/*
 * Copyright 2016-present Open Networking Laboratory
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.onosproject.openstacknetworking.routing;

import com.google.common.collect.Maps;
import org.onlab.packet.Ethernet;
import org.onlab.packet.ICMP;
import org.onlab.packet.IPv4;
import org.onlab.packet.Ip4Address;
import org.onlab.packet.IpAddress;
import org.onlab.packet.MacAddress;
import org.onosproject.core.ApplicationId;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Host;
import org.onosproject.net.Port;
import org.onosproject.net.PortNumber;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.host.HostService;
import org.onosproject.net.packet.DefaultOutboundPacket;
import org.onosproject.net.packet.OutboundPacket;
import org.onosproject.net.packet.PacketContext;
import org.onosproject.net.packet.PacketPriority;
import org.onosproject.net.packet.PacketService;
import org.onosproject.openstacknetworking.Constants;
import org.onosproject.openstackinterface.OpenstackInterfaceService;
import org.onosproject.openstackinterface.OpenstackPort;
import org.onosproject.openstacknode.OpenstackNode;
import org.onosproject.openstacknode.OpenstackNodeService;
import org.onosproject.scalablegateway.api.ScalableGatewayService;
import org.slf4j.Logger;

import java.nio.ByteBuffer;
import java.util.Map;
import java.util.Optional;

import static com.google.common.base.Preconditions.checkNotNull;

import static org.slf4j.LoggerFactory.getLogger;


/**
 * Handle ICMP packet sent from Openstack Gateway nodes.
 */
public class OpenstackIcmpHandler {
    protected final Logger log = getLogger(getClass());


    private static final String NETWORK_ROUTER_INTERFACE = "network:router_interface";
    private static final String PORTNAME = "portName";
    private static final String NETWORK_ROUTER_GATEWAY = "network:router_gateway";
    private static final String NETWORK_FLOATING_IP = "network:floatingip";

    private final PacketService packetService;
    private final DeviceService deviceService;
    private final ScalableGatewayService gatewayService;
    private final HostService hostService;
    private final Map<String, Host> icmpInfoMap = Maps.newHashMap();
    private final OpenstackInterfaceService openstackService;
    private final OpenstackNodeService nodeService;

    /**
     * Default constructor.
     *
     * @param packetService             packet service
     * @param deviceService             device service
     * @param openstackService          openstackInterface service
     */
    OpenstackIcmpHandler(PacketService packetService,
                         DeviceService deviceService,
                         HostService hostService,
                         OpenstackInterfaceService openstackService,
                         OpenstackNodeService nodeService,
                         ScalableGatewayService gatewayService
                         ) {
        this.packetService = packetService;
        this.deviceService = deviceService;
        this.hostService = hostService;
        this.openstackService = checkNotNull(openstackService);
        this.nodeService = nodeService;
        this.gatewayService = gatewayService;
    }

    /**
     * Requests ICMP packet.
     *
     * @param appId Application Id
     */
    public void requestPacket(ApplicationId appId) {
        TrafficSelector icmpSelector = DefaultTrafficSelector.builder()
                .matchEthType(Ethernet.TYPE_IPV4)
                .matchIPProtocol(IPv4.PROTOCOL_ICMP)
                .build();

       // TODO: Return the correct gateway node
        Optional<OpenstackNode> gwNode =  nodeService.nodes().stream()
                .filter(n -> n.type().equals(OpenstackNodeService.NodeType.GATEWAY))
                .findFirst();

        if (!gwNode.isPresent()) {
            log.warn("No Gateway is defined.");
            return;
        }

        packetService.requestPackets(icmpSelector,
                PacketPriority.CONTROL,
                appId,
                Optional.of(gwNode.get().intBridge()));
    }

    /**
     * Handles ICMP packet.
     *
     * @param context  packet context
     * @param ethernet ethernet
     */
    public void processIcmpPacket(PacketContext context, Ethernet ethernet) {
        checkNotNull(context, "context can not be null");
        checkNotNull(ethernet, "ethernet can not be null");

        IPv4 ipPacket = (IPv4) ethernet.getPayload();

        log.debug("icmpEvent called from ip {}, mac {}", Ip4Address.valueOf(ipPacket.getSourceAddress()).toString(),
                ethernet.getSourceMAC().toString());

        ICMP icmp = (ICMP) ipPacket.getPayload();
        short icmpId = getIcmpId(icmp);

