% 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

% Menu that obtains 'yes' or 'no' answer

question(Result,T):-
   jpl_call('javax.swing.JOptionPane','showConfirmDialog',[(@null),T,'Question',0],X),
   change(X,Result).   
info(X):-
   jpl_call('javax.swing.JOptionPane','showMessageDialog',[(@null),X],F).
   
get_yes_or_no(Q,Result) :- 
                           ask_question(Q,X),
                           question(Result,X).                 
change(0,yes).
change(1,no).
        
% 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
%

start :-
   info('This program diagnoses why a car won''t start. \n Answer all questions with Y for yes or N for no.'),
   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)
%



   % (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(_,_)),fail.
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,_),
                  get_yes_or_no(Q,Response),
                  asserta(stored_answer(Q,Response)),
                  Response = A.


%
% Texts of the questions
%

ask_question(starter_was_ok,'When you first started trying to start the car, \n did the starter crank the engine normally? ').

ask_question(starter_is_ok,'Does the starter crank the engine normally now? ').

ask_question(fuel_is_ok,'Look in the carburetor.  Can you see or smell gasoline?').

%
%  Explanations for the various diagnoses
%

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

explain(starting_system) :-
   info('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) :-
   info('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) :-
   info('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) :-
   info('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.').

   :- dynamic(stored_answer/2).
nth_char('234',X).