% FILE: melds.pl
% LINE: Defines rules for finding melds in a player's hand
% DATE: March 14, 2021


% checks if a hand has N of one card in it
find_same_card([], _, [], []).
find_same_card([card(Face1, Suit1, Rank1)|RestHand], card(Face1, _, _), [card(Face1, Suit1, Rank1)|Move], NewHand) :- find_same_card(RestHand, card(Face1, _, _), Move, NewHand).
find_same_card([card(Face1, Suit1, Rank1)|RestHand], card(Face2, Suit2, Rank2), Move, [card(Face1, Suit1, Rank1)|NewHand]) :-
    find_same_card(RestHand, card(Face2, Suit2, Rank2), Move, NewHand).

% finds three of a kind in a player's hand
% Original Hand, Hand to iterate through, 
find_set(OrigHand, [], OldMelds, OldMelds, OrigHand).
find_set(OrigHand, [card(Face1, Suit1, Rank1)|_], OldMelds, [Move|OldMelds], NewHand) :-
    find_same_card(OrigHand, card(Face1, Suit1, Rank1), Move, NewHand),
    length(Move, L), L>=2.
find_set(OrigHand, [_|RestHand], OldMelds, NewMelds, NewHand) :- find_set(OrigHand, RestHand, OldMelds, NewMelds, NewHand).

% finds three of a kind in a player's hand
% Original Hand, Hand to iterate through, 
find_four_of_a_kind(OrigHand, [], OldMelds, OldMelds, OrigHand).
find_four_of_a_kind(OrigHand, [card(Face1, Suit1, Rank1)|_], OldMelds, [Move|OldMelds], NewHand) :-
    find_same_card(OrigHand, card(Face1, Suit1, Rank1), Move, NewHand),
    length(Move, L), L=4.
find_four_of_a_kind(OrigHand, [_|RestHand], OldMelds, NewMelds, NewHand) :- find_four_of_a_kind(OrigHand, RestHand, OldMelds, NewMelds, NewHand).


% finds a run of any length greater than or equal to three in a player's hand
% Hand must be sorted before calling this method
% try with suit, if move is found, add it to melds, repeat until no more suits
find_run(Hand, Hand, [], Melds, Melds).
find_run(Hand, NewHand, [FirstSuit|_], Melds, [CardsFound|Melds]) :-
    find_run_suit(Hand, NewHand, 1, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 2, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 3, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 4, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 5, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 6, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 7, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;
    
    find_run_suit(Hand, NewHand, 8, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 9, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 10, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2 ;

    find_run_suit(Hand, NewHand, 11, FirstSuit, CardsFound),
    length(CardsFound, L), L >= 2.

find_run(Hand, NewHand, [_|RestSuits], Melds, NewMelds) :- find_run(Hand, NewHand, RestSuits, Melds, NewMelds).

% finds a run in the suit provided starting at rank NextRank
find_run_suit([], [], _, _,[]).
find_run_suit([card(Face, Suit, Rank)|Hand], NewHand, Rank, Suit, [card(Face, Suit, Rank)|CardsFound]) :-
    NewRank is Rank +1,
    find_run_suit(Hand, NewHand, NewRank, Suit, CardsFound).

find_run_suit([card(Face, Suit, Rank)|Hand], [card(Face, Suit, Rank)|NewHand], AnotherRank, Suit2, CardsFound) :-
    find_run_suit(Hand, NewHand, AnotherRank, Suit2, CardsFound).



% Sorts hand in order by the following rule
% A - K with suit order being Diamonds, Clubs, Hearts, Spade
merge_sort([], []). 
merge_sort([Item], [Item]).
merge_sort(List,Sorted):-
    List=[_,_|_],
    split(List, L1, L2),
	merge_sort(L1,Sorted1),
    merge_sort(L2,Sorted2),  
	merge(Sorted1,Sorted2,Sorted).                  

% merges two lists together, sorting them on the way up
merge([], L, L).
merge(L, [], L) :- L \= [].
merge([card(Face1, Suit1, Rank1)|T1], [card(Face2, Suit2, Rank2)|T2], [card(Face1, Suit1, Rank1)|T]) :- less_than(card(Face1, Suit1, Rank1), card(Face2, Suit2, Rank2)), merge(T1, [card(Face2, Suit2, Rank2)|T2], T).
merge([X|T1],[Y|T2],[Y|T]) :- merge([X|T1],T2,T).

% true if card 1 is less than card 2
less_than(card(_, _, Rank1), card(_, _, Rank2)) :-
    Rank1 < Rank2.

less_than(card(_, Suit1, Rank1), card(_, _, Rank2)) :-
    Rank1 = Rank2,
    Suit1 = diamonds.

less_than(card(_, Suit1, Rank1), card(_, Suit2, Rank2)) :-
    Rank1 = Rank2,
    Suit1 = clubs,
    Suit2 = hearts.

less_than(card(_, Suit1, Rank1), card(_, Suit2, Rank2)) :-
    Rank1 = Rank2,
    Suit1 = clubs,
    Suit2 = spades.

less_than(card(_, Suit1, Rank1), card(_, Suit2, Rank2)) :-
    Rank1 = Rank2,
    Suit1 = hearts,
    Suit2 = spades.

split([], [], []).
split([Card], [Card|[]], []).
split([Card1, Card2|RestCards], [Card1|RestCards1], [Card2|RestCards2]) :- split(RestCards, RestCards1, RestCards2).