#include "SDL.h"
#include "SDL_thread.h"
#include "SDL_ttf.h"
#include <stdio.h>
#include <stdlib.h>

SDL_mutex * Lock;
char buffer[50];

int Leibniz(void * nothing);

int main(int argc, char *argv[]) {
	SDL_Surface * Surface;
	SDL_Surface * Temp;
	SDL_Surface * Formula;
	SDL_Event Event;
	SDL_Thread * Thread;
	SDL_Rect box;
	TTF_Font * Font;
	unsigned long counter = 0;
	SDL_Color white;
	white.r = 255;
	white.g = 255;
	white.b = 255;
	
	SDL_Init(SDL_INIT_VIDEO);
	atexit(SDL_Quit);
	TTF_Init();
	atexit(TTF_Quit);
	
	Font = TTF_OpenFont("DejaVuSans.ttf", 18);
	
	Surface = SDL_SetVideoMode(210, 28, 0, SDL_HWSURFACE);
	SDL_WM_SetCaption("Leibniz", "Leibniz");
	
	box.x = 0;
	box.y = 0;
	box.w = 210;
	box.h = 28;
	
	Lock = SDL_CreateMutex();
	Thread = SDL_CreateThread(Leibniz, NULL);
	
	for (;;) {
		if ( SDL_PollEvent(&Event) != 0 ) {
			if ( Event.type == SDL_QUIT ) {
				return 0;
			} else if ( Event.type == SDL_KEYDOWN ) {
				if ( Event.key.keysym.sym == SDLK_ESCAPE ) {
					return 0;
				}
			}
		}
		if ( counter > 20 ) {
			SDL_LockMutex(Lock);
			Temp = TTF_RenderText_Blended(Font, buffer, white);
			SDL_UnlockMutex(Lock);
			Formula = SDL_DisplayFormatAlpha(Temp);
			SDL_FillRect(Surface, &box, 0);
			SDL_UpdateRect(Surface, box.x, box.y, box.w, box.h);
			SDL_BlitSurface(Formula, NULL, Surface, &box);
			SDL_UpdateRect(Surface, box.x, box.y, box.w, box.h);
			counter = 0;
		}
		counter++;
	}
	return 0;
}

int Leibniz(void * nothing) {
	double formula = 1.0;
	double denominator = 3;
	int numerator = 1;
	double temp;
	unsigned long counter = 0;
	
	for (;;) {
		numerator = -numerator;
		temp = numerator;
		temp /= denominator;
		formula += temp;
		denominator += 2;
		counter++;
		if ( counter > 1000000 ) {
			SDL_LockMutex(Lock);
			sprintf(buffer, "%19.17f", formula);
			SDL_UnlockMutex(Lock);
			counter = 0;
		}
	}
	return 0;
}