#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <SDL2/SDL_timer.h>

#include <time.h>
#include <math.h>

#define NUM_BODIES 500
#define PARTSIZE 10
#define WIDTH 512
#define HEIGHT 512

struct body { double x, y, dx, dy; };
typedef struct vec { float x, y; } vector;
struct body B[NUM_BODIES];

void init()
{
	srand(time(NULL));
	for(int i = 0; i < NUM_BODIES; i++) {
		B[i].x = WIDTH/2 + rand() % 20 - 40;
		B[i].y = HEIGHT/2 + rand() % 20 - 40;
		B[i].dx = rand() % 50 - 100;
		B[i].dy = rand() % 50 - 100;
	}
}

float geomdist(int i, int j)
{
	return sqrt(pow( B[i].x - B[j].x, 2 ) + pow( B[i].y - B[j].y, 2 ));
}

void updatePos() {
	for(int i = 0; i < NUM_BODIES; i++) {
		B[i].x += B[i].dx;
		B[i].y += B[i].dy;
		printf("%f %f |", B[i].dx, B[i].dy);

		vector mass_centre_vec;
		for(int j = 0; j < NUM_BODIES; j++) {
			if(i == j) continue;
			mass_centre_vec.x += (B[j].x - B[i].x) /geomdist(i, j);
			mass_centre_vec.y += (B[j].y - B[i].y) /geomdist(i, j);
		}
		mass_centre_vec.x /= NUM_BODIES - 1;
		mass_centre_vec.y /= NUM_BODIES - 1;

		B[i].dx = mass_centre_vec.x;
		B[i].dy = mass_centre_vec.y;
	}
}

int processEvents(SDL_Window *window) 
{
	SDL_Event event;

	while(SDL_PollEvent(&event))
	{
		switch(event.type)
		{	
			case SDL_WINDOWEVENT_CLOSE:
				if(window)
				{
					SDL_DestroyWindow(window);
					window = NULL;
					return 1;
				}
				break;
			
			case SDL_KEYDOWN:
				switch(event.key.keysym.sym) {
					case SDLK_ESCAPE:
						return 1;
				}
		}
	}
	return 0;
}

void render(SDL_Renderer *renderer, SDL_Rect particles[NUM_BODIES])
{
	SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255); // фон
	SDL_RenderClear(renderer);
	SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);

	for(int i = 0; i < NUM_BODIES; i++) {
		particles[i].h = PARTSIZE;
		particles[i].w = PARTSIZE;
		particles[i].x = B[i].x - PARTSIZE/2;
		particles[i].y = B[i].y - PARTSIZE/2;
		SDL_RenderDrawRect(renderer, &particles[i]);
	}

	SDL_RenderPresent(renderer);
}

int main(int argc, char *argv[])
{
	SDL_Window *window = NULL;
	SDL_Renderer *renderer = NULL;

	init();
	SDL_Init(SDL_INIT_VIDEO);
	SDL_Rect particles[NUM_BODIES];

	window = SDL_CreateWindow("Universe simulation",
				  SDL_WINDOWPOS_CENTERED,
				  SDL_WINDOWPOS_CENTERED,
				  WIDTH,
				  HEIGHT,
				  0);
	renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

	while(1) {
		if(processEvents(window) == 1)
			break;
		render(renderer, particles);
		updatePos(renderer);
		SDL_Delay(10);
	}

	return 0;
}