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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.event;

import net.sf.saxon.om.AttributeMap;
import net.sf.saxon.om.NamespaceMap;
import net.sf.saxon.om.NamespaceUri;
import net.sf.saxon.om.NodeName;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.SchemaType;

/**
 * A Valve is a general-purpose component for use in a pipeline of receivers. It selects an alternative
 * destination for the pipeline events based on the namespace of the first startElement event.
 *
 * There is a primary destination which is selected initially. If the namespace of the first element has
 * a given value, then subsequent output is sent to an alternative destination.
 * */

public class Valve extends ProxyReceiver {

    private boolean started = false;
    private final NamespaceUri testNamespace;
    private final Receiver alternativeReceiver;

    /**
     * Create a {@code Valve}. Events sent to this {@code Valve} will be forwarded
     * to the primary receiver, unless the namespace of the first element node matches
     * the test namespace, in which case the events will be forwarded to the secondary receiver
     * @param testNamespace the test namespace
     * @param primary the primary Receiver
     * @param secondary the secondary Receiver
     */

    public Valve(NamespaceUri testNamespace, Receiver primary, Receiver secondary) {
        super(primary);
        this.testNamespace = testNamespace;
        this.alternativeReceiver = secondary;
    }

    @Override
    public void startElement(NodeName elemName, SchemaType type,
                             AttributeMap attributes, NamespaceMap namespaces,
                             Location location, int properties) throws XPathException {
        if (!started) {
            started = true;
            if (elemName.getNamespaceUri().equals(testNamespace)) {
                alternativeReceiver.open();
                alternativeReceiver.startDocument(ReceiverOption.NONE);
                try {
                    getNextReceiver().close();
                } catch (XPathException err) {
                    // ignore the failure
                }
                setUnderlyingReceiver(alternativeReceiver);
            }
        }
        super.startElement(elemName, type, attributes, namespaces, location, properties);
    }

    /**
     * Ask (after the first element event has been received) whether output was diverted to the
     * secondary receiver
     * @return true if output was diverted, that is, if the first element node was in the test namespace.
     */

    public boolean wasDiverted() {
        return getNextReceiver() == alternativeReceiver;
    }
}