#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);

// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

const char *vertexShaderSource = "#version 330 core\n"
    "layout (location = 0) in vec3 aPos;\n"
    "void main()\n"
    "{\n"
    "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
    "}\0";
const char *fragmentShaderSource = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "void main()\n"
    "{\n"
    "   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
    "}\n\0";

int main()
{
    // glfw: initialize and configure
    // ------------------------------
   
     glfwInit(
    );
   
     glfwWindowHint(
    GLFW_CONTEXT_VERSION_MAJOR, 3);
   
     glfwWindowHint(
    GLFW_CONTEXT_VERSION_MINOR, 3);
   
     glfwWindowHint(
    GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
   
     glfwWindowHint(
    GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

    // glfw window creation
    // --------------------
    GLFWwindow* window =
     glfwCreateWindow(
    SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
       
     glfwTerminate(
    );
        return -1;
    }
   
     glfwMakeContextCurrent(
    window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // glad: load all OpenGL function pointers
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }


    // build and compile our shader program
    // ------------------------------------
    // vertex shader
    unsigned int vertexShader =
     glCreateShader(
    GL_VERTEX_SHADER);
   
     glShaderSource(
    vertexShader, 1, &vertexShaderSource, NULL);
   
     glCompileShader(
    vertexShader);
    // check for shader compile errors
    int success;
    char infoLog[512];
   
     glGetShaderiv(
    vertexShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
       
     glGetShaderInfoLog(
    vertexShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    // fragment shader
    unsigned int fragmentShader =
     glCreateShader(
    GL_FRAGMENT_SHADER);
   
     glShaderSource(
    fragmentShader, 1, &fragmentShaderSource, NULL);
   
     glCompileShader(
    fragmentShader);
    // check for shader compile errors
   
     glGetShaderiv(
    fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
       
     glGetShaderInfoLog(
    fragmentShader, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }
    // link shaders
    unsigned int shaderProgram =
     glCreateProgram(
    );
   
     glAttachShader(
    shaderProgram, vertexShader);
   
     glAttachShader(
    shaderProgram, fragmentShader);
   
     glLinkProgram(
    shaderProgram);
    // check for linking errors
   
     glGetProgramiv(
    shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
    }
   
     glDeleteShader(
    vertexShader);
   
     glDeleteShader(
    fragmentShader);

    // set up vertex data (and buffer(s)) and configure vertex attributes
    // ------------------------------------------------------------------
    float vertices[] = {
        -0.5f, -0.5f, 0.0f, // left  
         0.5f, -0.5f, 0.0f, // right 
         0.0f,  0.5f, 0.0f  // top   
    }; 

    unsigned int VBO, VAO;
   
     glGenVertexArrays(
    1, &VAO);
   
     glGenBuffers(
    1, &VBO);
    // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
   
     glBindVertexArray(
    VAO);

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

   
     glVertexAttribPointer(
    0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
   
    
      glEnableV
     ertexAttribArray(
    0);

    // note that this is allowed, the call to
     glVertexAttribPointer 
    registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
   
     glBindBuffer(
    GL_ARRAY_BUFFER, 0); 

    // You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
    // VAOs requires a call to
     glBindVertexArray 
    anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
   
     glBindVertexArray(
    0); 


    // uncomment this call to draw in wireframe polygons.
    /
    /glPolygonMode(
    GL_FRONT_AND_BACK, GL_LINE);

    // render loop
    // -----------
    while (
    !glfwWindowShouldClose(
    window))
    {
        // input
        // -----
        processInput(window);

        // render
        // ------
       
    
      glClearC
     olor(
    0.2f, 0.3f, 0.3f, 1.0f);
       
     glClear(
    GL_COLOR_BUFFER_BIT);

        // draw our first triangle
       
     glUseProgram(
    shaderProgram);
       
     glBindVertexArray(
    VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized
       
     glDrawArrays(
    GL_TRIANGLES, 0, 3);
        //
     glBindVertexArray(
    0); // no need to unbind it every time 
 
        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
       
     glfwSwapBuffers(
    window);
       
     glfwPollEvents(
    );
    }

    // optional: de-allocate all resources once they've outlived their purpose:
    // ------------------------------------------------------------------------
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);
    glDeleteProgram(shaderProgram);

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
   
     glfwTerminate(
    );
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and 
    // height will be significantly larger than specified on retina displays.
   
     glViewport(
    0, 0, width, height);
}