-module(accept_neg).

-export([alt_tag/1,
         sort_scored/1,
         find_preferred_best/1,
         score_params/2]).



%%====================================================================
%% Public API
%%====================================================================

alt_tag(Alt) ->
  case Alt of
    {_, _} -> Alt;
    _ -> {Alt, Alt}
  end.

sort_scored(Scored) ->
  lists:sort(fun scored_cmp/2, Scored).

%% find alternative with the best score
%% keysort is stable so order of Alternatives preserved
%% after sorting Tail has the best score.
%% However if multiple alternatives have the same score as Tail
%% we should find first best alternative to respect user's priority.
find_preferred_best(Alts) ->
  Sorted = lists:keysort(1, Alts),
  [B | R] = lists:reverse(Sorted),
  find_preferred_best(B, R).

score_params([], _) ->
  1;
score_params(CCParams, AltParams) when length(CCParams) == length(AltParams) ->
  case lists:sort(CCParams) == lists:sort(AltParams) of
    true -> 2;
    _ -> 0
  end;
score_params(_, _) ->
  0.

%%====================================================================
%% Private Parts
%%====================================================================

scored_cmp({S1, _}, {S2, _}) ->
  S1 > S2.

find_preferred_best({Q, _}, [{Q, _} = H | R]) ->
  find_preferred_best(H, R);
find_preferred_best(B, []) ->
  B;
find_preferred_best(B, _) ->
  B.