%% INPUT ACQUISITION IN A CONVENIENT FORMAT

chat :- repeat, readLine(Sentence), parse(Clause, Sentence, _), respondTo(Clause), Clause = stop.
	
%% read text as a list (words) of lists of ASCII (word) until LF terminator an split off word suffixes	
readLine(Sentence) :- readCharLists(Words), morphs(Words, Sentence), ! .
	
%% read text as a list (words) of lists of ASCII (word) until LF terminator	
readCharLists([Word | Words]) :- readWord(Word, Term), ( Term = 10, Words = []   ;   readCharLists(Words)).

%% read a word as a list of ASCII	
readWord(W, Term) :- get0(C), ((C = 10 ; C = 32), Term = C, W = []   ;   readWord(Chars, Term), W = [C | Chars]).
	
%% split suffixes on elements of a list that are lists of ASCII and convert them to atoms (result is a list of atoms)
morphs([], []).
morphs([Word | Rest], Atoms) :- morph(Word, Atom), morphs(Rest, Atoms2), append(Atom, Atoms2, Atoms).
	
%% split core/suffix on a word (list of ASCII) and convert it to a list of atoms
morph([], []).
morph(Word, Atoms) :- morphrules(Word, Comps), maplist(name, Atoms, Comps).
	
%% the "split suffix" rule for now, others can be plugged in later
morphrules(Chars, Comps) :- append(X1, X2, Chars), suffix(X2), Comps = [X1, X2].
morphrules(Chars, [Chars]).

%% used by the (only) "split suffix" rule	
suffix("?").
suffix(".").
suffix("'s").

%% utility to slap a pericate to all elements of a list quickly
mapcar(_, [], []).
mapcar(P, [H1 | T1], [H2 | T2]) :- Q =..[P, H1, H2], call(Q), mapcar(P, T1, T2).

%% THE LANGUAGE UNDERSTANDING

%% parse(Clause, S, Srem) :- det1(S, S0), det2(S0, S1), det3(S1, S2), det4(S2, Srem).
%% [P] aka det1([P | St], St).
%% type(T, S, Srem) :- det8(S, Strem).
%% det8([ T | St ], St).

parse(stop, ['Stop', '.'], []).
parse(C) --> thing(Name), [is], particle(a), type(T), ['.'], {C=..[T, Name], !}.
parse(C) --> particle('A'), type(T1), [is], particle(a), type(T2), ['.'], {Head=..[T2, X], Condition=..[T1,X], C = (Head :- Condition), !}.
parse(C) --> ['Is'], thing(Name), particle(a), type(T), ['?'], {G=..[T, Name], C = '?-'(G), !}.
parse(C) --> particle('A'), type(T1), [is], particle(a), type(T2), ['.'], {Head=..[T2, X], Condition=..[T1,X], C = (Head :- Condition), !}.
parse(C) --> ['List', 'all'], type(T), ['.'], {C = '?-2'(T), !}.
parse(noparse, _ , _).

particle(a) --> [a].
particle(a) --> [an].
particle('A') --> ['A'].
particle('A') --> ['An'].

thing(N) --> [N], {capital(N)}.
capital(N) :- name(N, [F|_]), F < 96.
type(T) --> [T], {not(capital(T))}.

%% THE ACTIONS FOR UNDERSTOOD PARTS

respondTo(stop) :- write('All done.'), nl, !.
respondTo(noparse) :- write( 'I don''t understand that.') , nl, !.
respondTo( '?-'(G)) :- (G -> write('Yes') ; write('No')), !, nl, nl.
respondTo( '?-2'(T)) :- P=..[T,X], write(P), bagof(X,P,XS), write(XS), !, nl, nl.
respondTo(C) :- asserta(C), write('Ok'), nl, !.