#include <fstream>
#include <iostream>
#include "Shader.hpp"

Shader::Shader(const char* vertexShaderFileName, const char* fragmentShaderFileName) {
    shaderId = createShader(vertexShaderFileName, fragmentShaderFileName);
}

Shader::~Shader() {
    glDeleteProgram(shaderId);
}

void Shader::bind() {
    glUseProgram(shaderId);
}

void Shader::unbind() {
    glUseProgram(0);
}

GLuint Shader::compile(std::string shaderSource, GLenum shaderType) {
    GLuint id = glCreateShader(shaderType);
    const char* src = shaderSource.c_str();
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE) {
        int length = 0;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        char* message = new char[length];
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << "Shader Compilation Error" << message << std::endl;
        delete[] message;
        return 0;
    }
    return id;
}

std::string Shader::parse(const char* filename) {
    FILE* file;
    file = fopen(filename, "rb");
    if (file == nullptr) {
        std::cout << "File " << filename << " not found" << std::endl;
    }
    std::string contents;
    fseek(file, 0, SEEK_END);
    size_t filesize = ftell(file);
    rewind(file);
    contents.resize(filesize);
    fread(&contents[0], 1, filesize, file);
    fclose(file);

    return contents;
}

GLuint Shader::createShader(const char* vertexShaderFileName, const char* fragmentShaderFileName) {
    std::string vertexShaderSource = parse(vertexShaderFileName);
    std::string fragmentShaderSource = parse(fragmentShaderFileName);

    GLuint program = glCreateProgram();
    GLuint vert = compile(vertexShaderSource, GL_VERTEX_SHADER);
    GLuint frag = compile(fragmentShaderSource, GL_FRAGMENT_SHADER);

    glAttachShader(program, vert);
    glAttachShader(program, frag);
    glLinkProgram(program);

    // ATTENTION: use only for release
    // NOTE: if you do not detach and delete the program from the gpu, it's easier to debug if errors happen with the shaders
    // glDetachShader(program, vert);
    // glDetachShader(program, frag);
    // glDeleteShader(vert);
    // glDeleteShader(frag);

    return program;
}