/*
 * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
 *
 * This file is part of Resin(R) Open Source
 *
 * Each copy or derived work must preserve the copyright notice and this
 * notice unmodified.
 *
 * Resin Open Source 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.
 *
 * Resin Open Source 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, or any warranty
 * of NON-INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Resin Open Source; if not, write to the
 *   Free SoftwareFoundation, Inc.
 *   59 Temple Place, Suite 330
 *   Boston, MA 02111-1307  USA
 *
 * @author Scott Ferguson
 */

package com.caucho.ejb.ql;

import java.lang.reflect.Method;

import com.caucho.util.CharBuffer;

import com.caucho.config.ConfigException;

import com.caucho.ejb.cfg.EjbEntityBean;

/**
 * An 'is' expression
 */
class EmptyExpr extends Expr {
  // value expression
  private CollectionExpr _collection;
  // true for negative
  private boolean _isNot;
  //
  private Query _parent;

  /**
   * Creates a like expression.
   *
   * @param value the value expression
   * @param isNot if true, this the like is negated
   */
  EmptyExpr(Expr collection, boolean isNot)
    throws ConfigException
  {
    _isNot = isNot;
    
    if (collection instanceof CollectionExpr)
      _collection = (CollectionExpr) collection;
    else
      throw error(L.l("IS EMPTY needs a collection-path at `{0}'.",
                      collection));

    evalTypes();
  }

  /**
   * Evaluates the types for the expression
   */
  void evalTypes()
    throws ConfigException
  {
    setJavaType(boolean.class);
  }

  public String addRelation(EjbEntityBean bean, FieldExpr id)
    throws ConfigException
  {
    return null;
  }

  public Method getMethod()
  {
    //return _parent.getMethod();
    throw new UnsupportedOperationException();
  }

  public EjbEntityBean getPersistentBean()
  {
    //return _parent.getPersistentBean();
    throw new UnsupportedOperationException();
  }
  
  public void addArg(Expr arg)
  {
    //_parent.addArg(arg);
    throw new UnsupportedOperationException();
  }

  /**
   * Prints the where SQL for this expression
   *
   * @param gen the java code generator
   */
  void generateWhere(CharBuffer cb)
  {
    if (_collection != null) {
      _collection.generateSelect(cb);
      
      if (_isNot)
        cb.append(" IS NOT EMPTY");
      else
        cb.append(" IS EMPTY");

      /*
      String tableSQL = _collection.getRelation().getSQLTable();
      String []tableSrc = _collection.getRelation().getSourceSQLColumns();
      String []tableDst = _collection.getRelation().getTargetSQLColumns();
    
      String id = "caucho" + gen.getUnique();
    
      cb.append("EXISTS(SELECT * FROM " + tableSQL + " " + id + " ");
      cb.append("WHERE ");

      for (int i = 0; i < tableSrc.length; i++) {
        if (i != 0)
          cb.append(" AND ");
        
        cb.append(id + "." + tableSrc[i] + " = ");

        _collection.getBase().printComponent(gen, i);
      }
    
      cb.append(")");
      */
    }
    else {
      cb.append("TRUE");
    }
  }
  
  public String toString()
  {
    String str = _collection.toString();

    if (_isNot)
      return str + " IS NOT EMPTY";
    else
      return str + " IS EMPTY";
  }
}
