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

#include <iostream>

static void framebuffer_size_callback(GLFWwindow* window, int width, int height);
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods);
static void mouse_button_callback(GLFWwindow* window, int button, int action, int mods);

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

float r = 0.0, g = 0.0, b = 0.0;

int main() {
    
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    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", nullptr, nullptr);
    if (window == nullptr) {
        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;
    }
    
    glfwSetKeyCallback(window, key_callback);
    glfwSetMouseButtonCallback(window, mouse_button_callback);
    
    // render loop
    // -----------
    while (!glfwWindowShouldClose(window)) {   
        // render
        // ------
        glClearColor(r, g, b, 1.0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        
        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    
    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}

static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
    
    if(glfwGetKey(window, GLFW_KEY_R) == GLFW_PRESS) {
        if(r < 1.0 )
            r += 0.1;
        else
            r = 0.0;
    }
    if(glfwGetKey(window, GLFW_KEY_G) == GLFW_PRESS) {
        if(g < 1.0 )
            g += 0.1;
        else
            g = 0.0;
    }
    if(glfwGetKey(window, GLFW_KEY_B) == GLFW_PRESS) {
        if(b < 1.0 )
            b += 0.1;
        else
            b = 0.0;
    }
}

static void mouse_button_callback(GLFWwindow* window, int button, int action, int mods) {
    if(button == GLFW_MOUSE_BUTTON_LEFT && action == GLFW_PRESS) {
        double xpos, ypos;
        //getting cursor position
        glfwGetCursorPos(window, &xpos, &ypos);
        std::cout << "Cursor Position at (" << xpos << " : " << ypos << "\n";
    }
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
static 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);
}