/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */

package org.opendaylight.controller.netconf.client;

import com.google.common.base.Function;
import com.google.common.collect.Collections2;
import io.netty.channel.Channel;
import io.netty.util.Timer;
import io.netty.util.concurrent.Promise;
import org.opendaylight.controller.netconf.api.NetconfMessage;
import org.opendaylight.controller.netconf.api.NetconfSessionPreferences;
import org.opendaylight.controller.netconf.util.AbstractNetconfSessionNegotiator;
import org.opendaylight.controller.netconf.util.xml.XMLNetconfUtil;
import org.opendaylight.controller.netconf.util.xml.XmlElement;
import org.opendaylight.controller.netconf.util.xml.XmlNetconfConstants;
import org.opendaylight.controller.netconf.util.xml.XmlUtil;
import org.opendaylight.protocol.framework.SessionListener;
import org.w3c.dom.Document;
import org.w3c.dom.Node;

import javax.annotation.Nullable;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import java.util.Collection;
import java.util.List;

public class NetconfClientSessionNegotiator extends
        AbstractNetconfSessionNegotiator<NetconfSessionPreferences, NetconfClientSession> {

    protected NetconfClientSessionNegotiator(NetconfSessionPreferences sessionPreferences,
            Promise<NetconfClientSession> promise, Channel channel, Timer timer, SessionListener sessionListener,
            long connectionTimeoutMillis) {
        super(sessionPreferences, promise, channel, timer, sessionListener, connectionTimeoutMillis);
    }

    private static Collection<String> getCapabilities(Document doc) {
        XmlElement responseElement = XmlElement.fromDomDocument(doc);
        XmlElement capabilitiesElement = responseElement
                .getOnlyChildElementWithSameNamespace(XmlNetconfConstants.CAPABILITIES);
        List<XmlElement> caps = capabilitiesElement.getChildElements(XmlNetconfConstants.CAPABILITY);
        return Collections2.transform(caps, new Function<XmlElement, String>() {

            @Nullable
            @Override
            public String apply(@Nullable XmlElement input) {
                // Trim possible leading/tailing whitespace
                return input.getTextContent().trim();
            }
        });
    }

    private static final XPathExpression sessionIdXPath = XMLNetconfUtil
            .compileXPath("/netconf:hello/netconf:session-id");

    private long extractSessionId(Document doc) {
        final Node sessionIdNode = (Node) XmlUtil.evaluateXPath(sessionIdXPath, doc, XPathConstants.NODE);
        String textContent = sessionIdNode.getTextContent();
        if (textContent == null || textContent.equals("")) {
            throw new IllegalStateException("Session id not received from server");
        }

        return Long.valueOf(textContent);
    }

    @Override
    protected NetconfClientSession getSession(SessionListener sessionListener, Channel channel, NetconfMessage message) {
        return new NetconfClientSession(sessionListener, channel, extractSessionId(message.getDocument()),
                getCapabilities(message.getDocument()));
    }
}