% explications nécessaires
solve(_SokobanPos, BoxsPos, Plan, Len) :-
    end(BoxsPos),
    !,
    Plan = [],
    Len = 0.

solve(SokobanPos, BoxsPos, [push(BoxPos, Dir, Destination) | Plan], Len) :-
    select(BoxPos, BoxsPos, NewBoxsPos),
    next_location(PrevNextLoc, BoxPos, Dir),
    \+ member(PrevNextLoc, NewBoxsPos),
    next_location(BoxPos, NextNextLoc, Dir),
    possible_dest(NextNextLoc, BoxPos1),
    reachable(SokobanPos, PrevNextLoc, BoxsPos),
    next_dest(BoxPos, NextNextLoc, Dir, Destination, NewSokobanPos, BoxPos1),
    insert_list(Destination, NewBoxsPos, NexBoxsPos),
    solve(NewSokobanPos, NexBoxsPos, Plan, Len1),
    Len is Len1 + 1.

% explication nécessaires
reachable(Pos, Pos, BoxsPos).
reachable(X, Y, BoxsPos) :-
    next_location(X, Z, _),
    \+ member(Z, BoxsPos),
    reachable(Z, Y, BoxsPos).

% good_dest(Loc,BoxLocs):-
%   \+ member(Loc,BoxLocs), 
%   (corner(Loc)->storage(Loc);true),
%   foreach(BoxLoc in BoxLocs, \+ stuck(BoxLoc,Loc)).

possible_dest(Pos, []).
possible_dest(Pos, [BoxPos|BoxPosSuite]) :-
    \+ Pos = BoxPos,
    (corner(Pos)->storage(Pos);true),
    \+ stuck(BoxPos, Pos),
    possible_dest(Pos, BoxPosSuite).

next_dest(Pos, NextPos, _Dir, Destination, NewSokobanPos, _BoxsPos) :-
    Destination = NextPos,
    NewSokobanPos = BoxPos.
next_dest(Pos, NextPos, Dir, Destination, NewSokobanPos, BoxsPos) :-
    next_location(NextPos, NextNextPos, Dir),
    possible_dest(NextNextPos, BoxsPos),
    next_dest(NextPos, NextNextPos, Dir, Destination, NewSokobanPos, BoxsPos).