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

#include <iterator>
#include <glad/glad.h>
#include "common/logging/log.h"
#include "video_core/renderer_opengl/gl_state.h"

namespace OpenGL {

OpenGLState OpenGLState::cur_state;

OpenGLState::OpenGLState() {
    // These all match default OpenGL values
    cull.enabled = false;
    cull.mode = GL_BACK;
    cull.front_face = GL_CCW;

    depth.test_enabled = false;
    depth.test_func = GL_LESS;
    depth.write_mask = GL_TRUE;

    color_mask.red_enabled = GL_TRUE;
    color_mask.green_enabled = GL_TRUE;
    color_mask.blue_enabled = GL_TRUE;
    color_mask.alpha_enabled = GL_TRUE;

    stencil.test_enabled = false;
    auto reset_stencil = [](auto& config) {
        config.test_func = GL_ALWAYS;
        config.test_ref = 0;
        config.test_mask = 0xFFFFFFFF;
        config.write_mask = 0xFFFFFFFF;
        config.action_depth_fail = GL_KEEP;
        config.action_depth_pass = GL_KEEP;
        config.action_stencil_fail = GL_KEEP;
    };
    reset_stencil(stencil.front);
    reset_stencil(stencil.back);

    blend.enabled = true;
    blend.rgb_equation = GL_FUNC_ADD;
    blend.a_equation = GL_FUNC_ADD;
    blend.src_rgb_func = GL_ONE;
    blend.dst_rgb_func = GL_ZERO;
    blend.src_a_func = GL_ONE;
    blend.dst_a_func = GL_ZERO;
    blend.color.red = 0.0f;
    blend.color.green = 0.0f;
    blend.color.blue = 0.0f;
    blend.color.alpha = 0.0f;

    logic_op.enabled = false;
    logic_op.operation = GL_COPY;

    for (auto& texture_unit : texture_units) {
        texture_unit.Reset();
    }

    draw.read_framebuffer = 0;
    draw.draw_framebuffer = 0;
    draw.vertex_array = 0;
    draw.vertex_buffer = 0;
    draw.uniform_buffer = 0;
    draw.shader_program = 0;
    draw.program_pipeline = 0;

    scissor.enabled = false;
    scissor.x = 0;
    scissor.y = 0;
    scissor.width = 0;
    scissor.height = 0;

    viewport.x = 0;
    viewport.y = 0;
    viewport.width = 0;
    viewport.height = 0;

    clip_distance = {};
}

void OpenGLState::Apply() const {
    // Culling
    if (cull.enabled != cur_state.cull.enabled) {
        if (cull.enabled) {
            glEnable(GL_CULL_FACE);
        } else {
            glDisable(GL_CULL_FACE);
        }
    }

    if (cull.mode != cur_state.cull.mode) {
        glCullFace(cull.mode);
    }

    if (cull.front_face != cur_state.cull.front_face) {
        glFrontFace(cull.front_face);
    }

    // Depth test
    if (depth.test_enabled != cur_state.depth.test_enabled) {
        if (depth.test_enabled) {
            glEnable(GL_DEPTH_TEST);
        } else {
            glDisable(GL_DEPTH_TEST);
        }
    }

    if (depth.test_func != cur_state.depth.test_func) {
        glDepthFunc(depth.test_func);
    }

    // Depth mask
    if (depth.write_mask != cur_state.depth.write_mask) {
        glDepthMask(depth.write_mask);
    }

    // Color mask
    if (color_mask.red_enabled != cur_state.color_mask.red_enabled ||
        color_mask.green_enabled != cur_state.color_mask.green_enabled ||
        color_mask.blue_enabled != cur_state.color_mask.blue_enabled ||
        color_mask.alpha_enabled != cur_state.color_mask.alpha_enabled) {
        glColorMask(color_mask.red_enabled, color_mask.green_enabled, color_mask.blue_enabled,
                    color_mask.alpha_enabled);
    }

