:- module(shiritori, [shiritori_load_data/2, shiritori/4]).

shiritori_load_data(Path,Data) :-
    open(Path,read,Stream,[encoding(utf8)]),
    construct_array(Stream,[],Data),
    close(Stream).

construct_array(Stream,Buffer,Data) :-
    construct_word(Stream,[],Last,Word),
    (Word == [] ->
     Added = Buffer;
     Added = [Word|Buffer]),
    (Last == end_of_file ->
     reverse(Added,Data);
     construct_array(Stream,Added,Data)).

construct_word(Stream,Buffer,Last,Word) :-
    get_char(Stream,Char),
    ((Char == end_of_file; Char == ','; Char == '\n') ->
     Last = Char, reverse(Buffer,Word);
     construct_word(Stream,[Char|Buffer],Last,Word)).

shiritori(W0,W1) :- W1 = [H|_], last(W0,H).

shiritori([],Data,Data,0).
shiritori([W],Data,Rest,1) :- select(W,Data,Rest).
shiritori([W0,W1|S],Data,Rest,N) :-
    N>1, N1 is N-1,
    select(W0,Data,R0),
    shiritori(W0,W1),
    shiritori([W1|S],R0,Rest,N1).