-module(day2).

-export([solve/1]).

solve(InputData) ->
	RoundData = binary:split(InputData, <<$\n>>, [trim_all, global]),
	Rounds = lists:map(fun parse_round/1, RoundData),
	RoundPoints = lists:map(fun score_round/1, Rounds),
	{lists:sum(RoundPoints), none}.

parse_round(<<TheirCode, $\s, YourCode>>) -> {parse_theirs(TheirCode), parse_yours(YourCode)}.

score_round(Round = {_Theirs, Yours}) -> round_points(Round) + shape_points(Yours).

parse_theirs($A) -> rock;
parse_theirs($B) -> paper;
parse_theirs($C) -> scissors.

parse_yours($X) -> rock;
parse_yours($Y) -> paper;
parse_yours($Z) -> scissors.

round_points({rock, paper}) -> 6;
round_points({paper, scissors}) -> 6;
round_points({scissors, rock}) -> 6;
round_points({Shape, Shape}) -> 3;
round_points({_Theirs, _Yours}) -> 0.

shape_points(rock) -> 1;
shape_points(paper) -> 2;
shape_points(scissors) -> 3.