% 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]).

badSpot([X,Y]) :- wall([X,Y]).
badSpot([X,Y]) :- X < 1; Y < 1.
badSpot([X,Y]) :- mazeSize([W, H]), (X > W; Y > H).



move([CurrX, CurrY], [CurrX, NextY]) :- NextY is CurrY - 1.

move([CurrX, CurrY], [NextX, NextY]) :- NextY is CurrY + 1, NextX = CurrX.

move([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX - 1.

move([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX + 1.


%up
up([CurrX, CurrY], [CurrX, NextY]) :- NextY is CurrY - 1.
%down
down([CurrX, CurrY], [NextX, NextY]) :- NextY is CurrY + 1, NextX = CurrX.
%left
left([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX - 1.
%right
right([CurrX, CurrY], [NextX, NextY]) :- NextY = CurrY, NextX is CurrX + 1.


compareX([CurrX, _], [EndX, _]) :- CurrX > EndX.


compareY([_, CurrY], [_, EndY]) :- CurrY > EndY.


% 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, BeenThere, Path) :-

end(EndLocation),
%if current x is > end x go left
(((compareX(CurrentLocation, EndLocation), left(CurrentLocation, NewLocation), \+badSpot(NewLocation), \+member(NewLocation, BeenThere), !);
%if current y is > end y go up
(compareY(CurrentLocation, EndLocation), up(CurrentLocation, NewLocation),
 \+badSpot(NewLocation), \+member(NewLocation, BeenThere), !);
%if current x is < end x go left
(\+compareX(CurrentLocation, EndLocation), right(CurrentLocation, NewLocation), \+badSpot(NewLocation), \+member(NewLocation, BeenThere), !);
%if current y is < end y go down
(\+compareY(CurrentLocation, EndLocation), down(CurrentLocation, NewLocation), \+badSpot(NewLocation), \+member(NewLocation, BeenThere), !);
 
 move(CurrentLocation, NewLocation)),
         
solve(NewLocation, [NewLocation | BeenThere], RestOfPath),
Path = [CurrentLocation | RestOfPath]).

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