// Std. Includes
#include <string>
#include <map>

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

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

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

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

// Other Libs
#include <SOIL.h>

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

// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void Do_Movement();
GLuint loadTexture(GLchar* path, GLboolean alpha = false);

// 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);
    glfwSetScrollCallback(window, scroll_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 some OpenGL options
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    // Setup and compile our shaders
    Shader shader("Path/To/Shaders/shader.vs", "Path/To/Shaders/shader.frag");

#pragma region "object_initialization"
    // Set the object data (buffers, vertex attributes)
    GLfloat cubeVertices[] = {
        // Positions          // Texture Coords
        -0.5f, -0.5f, -0.5f,  0.0f,  0.0f,
         0.5f, -0.5f, -0.5f,  1.0f,  0.0f,
         0.5f,  0.5f, -0.5f,  1.0f,  1.0f,
         0.5f,  0.5f, -0.5f,  1.0f,  1.0f,
        -0.5f,  0.5f, -0.5f,  0.0f,  1.0f,
        -0.5f, -0.5f, -0.5f,  0.0f,  0.0f,

        -0.5f, -0.5f,  0.5f,  0.0f,  0.0f,
         0.5f, -0.5f,  0.5f,  1.0f,  0.0f,
         0.5f,  0.5f,  0.5f,  1.0f,  1.0f,
         0.5f,  0.5f,  0.5f,  1.0f,  1.0f,
        -0.5f,  0.5f,  0.5f,  0.0f,  1.0f,
        -0.5f, -0.5f,  0.5f,  0.0f,  0.0f,

        -0.5f,  0.5f,  0.5f,  1.0f,  0.0f,
        -0.5f,  0.5f, -0.5f,  1.0f,  1.0f,
        -0.5f, -0.5f, -0.5f,  0.0f,  1.0f,
        -0.5f, -0.5f, -0.5f,  0.0f,  1.0f,
        -0.5f, -0.5f,  0.5f,  0.0f,  0.0f,
        -0.5f,  0.5f,  0.5f,  1.0f,  0.0f,

         0.5f,  0.5f,  0.5f,  1.0f,  0.0f,
         0.5f,  0.5f, -0.5f,  1.0f,  1.0f,
         0.5f, -0.5f, -0.5f,  0.0f,  1.0f,
         0.5f, -0.5f, -0.5f,  0.0f,  1.0f,
         0.5f, -0.5f,  0.5f,  0.0f,  0.0f,
         0.5f,  0.5f,  0.5f,  1.0f,  0.0f,

        -0.5f, -0.5f, -0.5f,  0.0f,  1.0f,
         0.5f, -0.5f, -0.5f,  1.0f,  1.0f,
         0.5f, -0.5f,  0.5f,  1.0f,  0.0f,
         0.5f, -0.5f,  0.5f,  1.0f,  0.0f,
        -0.5f, -0.5f,  0.5f,  0.0f,  0.0f,
        -0.5f, -0.5f, -0.5f,  0.0f,  1.0f,

        -0.5f,  0.5f, -0.5f,  0.0f,  1.0f,
         0.5f,  0.5f, -0.5f,  1.0f,  1.0f,
         0.5f,  0.5f,  0.5f,  1.0f,  0.0f,
         0.5f,  0.5f,  0.5f,  1.0f,  0.0f,
        -0.5f,  0.5f,  0.5f,  0.0f,  0.0f,
        -0.5f,  0.5f, -0.5f,  0.0f,  1.0f
    };
    GLfloat planeVertices[] = {
        // Positions          // Texture Coords (note we set these higher than 1 that together with GL_REPEAT as texture wrapping mode will cause the floor texture to repeat)
         5.0f, -0.5f,  5.0f,  2.0f,  0.0f,
        -5.0f, -0.5f,  5.0f,  0.0f,  0.0f,
        -5.0f, -0.5f, -5.0f,  0.0f,  2.0f,

         5.0f, -0.5f,  5.0f,  2.0f,  0.0f,
        -5.0f, -0.5f, -5.0f,  0.0f,  2.0f,
         5.0f, -0.5f, -5.0f,  2.0f,  2.0f
    };
    GLfloat transparentVertices[] = {
        // Positions         // Texture Coords (swapped y coordinates because texture is flipped upside down)
        0.0f,  0.5f,  0.0f,  0.0f,  0.0f,
        0.0f, -0.5f,  0.0f,  0.0f,  1.0f,
        1.0f, -0.5f,  0.0f,  1.0f,  1.0f,

