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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 
*/
//#########################################################################
//	PredicateEntry
//#########################################################################

package ubc.cs.JLog.Parser;

import java.lang.*;
import java.util.*;
import ubc.cs.JLog.Foundation.*;
import ubc.cs.JLog.Terms.*;

/**
* Abstract base class for entries in the pPredicateRegistry. Each
* predicate entry subclass represents a type of prolog predicate at the 
* level needed for the parser (they are parse time representations).
* Predicate entries contain information about the corresponding predicate, such
* as name and arity.
* Predicate entries generate the corresponding real Prolog predicate
* objects. 
*  
* @author       Glendon Holst
* @version      %I%, %G%
*/
abstract public class pPredicateEntry implements iNameArity
{
 public static final int		NARY_ARITY = -1;
 
 protected String 		name;
 protected int 			arity;
 protected String		library = null; 

 public 	pPredicateEntry(String name,int arity)
 {
  this.name = name;
  this.arity = arity;
  
   // prevent invalid entries
  if (name == null || name.length() <= 0)
   throw new InvalidPredicateNameException();
 };
 
 public String 			getName()
 {
  return name;
 };
 
 public int 			getArity()
 {
  return arity;
 };

 /**
  * Tests the arity of this entry.  Most predicates entries will only return true
  * if there is an exact match, however, for n-ary predicates, arity should be set
  * to NARY_ARITY, and isArity should always return true for supported arities.
  *
  * @param a		The arity to test this entry for.
  *
  * @return 		boolean which is true if entry can be of this arity.
  */
 public boolean 		isArity(int a)
 {
  return arity == a;
 };

 /**
  * Set the name of the library associated with this predicate.  Once an association is made
  * it is an error to change it (throws InvalidLibraryEntryException in this case).
  * Predicates default to a null valued library.
  *
  * @param lib		The name of the library.
  */
 public void			setLibrary(String lib)
 {
  if (library == null)
   library = lib;
  else
   throw new InvalidLibraryEntryException();
 };

 /**
  * Get the name of the library associated with this predicate.
  *
  * @return		The name of the library. May be null.
  */
 public String			getLibrary()
 {
  return library;
 };

 public boolean			sameLibrary(String lib)
 {
  if (library == null && lib == null)
   return true;
  if (library == null || lib == null)
   return false;
  
   return library.equals(lib); 
 };
  
 /**
  * Public interface for generating the real prolog term objects.  May generate syntax errors.
  * Invokes internal createPredicate to perform actual construction of term.
  *
  * @param pt 		The parsing token representing the operator. Used for generating 
  * 			information about the location of the operator in the input stream.
  * @param cterm 	A terms belonging to this predicate.
  *
  * @return 		iPredicat representing this predicate and its terms.
  */
 public iPredicate 			createPredicate(pToken pt,jCompoundTerm cterm)
 {
  if (!isArity(cterm.size()))
   throw new SyntaxErrorException("Term with arity "+String.valueOf(arity)+" expected for predicate at ",
                                   pt.getPosition(),pt.getLine(),pt.getCharPos()); 

  return createPredicate(cterm);
 };
 
 /**
  * Public interface for generating the real prolog term objects.  May generate syntax errors.
  * Invokes internal createPredicate to perform actual construction of term.
  *  
  * @return 		iPredicat representing this predicate with given arity,  
  * 			with unamed variables for terms.
  */
 public iPredicate 			createPredicate()
 {jCompoundTerm 	cterm = new jCompoundTerm();
  int 				i;
  
  for (i = 0; i < arity; i++)
   cterm.addTerm(new jVariable("_"));
  
  return createPredicate(cterm);
 };
 
 /**
  * The internal method for creating the iPredicate representation of this 
  * predicate representation.  Subclasses must override.  The terms are provided, already created.
  * The caller is responsible to ensure that arity and cterm.size match.
  *
  * @param cterm 	The collection of jTerms.
  *
  * @return 		iPredicate representing this predicate and its terms.
  */
 abstract public iPredicate 		createPredicate(jCompoundTerm cterm);

 public String			toString()
 {StringBuffer			sb = new StringBuffer();

  sb.append(getName() + "/" + Integer.toString(getArity()));
   
  {String   lib = getLibrary();
  
   if (lib != null)
    sb.append(" library:"+lib);
  }
  
  return sb.toString();
 };
};