#include "XCEngine/RHI/OpenGL/OpenGLShader.h"
#include <glad/glad.h>
#include <fstream>
#include <sstream>
#include <iostream>

namespace XCEngine {
namespace RHI {

OpenGLShader::OpenGLShader()
    : m_program(0), m_uniformsCached(false) {
}

OpenGLShader::~OpenGLShader() {
    Shutdown();
}

bool OpenGLShader::CompileFromFile(const char* vertexPath, const char* fragmentPath) {
    std::string vertexCode, fragmentCode;
    std::ifstream vShaderFile(vertexPath), fShaderFile(fragmentPath);
    
    if (!vShaderFile.is_open() || !fShaderFile.is_open()) {
        return false;
    }
    
    std::stringstream vShaderStream, fShaderStream;
    vShaderStream << vShaderFile.rdbuf();
    fShaderStream << fShaderFile.rdbuf();
    vShaderFile.close();
    fShaderFile.close();
    
    vertexCode = vShaderStream.str();
    fragmentCode = fShaderStream.str();
    
    return Compile(vertexCode.c_str(), fragmentCode.c_str());
}

bool OpenGLShader::CompileFromFile(const char* vertexPath, const char* fragmentPath, const char* geometryPath) {
    std::string vertexCode, fragmentCode, geometryCode;
    std::ifstream vShaderFile(vertexPath), fShaderFile(fragmentPath), gShaderFile(geometryPath);
    
    if (!vShaderFile.is_open() || !fShaderFile.is_open() || !gShaderFile.is_open()) {
        return false;
    }
    
    std::stringstream vShaderStream, fShaderStream, gShaderStream;
    vShaderStream << vShaderFile.rdbuf();
    fShaderStream << fShaderFile.rdbuf();
    gShaderStream << gShaderFile.rdbuf();
    vShaderFile.close();
    fShaderFile.close();
    gShaderFile.close();
    
    vertexCode = vShaderStream.str();
    fragmentCode = fShaderStream.str();
    geometryCode = gShaderStream.str();
    
    return Compile(vertexCode.c_str(), fragmentCode.c_str(), geometryCode.c_str());
}

bool OpenGLShader::Compile(const char* vertexSource, const char* fragmentSource) {
    unsigned int vertex, fragment;
    
    vertex = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex, 1, &vertexSource, nullptr);
    glCompileShader(vertex);
    if (!CheckCompileErrors(vertex, "VERTEX")) {
        return false;
    }
    
    fragment = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment, 1, &fragmentSource, nullptr);
    glCompileShader(fragment);
    if (!CheckCompileErrors(fragment, "FRAGMENT")) {
        return false;
    }
    
    m_program = glCreateProgram();
    glAttachShader(m_program, vertex);
    glAttachShader(m_program, fragment);
    glLinkProgram(m_program);
    
    if (!CheckLinkErrors(m_program)) {
        return false;
    }
    
    glDeleteShader(vertex);
    glDeleteShader(fragment);
    
    m_uniformsCached = false;
    
    return true;
}

bool OpenGLShader::Compile(const char* vertexSource, const char* fragmentSource, const char* geometrySource) {
    unsigned int vertex, fragment, geometry;
    
    vertex = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex, 1, &vertexSource, nullptr);
    glCompileShader(vertex);
    if (!CheckCompileErrors(vertex, "VERTEX")) {
        return false;
    }
    
    fragment = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment, 1, &fragmentSource, nullptr);
    glCompileShader(fragment);
    if (!CheckCompileErrors(fragment, "FRAGMENT")) {
        return false;
    }
    
    geometry = glCreateShader(GL_GEOMETRY_SHADER);
    glShaderSource(geometry, 1, &geometrySource, nullptr);
    glCompileShader(geometry);
    if (!CheckCompileErrors(geometry, "GEOMETRY")) {
        return false;
    }
    
    m_program = glCreateProgram();
    glAttachShader(m_program, vertex);
    glAttachShader(m_program, fragment);
    glAttachShader(m_program, geometry);
    glLinkProgram(m_program);
    
    if (!CheckLinkErrors(m_program)) {
        return false;
    }
    
    glDeleteShader(vertex);
    glDeleteShader(fragment);
    glDeleteShader(geometry);
    
    m_uniformsCached = false;
    
    return true;
}

bool OpenGLShader::CompileCompute(const char* computeSource) {
    unsigned int compute = glCreateShader(GL_COMPUTE_SHADER);
    glShaderSource(compute, 1, &computeSource, nullptr);
    glCompileShader(compute);
    if (!CheckCompileErrors(compute, "COMPUTE")) {
        return false;
    }
    
    m_program = glCreateProgram();
    glAttachShader(m_program, compute);
    glLinkProgram(m_program);
    
    if (!CheckLinkErrors(m_program)) {
        return false;
    }
    
    glDeleteShader(compute);
    
    m_type = ShaderType::Compute;
    m_uniformsCached = false;
    
    return true;
}

bool OpenGLShader::Compile(const char* source, ShaderType type) {
    unsigned int shader = 0;
    
    switch (type) {
        case ShaderType::Vertex:
            shader = glCreateShader(GL_VERTEX_SHADER);
            break;
        case ShaderType::Fragment:
            shader = glCreateShader(GL_FRAGMENT_SHADER);
            break;
        case ShaderType::Geometry:
            shader = glCreateShader(GL_GEOMETRY_SHADER);
            break;
        case ShaderType::Compute:
            shader = glCreateShader(GL_COMPUTE_SHADER);
            break;
        case ShaderType::TessControl:
            shader = glCreateShader(GL_TESS_CONTROL_SHADER);
            break;
        case ShaderType::TessEvaluation:
            shader = glCreateShader(GL_TESS_EVALUATION_SHADER);
            break;
        default:
            return false;
    }
    