    // Stencil test
    if (stencil.test_enabled != cur_state.stencil.test_enabled) {
        if (stencil.test_enabled) {
            glEnable(GL_STENCIL_TEST);
        } else {
            glDisable(GL_STENCIL_TEST);
        }
    }
    auto config_stencil = [](GLenum face, const auto& config, const auto& prev_config) {
        if (config.test_func != prev_config.test_func || config.test_ref != prev_config.test_ref ||
            config.test_mask != prev_config.test_mask) {
            glStencilFuncSeparate(face, config.test_func, config.test_ref, config.test_mask);
        }
        if (config.action_depth_fail != prev_config.action_depth_fail ||
            config.action_depth_pass != prev_config.action_depth_pass ||
            config.action_stencil_fail != prev_config.action_stencil_fail) {
            glStencilOpSeparate(face, config.action_stencil_fail, config.action_depth_fail,
                                config.action_depth_pass);
        }
        if (config.write_mask != prev_config.write_mask) {
            glStencilMaskSeparate(face, config.write_mask);
        }
    };
    config_stencil(GL_FRONT, stencil.front, cur_state.stencil.front);
    config_stencil(GL_BACK, stencil.back, cur_state.stencil.back);

    // Blending
    if (blend.enabled != cur_state.blend.enabled) {
        if (blend.enabled) {
            ASSERT(!logic_op.enabled);
            glEnable(GL_BLEND);
        } else {
            glDisable(GL_BLEND);
        }
    }

    if (blend.color.red != cur_state.blend.color.red ||
        blend.color.green != cur_state.blend.color.green ||
        blend.color.blue != cur_state.blend.color.blue ||
        blend.color.alpha != cur_state.blend.color.alpha) {
        glBlendColor(blend.color.red, blend.color.green, blend.color.blue, blend.color.alpha);
    }

    if (blend.src_rgb_func != cur_state.blend.src_rgb_func ||
        blend.dst_rgb_func != cur_state.blend.dst_rgb_func ||
        blend.src_a_func != cur_state.blend.src_a_func ||
        blend.dst_a_func != cur_state.blend.dst_a_func) {
        glBlendFuncSeparate(blend.src_rgb_func, blend.dst_rgb_func, blend.src_a_func,
                            blend.dst_a_func);
    }

    if (blend.rgb_equation != cur_state.blend.rgb_equation ||
        blend.a_equation != cur_state.blend.a_equation) {
        glBlendEquationSeparate(blend.rgb_equation, blend.a_equation);
    }

    // Logic Operation
    if (logic_op.enabled != cur_state.logic_op.enabled) {
        if (logic_op.enabled) {
            ASSERT(!blend.enabled);
            glEnable(GL_COLOR_LOGIC_OP);
        } else {
            glDisable(GL_COLOR_LOGIC_OP);
        }
    }

    if (logic_op.operation != cur_state.logic_op.operation) {
        glLogicOp(logic_op.operation);
    }

    // Textures
    for (std::size_t i = 0; i < std::size(texture_units); ++i) {
        const auto& texture_unit = texture_units[i];
        const auto& cur_state_texture_unit = cur_state.texture_units[i];

        if (texture_unit.texture != cur_state_texture_unit.texture) {
            glActiveTexture(TextureUnits::MaxwellTexture(static_cast<int>(i)).Enum());
            glBindTexture(texture_unit.target, texture_unit.texture);
        }
        if (texture_unit.sampler != cur_state_texture_unit.sampler) {
            glBindSampler(static_cast<GLuint>(i), texture_unit.sampler);
        }
        // Update the texture swizzle
        if (texture_unit.swizzle.r != cur_state_texture_unit.swizzle.r ||
            texture_unit.swizzle.g != cur_state_texture_unit.swizzle.g ||
            texture_unit.swizzle.b != cur_state_texture_unit.swizzle.b ||
            texture_unit.swizzle.a != cur_state_texture_unit.swizzle.a) {
            std::array<GLint, 4> mask = {texture_unit.swizzle.r, texture_unit.swizzle.g,
                                         texture_unit.swizzle.b, texture_unit.swizzle.a};
            glTexParameteriv(texture_unit.target, GL_TEXTURE_SWIZZLE_RGBA, mask.data());
        }
    }

