% From the book
% PROLOG PROGRAMMING IN DEPTH
% by Michael A. Covington, Donald Nute, and Andre Vellino
% (Prentice Hall, 1997).
% Copyright 1997 Prentice-Hall, Inc.
% For educational use only

% File CAR.PL
% Simple automotive expert system



%
% Main control procedures
%
 %  write('This program diagnoses why a car won''t start.'),nl,
 %  write('Answer all questions with Y for yes or N for no.'),nl,
 
start :-
   clear_stored_answers,
   try_all_possibilities.

try_all_possibilities :-     % Backtrack through all possibilities...
   defect_may_be(D),
   explain(D),
   fail.

try_all_possibilities.       % ...then succeed with no further action.


%
% Diagnostic knowledge base
%   (conditions under which to give each diagnosis)
%

defect_may_be(drained_battery) :-
   user_says(starter_was_ok,yes),
   user_says(starter_is_ok,no).

defect_may_be(wrong_gear) :-
   user_says(starter_was_ok,no).

defect_may_be(starting_system) :-
   user_says(starter_was_ok,no).

defect_may_be(fuel_system) :-
   user_says(starter_was_ok,yes),
   user_says(fuel_is_ok,no).

defect_may_be(ignition_system) :-
   user_says(starter_was_ok,yes),
   user_says(fuel_is_ok,yes).


%
% Case knowledge base
%   (information supplied by the user during the consultation)
%

:- dynamic(stored_answer/2).

   % (Clauses get added as user answers questions.)


%
% Procedure to get rid of the stored answers
% without abolishing the dynamic declaration
%

clear_stored_answers :- retract(stored_answer(_,_)).
clear_stored_answers.


%
% Procedure to retrieve the user's answer to each question when needed,
% or ask the question if it has not already been asked
%

user_says(Q,A) :- stored_answer(Q,A).

user_says(Q,A) :- \+ stored_answer(Q,_),
                  ask_question(Q,Response),
		  		  asserta(stored_answer(Q,Response)),
                  Response = A.
	
% Texts of the questions
%
ask_question(starter_was_ok,Res) :-
	show_yes_no_dialog('When you first started trying to start the car\n did the starter crank the engine normally?',Res).

ask_question(starter_was_ok,Res) :-
	show_yes_no_dialog('Does the starter crank the engine normally now? ',Res).

ask_question(starter_was_ok,Res) :-
	show_yes_no_dialog('Look in the carburetor.  Can you see or smell gasoline?',Res).


show_yes_no_dialog(Tekst,Response) :-
		jpl_new(array(class([java,lang],['String'])),['yes','no'], ArrayRef),
		jpl_get(ArrayRef,0,ArrayPosRef),
		jpl_get('javax.swing.JOptionPane', 'YES_NO_OPTION', YesNoRef),
		jpl_get('javax.swing.JOptionPane', 'QUESTION_MESSAGE', QuestionRef),
		jpl_call('javax.swing.JOptionPane', 'showOptionDialog', [@('null'),
					       Tekst, 
					       'Question',
					       YesNoRef,
					       QuestionRef,
					       @(null), 
					       ArrayRef, 
					       ArrayPosRef], 
					       RetVal),
		interpret(RetVal,Response).

interpret(1,no).  % ASCII 89  = 'Y'
interpret(0,yes). % ASCII 121 = 'y'


show_explain_dialog(Tekst) :-
		jpl_call('javax.swing.JOptionPane', 'showMessageDialog', [@('null'),Tekst],_).
	

%
%  Explanations for the various diagnoses
%

explain(wrong_gear) :-
	show_explain_dialog('Check that the gearshift is set to Park or Neutral.Try jiggling the gearshift lever.').

explain(starting_system) :-
	show_explain_dialog('Check for a defective battery, voltage regulator, or alternator; if any of these is the problem, charging the battery or jump-starting may get the car going temporarily.Or the starter itself may be defective').


explain(drained_battery) :-
	show_explain_dialog('Your attempts to start the car have run down the battery.Recharging or jump-starting will be necessary.But there is probably nothing wrong with the battery itself.').


explain(fuel_system) :-
	 show_explain_dialog('Check whether there is fuel in the tank.If so, check for a clogged fuel line or filter or a defective fuel pump.').

explain(ignition_system) :-
	show_explain_dialog('Check the spark plugs, cables, distributor,coil, and other parts of the ignition system.If any of these are visibly defective or long overdue for replacement, replace them; if this does not solve the problem, consult a mechanic.').