/*
 * EqualityExpr.java
 * Copyright (C) 2004 The Free Software Foundation
 * 
 * This file is part of GNU JAXP, a library.
 *
 * GNU JAXP 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.
 * 
 * GNU JAXP 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
 *
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * 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
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version. 
 */

package gnu.xml.xpath;

import java.util.Collection;
import java.util.Iterator;
import org.w3c.dom.Node;

/**
 * Boolean equality expression.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 */
final class EqualityExpr
  extends Expr
{

  final Expr lhs;
  final Expr rhs;
  final boolean invert;

  EqualityExpr(Expr lhs, Expr rhs, boolean invert)
  {
    this.lhs = lhs;
    this.rhs = rhs;
    this.invert = invert;
  }

  public Object evaluate(Node context, int pos, int len)
  {
    boolean val = evaluateImpl(context, pos, len);
    if (invert)
      {
        return val ? Boolean.FALSE : Boolean.TRUE;
      }
    else
      {
        return val ? Boolean.TRUE : Boolean.FALSE;
      }
  }

  private boolean evaluateImpl(Node context, int pos, int len)
  {
    Object left = lhs.evaluate(context, pos, len);
    Object right = rhs.evaluate(context, pos, len);

    /*
     * If both objects to be compared are node-sets, then the comparison
     * will be true if and only if there is a node in the first node-set and
     * a node in the second node-set such that the result of performing the
     * comparison on the string-values of the two nodes is true.
     */
    boolean flns = left instanceof Collection;
    boolean frns = right instanceof Collection;
    if (flns && frns)
      {
        Collection lns = (Collection) left;
        Collection rns = (Collection) right;
        boolean all = true;
        for (Iterator i = lns.iterator(); i.hasNext(); )
          {
            Node ltest = (Node) i.next();
            for (Iterator j = rns.iterator(); j.hasNext(); )
              {
                Node rtest = (Node) j.next();
                if (ltest == rtest || ltest.equals(rtest))
                  {
                    // much shorter
                    if (!invert)
                      {
                        return true;
                      }
                  }
                else if (stringValue(ltest).equals(stringValue(rtest)))
                  {
                    if (!invert)
                      {
                        return true;
                      }
                  }
                else
                  {
                    all = false;
                  }
              }
          }
        return false;
      }
    /* 
     * If one object to be compared is a node-set and the other is a number,
     * then the comparison will be true if and only if there is a node in
     * the node-set such that the result of performing the comparison on the
     * number to be compared and on the result of converting the
     * string-value of that node to a number using the number function is
     * true.
     */
    boolean fln = left instanceof Double;
    boolean frn = right instanceof Double;
    if ((flns && frn) || (frns && fln))
      {
        Collection ns = flns ? (Collection) left : (Collection) right;
        double n = fln ? ((Double) left).doubleValue() :
          ((Double) right).doubleValue();
        boolean all = true;
        for (Iterator i = ns.iterator(); i.hasNext(); )
          {
            Node test = (Node) i.next();
            double nn = _number(context, stringValue(test));
            if (nn == n)
              {
                if (!invert)
                  {
                    return true;
                  }
              }
            else
              {
                all = false;
              }
          }
        return invert ? all : false;
      }
    /*
     * If one object to be compared is a node-set and the other is a
     * string, then the comparison will be true if and only if there is a
     * node in the node-set such that the result of performing the
     * comparison on the string-value of the node and the other string is
     * true.
     */
    boolean fls = left instanceof String;
    boolean frs = right instanceof String;
    if ((flns && frs) || (frns && fls))
      {
        Collection ns = flns ? (Collection) left : (Collection) right;
        String s = fls ? (String) left : (String) right;
        boolean all = true;
        for (Iterator i = ns.iterator(); i.hasNext(); )
          {
            Node test = (Node) i.next();
            if (stringValue(test).equals(s))
              {
                if (!invert)
                  {
                    return true;
                  }
              }
            else
              {
                all = false;
              }
          }
        return invert ? all : false;
      }
    /*
     * If one object to be compared is a node-set and the other is a
     * boolean, then the comparison will be true if and only if the result
     * of performing the comparison on the boolean and on the result of
     * converting the node-set to a boolean using the boolean function is
     * true.
     */
    boolean flb = left instanceof Boolean;
    boolean frb = right instanceof Boolean;
    if ((flns && frb) || (frns && flb))
      {
        Collection ns = flns ? (Collection) left : (Collection) right;
        boolean b = flb ? ((Boolean) left).booleanValue() :
          ((Boolean) right).booleanValue();
        return _boolean(context, ns) == b;
      }
    /*
     * If at least one object to be compared is a boolean, then each object
     * to be compared is converted to a boolean as if by applying the
     * boolean function.
     */
    if (flb || frb)
      {
        boolean lb = flb ? ((Boolean) left).booleanValue() :
          _boolean(context, left);
        boolean rb = frb ? ((Boolean) right).booleanValue() :
          _boolean(context, right);
        return lb == rb;
      }
    /*
     * Otherwise, if at least one object to be compared is
     * a number, then each object to be compared is converted to a number as
     * if by applying the number function.
     */
    if (fln || frn)
      {
        double ln = fln ? ((Double) left).doubleValue() :
          _number(context, left);
        double rn = frn ? ((Double) right).doubleValue() :
          _number(context, right);
        return ln == rn;
      }
    /*
     * Otherwise, both objects to be
     * compared are converted to strings as if by applying the string
     * function.
     */
    String ls = fls ? (String) left : _string(context, left);
    String rs = frs ? (String) right : _string(context, right);
    return ls.equals(rs);
  }

  public Expr clone(Object context)
  {
    return new EqualityExpr(lhs.clone(context), rhs.clone(context), invert);
  }

  public String toString()
  {
    if (invert)
      {
        return lhs + " != " + rhs;
      }
    else
      {
        return lhs + " = " + rhs;
      }
  }
  
}
