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/*
    This file is part of JLog.

    Created by Glendon Holst for Alan Mackworth and the 
    "Computational Intelligence: A Logical Approach" text.
    
    Copyright 1998, 2000, 2002 by University of British Columbia and 
    Alan Mackworth.
    
    This notice must remain in all files which belong to, or are derived 
    from JLog.
    
    Check  or 
     for further information
    about JLog, or to contact the authors.
     
    JLog is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    JLog is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with JLog; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    URLs:  or 
*/
//#########################################################################
//	pParseStream
//#########################################################################

package ubc.cs.JLog.Parser;

import java.io.*;
import java.util.*;
import ubc.cs.JLog.Foundation.*;
import ubc.cs.JLog.Terms.*;
import ubc.cs.JLog.Builtins.*;

/**
* The main parsing class that converts packets into their correspoding prolog terms.  
* Used to process user queries, and consult a database. Directly or indirectly uses 
* the pPreTokenizeStream, pTokenizeStream, and 
* pPreParseStream.
*  
* @author       Glendon Holst
* @version      %I%, %G%
*/
public class pParseStream
{
 protected pPreParseStream 		parser;
 protected jKnowledgeBase 		database;
 
 public pParseStream(String s,jKnowledgeBase kb,pPredicateRegistry pr,pOperatorRegistry or)
 { 
  parser = new pPreParseStream(s,pr,or);
  database = kb;
 };
 
 public pParseStream(Reader r,jKnowledgeBase kb,pPredicateRegistry pr,pOperatorRegistry or)
 {
  parser = new pPreParseStream(r,pr,or);
  database = kb;
 };

 /**
  * Parse the source stream as a query, producing a term representation. 
  *
  * @return		The jPredicateTerms instance representing the parsed query string.
  */  
 public jPredicateTerms 	parseQuery()
 {
  return parseQuery(null);
 };
 
 /**
  * Parse the source stream as a query, producing a term representation. 
  *
  * @param assignments		A Hashtable representing variable names as keys,
  *							and their corresponding jTerm value.  The keys must
  *							String types, and be valid variable names.  Values must be
  *							jTerm objects (or sub-classes)
  * @return		The jPredicateTerms instance representing the parsed query string.
  */  
 public jPredicateTerms 	parseQuery(Hashtable assignments)
 {pPacket 					pp;
  
  if ((pp = parser.parse()) != null)
  {pVariableRegistry 		vars = new pVariableRegistry();
   pTermToPacketHashtable 	phash = new pTermToPacketHashtable();
   jTerm 					term;
   jPredicateTerms 			base;

   // add predefined variables to variable registry
   if (assignments != null)
   {Enumeration		e = assignments.keys();
   
    while (e.hasMoreElements())
	{String		s = (String) e.nextElement();
	 jTerm		t = (jTerm) assignments.get(s);
	 jVariable  v = vars.getVariable(s);
	 
	 v.setBinding(t);
	}
   }

   // ensure that query terms use non-generic predicates
   pp.setGeneric(false);

   term = pp.getTerm(vars,phash);
   
   if (term instanceof jCommand)
    term = ((jCommand) term).getRHS();
    
   try
   {
    base = new jPredicateTerms();
    base.makePredicateTerms(term);
   }
   catch (PredicateExpectedException e)
   {pToken 		pt = phash.getToken(e.getTerm(),pp);
    
    throw new SyntaxErrorException("Expected predicate at ",
                                      pt.getPosition(),pt.getLine(),pt.getCharPos());
   }
    
   return base;
  }
  return null;
 };
  
 public jTerm 				parseTerm()
 {pPacket 					pp;
  
  if ((pp = parser.parse()) != null)
  {pVariableRegistry 		vars = new pVariableRegistry();
   pTermToPacketHashtable 	phash = new pTermToPacketHashtable();
   jTerm 					term;

   // ensure that terms use non-generic predicates. commands and if operators
   // ensure that predicates to their left are generic and to the right are non-generic.
   pp.setGeneric(false);

   term = pp.getTerm(vars,phash);
   
   if (term instanceof jCommand)
    term = ((jCommand) term).getRHS();
    
   return term;
  }
  return null;
 };
  
 public void 				parseSource()
 {pPacket 					pp;
  pUpdateDatabaseRules 		dhash = new pUpdateDatabaseRules(database); 					

  while ((pp = parser.parse()) != null)
  {pVariableRegistry 		vars = new pVariableRegistry();
   pTermToPacketHashtable 	phash = new pTermToPacketHashtable();
   jTerm 					term;
   jPredicate 				head;
   jPredicateTerms 			base;

   // ensure that head predicates use generic predicates.  commands and if operators
   // ensure that predicates to their right use non-generic predicates.
   pp.setGeneric(true);
      
   term = pp.getTerm(vars,phash);

   if (term instanceof jIf)
   {jIf 		jif = (jIf) term;
    jTerm 		lhs = jif.getLHS();
    
    if (lhs instanceof jPredicate)
     head = (jPredicate) lhs;
    else
    {pToken 		pt = phash.getToken(term,pp);
    
     throw new SyntaxErrorException("Expected single predicate before if operator at ",
     									pt.getPosition(),pt.getLine(),pt.getCharPos());
    } 
    
    try
    {
     base = new jPredicateTerms();
     base.makePredicateTerms(jif.getRHS());
    }
    catch (PredicateExpectedException e)
    {pToken 		pt = phash.getToken(e.getTerm(),pp);
    
     throw new SyntaxErrorException("Expected predicate at ",
     									pt.getPosition(),pt.getLine(),pt.getCharPos());
    }
     
    dhash.addRule(new jRule(head,base));
   }
   else if (term instanceof jCommand)
   {jCommand 		command = (jCommand) term;
   
    try
    {
     base = new jPredicateTerms();
     base.makePredicateTerms(command.getRHS());
    }
    catch (PredicateExpectedException e)
    {pToken 		pt = phash.getToken(e.getTerm(),pp);
    
     throw new SyntaxErrorException("Expected predicate at ",
     									pt.getPosition(),pt.getLine(),pt.getCharPos());
    }
    
    query(base);
   }
   else if (term instanceof jDCG)
   {jDCG 		dcg = (jDCG) term;

    try
    {
     dhash.addRule(dcg.makeDCGRule());
    }
    catch (PredicateExpectedException e)
    {pToken 		pt = phash.getToken(e.getTerm(),pp);
    
     throw new SyntaxErrorException("Expected predicate at ",
     									pt.getPosition(),pt.getLine(),pt.getCharPos());
    }
   }
   else if (term instanceof jPredicate)
   {
    head = (jPredicate) term;
    base = new jPredicateTerms();
    
    dhash.addRule(new jRule(head,base));
   }
   else
   {pToken 		pt = phash.getToken(term,pp);

    throw new SyntaxErrorException("Expected predicate or rule at ",
    									pt.getPosition(),pt.getLine(),pt.getCharPos());
   }
  }
 };
 
 protected void 	query(jPredicateTerms q)
 {jProver 			prover;
 
  prover = new jProver(database);
  prover.prove(q);
 };
};