%---FARMER SECTION---

change(w,e).
change(e,w).

unsafe(F,X,X,C) :-
    change(F,X).
unsafe(F,W,X,X) :-
    change(F,X).


%move wolf
move(state(X,X,G,C), state(Y,Y,G,C)) :-
    change(X,Y), not(unsafe(Y,Y,G,C)).

%move goat
move(state(X,W,X,C), state(Y,W,Y,C)) :-
    change(X,Y), not(unsafe(Y,W,Y,C)).

%move cabbage
move(state(X,W,G,X), state(Y,W,G,Y)) :-
    change(X,Y), not(unsafe(Y,W,G,Y)).

%move farmer alone
move(state(X,W,G,C), state(Y,W,G,C)) :-
    change(X,Y), not(unsafe(Y,W,G,C)).

start(state(w,w,w,w)).
goal(state(e,e,e,e)).


showFarm(S) :-
    showFW(S), write('|~~~~~~~|'), showFE(S),nl.

showFW(state(F,W,G,C)) :-
    (F == w, write('F'), !; write(' ')),
    (W == w, write('W'), !; write(' ')),
    (G == w, write('G'), !; write(' ')),
    (C == w, write('C'), !; write(' ')).

showFE(state(F,W,G,C)) :-
    (F == e, write('F'), !; true),
    (W == e, write('W'), !; true),
    (G == e, write('G'), !; true),
    (C == e, write('C'), !; true).


showSol([]).
showSol([H|T]) :- showFarm(H), showSol(T).


%---MISSIONARY/CANNIBAL SECTION---

% state(me,ce,mw,cw,b)

%safe(Me,Ce,MW,CW) :- Me >= Ce, MW >= CW.

unsafe(Me,Ce,MW,CW, B) :- Me > 0, Ce > Me.
unsafe(Me,Ce,MW,CW, B) :- MW > 0, CW > MW.


%%%%%   East to West %%%%%%%
% move 2 missionaries from east to west
move(state(Me,Ce, Mw, Cw, 1), state(ME,CE,MW,CW, -1)) :-
        Me > 1,
        ME is Me-2,
        MW is Mw+2,
        CW = Cw,
        CE = Ce,
        not(unsafe(ME,CE,MW,CW,-1)).

% move 1 missionaries from east to west
move(state(Me,Ce, Mw, Cw, 1), state(ME,CE,MW,CW, -1)) :-
        Me > 0,
        ME is Me-1,
        MW is Mw+1,
        CW = Cw,
        CE = Ce,
        not(unsafe(ME,CE,MW,CW,-1)).

% move 1 missionarie and 1 cannibal from east to west
move(state(Me,Ce, Mw, Cw, 1), state(ME,CE,MW,CW, -1)) :-
        Me > 0,
        Ce > 0,
        ME is Me-1,
        MW is Mw+1,
        CW is Cw+1,
        CE is Ce-1,
        not(unsafe(ME,CE,MW,CW,-1)).

% move 2 cannibals from east to west
move(state(Me,Ce, Mw, Cw, 1), state(ME,CE,MW,CW, -1)) :-
        Ce > 1,
        ME = Me,
        MW = Mw,
        CW is Cw + 2,
        CE is Ce - 2,
        not(unsafe(ME,CE,MW,CW,-1)).

% move 1 cannibals from east to west
move(state(Me,Ce, Mw, Cw, 1), state(ME,CE,MW,CW, -1)) :-
        Ce > 0,
        ME is Me,
        MW is Mw,
        CW is Cw+1,
        CE is Ce-1,
        not(unsafe(ME,CE,MW,CW,-1)).

%%%%%       West to East        %%%%%

% move 2 missionaries from west to east
move(state(Me,Ce, Mw, Cw, -1), state(ME,CE,MW,CW, 1)) :-
        Mw > 1,
        ME is Me+2,
        MW is Mw-2,
        CW = Cw,
        CE = Ce,
        not(unsafe(ME,CE,MW,CW,1)).

% move 1 missionaries from west to east
move(state(Me,Ce, Mw, Cw, -1), state(ME,CE,MW,CW, 1)) :-
        Mw > 0,
        ME is Me+1,
        MW is Mw-1,
        CW = Cw,
        CE = Ce,
        not(unsafe(ME,CE,MW,CW,1)).

% move 1 missionary and 1 cannibal from west to east
move(state(Me,Ce, Mw, Cw, -1), state(ME,CE,MW,CW, 1)) :-
        Mw > 0,
        Cw > 0,
        ME is Me+1,
        MW is Mw-1,
        CW is Cw-1,
        CE is Ce+1,
        not(unsafe(ME,CE,MW,CW,1)).

% move 2 cannibals from west to east
move(state(Me,Ce, Mw, Cw, -1), state(ME,CE,MW,CW, 1)) :-
        Cw > 1,
        ME = Me,
        MW = Mw,
        CW is Cw - 2,
        CE is Ce + 2,
        not(unsafe(ME,CE,MW,CW,1)).

% move 1 cannibals from east to west
move(state(Me,Ce, Mw, Cw, -1), state(ME,CE,MW,CW, 1)) :-
        Cw > 0,
        ME is Me,
        MW is Mw,
        CW is Cw-1,
        CE is Ce+1,
        not(unsafe(ME,CE,MW,CW,1)).



start(state(3,3,0,0,1)).
goal(state(0,0,3,3,-1)).



showMission(S) :-
    showMW(S), write('|~~~~~~~|'), showME(S), nl.

showMW(state(Me, Ce, Mw, Cw, B)) :-
    (write(Mw), write(' '), !; write('  ')),
    (write(Cw), write(' '), !; write('  ')),
    (write('W'), !; write(' ')).

showME(state(Me, Ce, Mw, Cw, B)) :-
    (write(Me), write(' '), !; write('  ')),
    (write(Ce), write(' '), !; write('  ')),
    (write('E'), !; write(' ')).

showSol([]).
showSol([H|T]) :- showMission(H), showSol(T).

%---STATE SEARCHING SECTION---

farm :- solve(state(w,w,w,w), X), showSol(X).
mission :- solve(state(3,3,0,0,1), X), showSol(X).

solve(X,Soln):-
    solve(X,[],Sol),
    reverse(Sol,Soln).

solve(State,Path,[State|Path]):-
    goal(State).

solve(State,Path,Sol):-
    move(State,NewState),
    not(member(NewState,Path)),
    solve(NewState,[State|Path],Sol).