// Copyright 2015 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#pragma once

#include <array>
#include <cstring>
#include <functional>
#include <string>
#include <type_traits>
#include "video_core/regs.h"

namespace GLShader {

enum Attributes {
    ATTRIBUTE_POSITION,
    ATTRIBUTE_COLOR,
    ATTRIBUTE_TEXCOORD0,
    ATTRIBUTE_TEXCOORD1,
    ATTRIBUTE_TEXCOORD2,
    ATTRIBUTE_TEXCOORD0_W,
    ATTRIBUTE_NORMQUAT,
    ATTRIBUTE_VIEW,
};

/**
 * This struct contains all state used to generate the GLSL shader program that emulates the current
 * Pica register configuration. This struct is used as a cache key for generated GLSL shader
 * programs. The functions in gl_shader_gen.cpp should retrieve state from this struct only, not by
 * directly accessing Pica registers. This should reduce the risk of bugs in shader generation where
 * Pica state is not being captured in the shader cache key, thereby resulting in (what should be)
 * two separate shaders sharing the same key.
 *
 * We use a union because "implicitly-defined copy/move constructor for a union X copies the object
 * representation of X." and "implicitly-defined copy assignment operator for a union X copies the
 * object representation (3.9) of X." = Bytewise copy instead of memberwise copy. This is important
 * because the padding bytes are included in the hash and comparison between objects.
 */
union PicaShaderConfig {

    /// Construct a PicaShaderConfig with the given Pica register configuration.
    static PicaShaderConfig BuildFromRegs(const Pica::Regs& regs);

    bool TevStageUpdatesCombinerBufferColor(unsigned stage_index) const {
        return (stage_index < 4) && (state.combiner_buffer_input & (1 << stage_index));
    }

    bool TevStageUpdatesCombinerBufferAlpha(unsigned stage_index) const {
        return (stage_index < 4) && ((state.combiner_buffer_input >> 4) & (1 << stage_index));
    }

    bool operator==(const PicaShaderConfig& o) const {
        return std::memcmp(&state, &o.state, sizeof(PicaShaderConfig::State)) == 0;
    };

    // NOTE: MSVC15 (Update 2) doesn't think `delete`'d constructors and operators are TC.
    //       This makes BitField not TC when used in a union or struct so we have to resort
    //       to this ugly hack.
    //       Once that bug is fixed we can use Pica::Regs::TevStageConfig here.
    //       Doesn't include const_color because we don't sync it, see comment in BuildFromRegs()
    struct TevStageConfigRaw {
        u32 sources_raw;
        u32 modifiers_raw;
        u32 ops_raw;
        u32 scales_raw;
        explicit operator Pica::TexturingRegs::TevStageConfig() const noexcept {
            Pica::TexturingRegs::TevStageConfig stage;
            stage.sources_raw = sources_raw;
            stage.modifiers_raw = modifiers_raw;
            stage.ops_raw = ops_raw;
            stage.const_color = 0;
            stage.scales_raw = scales_raw;
            return stage;
        }
    };

    struct State {
        Pica::FramebufferRegs::CompareFunc alpha_test_func;
        Pica::RasterizerRegs::ScissorMode scissor_test_mode;
        Pica::TexturingRegs::TextureConfig::TextureType texture0_type;
        std::array<TevStageConfigRaw, 6> tev_stages;
        u8 combiner_buffer_input;

        Pica::RasterizerRegs::DepthBuffering depthmap_enable;
        Pica::TexturingRegs::FogMode fog_mode;
        bool fog_flip;

        struct {
            struct {
                unsigned num;
                bool directional;
                bool two_sided_diffuse;
                bool dist_atten_enable;
            } light[8];

            bool enable;
            unsigned src_num;
            Pica::LightingRegs::LightingBumpMode bump_mode;
            unsigned bump_selector;
            bool bump_renorm;
            bool clamp_highlights;

            Pica::LightingRegs::LightingConfig config;
            Pica::LightingRegs::LightingFresnelSelector fresnel_selector;

            struct {
                bool enable;
                bool abs_input;
                Pica::LightingRegs::LightingLutInput type;
                float scale;
            } lut_d0, lut_d1, lut_fr, lut_rr, lut_rg, lut_rb;
        } lighting;

    } state;
};
#if (__GNUC__ >= 5) || defined(__clang__) || defined(_MSC_VER)
static_assert(std::is_trivially_copyable<PicaShaderConfig::State>::value,
              "PicaShaderConfig::State must be trivially copyable");
#endif

/**
 * Generates the GLSL vertex shader program source code for the current Pica state
 * @returns String of the shader source code
 */
std::string GenerateVertexShader();

/**
 * Generates the GLSL fragment shader program source code for the current Pica state
 * @param config ShaderCacheKey object generated for the current Pica state, used for the shader
 *               configuration (NOTE: Use state in this struct only, not the Pica registers!)
 * @returns String of the shader source code
 */
std::string GenerateFragmentShader(const PicaShaderConfig& config);

} // namespace GLShader

namespace std {
template <>
struct hash<GLShader::PicaShaderConfig> {
    size_t operator()(const GLShader::PicaShaderConfig& k) const {
        return Common::ComputeHash64(&k.state, sizeof(GLShader::PicaShaderConfig::State));
    }
};
} // namespace std