    glShaderSource(shader, 1, &source, nullptr);
    glCompileShader(shader);
    
    const char* typeName[] = { "VERTEX", "FRAGMENT", "GEOMETRY", "COMPUTE", "TESS_CONTROL", "TESS_EVALUATION" };
    if (!CheckCompileErrors(shader, typeName[(int)type])) {
        return false;
    }
    
    if (m_program == 0) {
        m_program = glCreateProgram();
    }
    glAttachShader(m_program, shader);
    glLinkProgram(m_program);
    
    if (!CheckLinkErrors(m_program)) {
        return false;
    }
    
    glDeleteShader(shader);
    
    m_uniformsCached = false;
    
    return true;
}

bool OpenGLShader::CompileFromFile(const wchar_t* filePath, const char* entryPoint, const char* target) {
    std::wstring ws(filePath);
    std::string path(ws.begin(), ws.end());
    return CompileFromFile(path.c_str(), nullptr);
}

bool OpenGLShader::Compile(const void* sourceData, size_t sourceSize, const char* entryPoint, const char* target) {
    if (!sourceData || sourceSize == 0) {
        return false;
    }
    
    ShaderType type = ShaderType::Fragment;
    if (target) {
        if (strstr(target, "vs_")) {
            type = ShaderType::Vertex;
        } else if (strstr(target, "ps_")) {
            type = ShaderType::Fragment;
        } else if (strstr(target, "gs_")) {
            type = ShaderType::Geometry;
        } else if (strstr(target, "cs_")) {
            type = ShaderType::Compute;
        }
    }
    return Compile(static_cast<const char*>(sourceData), type);
}

void OpenGLShader::Shutdown() {
    if (m_program) {
        glDeleteProgram(m_program);
        m_program = 0;
    }
    m_uniformInfos.clear();
    m_uniformsCached = false;
}

void OpenGLShader::Use() const {
    glUseProgram(m_program);
}

void OpenGLShader::CacheUniformInfos() const {
    if (m_uniformsCached || m_program == 0) {
        return;
    }
    
    m_uniformInfos.clear();
    
    GLint numUniforms = 0;
    glGetProgramInterfaceiv(m_program, GL_UNIFORM, GL_ACTIVE_RESOURCES, &numUniforms);
    
    for (GLint i = 0; i < numUniforms; ++i) {
        GLenum props[] = { GL_NAME_LENGTH, GL_TYPE, GL_OFFSET, GL_ARRAY_SIZE };
        GLint values[4] = { 0 };
        glGetProgramResourceiv(m_program, GL_UNIFORM, i, 4, props, 4, nullptr, values);
        
        std::vector<char> nameBuffer(values[0]);
        glGetProgramResourceName(m_program, GL_UNIFORM, i, values[0], nullptr, nameBuffer.data());
        
        UniformInfo info;
        info.name = nameBuffer.data();
        info.bindPoint = static_cast<uint32_t>(i);
        info.type = static_cast<uint32_t>(values[1]);
        info.offset = static_cast<uint32_t>(values[2]);
        info.arraySize = static_cast<uint32_t>(values[3]);
        
        GLint size = values[3];
        switch (values[1]) {
            case GL_FLOAT: info.size = sizeof(GLfloat) * size; break;
            case GL_FLOAT_VEC2: info.size = sizeof(GLfloat) * 2 * size; break;
            case GL_FLOAT_VEC3: info.size = sizeof(GLfloat) * 3 * size; break;
            case GL_FLOAT_VEC4: info.size = sizeof(GLfloat) * 4 * size; break;
            case GL_INT: info.size = sizeof(GLint) * size; break;
            case GL_BOOL: info.size = sizeof(GLboolean) * size; break;
            case GL_FLOAT_MAT4: info.size = sizeof(GLfloat) * 16 * size; break;
            case GL_FLOAT_MAT3: info.size = sizeof(GLfloat) * 9 * size; break;
            case GL_FLOAT_MAT2: info.size = sizeof(GLfloat) * 4 * size; break;
            default: info.size = 0; break;
        }
        
        m_uniformInfos.push_back(info);
    }
    
    m_uniformsCached = true;
}

const std::vector<RHIShader::UniformInfo>& OpenGLShader::GetUniformInfos() const {
    CacheUniformInfos();
    return m_uniformInfos;
}

const RHIShader::UniformInfo* OpenGLShader::GetUniformInfo(const char* name) const {
    CacheUniformInfos();
    for (const auto& info : m_uniformInfos) {
        if (info.name == name) {
            return &info;
        }
    }
    return nullptr;
}

int OpenGLShader::GetUniformLocation(const char* name) const {
    return glGetUniformLocation(m_program, name);
}

bool OpenGLShader::CheckCompileErrors(unsigned int shader, const char* type) {
    int success;
    char infoLog[1024];
    
    glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
    if (!success) {
        glGetShaderInfoLog(shader, 1024, nullptr, infoLog);
        std::cout << "ERROR::SHADER_COMPILATION_ERROR: " << type << "\n" << infoLog << std::endl;
        return false;
    }
    return true;
}

bool OpenGLShader::CheckLinkErrors(unsigned int program) {
    int success;
    char infoLog[1024];
    
    glGetProgramiv(program, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(program, 1024, nullptr, infoLog);
        std::cout << "ERROR::PROGRAM_LINKING_ERROR\n" << infoLog << std::endl;
        return false;
    }
    return true;
}

} // namespace RHI
} // namespace XCEngine