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

#include <iostream>

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

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()
{
    const unsigned int SCR_WIDTH = 800;
    const unsigned int SCR_HEIGHT = 600;

    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 5);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

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

    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);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);
    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;
    }
    unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    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;
    }
    unsigned int shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    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);

    float vertices[] = {
         0.5f,  0.5f, 0.0f,
         0.5f, -0.5f, 0.0f,
        -0.5f, -0.5f, 0.0f,
        -0.5f,  0.5f, 0.0f
    };
    // Here we create the VBO with DSA.
    GLuint vbo = 0;
    // Note how we do not have to call glBindBuffer() after the create call.
    glCreateBuffers(1, &vbo);
    glNamedBufferStorage(vbo, sizeof(vertices), vertices, 0x0);

    unsigned int indices[] = {
        0, 1, 3,
        1, 2, 3
    };
    // Here we create the EBO with DSA while also specifying that the buffer is mutable from the client side.
    GLuint ebo = 0;
    glCreateBuffers(1, &ebo);
    glNamedBufferStorage(ebo, sizeof(indices), nullptr, GL_DYNAMIC_STORAGE_BIT);
    glNamedBufferSubData(ebo, 0, sizeof(indices), indices);

    // Here we create the VAO with DSA and specify its format.
    GLuint vao = 0;
    glCreateVertexArrays(1, &vao);

    // Specifying our vertex layout with the VAO.
    glEnableVertexArrayAttrib(vao, 0);
    glVertexArrayAttribFormat(vao, 0, 3, GL_FLOAT, GL_FALSE, 0);
    glVertexArrayAttribBinding(vao, 0, 0);

    // Binding the VBO and Element Buffer to the VAO.
    glVertexArrayVertexBuffer(vao, 0, vbo, 0, sizeof(float) * 3);
    glVertexArrayElementBuffer(vao, ebo);

    while (!glfwWindowShouldClose(window))
    {
        processInput(window);
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glUseProgram(shaderProgram);
        glBindVertexArray(vao);
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glDeleteVertexArrays(1, &vao);
    glDeleteBuffers(1, &vbo);
    glDeleteBuffers(1, &ebo);
    glDeleteProgram(shaderProgram);
    glfwTerminate();
    return 0;
}

void processInput(GLFWwindow* window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}