function love.load()
   --Call external sources
   require 'graphics';
   
   --Run the Game
   demo_robots();
end

function robots()

   --Game Constants
   _H = 24;	--height of game world
   _W = 32;	--width of game world
   _N = 10;	--number of robots
   
   --Define movement keys
   directions = {	q = -_W - 1, 	w = -_W, 		e = -_W +1,
									a = -1,				s = 0,			d = 1,
									z = _W - 1, 		x = _W, 		c = _W+1};

   --Shake the dice
   math.randomseed(os.time());
	
	--Fresh Start all relavant paramters
	new_start();
end

function new_start()
   --Init Game Parameters
   POS = math.random(_W*_H);	--player's position
   R = {};												--robot's position
   game_status = "no news";			--Hook for win/lose/not text
   
   --Set the Robots at random locations
   for i=1, _N do table.insert(R, math.random(_H * _W)); end
end

function is_all_scrapped()
   --Determines if all robots are scrapped
   for i, v in ipairs(R) do
      if not (count(R, v) > 1) then return false; end
   end
   return true; --can only get here if all are scrapped
end

function count(list, item)
   --Count number of imatching tems in this list
   cnt = 0;
   for k = 1, _N do
      if (list[k] == item) then cnt = cnt + 1; end
   end
   
   return cnt;
end

function largest_fixnum()
   return 999999999;  --return really big number
end

function choose_direction(robot, player)
   --Try each direction and choose the one with minimal distance to the player
   lowest = largest_fixnum();
   
   for i,v in pairs(directions) do
      dist = manhattan_distance(robot + v, player);
      if (dist < lowest) then lowest = dist; dir = i; end
   end

   return dir;
end

function love.keypressed(key, unicode)
	if not (game_status == bad_news_string) then 
	
		--Movement Keys
		if not (directions[key] == nil) then POS = POS + directions[key];
		
		--Teleport Key
		elseif key == 't' then POS = math.random(_W*_H); end
		
		--Robots take a move
		robots_move();

		--Check Win Condition
		if (is_all_scrapped()) then game_status = "good news"; end

		--Check Lose Condition
		if (count(R, POS) > 0) then game_status = "bad news"; end
	else
	
	   --Restart Key
		 if key == 'r' then new_start(); end
		 
		 --Leave Key
		 if key == 'l' then player_exit(); end
	end
	
	--Restart Key
	if key == 'r' then new_start(); end
	
	--Leave Key
	if key == 'l' then player_exit(); end
end

function player_exit()
   os.exit();
end

function robots_move()
   --Robots move towards the player
      for i,v in ipairs(R) do
	     --Ignore scrap
         if not (count(R, v) > 1) then R[i] = R[i] + directions[choose_direction(v, POS)]; end
      end
end

function manhattan_distance(p, q)
   --Calculates manhattan distance between two locations
   A = convert(p);
   B = convert(q);
   return math.abs(A.x- B.x) + math.abs(A.y - B.y);
end

function convert(i)
   --Convert single integer location to 2d-coordinates
   D = {};
   D.x = math.mod(i, _W);
   D.y = ((i - D.x)/_W) + 1;
   return D;
end

function demo_robots()
	load_images();
   robots();
end