#include <stdio.h>
#include <stdlib.h>

#include <allegro5/allegro5.h>
#include <allegro5/allegro_font.h>
#include <allegro5/allegro_primitives.h>

#define framerate 	8.0

#define screen_width	640
#define screen_height	480

#define BLOCK_LEN 10

#define GRID_HEIGHT 16
#define GRID_WIDTH 16
#define GRID_BORDER_WIDTH 10

_Bool is_snake(int x, int y, int* snake_x, int* snake_y,int snake_length){
	for(int i=0; i<snake_length; i++){
		if(snake_x[i]==x && snake_y[i]==y)
			return 1;
	}
	return 0;
}

void create_apple(int* x, int* y,int* snake_x, int* snake_y,int snake_length){
	do{
		*x = random()%GRID_WIDTH;
		*y = random()%GRID_HEIGHT;
	}while(is_snake(*x,*y,snake_x,snake_y,snake_length));
}

void draw_box(int x, int y, ALLEGRO_COLOR color){
	al_draw_filled_rectangle(GRID_BORDER_WIDTH+BLOCK_LEN*x,
			GRID_BORDER_WIDTH+BLOCK_LEN*y,
			GRID_BORDER_WIDTH+BLOCK_LEN*x+BLOCK_LEN,
			GRID_BORDER_WIDTH+BLOCK_LEN*y+BLOCK_LEN,
					color);
}


int main()
{
	if(!al_init())
	{
		printf("couldn't initialize allegro\n");
		return 1;
	}
	if(!al_init_primitives_addon()){
		printf("couldn't initialize primitives addon\n");
		return 1;
	}

	if(!al_install_keyboard())
	{
		printf("couldn't initialize keyboard\n");
		return 1;
	}

	ALLEGRO_TIMER* timer = al_create_timer(1.0 / framerate);
	if(!timer)
	{
		printf("couldn't initialize timer\n");
		return 1;
	}

	ALLEGRO_EVENT_QUEUE* queue = al_create_event_queue();
	if(!queue)
	{
		printf("couldn't initialize queue\n");
		return 1;
	}

	ALLEGRO_DISPLAY* disp = al_create_display(screen_width, screen_height);
	if(!disp)
	{
		printf("couldn't initialize display\n");
		return 1;
	}

	ALLEGRO_FONT* font = al_create_builtin_font();
	if(!font)
	{
		printf("couldn't initialize font\n");
		return 1;
	}

	al_register_event_source(queue, al_get_keyboard_event_source());
	al_register_event_source(queue, al_get_display_event_source(disp));
	al_register_event_source(queue, al_get_timer_event_source(timer));

	bool done = false;
	bool redraw = true;
	ALLEGRO_EVENT event;

	int direction_x =1;
	int direction_y =0;


	int length = 1;
	int head_i = 0;
	int pos_x[100]; 
	pos_x[0] = 0;
	pos_x[1] = 0;
	int pos_y[100]; 
	pos_y[0] = 0;
	pos_y[1] = 0;
	
	
	int apple_x;
	int apple_y;

	create_apple(&apple_x, &apple_y,pos_x,pos_y,length);


	al_start_timer(timer);
	_Bool changed_direction = 0;//variable ensures that the direction only
				   //gets changed once per frame
	while(1)
	{
		al_wait_for_event(queue, &event);

		switch(event.type)
		{
			case ALLEGRO_EVENT_TIMER:
				// game logic goes here.
				redraw = true;
				break;

			case ALLEGRO_EVENT_KEY_DOWN:
				switch(event.keyboard.keycode){
				case(ALLEGRO_KEY_DOWN):
					if(!changed_direction &&direction_y!=-1){
					direction_x=0;
					direction_y=1;
					}
					changed_direction = 1;
					break;
				case(ALLEGRO_KEY_UP):
					if(!changed_direction &&direction_y!=1){
					direction_x=0;
					direction_y=-1;
					}
					changed_direction = 1;
					break;
				case(ALLEGRO_KEY_RIGHT):
					if(!changed_direction &&direction_x!=-1){
					direction_x=1;
					direction_y=0;
					}
					changed_direction = 1;
					break;
				case(ALLEGRO_KEY_LEFT):
					if(!changed_direction &&direction_x!=1){
					direction_x=-1;
					direction_y=0;
					}
					changed_direction = 1;
					break;
				}
				break;
			case ALLEGRO_EVENT_DISPLAY_CLOSE:
				done = true;
				break;
		}

		if(done)
			break;

		if(redraw && al_is_event_queue_empty(queue))
		{
			changed_direction=0;
			al_draw_rectangle(0,0,2*GRID_BORDER_WIDTH+BLOCK_LEN*GRID_WIDTH,
					2*GRID_BORDER_WIDTH+BLOCK_LEN*GRID_HEIGHT,
					al_map_rgb(0,0,255),GRID_BORDER_WIDTH);

			int next_pos_x;
			int next_pos_y;

			next_pos_x=direction_x+pos_x[head_i];
			next_pos_y=direction_y+pos_y[head_i];

			if(is_snake(next_pos_x,next_pos_y,pos_x,pos_y,length))
				return 0;
			
			if(next_pos_x>=GRID_WIDTH)
				next_pos_x=0;
			if(next_pos_x<0)
				next_pos_x=GRID_WIDTH-1;
			if(next_pos_y>=GRID_HEIGHT)
				next_pos_y=0;
			if(next_pos_y<0)
				next_pos_y=GRID_HEIGHT-1;

			if(next_pos_x==apple_x && next_pos_y==apple_y){
				memmove(pos_x+head_i+2,pos_x+head_i+1,sizeof(int)*(length-head_i-1));
				memmove(pos_y+head_i+2,pos_y+head_i+1,sizeof(int)*(length-head_i-1));
				length++;
				create_apple(&apple_x,&apple_y,pos_x,pos_y,length);
			}

			head_i++;
			if(head_i>=length)
				head_i=0;
			draw_box(pos_x[head_i],pos_y[head_i],al_map_rgb(0,0,0));
			pos_x[head_i]=next_pos_x;
			pos_y[head_i]=next_pos_y;
			
			
			draw_box(apple_x,apple_y,al_map_rgb(255,0,0));
			//for(int i =0;i<length;i++){
			draw_box(pos_x[head_i],pos_y[head_i],al_map_rgb(0,255,0));
			//}
			al_flip_display();

			redraw = false;
		}
	}

	al_destroy_font(font);
	al_destroy_display(disp);
	al_destroy_timer(timer);
	al_destroy_event_queue(queue);

	return 0;
}

// vim: cc=100