// Copyright (c) 2008-2023 the Urho3D project
// License: MIT

#pragma once

#include "../Container/ArrayPtr.h"
#include "../Container/HashMap.h"
#include "../Container/RefCounted.h"
#include "../GraphicsAPI/GPUObject.h"
#include "../GraphicsAPI/GraphicsDefs.h"

namespace Urho3D
{

class ConstantBuffer;
class Shader;

/// %Shader parameter definition.
struct ShaderParameter
{
    /// Construct with defaults.
    ShaderParameter() = default;
    /// Construct with name, glType and location, leaving the remaining attributes zero-initialized (used only in OpenGL).
    ShaderParameter(const String& name, unsigned glType, int location);
    /// Construct with type, name, offset, size, and buffer, leaving the remaining attributes zero-initialized (used only in Direct3D11).
    ShaderParameter(ShaderType type, const String& name, unsigned offset, unsigned size, unsigned buffer);
    /// Construct with type, name, register, and register count, leaving the remaining attributes zero-initialized (used only in Direct3D9).
    ShaderParameter(ShaderType type, const String& name, unsigned reg, unsigned regCount);

    /// %Shader type.
    ShaderType type_{};
    /// Name of the parameter.
    String name_{};

    union
    {
        /// Offset in constant buffer.
        unsigned offset_;
        /// OpenGL uniform location.
        int location_;
        /// Direct3D9 register index.
        unsigned register_;
    };

    union
    {
        /// Parameter size. Used only on Direct3D11 to calculate constant buffer size.
        unsigned size_;
        /// Parameter OpenGL type.
        unsigned glType_;
        /// Number of registers on Direct3D9.
        unsigned regCount_;
    };

    /// Constant buffer index. Only used on Direct3D11.
    unsigned buffer_{};
    /// Constant buffer pointer. Defined only in shader programs.
    ConstantBuffer* bufferPtr_{};
};

/// Vertex or pixel shader on the GPU.
class URHO3D_API ShaderVariation : public RefCounted, public GPUObject
{
public:
    /// Construct.
    ShaderVariation(Shader* owner, ShaderType type);
    /// Destruct.
    ~ShaderVariation() override;

    /// Mark the GPU resource destroyed on graphics context destruction.
    void OnDeviceLost() override;
    /// Release the shader.
    void Release() override;

    /// Compile the shader. Return true if successful.
    bool Create();
    /// Set name.
    void SetName(const String& name);
    /// Set defines.
    void SetDefines(const String& defines);

    /// Return the owner resource.
    Shader* GetOwner() const;

    /// Return shader type.
    ShaderType GetShaderType() const { return type_; }

    /// Return shader name.
    const String& GetName() const { return name_; }

    /// Return full shader name.
    String GetFullName() const { return name_ + "(" + defines_ + ")"; }

    /// Return whether uses a parameter. Not applicable on OpenGL, where this information is contained in ShaderProgram instead.
    bool HasParameter(StringHash param) const { return parameters_.Contains(param); }

    /// Return whether uses a texture unit (only for pixel shaders). Not applicable on OpenGL, where this information is contained in ShaderProgram instead.
    bool HasTextureUnit(TextureUnit unit) const { return useTextureUnits_[unit]; }

    /// Return all parameter definitions. Not applicable on OpenGL, where this information is contained in ShaderProgram instead.
    const HashMap<StringHash, ShaderParameter>& GetParameters() const { return parameters_; }

    /// Return vertex element hash.
    hash64 GetElementHash() const { return elementHash_; }

    /// Return shader bytecode. Stored persistently on Direct3D11 only.
    const Vector<unsigned char>& GetByteCode() const { return byteCode_; }

    /// Return defines.
    const String& GetDefines() const { return defines_; }

    /// Return compile error/warning string.
    const String& GetCompilerOutput() const { return compilerOutput_; }

    /// Return constant buffer data sizes.
    const unsigned* GetConstantBufferSizes() const { return &constantBufferSizes_[0]; }

    /// Return defines with the CLIPPLANE define appended. Used internally on Direct3D11 only, will be empty on other APIs.
    const String& GetDefinesClipPlane() { return definesClipPlane_; }

    /// OpenGL vertex semantic names. Used internally.
    static const char* elementSemanticNames_OGL[];

    /// D3D11 vertex semantic names. Used internally.
    static const char* elementSemanticNames_D3D11[];

private:

    // Internal functions

#ifdef URHO3D_D3D11
    /// Load bytecode from a file. Return true if successful.
    bool LoadByteCode_D3D11(const String& binaryShaderName);

    /// Compile from source. Return true if successful.
    bool Compile_D3D11();

    /// Inspect the constant parameters and input layout (if applicable) from the shader bytecode.
    void ParseParameters_D3D11(unsigned char* bufData, unsigned bufSize);

    /// Save bytecode to a file.
    void SaveByteCode_D3D11(const String& binaryShaderName);

    /// Calculate constant buffer sizes from parameters.
    void CalculateConstantBufferSizes_D3D11();
#endif // def URHO3D_D3D11

    // For proxy functions

#ifdef URHO3D_OPENGL
    void OnDeviceLost_OGL();
    void Release_OGL();
    bool Create_OGL();
    void SetDefines_OGL(const String& defines);
#endif // def URHO3D_OPENGL

#ifdef URHO3D_D3D11
    void OnDeviceLost_D3D11();
    void Release_D3D11();
    bool Create_D3D11();
    void SetDefines_D3D11(const String& defines);
#endif // def URHO3D_D3D11

    /// Shader this variation belongs to.
    WeakPtr<Shader> owner_;
    /// Shader type.
    ShaderType type_;
    /// Vertex element hash for vertex shaders. Zero for pixel shaders. Note that hashing is different than vertex buffers.
    hash64 elementHash_{};
    /// Shader parameters.
    HashMap<StringHash, ShaderParameter> parameters_;
    /// Texture unit use flags.
    bool useTextureUnits_[MAX_TEXTURE_UNITS]{};
    /// Constant buffer sizes. 0 if a constant buffer slot is not in use.
    unsigned constantBufferSizes_[MAX_SHADER_PARAMETER_GROUPS]{};
    /// Shader bytecode. Needed for inspecting the input signature and parameters. Not used on OpenGL.
    Vector<unsigned char> byteCode_;
    /// Shader name.
    String name_;
    /// Defines to use in compiling.
    String defines_;
    /// Defines to use in compiling + CLIPPLANE define appended. Used only on Direct3D11.
    String definesClipPlane_;
    /// Shader compile error string.
    String compilerOutput_;
};

}