// GLEW
#define GLEW_STATIC
#include <GL/glew.h>

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

// GL includes
#include "Shader.h"
#include "Camera.h"
#include "Model.h"

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

// Properties
GLuint screenWidth = 800, screenHeight = 600;

// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void Do_Movement();

// Camera
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
bool keys[1024];
GLfloat lastX = 400, lastY = 300;
bool firstMouse = true;

GLfloat deltaTime = 0.0f;
GLfloat lastFrame = 0.0f;

// The MAIN function, from here we start our application and run our Game loop
int main()
{
    // Init GLFW
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);

    GLFWwindow* window = glfwCreateWindow(screenWidth, screenHeight, "LearnOpenGL", nullptr, nullptr); // Windowed
    glfwMakeContextCurrent(window);

    // Set the required callback functions
    glfwSetKeyCallback(window, key_callback);
    glfwSetCursorPosCallback(window, mouse_callback);

    // Options
    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);	

    // Initialize GLEW to setup the OpenGL Function pointers
    glewExperimental = GL_TRUE;
    glewInit();

    // Define the viewport dimensions
    glViewport(0, 0, screenWidth, screenHeight);

    // Setup OpenGL options
    glEnable(GL_DEPTH_TEST);

    // Setup and compile our shaders
    Shader shader("shaders/geometry.vs", "shaders/geometry.frag");
    Shader normalShader("shaders/normals.vs", "shaders/normals.frag", "shaders/normals.gs");

    // Load models
    Model nanosuit("objects/nanosuit/nanosuit.obj");

    // Set projection matrix
    glm::mat4 projection = glm::perspective(45.0f, (GLfloat)screenWidth/(GLfloat)screenHeight, 1.0f, 100.0f);
    shader.Use();
    glUniformMatrix4fv(glGetUniformLocation(shader.Program, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
    // Also one for normal shader
    normalShader.Use();
    glUniformMatrix4fv(glGetUniformLocation(normalShader.Program, "projection"), 1, GL_FALSE, glm::value_ptr(projection));

    // Game loop
    while(!glfwWindowShouldClose(window))
    {
        // Set frame time
        GLfloat currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        // Check and call events
        glfwPollEvents();
        Do_Movement();

        // Clear buffers
        glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // Add transformation matrices
        shader.Use();
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "view"), 1, GL_FALSE, glm::value_ptr(camera.GetViewMatrix()));
        glm::mat4 model;
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));

        // Draw model
        nanosuit.Draw(shader);

        // Now set transformation matrices for drawing normals
        normalShader.Use();
        glUniformMatrix4fv(glGetUniformLocation(normalShader.Program, "view"), 1, GL_FALSE, glm::value_ptr(camera.GetViewMatrix()));
        model = glm::mat4();
        glUniformMatrix4fv(glGetUniformLocation(normalShader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));

        // And draw model again, this time only drawing normal vectors using the geometry shaders (on top of previous model)
        nanosuit.Draw(normalShader);
        
        // Swap the buffers
        glfwSwapBuffers(window);
    }

    glfwTerminate();
    return 0;
}

#pragma region "User input"

// Moves/alters the camera positions based on user input
void Do_Movement()
{
    // Camera controls
    if(keys[GLFW_KEY_W])
        camera.ProcessKeyboard(FORWARD, deltaTime);
    if(keys[GLFW_KEY_S])
        camera.ProcessKeyboard(BACKWARD, deltaTime);
    if(keys[GLFW_KEY_A])
        camera.ProcessKeyboard(LEFT, deltaTime);
    if(keys[GLFW_KEY_D])
        camera.ProcessKeyboard(RIGHT, deltaTime);
}

// Is called whenever a key is pressed/released via GLFW
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode)
{
    if(key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
        glfwSetWindowShouldClose(window, GL_TRUE);

    if(action == GLFW_PRESS)
        keys[key] = true;
    else if(action == GLFW_RELEASE)
        keys[key] = false;	
}

void mouse_callback(GLFWwindow* window, double xpos, double ypos)
{
    if(firstMouse)
    {
        lastX = xpos;
        lastY = ypos;
        firstMouse = false;
    }

    GLfloat xoffset = xpos - lastX;
    GLfloat yoffset = lastY - ypos; 
    
    lastX = xpos;
    lastY = ypos;

    camera.ProcessMouseMovement(xoffset, yoffset);
}	

#pragma endregion