    // Framebuffer
    if (draw.read_framebuffer != cur_state.draw.read_framebuffer) {
        glBindFramebuffer(GL_READ_FRAMEBUFFER, draw.read_framebuffer);
    }
    if (draw.draw_framebuffer != cur_state.draw.draw_framebuffer) {
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, draw.draw_framebuffer);
    }

    // Vertex array
    if (draw.vertex_array != cur_state.draw.vertex_array) {
        glBindVertexArray(draw.vertex_array);
    }

    // Vertex buffer
    if (draw.vertex_buffer != cur_state.draw.vertex_buffer) {
        glBindBuffer(GL_ARRAY_BUFFER, draw.vertex_buffer);
    }

    // Uniform buffer
    if (draw.uniform_buffer != cur_state.draw.uniform_buffer) {
        glBindBuffer(GL_UNIFORM_BUFFER, draw.uniform_buffer);
    }

    // Shader program
    if (draw.shader_program != cur_state.draw.shader_program) {
        glUseProgram(draw.shader_program);
    }

    // Program pipeline
    if (draw.program_pipeline != cur_state.draw.program_pipeline) {
        glBindProgramPipeline(draw.program_pipeline);
    }

    // Scissor test
    if (scissor.enabled != cur_state.scissor.enabled) {
        if (scissor.enabled) {
            glEnable(GL_SCISSOR_TEST);
        } else {
            glDisable(GL_SCISSOR_TEST);
        }
    }

    if (scissor.x != cur_state.scissor.x || scissor.y != cur_state.scissor.y ||
        scissor.width != cur_state.scissor.width || scissor.height != cur_state.scissor.height) {
        glScissor(scissor.x, scissor.y, scissor.width, scissor.height);
    }

    if (viewport.x != cur_state.viewport.x || viewport.y != cur_state.viewport.y ||
        viewport.width != cur_state.viewport.width ||
        viewport.height != cur_state.viewport.height) {
        glViewport(viewport.x, viewport.y, viewport.width, viewport.height);
    }

    // Clip distance
    for (size_t i = 0; i < clip_distance.size(); ++i) {
        if (clip_distance[i] != cur_state.clip_distance[i]) {
            if (clip_distance[i]) {
                glEnable(GL_CLIP_DISTANCE0 + static_cast<GLenum>(i));
            } else {
                glDisable(GL_CLIP_DISTANCE0 + static_cast<GLenum>(i));
            }
        }
    }

    cur_state = *this;
}

OpenGLState& OpenGLState::UnbindTexture(GLuint handle) {
    for (auto& unit : texture_units) {
        if (unit.texture == handle) {
            unit.Unbind();
        }
    }
    return *this;
}

OpenGLState& OpenGLState::ResetSampler(GLuint handle) {
    for (auto& unit : texture_units) {
        if (unit.sampler == handle) {
            unit.sampler = 0;
        }
    }
    return *this;
}

OpenGLState& OpenGLState::ResetProgram(GLuint handle) {
    if (draw.shader_program == handle) {
        draw.shader_program = 0;
    }
    return *this;
}

OpenGLState& OpenGLState::ResetPipeline(GLuint handle) {
    if (draw.program_pipeline == handle) {
        draw.program_pipeline = 0;
    }
    return *this;
}

OpenGLState& OpenGLState::ResetBuffer(GLuint handle) {
    if (draw.vertex_buffer == handle) {
        draw.vertex_buffer = 0;
    }
    if (draw.uniform_buffer == handle) {
        draw.uniform_buffer = 0;
    }
    return *this;
}

OpenGLState& OpenGLState::ResetVertexArray(GLuint handle) {
    if (draw.vertex_array == handle) {
        draw.vertex_array = 0;
    }
    return *this;
}

OpenGLState& OpenGLState::ResetFramebuffer(GLuint handle) {
    if (draw.read_framebuffer == handle) {
        draw.read_framebuffer = 0;
    }
    if (draw.draw_framebuffer == handle) {
        draw.draw_framebuffer = 0;
    }
    return *this;
}

} // namespace OpenGL
