#include <GL/freeglut.h>
#define _USE_MATH_DEFINES
#include <math.h>

double WINDOW_HEIGHT = 500;
double aspect_ratio = 4.0 / 3.0;
double HEIGHT = 10.0;
double WIDTH = HEIGHT * aspect_ratio;

void drawCircle(GLfloat x, GLfloat y, GLfloat r) {
	const size_t points = 30;

	glBegin(GL_POLYGON);
	for (size_t i = 0; i < points; i++) {
		glVertex3f(x + r * cos(2 * i * M_PI / points), y + r * sin(2 * i * M_PI / points), 0.0);
	}
	glEnd();
}

void drawPoint(GLfloat x, GLfloat y) {
	glBegin(GL_POINTS);
	glVertex3f(x, y, 0.0);
	glEnd();
}

void drawLine(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2) {
	glBegin(GL_LINES);
	glVertex3f(x1, y1, 0.0);
	glVertex3f(x2, y2, 0.0);
	glEnd();
}

GLfloat sunR = 1.0;
GLfloat sunX = WIDTH / 2;
GLfloat sunY = HEIGHT * 0.9 - sunR;
GLfloat sunCenterX = WIDTH / 2, sunCenterY = 0.0, sunRotationAngle = 0.05;

void drawSun() {
	glColor3f(1.0, 1.0, 0.0);

	drawCircle(sunX, sunY, sunR);
}

GLfloat wmW = 3.0, wmH = 6.0;
GLfloat wmX = WIDTH / 2, wmY = wmH * 0.8, wmRotationAngle = 0.05, wmAngle = 0.0;
GLfloat wmSize = 2.6;

void drawWindmill() {
	wmAngle += wmRotationAngle;

	glColor3ub(163, 104, 8);
	glRectf(WIDTH / 2 - wmW / 2, 0.0, WIDTH / 2 + wmW / 2, wmH);

	glColor3ub(201, 201, 201);
	for (size_t i = 0; i < 4; i++)
	{
		glBegin(GL_POLYGON);
		glVertex3f(wmX, wmY, 0.0);
		glVertex3f(wmX + cos(i * (M_PI / 2) - M_PI / 8 + wmAngle) * wmSize, wmY + sin(i * (M_PI / 2) - M_PI / 8 + wmAngle) * wmSize, 0.0);
		glVertex3f(wmX + cos(i * (M_PI / 2) + M_PI / 8 + wmAngle) * wmSize, wmY + sin(i * (M_PI / 2) + M_PI / 8 + wmAngle) * wmSize, 0.0);
		glEnd();
	}
}

void moveSun() {
	sunX -= sunCenterX;
	sunY -= sunCenterY;

	GLfloat newX = sunX * cos(sunRotationAngle) - sunY * sin(sunRotationAngle);
	GLfloat newY = sunX * sin(sunRotationAngle) + sunY * cos(sunRotationAngle);

	sunX = newX + sunCenterX;
	sunY = newY + sunCenterY;
}

void display()
{
	glClear(GL_COLOR_BUFFER_BIT);

	drawSun();
	drawWindmill();

	Sleep(30);

	glFlush();

	glutPostRedisplay();
}

void onMouseClick(int button, int state, int x, int y) {
	switch (button)
	{
	case GLUT_LEFT_BUTTON:
		if (state == GLUT_DOWN) {
			glutIdleFunc(moveSun);
		}
		else {
			glutIdleFunc(NULL);
		}
		break;
	default:
		break;
	}
}

void onReshape(int w, int h) {
	if (w / h) {
		WINDOW_HEIGHT = w / aspect_ratio;
	}
	else {
		WINDOW_HEIGHT = h;
	}

	glViewport(0, 0, WINDOW_HEIGHT * aspect_ratio, WINDOW_HEIGHT);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0.0, WIDTH, 0.0, HEIGHT, -1.0, 1.0);
}

void init()
{
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0.0, 5.0, 0.0, 5.0, -5.0, 5.0);
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(WINDOW_HEIGHT * aspect_ratio, WINDOW_HEIGHT);
	glutInitWindowPosition(300, 180);
	glutCreateWindow("hello");

	init();

	glutDisplayFunc(display);
	glutReshapeFunc(onReshape);
	glutMouseFunc(onMouseClick);
	glutMainLoop();

	return 0;
}