/*
 * Copyright (c) 2015 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.rib.impl;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.primitives.UnsignedInteger;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.NotThreadSafe;
import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeChangeListener;
import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeChangeService;
import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeIdentifier;
import org.opendaylight.controller.md.sal.dom.api.DOMDataWriteTransaction;
import org.opendaylight.controller.md.sal.dom.api.DOMTransactionChain;
import org.opendaylight.protocol.bgp.rib.impl.spi.RIBSupportContextRegistry;
import org.opendaylight.protocol.bgp.rib.spi.RIBSupport;
import org.opendaylight.protocol.bgp.rib.spi.RibSupportUtils;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.inet.types.rev100924.AsNumber;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.PeerId;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.PeerRole;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.bgp.rib.rib.LocRib;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.bgp.rib.rib.Peer;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.bgp.rib.rib.peer.AdjRibOut;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.bgp.rib.rib.peer.EffectiveRibIn;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.bgp.rib.rib.peer.SupportedTables;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.rib.Tables;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.rib.TablesKey;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.rib.tables.Attributes;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.bgp.rib.rev130925.rib.tables.Routes;
import org.opendaylight.yangtools.concepts.ListenerRegistration;
import org.opendaylight.yangtools.yang.common.QName;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifier;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifierWithPredicates;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
import org.opendaylight.yangtools.yang.data.api.schema.ContainerNode;
import org.opendaylight.yangtools.yang.data.api.schema.LeafNode;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateNode;
import org.opendaylight.yangtools.yang.data.api.schema.tree.ModificationType;
import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@NotThreadSafe
final class LocRibWriter implements AutoCloseable, DOMDataTreeChangeListener {

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

    private static final LeafNode<Boolean> ATTRIBUTES_UPTODATE_TRUE = ImmutableNodes.leafNode(QName.create(Attributes.QNAME, "uptodate"), Boolean.TRUE);
    private static final NodeIdentifier ROUTES_IDENTIFIER = new NodeIdentifier(Routes.QNAME);
    private static final NodeIdentifier EFFRIBIN_NID = new NodeIdentifier(EffectiveRibIn.QNAME);
    private static final NodeIdentifier TABLES_NID = new NodeIdentifier(Tables.QNAME);

    private final Map<PathArgument, AbstractRouteEntry> routeEntries = new HashMap<>();
    private final YangInstanceIdentifier locRibTarget;
    private final DOMTransactionChain chain;
    private final ExportPolicyPeerTracker peerPolicyTracker;
    private final NodeIdentifier attributesIdentifier;
    private final Long ourAs;
    private final RIBSupport ribSupport;
    private final NodeIdentifierWithPredicates tableKey;
    private final TablesKey localTablesKey;
    private final RIBSupportContextRegistry registry;
    private final ListenerRegistration<LocRibWriter> reg;

    private LocRibWriter(final RIBSupportContextRegistry registry, final DOMTransactionChain chain, final YangInstanceIdentifier target, final Long ourAs,
        final DOMDataTreeChangeService service, final PolicyDatabase pd, final TablesKey tablesKey) {
        this.chain = Preconditions.checkNotNull(chain);
        this.tableKey = RibSupportUtils.toYangTablesKey(tablesKey);
        this.localTablesKey = tablesKey;
        this.locRibTarget = YangInstanceIdentifier.create(target.node(LocRib.QNAME).node(Tables.QNAME).node(this.tableKey).getPathArguments());
        this.ourAs = Preconditions.checkNotNull(ourAs);
        this.registry = registry;
        this.ribSupport = this.registry.getRIBSupportContext(tablesKey).getRibSupport();
        this.attributesIdentifier = this.ribSupport.routeAttributesIdentifier();
        this.peerPolicyTracker = new ExportPolicyPeerTracker(pd);

        final DOMDataWriteTransaction tx = this.chain.newWriteOnlyTransaction();
        tx.merge(LogicalDatastoreType.OPERATIONAL, this.locRibTarget.node(Routes.QNAME), this.ribSupport.emptyRoutes());
        tx.merge(LogicalDatastoreType.OPERATIONAL, this.locRibTarget.node(Attributes.QNAME).node(ATTRIBUTES_UPTODATE_TRUE.getNodeType()), ATTRIBUTES_UPTODATE_TRUE);
        tx.submit();

        final YangInstanceIdentifier tableId = target.node(Peer.QNAME).node(Peer.QNAME);

        this.reg = service.registerDataTreeChangeListener(new DOMDataTreeIdentifier(LogicalDatastoreType.OPERATIONAL, tableId), this);
    }

    public static LocRibWriter create(@Nonnull final RIBSupportContextRegistry registry, @Nonnull final TablesKey tablesKey, @Nonnull final DOMTransactionChain chain, @Nonnull final YangInstanceIdentifier target,
        @Nonnull final AsNumber ourAs, @Nonnull final DOMDataTreeChangeService service, @Nonnull final PolicyDatabase pd) {
        return new LocRibWriter(registry, chain, target, ourAs.getValue(), service, pd, tablesKey);
    }

