/*
 * LispStackFrame.java
 *
 * Copyright (C) 2009 Mark Evenson
 * $Id: LispStackFrame.java 14572 2013-08-10 08:24:46Z mevenson $
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obligated to do so.  If you do not wish to do so, delete this
 * exception statement from your version.
 */

package org.armedbear.lisp;

import static org.armedbear.lisp.Lisp.*;

public class LispStackFrame 
  extends StackFrame
{
  public final LispObject operator;
  private final LispObject[] args;

  private final static class UnavailableArgument extends LispObject 
  {
    public UnavailableArgument () { }
     
    public LispObject printObject() { 
      return new SimpleString(unreadableString("unavailable arg", false)); 
    }
  }

  private final static LispObject UNAVAILABLE_ARG = new UnavailableArgument();

  public LispStackFrame(Object[] stack, int framePos, int numArgs)
  {
    operator = (LispObject) stack[framePos];
    args = new LispObject[numArgs];
    for (int i = 0; i < numArgs; i++) 
    {
      args[i] = (LispObject) stack[framePos + 1 + i];
    }
  }

    
   public LispObject typeOf() { 
     return Symbol.LISP_STACK_FRAME; 
   }
  
    
   public LispObject classOf() { 
     return BuiltInClass.LISP_STACK_FRAME; 
   }

    
   public LispObject printObject() 
   { 
     String result = "";
     final String LISP_STACK_FRAME = "LISP-STACK-FRAME";
     try {
       result = unreadableString(LISP_STACK_FRAME + " " + toLispList().printObject());
     } catch (Throwable t) { // error while printing stack
       Debug.trace("Serious printing error: ");
       Debug.trace(t);
       result = unreadableString(LISP_STACK_FRAME);
     }
     return new SimpleString(result);
   }

   
  public LispObject typep(LispObject typeSpecifier) 

  {
    if (typeSpecifier == Symbol.LISP_STACK_FRAME)
      return T;
    if (typeSpecifier == BuiltInClass.LISP_STACK_FRAME)
      return T;
    return super.typep(typeSpecifier);
   }

  public LispObject toLispList() 

  {
    LispObject result = argsToLispList();
    if (operator instanceof Operator) {
      LispObject lambdaName = ((Operator)operator).getLambdaName();
      if (lambdaName != null && lambdaName != Lisp.NIL)
	return result.push(lambdaName);
    }
    return result.push(operator);
  }

  private LispObject argsToLispList()

  {
    LispObject result = Lisp.NIL;
    for (int i = 0; i < args.length; i++)
      // `args' come here from LispThread.execute. I don't know
      // how it comes that some callers pass NULL ptrs around but
      // we better do not create conses with their CAR being NULL;
      // it'll horribly break printing such a cons; and probably
      // other bad things may happen, too. --TCR, 2009-09-17.
      if (args[i] == null)
        result = result.push(UNAVAILABLE_ARG);
      else
        result = result.push(args[i]);
    return result.nreverse();
  }

  public SimpleString toLispString() 

  {
    String result;
    try {
      result = this.toLispList().printObject().toString();
    } catch (Throwable t) { // error while printing stack
      Debug.trace("Serious printing error: ");
      Debug.trace(t);
      result = unreadableString("LISP-STACK-FRAME");
    }
    return new SimpleString(result);
  }

  public int getNumArgs()
  {
    return args.length;
  }

  public LispObject getOperator() {
    return operator;
  }

    
  public LispObject getParts() 

  {
    LispObject result = NIL;
    result = result.push(new Cons("OPERATOR", getOperator()));
    LispObject args = argsToLispList();
    if (args != NIL) {
      result = result.push(new Cons("ARGS", args));
    }
			 
    return result.nreverse();
  }
}
