#include <GL/glew.h>
#include <SFML/Graphics.hpp>
#include <iostream>
#include <ctime>
#include <cmath>
#include <string>

using namespace std;

#include "ShaderUtil.h"

/**
 * In this sample we switch to using the basics of the programmable pipeline of opengl without using VBO's yet.
 * We'll show those in the next sample.
 */

const GLfloat vertices[] = {
    0.75f ,  -0.75f, 0, 1, // bottom-right
    0.75f ,  0.75f , 0, 1, // top-right
    -0.75f,  -0.75f, 0, 1, // bottom-left
    -0.75f,   0.75f, 0, 1  // top-left
};

const GLfloat colors[] = {
    1,0,0,1,
    0,1,0,1,
    0,0,1,1,
    1,1,0,0
};

const GLubyte indices[] = {
    0,1,2,
    1,2,3
};


int main () {
    // create a window
    sf::Window window(sf::VideoMode (800, 600), "Wawsom!");
    // make it ready for opengl.
    window.setVerticalSyncEnabled( true );

    cout << "Initializing GlEW..." << endl;
    // bind the created opengl context that was created by sfml.
    bool glewInitResult = (glewInit() == GLEW_OK);
    cout << "GlEW Initialized:" << glewInitResult  << endl;

    GLuint programID = ShaderUtil::createProgam("vertexshader.vs", "fragmentshader.fs");
    glUseProgram (programID);

    // make a buffer
    GLuint vertexBufferId;
    glGenBuffers (1, &vertexBufferId);
    // bind it so we can interact with it.
    glBindBuffer (GL_ARRAY_BUFFER, vertexBufferId);
    // fill in the data.
    glBufferData (GL_ARRAY_BUFFER, sizeof (vertices), vertices, GL_STATIC_DRAW);
    // unbind.
    glBindBuffer (GL_ARRAY_BUFFER, 0);

    // make a buffer
    GLuint colorBufferId;
    glGenBuffers (1, &colorBufferId);
    // bind it so we can interact with it.
    glBindBuffer (GL_ARRAY_BUFFER, colorBufferId);
    // fill in the data.
    glBufferData (GL_ARRAY_BUFFER, sizeof (colors), colors, GL_STATIC_DRAW);
    // unbind.
    glBindBuffer (GL_ARRAY_BUFFER, 0);

    // black is clear.
    glClearColor(0,0,0,1);

    // get pointers for uniforms.
    GLint vertexIndex = glGetAttribLocation(programID, "vertex");
    GLint colorIndex = glGetAttribLocation(programID, "color");
    GLint offsetIndex = glGetUniformLocation(programID, "offset");
    GLint mouseIndex = glGetUniformLocation(programID, "mouse");

    // set the default mouse position to left bottom.
    GLfloat mouse[] = {0, 0};
    glUniform2fv (mouseIndex, 1, mouse);

    while (window.isOpen()) {
        // clear the screen.
        glClear( GL_COLOR_BUFFER_BIT );

        // set offset on a circle with radius of 0.25.
        GLfloat offset[] = {0.25f * cos (clock()/500.0f), 0.25f * sin (clock()/500.0f)};
        // send it to shader.
        glUniform2fv (offsetIndex, 1, offset);

        // update the mouse position.
        sf::Vector2i pos = sf::Mouse::getPosition(window);
        mouse[0] = pos.x;
        mouse[1] = window.getSize().y - pos.y;
        // set it only if we are within window bounds.
        if (mouse[0] > -1 && mouse[0] < window.getSize().x && mouse[1] > -1 && mouse[1] < window.getSize().y) {
            cout << "{" + to_string(mouse[0]) + ", " + to_string(mouse[1]) + "}" << endl;
            glUniform2fv(mouseIndex, 1, mouse);
        }

        // enable vertex array as they are disabled by default.
        glEnableVertexAttribArray(vertexIndex);
        // bind it so we can interact with it.
        glBindBuffer (GL_ARRAY_BUFFER, vertexBufferId);
        // tell opengl how to read it.
        // (
        //  memory index,
        //  number of values in each read,
        //  fixed point values so no normalization needed,
        //  data offset,
        //  null
        //  )
        glVertexAttribPointer(vertexIndex, 4, GL_FLOAT, GL_FALSE, 0, (void*)0);

        glEnableVertexAttribArray(colorIndex);
        glBindBuffer (GL_ARRAY_BUFFER, colorBufferId);
        glVertexAttribPointer(colorIndex, 4, GL_FLOAT, GL_FALSE, 0, (void*)0);

        // feed indices
        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, indices);

        // disable arrays as we are done.
        glDisableVertexAttribArray(vertexIndex);
        glDisableVertexAttribArray(colorIndex);

        // draw.
        window.display();

        // check for events to exit from loop or set the size of viewport.
        sf::Event event;
        while (window.pollEvent(event)) {
            if (event.type == sf::Event::Closed) window.close();
            if (event.type == sf::Event::Resized) glViewport(0, 0, event.size.width, event.size.height);
        }
    }

    return 0;
}