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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package net.sf.saxon.pattern;

import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;

import java.util.HashSet;
import java.util.Set;

/**
 * A pattern formed as the difference of two other patterns
 */

public class ExceptPattern extends VennPattern {

    /**
     * Constructor
     *
     * @param p1 the left-hand operand
     * @param p2 the right-hand operand
     */

    public ExceptPattern(Pattern p1, Pattern p2) {
        super(p1, p2);
    }

    /**
     * Get an ItemType that all the items matching this pattern must satisfy
     */
    @Override
    public ItemType getItemType() {
        return p1.getItemType();
    }


    /**
     * Determine if the supplied node matches the pattern
     * @param item the node to be compared
     * @return true if the node matches either of the operand patterns
     */

    public boolean matches(Item item, XPathContext context) throws XPathException {
        return p1.matches(item, context) && !p2.matches(item, context);
    }

    /**
     * Determine whether this pattern matches a given Node within the subtree rooted at a given
     * anchor node. This method is used when the pattern is used for streaming.
     * @param node    The NodeInfo representing the Element or other node to be tested against the Pattern
     * @param anchor  The anchor node, which must match any AnchorPattern subpattern
     * @param context The dynamic context. Only relevant if the pattern
     *                uses variables, or contains calls on functions such as document() or key().
     * @return true if the node matches the Pattern, false otherwise
     */

    public boolean matchesBeneathAnchor(NodeInfo node, NodeInfo anchor, XPathContext context) throws XPathException {
        return p1.matchesBeneathAnchor(node, anchor, context) &&
                !p2.matchesBeneathAnchor(node, anchor, context);
    }

    /**
     * Determine whether this pattern is the same as another pattern
     * @param other the other object
     */

    public boolean equals(/*@NotNull*/ Object other) {
        if (other instanceof ExceptPattern) {
            Set s0 = new HashSet(10);
            gatherComponentPatterns(s0);
            Set s1 = new HashSet(10);
            ((ExceptPattern)other).gatherComponentPatterns(s1);
            return s0.equals(s1);
        } else {
            return false;
        }
    }

    /**
     * Hashcode supporting equals()
     */

    public int hashCode() {
        return 0x9bd7dfa6 ^ p1.hashCode() ^ p2.hashCode();
    }


}