% Read a file with the puzzle and return the initial state of the game
read_board(Filename, Board) :-
    open(Filename, read, Stream),
    read_lines(Stream, Lines),
    maplist(atom_chars, Board, Lines).

read_lines(Stream, []) :-
    at_end_of_stream(Stream).
read_lines(Stream, [Line|Lines]) :-
    \+ at_end_of_stream(Stream),
    read_line(Stream, Line),
    read_lines(Stream, Lines).

read_line(Stream, Line) :-
    read_line_to_codes(Stream, Codes),
    maplist(char_code, Line, Codes).

% Solve the Sokoban puzzle using DFS
sokoban(Board, Moves, Solution) :-
    solved(Board),
    Solution = Board,
    Moves = [].
sokoban(Board, Moves, Solution) :-
    move(Board, Dir, NewBoard),
    \+ member(NewBoard, Moves),
    sokoban(NewBoard, [NewBoard|Moves], Solution1),
    Solution = [Dir|Solution1].

% Check if the board is solved (all boxes are on targets)
solved(Board) :-
    findall(Box, (member(Box, Board), member($, Box)), Boxes),
    findall(Target, (member(Target, Board), member(., Target)), Targets),
    subset(Boxes, Targets).

% Find the position of the player on the board
player(Board, row(Row), col(Col)) :-
    nth0(Row, Board, RowList),
    nth0(Col, RowList, '1').

% Find the cell at the given row and column
cell(Board, row(Row), col(Col), Cell) :-
    nth0(Row, Board, RowList),
    nth0(Col, RowList, Cell).

% Move the player in the given direction
% If the player pushes a box, move the box as well
move(Board, Dir, NewBoard) :-
    player(Board, row(Row), col(Col)),
    cell(Board, row(NewRow), col(NewCol), Cell),
    direction(Dir, dRow, dCol),
    NewRow is Row + dRow,
    NewCol is Col + dCol,
    (
        Cell = ' ' ; Cell = '.',
        replace(Board, Row, Col, ' ', Board1),
        replace(Board1, NewRow, NewCol, '1', NewBoard)
    ;
        Cell = '$' ; Cell = '*',
        cell(Board, row(NewRow2), col(NewCol2), Cell2),
        NewRow2 is NewRow + dRow,
        NewCol2 is NewCol + dCol,
        (Cell2 = ' ' ; Cell2 = '.'),
        replace(Board, Row, Col, ' ', Board1),
        replace(Board1, NewRow, NewCol, '1', Board2),
        replace(Board2, NewRow2, NewCol2, '$', NewBoard)
    ).

% Replace an element at the given row and column
replace(List, Row, Col, NewElem, NewList) :-
    nth0(Row, List, RowList),
    nth0(Col, RowList, _, RestRow),
    nth0(Col, NewRow, NewElem, RestRow),
    nth0(Row, NewList, NewRow, RestList).

% Define the directions
direction(up, -1, 0).
direction(down, 1, 0).
direction(left, 0, -1).
direction(right, 0, 1).

% Example usage
solve_sokoban(Filename, Solution) :-
    read_board(Filename, Board),
    sokoban(Board, [Board], Solution).