/*
* 当需要给图形赋予真实颜色的时候，不太可能为没一个顶点指定一个颜色，通常会采用纹理贴图
* 每个顶点关联一个纹理坐标 (Texture Coordinate) 其它片段上进行片段插值
* 
*/



#include <iostream>
#define STBI_NO_SIMD
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"


#include <glad/glad.h>   // 把这个头文件放在最上面
#include <GLFW/glfw3.h>
#include <string>
#include <fstream>
#include <sstream>


#include "glm/glm.hpp"



class MyShader {
public:
    unsigned int ID;	// 着色器程序 ID


    // 构造函数读取并构建 shader
    MyShader(const char* vertexPath, const char* fragmentPath);

    // 使用激活 Shader
    void use();

    // 设置 uniform 的工具函数
    void setBool(const std::string& name, bool value) const;
    void setInt(const std::string& name, int value) const;
    void setFloat(const std::string& name, float value) const;
    void setVec4(const std::string& name, const glm::vec4& value) const;

};


MyShader::MyShader(const char* vertexPath, const char* fragmentPath)
{
    // 从文件加载 shader 的源码
    // 1.0 从文件路径加载顶点 / 片段源代码
    std::string vertexCode, fragmentCode;
    std::ifstream vShaderFile, fShaderFile;

    // 确保 ifstream 对象可以引发异常
    vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
    fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);

    try
    {
        // 打开文件
        vShaderFile.open(vertexPath);
        fShaderFile.open(fragmentPath);

        std::stringstream vShaderStream, fShaderStream;
        // 将文件的缓冲区内容读入流
        vShaderStream << vShaderFile.rdbuf();
        fShaderStream << fShaderFile.rdbuf();

        // 关闭文件处理程序
        vShaderFile.close();
        fShaderFile.close();

        // 将流转换为字符串
        vertexCode = vShaderStream.str();
        fragmentCode = fShaderStream.str();

    }
    catch (const std::ifstream::failure e)
    {
        std::cout << "ERROR::SHADER::FILE_NOT_SUCCESSFULLY_READ" << std::endl;
    }
    const char* vShaderCode = vertexCode.c_str();
    const char* fShaderCode = fragmentCode.c_str();

    // 编译着色器

    unsigned int vertexShader, fragmentShader;
    int success;
    char infoLog[512];

    // 顶点着色器
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vShaderCode, nullptr);
    glCompileShader(vertexShader);
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);

    if (!success)	// 打印错误提示信息
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    //片元着色器
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fShaderCode, nullptr);
    glCompileShader(fragmentShader);
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }


    //着色器程序
    ID = glCreateProgram();
    glAttachShader(ID, vertexShader);
    glAttachShader(ID, fragmentShader);
    glLinkProgram(ID);
    glGetProgramiv(ID, GL_LINK_STATUS, &success);
    if (!success)
    {
        glGetProgramInfoLog(ID, 512, nullptr, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }

    //删除着色器
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

}

void MyShader::use()
{
    glUseProgram(ID);
}


void MyShader::setBool(const std::string& name, bool value) const
{
    glUniform1i(glGetUniformLocation(ID, name.c_str()), (int)value);
}

void MyShader::setInt(const std::string& name, int value) const
{
    glUniform1i(glGetUniformLocation(ID, name.c_str()), value);
}


void MyShader::setFloat(const std::string& name, float value) const
{
    glUniform1i(glGetUniformLocation(ID, name.c_str()), value);
}


void MyShader::setVec4(const std::string& name, const glm::vec4& value) const
{
    glUniform4fv(glGetUniformLocation(ID, name.c_str()), 1, &value[0]);
}



//响应键盘输入事件
//ESC推出窗口
void processInput(GLFWwindow* window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
    {
        glfwSetWindowShouldClose(window, true);
    }
}

//当用户改变窗口的大小的时候，视口也应该被调整。
//对窗口注册一个回调函数(Callback Function)，它会在每次窗口大小被调整的时候被调用
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    //glViewport函数前两个参数控制窗口左下角的位置。第三个和第四个参数控制渲染窗口的宽度和高度（像素）
    glViewport(0, 0, width, height);
}




int main()
{
    float vertices[] = {
        // 位置             // 颜色	         // 纹理坐标 
        0.5f,  0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,	// 右上
        0.5f, -0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f,	// 右下
       -0.5f, -0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f,	// 左下
       -0.5f,  0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0f	// 左上

    };

    unsigned int indices[] = {
            0, 1, 3,
            1, 2, 3,
    };


    /*******************************************定义常量************************************************/
    //设置窗口的宽和高
    const unsigned int SCR_WIDTH = 800;
    const unsigned int SCR_HEIGHT = 600;
    /*******************************************函数***************************************************/

     //初始化GLFW
    glfwInit();
    // 初始化GLFW
    if (!glfwInit())
    {
        std::cerr << "Failed to initialize GLFW" << std::endl;
        return -1;
    }

    //声明版本与核心
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); //主版本号
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6); //次版本号
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    //创建窗口并设置其大小，名称，与检测是否创建成功
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", nullptr, nullptr);
    if (window == nullptr)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }

    //创建完毕之后，需要让当前窗口的环境在当前线程上成为当前环境，就是接下来的画图都会画在我们刚刚创建的窗口上
    glfwMakeContextCurrent(window);
    //告诉GLFW我们希望每当窗口调整大小的时候调用这个函数
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);


    //glad寻找opengl的函数地址，调用opengl的函数前需要初始化glad
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    // 创建一个 shader 的类
    MyShader shader("shader/shader.vs", "shader/shader.fs");

    unsigned int VBO, VAO, EBO;
    glGenVertexArrays(1, &VAO);
    glBindVertexArray(VAO);         //绑定VAO对象

    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);



    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);


    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);


    // 绑定 EBO
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);


    //链接顶点属性，设置顶点属性指针

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    //以顶点属性位置值作为参数，启用顶点属性；顶点属性默认是禁用的。
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glBindVertexArray(0);


    // 读一张纹理图像

    int width, height, channels;
    unsigned char* data = stbi_load("lena.jpg", &width, &height, &channels, 0);

    if (data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
    {
        std::cout << "Failed to load texture" << std::endl;
    }
    stbi_image_free(data);



    //glfwWindowShouldClose()检查窗口是否需要关闭。如果是，游戏循环就结束了，接下来我们将会清理资源，结束程序
    while (!glfwWindowShouldClose(window))
    {
        //响应键盘输入
        processInput(window);

        //设置清除颜色
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        //清除当前窗口，把颜色设置为清除颜色
        glClear(GL_COLOR_BUFFER_BIT);

        shader.use();		// 选择流水线

        // 设置unifor 值
        float timeValue = glfwGetTime();
        float greenValue = sin(timeValue) / 2.0f + 0.5f;


        glm::vec4 color = glm::vec4(0.0f, greenValue, 0.0f, 1.0f);
        shader.setVec4("ourColor", color);


        //绑定VAO
        glBindVertexArray(VAO);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);


        //glDrawArrays(GL_TRIANGLES, 0, 3);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
        //线框绘制
        //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

        //交换颜色缓冲 
        glfwSwapBuffers(window);
        //处理事件
        glfwPollEvents();

    }

    //释放前面所申请的资源
    glfwTerminate();
     清理资源
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteBuffers(1, &EBO);
    glDeleteProgram(shader.ID);



 

    return 0;

}