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

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include <learnopengl/shader.h>
#include <learnopengl/camera.h>
#include <learnopengl/model.h>

#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
void processInput(GLFWwindow *window);

// settings
const unsigned int SCR_WIDTH = 1280;
const unsigned int SCR_HEIGHT = 720;

// camera
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = (float)SCR_WIDTH / 2.0;
float lastY = (float)SCR_HEIGHT / 2.0;
bool firstMouse = true;

// timing
float deltaTime = 0.0f;
float lastFrame = 0.0f;

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); // uncomment this statement to fix compilation on OS X
#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);
    glfwSetCursorPosCallback(window, mouse_callback);
    glfwSetScrollCallback(window, scroll_callback);

    // tell GLFW to capture our mouse
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

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

    // configure global opengl state
    // -----------------------------
    glEnable(GL_DEPTH_TEST);

    // build and compile shaders
    // -------------------------
    Shader shader("11.anti_aliasing.vs", "11.anti_aliasing.fs");
    Shader screenShader("11.aa_post.vs", "11.aa_post.fs");

    // set up vertex data (and buffer(s)) and configure vertex attributes
    // ------------------------------------------------------------------
    float cubeVertices[] = {
        // positions       
        -0.5f, -0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f,  0.5f, -0.5f,
         0.5f,  0.5f, -0.5f,
        -0.5f,  0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,

        -0.5f, -0.5f,  0.5f,
         0.5f, -0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f,  0.5f,
        -0.5f, -0.5f,  0.5f,

        -0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,
        -0.5f, -0.5f, -0.5f,
        -0.5f, -0.5f,  0.5f,
        -0.5f,  0.5f,  0.5f,

         0.5f,  0.5f,  0.5f,
         0.5f,  0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f, -0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,

        -0.5f, -0.5f, -0.5f,
         0.5f, -0.5f, -0.5f,
         0.5f, -0.5f,  0.5f,
         0.5f, -0.5f,  0.5f,
        -0.5f, -0.5f,  0.5f,
        -0.5f, -0.5f, -0.5f,

        -0.5f,  0.5f, -0.5f,
         0.5f,  0.5f, -0.5f,
         0.5f,  0.5f,  0.5f,
         0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f,  0.5f,
        -0.5f,  0.5f, -0.5f
    };
    float quadVertices[] = {   // vertex attributes for a quad that fills the entire screen in Normalized Device Coordinates.
        // positions   // texCoords
        -1.0f,  1.0f,  0.0f, 1.0f,
        -1.0f, -1.0f,  0.0f, 0.0f,
         1.0f, -1.0f,  1.0f, 0.0f,

        -1.0f,  1.0f,  0.0f, 1.0f,
         1.0f, -1.0f,  1.0f, 0.0f,
         1.0f,  1.0f,  1.0f, 1.0f
    };
    // setup cube VAO
    unsigned int cubeVAO, cubeVBO;
    glGenVertexArrays(1, &cubeVAO);
    glGenBuffers(1, &cubeVBO);
    glBindVertexArray(cubeVAO);
    glBindBuffer(GL_ARRAY_BUFFER, cubeVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(cubeVertices), &cubeVertices, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    // setup screen VAO
    unsigned int quadVAO, quadVBO;
    glGenVertexArrays(1, &quadVAO);
    glGenBuffers(1, &quadVBO);
    glBindVertexArray(quadVAO);
    glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), &quadVertices, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(float), (void*)(2 * sizeof(float)));


    // configure MSAA framebuffer
    // --------------------------
    unsigned int framebuffer;
    glGenFramebuffers(1, &framebuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
    // create a multisampled color attachment texture
    unsigned int textureColorBufferMultiSampled;
    glGenTextures(1, &textureColorBufferMultiSampled);
    glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, textureColorBufferMultiSampled);
    glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, 4, GL_RGB, SCR_WIDTH, SCR_HEIGHT, GL_TRUE);
    glBindTexture(GL_TEXTURE_2D_MULTISAMPLE, 0);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D_MULTISAMPLE, textureColorBufferMultiSampled, 0);
    // create a (also multisampled) renderbuffer object for depth and stencil attachments
    unsigned int rbo;
    glGenRenderbuffers(1, &rbo);
    glBindRenderbuffer(GL_RENDERBUFFER, rbo);
    glRenderbufferStorageMultisample(GL_RENDERBUFFER, 4, GL_DEPTH24_STENCIL8, SCR_WIDTH, SCR_HEIGHT);
    glBindRenderbuffer(GL_RENDERBUFFER, 0);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, rbo);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
        cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete!" << endl;
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    // configure second post-processing framebuffer
    unsigned int intermediateFBO;
    glGenFramebuffers(1, &intermediateFBO);
    glBindFramebuffer(GL_FRAMEBUFFER, intermediateFBO);
    // create a color attachment texture
    unsigned int screenTexture;
    glGenTextures(1, &screenTexture);
    glBindTexture(GL_TEXTURE_2D, screenTexture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, SCR_WIDTH, SCR_HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, screenTexture, 0);	// we only need a color buffer

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
        cout << "ERROR::FRAMEBUFFER:: Intermediate framebuffer is not complete!" << endl;
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    // shader configuration
    // --------------------
    shader.use();
    screenShader.setInt("screenTexture", 0);

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // per-frame time logic
        // --------------------
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        // input
        // -----
        processInput(window);

        // render
        // ------
        glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // 1. draw scene as normal in multisampled buffers
        glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
        glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glEnable(GL_DEPTH_TEST);

        // set transformation matrices		
        shader.use();
        glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 1000.0f);
        shader.setMat4("projection", projection);
        shader.setMat4("view", camera.GetViewMatrix());
        shader.setMat4("model", glm::mat4(1.0f));

        glBindVertexArray(cubeVAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);

        // 2. now blit multisampled buffer(s) to normal colorbuffer of intermediate FBO. Image is stored in screenTexture
        glBindFramebuffer(GL_READ_FRAMEBUFFER, framebuffer);
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, intermediateFBO);
        glBlitFramebuffer(0, 0, SCR_WIDTH, SCR_HEIGHT, 0, 0, SCR_WIDTH, SCR_HEIGHT, GL_COLOR_BUFFER_BIT, GL_NEAREST);

        // 3. now render quad with scene's visuals as its texture image
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);
        glDisable(GL_DEPTH_TEST);

        // draw Screen quad
        screenShader.use();
        glBindVertexArray(quadVAO);
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, screenTexture); // use the now resolved color attachment as the quad's texture
        glDrawArrays(GL_TRIANGLES, 0, 6);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    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);

    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
        camera.ProcessKeyboard(FORWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
        camera.ProcessKeyboard(BACKWARD, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
        camera.ProcessKeyboard(LEFT, deltaTime);
    if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
        camera.ProcessKeyboard(RIGHT, deltaTime);
}

// 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);
}

// glfw: whenever the mouse moves, this callback is called
// -------------------------------------------------------
void mouse_callback(GLFWwindow* window, double xpos, double ypos)
{
    if (firstMouse)
    {
        lastX = xpos;
        lastY = ypos;
        firstMouse = false;
    }

    float xoffset = xpos - lastX;
    float yoffset = lastY - ypos; // reversed since y-coordinates go from bottom to top

    lastX = xpos;
    lastY = ypos;

    camera.ProcessMouseMovement(xoffset, yoffset);
}

// glfw: whenever the mouse scroll wheel scrolls, this callback is called
// ----------------------------------------------------------------------
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
    camera.ProcessMouseScroll(yoffset);
}
HI