corresponding attribute info.
     */
    virtual const hlookup::string_map<AttributeBindInfo>& getActiveAttributes() const override;

    /**
     * Get uniform buffer size in bytes that can hold all the uniforms.
     * @param stage Specifies the shader stage. The symbolic constant can be either VERTEX or FRAGMENT.
     * @return The uniform buffer size in bytes.
     */
    virtual std::size_t getUniformBufferSize(ShaderStage stage) const override;

    /**
     * Get a uniformInfo in given location from the specific shader stage.
     * @param stage Specifies the shader stage. The symbolic constant can be either VERTEX or FRAGMENT.
     * @param location Specifies the uniform locaion.
     * @return The uniformInfo.
     */
    virtual const UniformInfo& getActiveUniformInfo(ShaderStage stage, int location) const override;

    /**
     * Get all uniformInfos.
     * @return The uniformInfos.
     */
    virtual const hlookup::string_map<UniformInfo>& getAllActiveUniformInfo(ShaderStage stage) const override;

    UniformBlockHandler& getUBOHandler() { return _ubo; };

private:
    void compileProgram();
    bool getAttributeLocation(std::string_view attributeName, unsigned int& location) const;
    void computeUniformInfos();
    void generateUniformBlockBuffers();
    void computeLocations();
#if AX_ENABLE_CACHE_TEXTURE_DATA
    virtual void reloadProgram();
    virtual int getMappedLocation(int location) const override;
    virtual int getOriginalLocation(int location) const override;
    virtual const std::unordered_map<std::string, int> getAllUniformsLocation() const override
    {
        return _originalUniformLocations;
    }
#endif

    GLuint _program                       = 0;
    ShaderModuleGL* _vertexShaderModule   = nullptr;
    ShaderModuleGL* _fragmentShaderModule = nullptr;

    UniformBlockHandler _ubo;

    std::vector<AttributeInfo> _attributeInfos;
    hlookup::string_map<UniformInfo> _activeUniformInfos;
    mutable hlookup::string_map<AttributeBindInfo> _activeAttribs;
#if AX_ENABLE_CACHE_TEXTURE_DATA
    std::unordered_map<std::string, int>
        _originalUniformLocations;  ///< record the uniform location when shader was first created.
    std::unordered_map<int, int> _mapToCurrentActiveLocation;  ///<
    std::unordered_map<int, int> _mapToOriginalLocation;       ///<
    EventListenerCustom* _backToForegroundListener = nullptr;
#endif

    std::size_t _totalFragBufferSize = 0;
    std::size_t _totalVertBufferSize = 0;
    int _maxLocation             = -1;
    UniformLocation _builtinUniformLocation[UNIFORM_MAX];
    int _builtinAttributeLocation[Attribute::ATTRIBUTE_MAX];
    std::unordered_map<int, int> _bufferOffset;
};
// end of _opengl group
/// @}
NS_AX_BACKEND_END