/* 

  Twelve Days of Christmas in Picat.

  From
  https://www.reddit.com/r/prolog/comments/kip3wg/coding_challenge_27_2_weeks_the_twelve_days_of/
  """
  The task is to output some version of the lyrics of the cumulative song 
  The Twelve Days of Christmas.
  """

  This model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/

import v3_utils.

main => go.

% Prolog approach
% (by kunstkritik)
go ?=>
  lyrics,
  
  nl.

go => true.

% Picat approach
go2 ?=>
  foreach(Day in 1..12)
    day(Day,DayStr,_What),
    printf("On the %w day of Christmas,%nMy true love gave to me:%n",DayStr),
    foreach(Prev in Day..-1..1) 
      day(Prev,_,What),
      println(What)
    end,
    nl
  end,
  
  nl.
go2 => true.


% From https://www.reddit.com/r/prolog/comments/kip3wg/coding_challenge_27_2_weeks_the_twelve_days_of/
% (by kunstkritik)
day(1, first, "A partridge in a pear tree").
day(2, second, "Two turtle doves and").
day(3, third, "Three french hens").
day(4, fourth, "Four calling birds").
day(5, fifth, "Five golden rings").
day(6, sixth, "Six geese a-laying").
day(7, seventh, "Seven swans a-swimming").
day(8, eighth, "Eight maids a-milking").
day(9, ninth, "Nine ladies dancing").
day(10,tenth, "Ten lords a-leaping").
day(11, eleventh, "Eleven pipers piping").
day(12, twelfth, "Twelve drummers drumming").

lyrics:-
    sing(1, []).
    
stanza(N, Presents):-
    between(1,11,N),
    nl,
    sing(N, Presents).
stanza(12, Presents):-
    sing(12, Presents).
stanza(13, _). % The end
    
sing(N0, PreviousPresents):-
    between(1,12,N0),
    day(N0, W, Present),
    printf("On the %w day of Christmas,%nMy true love gave to me:%n",W),
    maplist(println, [Present|PreviousPresents]),
    succ(N0, N1),
    % N1 = N0+1,
    stanza(N1, [Present|PreviousPresents]).


succ(X,Y), var(X) ?=> X = Y-1.
succ(X,Y), var(Y) ?=> Y = X+1.