%%%%%%% Maze: Heuristic Improvement %%%%%%%%
% Moving generally toward the end
% All walls
% Row 1
wall([X,1]) :- X =\= 2.
% Row 2
wall([X,2]) :- X = 1; X = 4; X = 6.
% Row 3
wall([X,3]) :- X = 1; X = 2; X = 6.
% Row 4
wall([X,4]) :- X =\= 3, X =\= 5.
% Row 5
wall([X,5]) :- X = 1; X = 4; X = 6. 
% Row 6
wall([X,6]) :- X =\= 2.

% Start / end
start([2,1]).
end([2,6]).

% Maze Size
mazeSize([6,6]).

% Spaces outside the bounds of the maze
badSpot([X,Y]) :- wall([X,Y]).
badSpot([X,Y]) :- X < 1; Y < 1.
badSpot([X,Y]) :- mazeSize([W, H]), (X > W; Y > H).

% Movement Options
% Move up if down last
moveUp([CurrX, CurrY], [CurrX, NextY]) :- NextY is CurrY - 1.
moveUp([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX - 1.
moveUp([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX + 1.
moveUp([CurrX, CurrY], [NextX, NextY]) :- NextY is CurrY + 1, NextX = CurrX.

% Move down if up last
moveDown([CurrX, CurrY], [NextX, NextY]) :- NextY is CurrY + 1, NextX = CurrX.
moveDown([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX - 1.
moveDown([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX + 1.
moveDown([CurrX, CurrY], [CurrX, NextY]) :- NextY is CurrY - 1.

% Move left if right last
moveLeft([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX - 1.
moveLeft([CurrX, CurrY], [CurrX, NextY]) :- NextY is CurrY - 1.
moveLeft([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX + 1.
moveLeft([CurrX, CurrY], [NextX, NextY]) :- NextY is CurrY + 1, NextX = CurrX.

% Move right if left last
moveRight([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX + 1.
moveRight([CurrX, CurrY], [CurrX, NextY]) :- NextY is CurrY - 1.
moveRight([CurrX, CurrY], [NextX, NextY]) :- NextY is CurrY + 1, NextX = CurrX.
moveRight([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX - 1.

% Direction of the end
endUp([CurrX, CurrY]) :- TestY is CurrY, end([X,Y]), TestY > Y.
endDown([CurrX, CurrY]) :- TestY is CurrY, end([X,Y]), TestY < Y.
endRight([CurrX, CurrY]) :- TestX is CurrX, end([X,Y]), TestX < X.
endLeft([CurrX, CurrY]) :- TestX is CurrX, end([X,Y]), TestX > X.

%Try to Move _
try(CurrentLocation, NewLocation) :- endDown(CurrentLocation), moveDown(CurrentLocation, NewLocation).
try(CurrentLocation, NewLocation) :- endRight(CurrentLocation), moveRight(CurrentLocation, NewLocation).
try(CurrentLocation, NewLocation) :- endLeft(CurrentLocation), moveLeft(CurrentLocation, NewLocation).
try(CurrentLocation, NewLocation) :- endUp(CurrentLocation), moveUp(CurrentLocation, NewLocation).

% A solution of the maze from our current location is [] if our current location is the end.
solve(CurrentLocation, Path) :- end(CurrentLocation), Path = [CurrentLocation].


solve(CurrentLocation, Path) :-
		try(CurrentLocation, NewLocation),
    	\+badSpot(NewLocation),
        solve(NewLocation, RestOfPath),
        Path = [CurrentLocation | RestOfPath].

% Convenience rule
solve(Path) :- start(Start), solve(Start, Path).

drawCell(Column, Row, _) :- wall([Column, Row]), write("X"), !.
drawCell(Column, Row, _) :- start([Column, Row]), write("S"), !.
drawCell(Column, Row, _) :- end([Column, Row]), write("E"), !.
drawCell(Column, Row, Path) :- member([Column, Row], Path), write("P"), !.
drawCell(_, _, _) :- write("O").

drawRow(Row, Path) :- drawCell(1, Row, Path), tab(1), drawCell(2, Row, Path), tab(1), 
        drawCell(3, Row, Path), tab(1), drawCell(4, Row, Path), tab(1), 
        drawCell(5, Row, Path), tab(1), drawCell(6, Row, Path), nl.
                
draw :- drawRow(1, []), drawRow(2, []), drawRow(3, []), drawRow(4, []), drawRow(5, []), 
        drawRow(6, []).
draw(Path) :- drawRow(1, Path), drawRow(2, Path), drawRow(3, Path), drawRow(4, Path),
        drawRow(5, Path), drawRow(6, Path).