        DeviceId deviceId = context.inPacket().receivedFrom().deviceId();
        PortNumber portNumber = context.inPacket().receivedFrom().port();
        if (icmp.getIcmpType() == ICMP.TYPE_ECHO_REQUEST) {
            //TODO: Considers icmp between internal subnets which are belonged to the same router.
            Optional<Host> host = hostService.getHostsByMac(ethernet.getSourceMAC()).stream().findFirst();
            if (!host.isPresent()) {
                log.warn("No host found for MAC {}", ethernet.getSourceMAC());
                return;
            }

            IpAddress gatewayIp = IpAddress.valueOf(host.get().annotations().value(Constants.GATEWAY_IP));
            if (ipPacket.getDestinationAddress() == gatewayIp.getIp4Address().toInt()) {
                processIcmpPacketSentToGateway(ipPacket, icmp, host.get());
            } else {
                Ip4Address pNatIpAddress = pNatIpForPort(host.get());
                checkNotNull(pNatIpAddress, "pNatIpAddress can not be null");

                sendRequestPacketToExt(ipPacket, icmp, deviceId, pNatIpAddress);

                String icmpInfoKey = String.valueOf(icmpId)
                        .concat(String.valueOf(pNatIpAddress.toInt()))
                        .concat(String.valueOf(ipPacket.getDestinationAddress()));
                icmpInfoMap.putIfAbsent(icmpInfoKey, host.get());
            }
        } else if (icmp.getIcmpType() == ICMP.TYPE_ECHO_REPLY) {
            String icmpInfoKey = String.valueOf(icmpId)
                    .concat(String.valueOf(ipPacket.getDestinationAddress()))
                    .concat(String.valueOf(ipPacket.getSourceAddress()));

            processResponsePacketFromExternalToHost(ipPacket, icmp, icmpInfoMap.get(icmpInfoKey));

            icmpInfoMap.remove(icmpInfoKey);
        }
    }

    private void processIcmpPacketSentToExtenal(IPv4 icmpRequestIpv4, ICMP icmpRequest,
                                                int destAddr, MacAddress destMac,
                                                DeviceId deviceId, PortNumber portNumber) {
        icmpRequest.setChecksum((short) 0);
        icmpRequest.setIcmpType(ICMP.TYPE_ECHO_REPLY).resetChecksum();
        icmpRequestIpv4.setSourceAddress(icmpRequestIpv4.getDestinationAddress())
                .setDestinationAddress(destAddr).resetChecksum();
        icmpRequestIpv4.setPayload(icmpRequest);
        Ethernet icmpResponseEth = new Ethernet();
        icmpResponseEth.setEtherType(Ethernet.TYPE_IPV4)
                // TODO: Get the correct GW MAC
                .setSourceMACAddress(Constants.GW_EXT_INT_MAC)
                .setDestinationMACAddress(destMac).setPayload(icmpRequestIpv4);
        TrafficTreatment treatment = DefaultTrafficTreatment.builder().setOutput(portNumber).build();
        OutboundPacket packet = new DefaultOutboundPacket(deviceId,
                treatment, ByteBuffer.wrap(icmpResponseEth.serialize()));
        packetService.emit(packet);
    }

    private void processIcmpPacketSentToGateway(IPv4 icmpRequestIpv4, ICMP icmpRequest,
                                                Host host) {
        icmpRequest.setChecksum((short) 0);
        icmpRequest.setIcmpType(ICMP.TYPE_ECHO_REPLY)
                .resetChecksum();

        Ip4Address ipAddress = host.ipAddresses().stream().findAny().get().getIp4Address();
        icmpRequestIpv4.setSourceAddress(icmpRequestIpv4.getDestinationAddress())
                .setDestinationAddress(ipAddress.toInt())
                .resetChecksum();

        icmpRequestIpv4.setPayload(icmpRequest);

        Ethernet icmpResponseEth = new Ethernet();

        icmpResponseEth.setEtherType(Ethernet.TYPE_IPV4)
                .setSourceMACAddress(Constants.GATEWAY_MAC)
                .setDestinationMACAddress(host.mac())
                .setPayload(icmpRequestIpv4);

        sendResponsePacketToHost(icmpResponseEth, host);
    }

    private void sendRequestPacketToExt(IPv4 icmpRequestIpv4, ICMP icmpRequest, DeviceId deviceId,
                                        Ip4Address pNatIpAddress) {
        icmpRequest.resetChecksum();
        icmpRequestIpv4.setSourceAddress(pNatIpAddress.toInt())
                .resetChecksum();
        icmpRequestIpv4.setPayload(icmpRequest);

