/*
 * 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.protocol.bgp.parser.impl.message;


import com.google.common.base.Preconditions;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.buffer.Unpooled;
import java.util.List;
import org.opendaylight.protocol.bgp.parser.BGPDocumentedException;
import org.opendaylight.protocol.bgp.parser.BGPError;
import org.opendaylight.protocol.bgp.parser.BGPParsingException;
import org.opendaylight.protocol.bgp.parser.spi.AttributeRegistry;
import org.opendaylight.protocol.bgp.parser.spi.MessageParser;
import org.opendaylight.protocol.bgp.parser.spi.MessageSerializer;
import org.opendaylight.protocol.bgp.parser.spi.MessageUtil;
import org.opendaylight.protocol.util.ByteArray;
import org.opendaylight.protocol.util.Ipv4Util;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.inet.types.rev100924.Ipv4Prefix;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.Update;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.UpdateBuilder;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.update.Nlri;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.update.NlriBuilder;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.update.PathAttributes;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.update.WithdrawnRoutes;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.message.rev130919.update.WithdrawnRoutesBuilder;
import org.opendaylight.yangtools.yang.binding.Notification;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * LENGTH fields, that denote the length of the fields with variable length, have fixed SIZE.
 *
 * @see <a href="http://tools.ietf.org/html/rfc4271#section-4.3">BGP-4 Update Message Format</a>
 */
public class BGPUpdateMessageParser implements MessageParser, MessageSerializer {
    public static final int TYPE = 2;

    private static final Logger LOG = LoggerFactory.getLogger(BGPUpdateMessageParser.class);

    /**
     * Size of the withdrawn_routes_length field, in bytes.
     */
    public static final int WITHDRAWN_ROUTES_LENGTH_SIZE = 2;
    /**
     * Size of the total_path_attr_length field, in bytes.
     */
    public static final int TOTAL_PATH_ATTR_LENGTH_SIZE = 2;

    private final AttributeRegistry reg;

    // Constructors -------------------------------------------------------
    public BGPUpdateMessageParser(final AttributeRegistry reg) {
        this.reg = Preconditions.checkNotNull(reg);
    }

    // Getters & setters --------------------------------------------------

    @Override
    public Update parseMessageBody(final ByteBuf buffer, final int messageLength) throws BGPDocumentedException {
        Preconditions.checkArgument(buffer != null && buffer.readableBytes() != 0, "Byte array cannot be null or empty.");
        LOG.trace("Started parsing of update message: {}", ByteBufUtil.hexDump(buffer));

        final int withdrawnRoutesLength = buffer.readUnsignedShort();
        final UpdateBuilder eventBuilder = new UpdateBuilder();

        if (withdrawnRoutesLength > 0) {
            final List<Ipv4Prefix> withdrawnRoutes = Ipv4Util.prefixListForBytes(ByteArray.readBytes(buffer, withdrawnRoutesLength));
            eventBuilder.setWithdrawnRoutes(new WithdrawnRoutesBuilder().setWithdrawnRoutes(withdrawnRoutes).build());
        }
        final int totalPathAttrLength = buffer.readUnsignedShort();

        if (withdrawnRoutesLength == 0 && totalPathAttrLength == 0) {
            return eventBuilder.build();
        }
        if (totalPathAttrLength > 0) {
            try {
                final PathAttributes pathAttributes = this.reg.parseAttributes(buffer.slice(buffer.readerIndex(), totalPathAttrLength));
                buffer.skipBytes(totalPathAttrLength);
                eventBuilder.setPathAttributes(pathAttributes);
            } catch (final BGPParsingException | RuntimeException e) {
                // Catch everything else and turn it into a BGPDocumentedException
                LOG.warn("Could not parse BGP attributes", e);
                throw new BGPDocumentedException("Could not parse BGP attributes.", BGPError.MALFORMED_ATTR_LIST, e);
            }
        }
        final List<Ipv4Prefix> nlri = Ipv4Util.prefixListForBytes(ByteArray.readAllBytes(buffer));
        if (nlri != null && !nlri.isEmpty()) {
            eventBuilder.setNlri(new NlriBuilder().setNlri(nlri).build());
        }
        final Update msg = eventBuilder.build();
        LOG.debug("BGP Update message was parsed {}.", msg);
        return msg;
    }

    @Override
    public void serializeMessage(final Notification message, final ByteBuf bytes) {
        Preconditions.checkArgument(message instanceof Update, "BGPUpdate message cannot be null");
        LOG.trace("Started serializing update message: {}", message);
        final Update update = (Update) message;

        final ByteBuf messageBody = Unpooled.buffer();
        final WithdrawnRoutes withdrawnRoutes = update.getWithdrawnRoutes();
        if (withdrawnRoutes != null) {
            final ByteBuf withdrawnRoutesBuf = Unpooled.buffer();
            for (final Ipv4Prefix prefix : withdrawnRoutes.getWithdrawnRoutes()) {
                withdrawnRoutesBuf.writeBytes(Ipv4Util.bytesForPrefixBegin(prefix));
            }
            messageBody.writeShort(withdrawnRoutesBuf.writerIndex());
            messageBody.writeBytes(withdrawnRoutesBuf);
        } else {
            messageBody.writeZero(WITHDRAWN_ROUTES_LENGTH_SIZE);
        }
        if (update.getPathAttributes() != null) {
            final ByteBuf pathAttributesBuf = Unpooled.buffer();
            this.reg.serializeAttribute(update.getPathAttributes(), pathAttributesBuf);
            messageBody.writeShort(pathAttributesBuf.writerIndex());
            messageBody.writeBytes(pathAttributesBuf);
        } else {
            messageBody.writeZero(TOTAL_PATH_ATTR_LENGTH_SIZE);
        }
        final Nlri nlri = update.getNlri();
        if (nlri != null) {
            for (final Ipv4Prefix prefix : nlri.getNlri()) {
                messageBody.writeBytes(Ipv4Util.bytesForPrefixBegin(prefix));
            }
        }
        LOG.trace("Update message serialized to {}", ByteBufUtil.hexDump(messageBody));
        MessageUtil.formatMessage(TYPE, messageBody, bytes);
    }
}