// sunt mentionate fisiere (biblioteci) care urmeaza sa fie incluse
#include <GL/freeglut.h> // nu trebuie uitat freeglut.h (sau glut.h sau gl.h & glu.h)
#include <iostream>
#include <conio.h>

using namespace std;

struct vect
{
	float x, y, z;
};


int nr_pct;
vect coord[100];

GLint winWidth = 1024, winHeight = 768;

vect vectpro(vect u, vect, v) {

	vect p;
	p.x = v.x - u.x;
	p.y = v.y - u.y;
	p.z = v.z - u.z;

	return p;
}


vect Produs(vect p1, vect p2, vect p3) {

	vect vector12 = vectpro(p1, p2);
	vect vector23 = vectpro(p2, p3);
	vect rezultat_produs;

	rezultat_produs.x = vector12.y * vector23.z - vector12.z * vector23.y;
	rezultat_produs.y = vector12.x * vector23.z - vector12.z * vector23.x;
	rezultat_produs.z = vector12.x * vector23.y - vector12.y * vector23.x;

	return rezultat_produs;
}


void afisare(vect vector1) {
	cout << vector1.x << "*i + " << vector1.y << "*j + " << vector1.z << "*k" << endl;
}

bool CheckAngle(vect point1, vect point2, vect point3, int i) {

	vect produs_vectori = Produs(point1, point2, point3);
	double f.produs_vectori = produs_vectori.x + produs_vectori.y + produs_vectori.z;

	if (produs_vectori.x < 0 || produs_vectori.y < 0 || produs_vectori.z < 0) {
		cout << "Punct: I = " << coord[i + 1].x << " / J = " << coord[i + 1].y << " / K = " << coord[i + 1].z << endl;
		return true;
	}
	else {
		cout << "Punct: I = " << coord[i + 1].x << " / J = " << coord[i + 1].y << " / K = " << coord[i + 1].z << endl;
		return false;
	}


}

void init(void)  // initializare fereastra de vizualizare
{
	glClearColor(1.0, 1.0, 1.0, 1.0); // precizeaza culoarea de fond a ferestrei de vizualizare
	glMatrixMode(GL_PROJECTION);  // se precizeaza este vorba de o reprezentare 2D, realizata prin proiectie ortogonala
	gluOrtho2D(0.0, 1024.0, 0.0, 768.0); // sunt indicate coordonatele extreme ale ferestrei de vizualizare
}


void mouse2(int button, int state, int x, int y)
{
	static int i = 0;
	switch (button) {
	case GLUT_LEFT_BUTTON:
		if (state == GLUT_DOWN) {
			coord[i].x = x;
			coord[i].y = y;
			i++;
		}
		break;

	}
}

void reshapeFcn(GLint newWidth, GLint newHeight)
{
	glViewport(0, 0, newWidth, newHeight);

	winWidth = newWidth;
	winHeight = newHeight;
}

//Punct rotund = concav
//Punct patrat = convex

void desen(void) // procedura desenare
{
	system("cls");
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_POLYGON);
	for (int i = 0; i < coordNr; i++) {
		glVertex2i(coord[i].x, coord[i].y);
	}
	glEnd();

	glcoordize(10.0);

	for (int i = 0; i < coordNr; i++) {
		if (i == coordNr - 2) {
			if (CheckAngle(coord[i], coord[i + 1], coord[0], i)) {
				glColor3f(1.0, 0.0, 0.0);
				glEnable(GL_POINT_SMOOTH);
				glBegin(GL_coord);
				glVertex2i(coord[i + 1].x, coord[i + 1].y);
				glEnd();
				glDisable(GL_POINT_SMOOTH);
			}
			else {
				glColor3f(0.0, 0.0, 1.0);
				glBegin(GL_coord);
				glVertex2i(coord[i + 1].x, coord[i + 1].y);
				glEnd();
			}
		}
		else
			if (i == coordNr - 1) {
				if (CheckAngle(coord[i], coord[0], coord[1], i)) {
					glColor3f(1.0, 0.0, 0.0);
					glEnable(GL_POINT_SMOOTH);
					glBegin(GL_coord);
					glVertex2i(coord[0].x, coord[0].y);
					glEnd();
					glDisable(GL_POINT_SMOOTH);
				}
				else {
					glColor3f(0.0, 0.0, 1.0);
					glBegin(GL_coord);
					glVertex2i(coord[0].x, coord[0].y);
					glEnd();
				}
			}
			else {
				if (CheckAngle(coord[i], coord[i + 1], coord[i + 2], i)) {
					glColor3f(1.0, 0.0, 0.0);
					glEnable(GL_POINT_SMOOTH);
					glBegin(GL_coord);
					glVertex2i(coord[i + 1].x, coord[i + 1].y);
					glEnd();
					glDisable(GL_POINT_SMOOTH);
				}
				else {
					glColor3f(0.0, 0.0, 1.0);
					glBegin(GL_coord);
					glVertex2i(coord[i + 1].x, coord[i + 1].y);
					glEnd();
				}
			}
	}
	glFlush(); // proceseaza procedurile OpenGL cat mai rapid
}


//100 100
//700 100
//350 350
//700 700
//100 700

int main(int argc, char** argv)
{
	glutInit(&argc, argv); // initializare GLUT
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); // se utilizeaza un singur buffer | modul de colorare RedGreenBlue (= default)
	glutInitWindowPosition(500, 500); // pozitia initiala a ferestrei de vizualizare (in coordonate ecran)
	glutInitWindowSize(1024, 768); // dimensiunile ferestrei
	cout << "Numarul de puncte: ";
	cin >> coordNr;
	//for (int i = 0; i < coordNr; i++) {
	//	cout << "Punctul: " << i + 1 << " Coordonata I: ";
	//	cin >> coord[i].x;
	//	cout << "Punctul: " << i + 1 << " Coordonata J: ";
	//	cin >> coord[i].y;
	//	coord[i].z = 0; //Pentru ca reprezentarea se face in 2D, nu mai are rost sa iau si a treia coordonata.
	//}

	for (int i = 0; i < coordNr; i++) {

	}

	glutCreateWindow("ConvexConcavePolygonEdges "); // creeaza fereastra, indicand numele ferestrei de vizualizare - apare in partea superioara


	init(); // executa procedura de initializare


	glClear(GL_COLOR_BUFFER_BIT); // reprezentare si colorare fereastra de vizualizare
	glutMouseFunc(mouse2);
	glutDisplayFunc(desen); // procedura desen este invocata ori de cate ori este nevoie
	glutMainLoop(); // ultima instructiune a programului, asteapta (eventuale) noi date de intrare
	_getch();

	return 0;
}