%  main.erl
-module(main).
-compile([export_all]).
%

% w = 119
% b = 98
% . = 46

deletePawn(Pos, Board) ->
    {List1,End} = lists:split(Pos, Board),
    Start = lists:droplast(List1),
    Start++[46]++End.

movePawn(Src, Dest, Board) ->
    Pawn = lists:nth(Src, Board),
    TmpBoard = deletePawn(Src, Board),
    {List1,End} = lists:split(Dest, TmpBoard),
    Start = lists:droplast(List1),
    Start++[Pawn]++End.

righMoveWhite(Src, Dest, Board) ->
    Left = lists:nth(Src+7, Board),
    Right = lists:nth(Src+9, Board),
    LeftHit = lists:nth(Src+14, Board),
    RightHit = lists:nth(Src+18, Board),

    if  Src > Dest -> false;
        Src+7 == Dest,  Left == 46, (Dest div 8 - Src div 8) == 1, Src < 57 -> true;
        Src+9 == Dest,  Right == 46, (Dest div 8 - Src div 8) == 1, Src < 57 -> true;
        Src+14 == Dest, Left /= 46, LeftHit == 46, (Dest div 8 - Src div 8) == 2, Src < 49 -> true;
        Src+18 == Dest, Right /= 46, RightHit == 46, (Dest div 8 - Src div 8) == 2, Src < 49 -> true;
        true -> false
    end.

righMoveBlack(Src, Dest, Board) ->
    Left = lists:nth(Src-9, Board),
    Right = lists:nth(Src-7, Board),
    LeftHit = lists:nth(Src-18, Board),
    RightHit = lists:nth(Src-14, Board),

    if  Src < Dest -> false;
        Src-9 == Dest,  Left == 46, (Src div 8 - Dest div 8) == 1, Src > 8 -> true;
        Src-7 == Dest,  Right == 46, (Src div 8 - Dest div 8) == 1, Src > 8 -> true;
        Src-18 == Dest, Left /= 46, LeftHit == 46, (Src div 8 - Dest div 8) == 2, Src > 16 -> true;
        Src-14 == Dest, Right /= 46, RightHit == 46, (Src div 8 - Dest div 8) == 2, Src >16 -> true;
        true -> false
    end.

moveWhite(Src, Dest, Board) ->
    RightMove = righMoveWhite(Src, Dest, Board),
    Diff = abs(Dest rem 8 - Src rem 8),
	Midway = Src + (Dest-Src) div 2,
	Pawn = lists:nth(Midway, Board),
    if  RightMove == true, (Diff == 2) or (Diff == 6), Pawn == 98 -> movePawn(Src,Dest,deletePawn(Src+((Dest-Src) div 2), Board));
		RightMove == true, (Diff == 2) or (Diff == 6), Pawn == 119 -> movePawn(Src,Dest,Board);
        RightMove == true -> movePawn(Src, Dest, Board)
    end.

moveBlack(Src, Dest, Board) ->
    RightMove = righMoveBlack(Src, Dest, Board),
    Diff = abs(Src rem 8 - Dest rem 8),
	Midway = Src - (Src-Dest) div 2,
	Pawn = lists:nth(Midway, Board),
    if  RightMove == true, (Diff == 2) or (Diff == 6), Pawn == 119 -> movePawn(Src,Dest,deletePawn(Src-((Src-Dest) div 2), Board));
		RightMove == true, (Diff == 2) or (Diff == 6), Pawn == 98 -> movePawn(Src,Dest,Board);
        RightMove == true -> movePawn(Src, Dest, Board)
    end.

endGame(Board) ->
    White = lists:member(119,Board),
    Black = lists:member(98,Board),
    if  White==true -> false;
        Black==true -> false;
        true -> true
    end.

test() ->
    moveBlack(45,31,".w.w.w.ww.w.w.w..w.w.w...............w..b.b.b.b..b.b.b.bb.b.b.b.\n").
    %deletePawn(45-((45-31) div 2),".w.w.w.ww.w.w.w..w.w.w...............w..b.b.b.b..b.b.b.bb.b.b.b.\n").