        0.0f,  0.5f,  0.0f,  0.0f,  0.0f,
        1.0f, -0.5f,  0.0f,  1.0f,  1.0f,
        1.0f,  0.5f,  0.0f,  1.0f,  0.0f
    };
    // Setup cube VAO
    GLuint 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, 5 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
    glBindVertexArray(0);
    // Setup plane VAO
    GLuint planeVAO, planeVBO;
    glGenVertexArrays(1, &planeVAO);
    glGenBuffers(1, &planeVBO);
    glBindVertexArray(planeVAO);
    glBindBuffer(GL_ARRAY_BUFFER, planeVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(planeVertices), &planeVertices, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
    glBindVertexArray(0);
    // Setup transparent plane VAO
    GLuint transparentVAO, transparentVBO;
    glGenVertexArrays(1, &transparentVAO);
    glGenBuffers(1, &transparentVBO);
    glBindVertexArray(transparentVAO);
    glBindBuffer(GL_ARRAY_BUFFER, transparentVBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(transparentVertices), transparentVertices, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
    glBindVertexArray(0);

    // Load textures
    GLuint cubeTexture = loadTexture("black_tiles.jpg");
    GLuint floorTexture = loadTexture("metal.png");
    GLuint transparentTexture = loadTexture("window.png", true);
#pragma endregion

    std::vector<glm::vec3> windows;
    windows.push_back(glm::vec3(-1.5f,  0.0f, -0.48f));
    windows.push_back(glm::vec3( 1.5f,  0.0f,  0.51f));
    windows.push_back(glm::vec3( 0.0f,  0.0f,  0.7f));
    windows.push_back(glm::vec3(-0.3f,  0.0f, -2.3f));
    windows.push_back(glm::vec3( 0.5f,  0.0f, -0.6f));

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

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

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

        // Sort windows
        std::map<GLfloat, glm::vec3> sorted;
        for (GLuint i = 0; i < windows.size(); i++)
        {
            GLfloat distance = glm::length(camera.Position - windows[i]);
            sorted[distance] = windows[i];
        }

        // Draw objects
        shader.Use();
        glm::mat4 model;
        glm::mat4 view = camera.GetViewMatrix();
        glm::mat4 projection = glm::perspective(camera.Zoom, (float)screenWidth / (float)screenHeight, 0.1f, 100.0f);
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "view"), 1, GL_FALSE, glm::value_ptr(view));
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
        // Cubes
        glBindVertexArray(cubeVAO);
        glBindTexture(GL_TEXTURE_2D, cubeTexture);  // We omit the glActiveTexture part since TEXTURE0 is already the default active texture unit. (a single sampler used in fragment is set to 0 as well by default)		
        model = glm::translate(model, glm::vec3(-1.0f, 0.0f, -1.0f));
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));
        glDrawArrays(GL_TRIANGLES, 0, 36);
        model = glm::mat4();
        model = glm::translate(model, glm::vec3(2.0f, 0.0f, 0.0f));
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));
        glDrawArrays(GL_TRIANGLES, 0, 36);
        // Floor
        glBindVertexArray(planeVAO);
        glBindTexture(GL_TEXTURE_2D, floorTexture);
        model = glm::mat4();
        glUniformMatrix4fv(glGetUniformLocation(shader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));
        glDrawArrays(GL_TRIANGLES, 0, 6);
        // Render windows (from furthest to nearest)
        glBindVertexArray(transparentVAO);
        glBindTexture(GL_TEXTURE_2D, transparentTexture);
        for (std::map<float, glm::vec3>::reverse_iterator it = sorted.rbegin(); it != sorted.rend(); ++it)
        {
            model = glm::mat4();
            model = glm::translate(model, it->second);
            glUniformMatrix4fv(glGetUniformLocation(shader.Program, "model"), 1, GL_FALSE, glm::value_ptr(model));
            glDrawArrays(GL_TRIANGLES, 0, 6);
        }
        glBindVertexArray(0);


        // Swap the buffers
        glfwSwapBuffers(window);
    }

    glfwTerminate();
    return 0;
}

// This function loads a texture from file. Note: texture loading functions like these are usually 
// managed by a 'Resource Manager' that manages all resources (like textures, models, audio). 
// For learning purposes we'll just define it as a utility function.
GLuint loadTexture(GLchar* path, GLboolean alpha)
{
    //Generate texture ID and load texture data 
    GLuint textureID;
    glGenTextures(1, &textureID);
    int width,height;
    unsigned char* image = SOIL_load_image(path, &width, &height, 0, alpha ? SOIL_LOAD_RGBA : SOIL_LOAD_RGB);
    // Assign texture to ID
    glBindTexture(GL_TEXTURE_2D, textureID);
    glTexImage2D(GL_TEXTURE_2D, 0, alpha ? GL_RGBA : GL_RGB, width, height, 0, alpha ? GL_RGBA : GL_RGB, GL_UNSIGNED_BYTE, image);
    glGenerateMipmap(GL_TEXTURE_2D);	

    // Parameters
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, alpha ? GL_CLAMP_TO_EDGE : GL_REPEAT );	// Use GL_CLAMP_TO_EDGE to prevent semi-transparent borders. Due to interpolation it takes value from next repeat 
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, alpha ? GL_CLAMP_TO_EDGE : GL_REPEAT );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);
    SOIL_free_image_data(image);
    return textureID;

}

#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 (key >= 0 && key < 1024)
    {
        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);
}

void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
    camera.ProcessMouseScroll(yoffset);
}

#pragma endregion