% this could be probably like ¼ the length
% but i wanted to write grammars and bidirectional predicates ok
% leave me alone

:- module day2.
:- interface.
:- import_module basics.
:- import_module list.

:- pred run(part::in, list(string)::in, answer::out) is cc_multi.

:- implementation.
:- import_module int.
:- import_module char.
:- import_module string.
:- import_module pair.

:- type move  ---> rock; paper; scissors.
:- type moves == pair(move).

:- type result ---> me; you; draw.
:- type move_res == pair(move, result).

:- type parser(T) == (pred(T, chars, chars)).
:- mode parser(I) == (pred(out(I), in, out) is semidet).
:- mode parser    == parser(ground).

:- pred hand(move::out, chars::in, chars::out) is semidet.
hand(rock)     --> ['A']; ['X'].
hand(paper)    --> ['B']; ['Y'].
hand(scissors) --> ['C']; ['Z'].

:- pred result(result::out, chars::in, chars::out) is semidet.
result(you)  --> ['X'].
result(draw) --> ['Y'].
result(me)   --> ['Z'].

:- pred two(parser(T)::parser, parser(U)::parser,
            T::out, U::out, chars::in, chars::out) is semidet.
two(P, Q, A, B) --> P(A), [' '], Q(B).

:- pred line1(moves::out, chars::in, chars::out) is semidet.
line1(A - B) --> two(hand, hand, A, B).

:- pred line2(move_res::out, chars::in, chars::out) is semidet.
line2(A - B) --> two(hand, result, A, B).


:- pred parse_line(parser(T)::parser, string::in, T::out) is semidet.
parse_line(P, Str, X) :- P(X, to_char_list(Str), []).


:- pred to_int(move, int).
:- mode to_int(in,   out) is det.
:- mode to_int(out,  in)  is semidet.
to_int(rock,     1).
to_int(paper,    2).
to_int(scissors, 3).

:- func to_int(move) = int.
to_int(A) = B :- to_int(A, B).


:- pred win(move, move, result).
:- mode win(in, in,  out) is det.
:- mode win(in, out, in)  is det.
%   you       me
win(rock,     rock,     draw).
win(rock,     paper,    me).
win(rock,     scissors, you).
win(paper,    rock,     you).
win(paper,    paper,    draw).
win(paper,    scissors, me).
win(scissors, rock,     me).
win(scissors, paper,    you).
win(scissors, scissors, draw).

:- func win_score(result) = int.
win_score(me)   = 6.
win_score(you)  = 0.
win_score(draw) = 3.

:- func score1(move, move) = int.
score1(You, Me) = to_int(Me) + win_score(Res) :- win(You, Me, Res).

:- func score2(move, result) = int.
score2(You, Res) = to_int(Me) + win_score(Res) :- win(You, Me, Res).


:- pred run(list(string)::in, parser(pair(T, U))::parser,
            (func(T, U) = int)::in, int::out) is det.
run(Lines, P, F, Out) :-
  if map(parse_line(P), Lines, Res) then
    Out = sum(map(func(X - Y) = F(X, Y), Res))
  else
    die("invalid input"). % lol

:- pragma no_determinism_warning(run/3).
run(one, Lines, int(Out)) :- run(Lines, line1, score1, Out).
run(two, Lines, int(Out)) :- run(Lines, line2, score2, Out).