#include <GL/freeglut.h>
#include <cstdio>
#define _USE_MATH_DEFINES
#include <cmath>

float lastFrameTime = 0;

int width, height;


struct Camera
{
	float posX = 0;
	float posY = -4;
	float rotX = 0;
	float rotY = 0;
} camera;

bool keys[255];


void drawCube()
{
	glBegin(GL_QUADS);
	glColor3f(1, 0, 0);
	glVertex3f(-1, -1, -1);
	glVertex3f(1, -1, -1);
	glVertex3f(1, 1, -1);
	glVertex3f(-1, 1, -1);

	glColor3f(1, 1, 0);
	glVertex3f(-1, -1, 1);
	glVertex3f(1, -1, 1);
	glVertex3f(1, 1, 1);
	glVertex3f(-1, 1, 1);

	glColor3f(0, 0, 1);
	glVertex3f(-1, -1, -1);
	glVertex3f(-1, 1, -1);
	glVertex3f(-1, 1, 1);
	glVertex3f(-1, -1, 1);

	glColor3f(1, -1, 1);
	glVertex3f(1, -1, -1);
	glVertex3f(1, 1, -1);
	glVertex3f(1, 1, 1);
	glVertex3f(1, -1, 1);

	glColor3f(0, 1, 0);
	glVertex3f(-1, -1, -1);
	glVertex3f(1, -1, -1);
	glVertex3f(1, -1, 1);
	glVertex3f(-1, -1, 1);

	glColor3f(1, 1, 0);
	glVertex3f(-1, 1, -1);
	glVertex3f(1, 1, -1);
	glVertex3f(1, 1, 1);
	glVertex3f(-1, 1, 1);
	glEnd();
}


void display()
{
	glClearColor(0.6f, 0.6f, 1, 1);
	glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(60.0f, (float)width/height, 0.1, 30);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glRotatef(camera.rotX, 1, 0, 0);
	glRotatef(camera.rotY, 0, 1, 0);
	glTranslatef(camera.posX, 0, camera.posY);


	glColor3f(0.1f, 1.0f, 0.2f);
	glBegin(GL_QUADS);
		glVertex3f(-15, -1, -15);
		glVertex3f( 15, -1, -15);
		glVertex3f( 15, -1,  15);
		glVertex3f(-15, -1,  15);
	glEnd();

	for (int x = -10; x <= 10; x += 5)
	{
		for (int y = -10; y <= 10; y += 5)
		{
			glPushMatrix();
			glTranslatef((float)x, 0.0f, (float)y);
			drawCube();
			glPopMatrix();
		}
	}

	glutSwapBuffers();
}

void move(float angle, float fac)
{
	camera.posX += (float)cos((camera.rotY + angle) / 180 * M_PI) * fac;
	camera.posY += (float)sin((camera.rotY + angle) / 180 * M_PI) * fac;
}

void idle()
{
	float frameTime = glutGet(GLUT_ELAPSED_TIME)/1000.0f;
	float deltaTime = frameTime - lastFrameTime;
	lastFrameTime = frameTime;

	const float speed = 3;
	if (keys['a']) move(0, deltaTime*speed);
	if (keys['d']) move(180, deltaTime*speed);
	if (keys['w']) move(90, deltaTime*speed);
	if (keys['s']) move(270, deltaTime*speed);

	glutPostRedisplay();
}

void mousePassiveMotion(int x, int y)
{
	int dx = x - width / 2;
	int dy = y - height / 2;
	if ((dx != 0 || dy != 0) && abs(dx) < 400 && abs(dy) < 400)
	{
		camera.rotY += dx / 10.0f;
		camera.rotX += dy / 10.0f;
		glutWarpPointer(width / 2, height / 2);
	}
}

void keyboard(unsigned char key, int, int)
{
	if (key == 27)
		exit(0);
	keys[key] = true;
}

void keyboardUp(unsigned char key, int,int)
{
	keys[key] = false;
}

int main(int argc, char* argv[])
{
	glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
	glutInitWindowSize(800, 600);
	glutInit(&argc, argv);
	glutCreateWindow("Hello World");

	memset(keys, 0, sizeof(keys));
	glEnable(GL_DEPTH_TEST);

	glutIdleFunc(idle);
	glutDisplayFunc(display);
	glutReshapeFunc([](int w, int h) { width = w; height = h; glViewport(0, 0, w, h); });
	glutKeyboardFunc(keyboard);
	glutKeyboardUpFunc(keyboardUp);
	glutPassiveMotionFunc(mousePassiveMotion);

	glutWarpPointer(width / 2, height / 2);

	glutMainLoop();


	return 0;
}