#include <iostream>
#include <cstdlib>
#include <cmath>

#include <OpenGL/gl.h>
#include <GLUT/GLUT.h>

#define CX_HEIGHT 5
#define CX_WIDTH 5 // tamanho da caixa de clique

using namespace std;

const int WINDOW_W = 500;
const int WINDOW_H = 500;

void display(); // funcao de impressao na tela
void handleKeypress(unsigned char key, int x, int y);
void handleMouseClick(int button, int state, int x, int y);
void reshape(int w, int h);
void drag(int x, int y);

// funcoes auxiliares

unsigned long long factorial(int n);
unsigned long long comb(int n, int p);
bool are_same(double a, double b);

int vertices = 0;
int a_vertices[30][3] = {0}; // array que ira conter os vertices

int indice = -1; // indice do vetor de vertices [caso vertice seja encontrado]

int main(int argc, char ** argv)
{
    //Inicalizate GLUT and OPENGL
    glutInit(&argc, argv);
    glutInitWindowPosition(0, 0);
    glutInitWindowSize(WINDOW_W, WINDOW_H);
    glutInitDisplayMode(GLUT_RGBA | GLUT_SINGLE | GLUT_DEPTH);

    // Create Window
    glutCreateWindow("Curva de Bezier");

    glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

    //Setup GLUT callback Functions
    glutDisplayFunc(display);
    glutKeyboardFunc(handleKeypress);
    glutMouseFunc(handleMouseClick);
    glutMotionFunc(drag);
    glutReshapeFunc(reshape);

    //Enter main loop
    glutMainLoop();

    return 0;
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

//    glMap1f(GL_MAP1_VERTEX_3, 0.0f, 1.0f, 3, vertices, &a_vertices[0][0]);
//    glEnable(GL_MAP1_VERTEX_3);
//
//    glBegin(GL_LINE_STRIP);
//        glColor3f(1.0f, 1.0f, 1.0f);
//        for (int i = 0; i <= 30; i++)
//        {
//            glEvalCoord1f((GLfloat) i/30);
//        }
//    glEnd();

    glBegin(GL_LINE_STRIP);
        glColor3f(1.0f, 1.0f, 1.0f);

        double x, y;

        if (vertices > 1)
        {
            double t = 0.0;

            for (t = 0; t <= 1.0; t += 0.01)
            {
                x = y = 0.0;

                for (int i = 0; i < vertices; i++)
                {
                    x += comb(vertices-1, i) * pow((1 - t), vertices-1-i) * pow(t, i) * a_vertices[i][0];
                    y += comb(vertices-1, i) * pow((1 - t), vertices-1-i) * pow(t, i) * a_vertices[i][1];
                }

                glVertex3d(x, y, 0);
                //cout << "Ponto2 (" << x << ", " << y << ")" << endl;
                //cout << "t: " << t << endl;
            }

            glVertex3d(a_vertices[vertices - 1][0], a_vertices[vertices - 1][1], 0);
        }
        else
        {
            x = (double)a_vertices[0][1];
            y = (double)a_vertices[0][1];

            glVertex3d(x, y, 0);
        }

    glEnd();

    // imprime os pontos de controle

    glPointSize(5.0f);
    glBegin(GL_POINTS);
        glColor3f(1.0f, 1.0f, 0.0f);
        for (int i = 0; i < vertices; i++)
        {
            glVertex3d(a_vertices[i][0], a_vertices[i][1], 0);
        }
    glEnd();

    // imprime retas base
    glBegin(GL_LINE_STRIP);
    glColor3f(1.0f, 1.0f, 1.0f);
    for (int i = 0; i < vertices; i++)
    {
        glVertex3d(a_vertices[i][0], a_vertices[i][1], 0);
    }
    glEnd();

    glFlush();
}

void reshape(int w, int h)
{
    glViewport(0, 0, (GLsizei) w, (GLsizei) h);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0f, WINDOW_W, WINDOW_H, 0.0f, -5.0, 5.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void handleKeypress(unsigned char key, int x, int y)
{
	switch (key)
    {
		case 27:
			exit(0); // fecha o programa quando aperta ESC
	}
}

void handleMouseClick(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON)
    {
        bool achou = false;

        if (state == GLUT_DOWN)
        {
            for (int i = 0; i < vertices; i++)
            {
                if ((a_vertices[i][0] <= x + CX_WIDTH && a_vertices[i][0] >= x - CX_WIDTH) &&
                    ((a_vertices[i][1] <= y + CX_HEIGHT) && a_vertices[i][1] >= y - CX_HEIGHT))
                {
                    achou = true;
                    indice = i;
                }
            }

            if (!achou)
            {
                // coloca ponto na tela
                a_vertices[vertices][0] = (float)x;
                a_vertices[vertices][1] = (float)y;
                a_vertices[vertices][2] = 0;

                vertices++;

                glutPostRedisplay();  // avisa que a janela atual deve ser reimpressa
            }
        }
    }
}

void drag(int x, int y)
{
    a_vertices[indice][0] = x;
    a_vertices[indice][1] = y;

    glutPostRedisplay();
}

// funcoes auxiliares

bool are_same(double a, double b)
{
    return (fabs(a - b) < 0.00001);
}

unsigned long long factorial(int n)
{
    long long fat;

    if (n <= 1)
    {
        fat = 1;
    }
    else
    {
        fat = n;

        while (n > 1)
        {
            fat *= (n - 1);
            n--;
        }
    }

    return fat;
}

unsigned long long comb(int n, int p)
{
    unsigned long long ret = factorial(n)/(factorial(p) * factorial(n - p));

    return ret;
}