        Ethernet icmpRequestEth = new Ethernet();

        icmpRequestEth.setEtherType(Ethernet.TYPE_IPV4)
                // TODO: Get the correct one - Scalable Gateway ...
                .setSourceMACAddress(Constants.GW_EXT_INT_MAC)
                .setDestinationMACAddress(Constants.PHY_ROUTER_MAC)
                .setPayload(icmpRequestIpv4);

        // TODO: Return the correct gateway node
        Optional<OpenstackNode> gwNode =  nodeService.nodes().stream()
                .filter(n -> n.type().equals(OpenstackNodeService.NodeType.GATEWAY))
                .findFirst();

        if (!gwNode.isPresent()) {
            log.warn("No Gateway is defined.");
            return;
        }

        TrafficTreatment treatment = DefaultTrafficTreatment.builder()
                // FIXME: please double check this.
                .setOutput(getPortForAnnotationPortName(gwNode.get().intBridge(),
                        // FIXME: please double check this.
                        org.onosproject.openstacknode.Constants.PATCH_INTG_BRIDGE))
                .build();

        OutboundPacket packet = new DefaultOutboundPacket(deviceId,
                treatment, ByteBuffer.wrap(icmpRequestEth.serialize()));

        packetService.emit(packet);
    }

    private void processResponsePacketFromExternalToHost(IPv4 icmpResponseIpv4, ICMP icmpResponse,
                                                         Host host) {
        icmpResponse.resetChecksum();

        Ip4Address ipAddress = host.ipAddresses().stream().findFirst().get().getIp4Address();
        icmpResponseIpv4.setDestinationAddress(ipAddress.toInt())
                .resetChecksum();
        icmpResponseIpv4.setPayload(icmpResponse);

        Ethernet icmpResponseEth = new Ethernet();

        icmpResponseEth.setEtherType(Ethernet.TYPE_IPV4)
                .setSourceMACAddress(Constants.GATEWAY_MAC)
                .setDestinationMACAddress(host.mac())
                .setPayload(icmpResponseIpv4);

        sendResponsePacketToHost(icmpResponseEth, host);
    }

    private void sendResponsePacketToHost(Ethernet icmpResponseEth, Host host) {

        TrafficTreatment treatment = DefaultTrafficTreatment.builder()
                .setOutput(host.location().port())
                .build();

        OutboundPacket packet = new DefaultOutboundPacket(host.location().deviceId(),
                treatment, ByteBuffer.wrap(icmpResponseEth.serialize()));

        packetService.emit(packet);
    }

    private short getIcmpId(ICMP icmp) {
        return ByteBuffer.wrap(icmp.serialize(), 4, 2).getShort();
    }

    private Ip4Address pNatIpForPort(Host host) {

        OpenstackPort openstackPort = openstackService.ports().stream()
                .filter(p -> p.deviceOwner().equals(NETWORK_ROUTER_INTERFACE) &&
                        p.networkId().equals(host.annotations().value(Constants.NETWORK_ID)))
                .findAny().orElse(null);

        checkNotNull(openstackPort, "openstackPort can not be null");

        return openstackService.router(openstackPort.deviceId())
                .gatewayExternalInfo().externalFixedIps().values()
                .stream().findAny().orElse(null);
    }

    private PortNumber getPortForAnnotationPortName(DeviceId deviceId, String match) {
        Port port = deviceService.getPorts(deviceId).stream()
                .filter(p -> p.annotations().value(PORTNAME).equals(match))
                .findAny().orElse(null);

        checkNotNull(port, "port cannot be null");

        return port.number();
    }

    private boolean requestToOpenstackRoutingNetwork(int destAddr) {
        OpenstackPort port = openstackService.ports().stream()
                .filter(p -> p.deviceOwner().equals(NETWORK_ROUTER_GATEWAY) ||
                        p.deviceOwner().equals(NETWORK_FLOATING_IP))
                .filter(p -> p.fixedIps().containsValue(
                        Ip4Address.valueOf(destAddr)))
                .findAny().orElse(null);
        if (port == null) {
            return false;
        }
        return true;
    }
    private Map<DeviceId, PortNumber> getExternalInfo() {
        Map<DeviceId, PortNumber> externalInfoMap = Maps.newHashMap();
        gatewayService.getGatewayDeviceIds().forEach(deviceId ->
                externalInfoMap.putIfAbsent(deviceId, gatewayService.getUplinkPort(deviceId)));
        return externalInfoMap;
    }
}