    @Override
    public void close() {
        this.reg.close();
        // FIXME: wipe the local rib
        // FIXME: wait for the chain to close? unfortunately RIBImpl is the listener, so that may require some work
        this.chain.close();
    }

    @Nonnull
    private AbstractRouteEntry createEntry(final PathArgument routeId) {
        final AbstractRouteEntry ret = this.ribSupport.isComplexRoute() ? new ComplexRouteEntry() : new SimpleRouteEntry();
        this.routeEntries.put(routeId, ret);
        LOG.trace("Created new entry for {}", routeId);
        return ret;
    }

    @Override
    public void onDataTreeChanged(final Collection<DataTreeCandidate> changes) {
        LOG.trace("Received data change {} to LocRib {}", changes, this);

        final DOMDataWriteTransaction tx = this.chain.newWriteOnlyTransaction();
        try {
            /*
             * We use two-stage processing here in hopes that we avoid duplicate
             * calculations when multiple peers have changed a particular entry.
             */
            final Map<YangInstanceIdentifier, PeerId> deletedPeers = new HashMap<>();
            final Map<RouteUpdateKey, AbstractRouteEntry> toUpdate = update(tx, changes, deletedPeers);

            // Now walk all updated entries
            walkThrough(tx, toUpdate, deletedPeers);
            removeDeletedPeersFromExportPolicyTracker(deletedPeers);
        } catch (final Exception e) {
            LOG.error("Failed to completely propagate updates {}, state is undefined", changes, e);
        } finally {
            tx.submit();
        }
    }

    private void removeDeletedPeersFromExportPolicyTracker(final Map<YangInstanceIdentifier, PeerId> deletedPeers) {
        for (final Entry<YangInstanceIdentifier, PeerId> peerPath : deletedPeers.entrySet()) {
            this.peerPolicyTracker.peerRoleChanged(peerPath.getKey(), null);
        }
    }

    private Map<RouteUpdateKey, AbstractRouteEntry> update(final DOMDataWriteTransaction tx,
        final Collection<DataTreeCandidate> changes, final Map<YangInstanceIdentifier, PeerId> deletedPeers) {
        final Map<RouteUpdateKey, AbstractRouteEntry> ret = new HashMap<>();

        for (final DataTreeCandidate tc : changes) {
            final YangInstanceIdentifier rootPath = tc.getRootPath();
            final DataTreeCandidateNode rootNode = tc.getRootNode();
            final NodeIdentifierWithPredicates peerKey = IdentifierUtils.peerKey(rootPath);
            final PeerId peerId = IdentifierUtils.peerId(peerKey);
            filterOutPeerRole(peerId, rootNode, rootPath, deletedPeers);
            filterOutChangesToSupportedTables(peerId, rootNode);
            filterOutAnyChangeOutsideEffRibsIn(peerId, rootNode, ret, rootPath, tx);
        }

        return ret;
    }

    private void filterOutAnyChangeOutsideEffRibsIn(final PeerId peerId, final DataTreeCandidateNode rootNode,
        final Map<RouteUpdateKey, AbstractRouteEntry> ret, final YangInstanceIdentifier rootPath, final DOMDataWriteTransaction tx) {
        final DataTreeCandidateNode ribIn = rootNode.getModifiedChild(EFFRIBIN_NID);
        if (ribIn == null) {
            LOG.trace("Skipping change {}", rootNode.getIdentifier());
            return;
        }
        final DataTreeCandidateNode table = ribIn.getModifiedChild(TABLES_NID).getModifiedChild(this.tableKey);
        if (table == null) {
            LOG.trace("Skipping change {}", rootNode.getIdentifier());
            return;
        }
        initializeTableWithExistenRoutes(table, peerId, rootPath, tx);
        updateNodes(table, peerId, tx, ret);
    }

    private void filterOutChangesToSupportedTables(final PeerId peerIdOfNewPeer, final DataTreeCandidateNode rootNode) {
        final DataTreeCandidateNode tablesChange = rootNode.getModifiedChild(AbstractPeerRoleTracker.PEER_TABLES);
        if (tablesChange != null) {
            final NodeIdentifierWithPredicates supTablesKey = RibSupportUtils.toYangKey(SupportedTables.QNAME, this.localTablesKey);
            final DataTreeCandidateNode containsLocalKeyTable = tablesChange.getModifiedChild(supTablesKey);
            if(containsLocalKeyTable != null) {
                this.peerPolicyTracker.onTablesChanged(peerIdOfNewPeer, containsLocalKeyTable);
            }
        }
    }

    private void initializeTableWithExistenRoutes(final DataTreeCandidateNode table, final PeerId peerIdOfNewPeer, final YangInstanceIdentifier rootPath,
        final DOMDataWriteTransaction tx) {
        if (!table.getDataBefore().isPresent() && isTableSupported(peerIdOfNewPeer)) {
            LOG.debug("Peer {} table has been created, inserting existent routes", peerIdOfNewPeer);
            final PeerRole newPeerRole = this.peerPolicyTracker.getRole(IdentifierUtils.peerPath(rootPath));
            final PeerExportGroup peerGroup = this.peerPolicyTracker.getPeerGroup(newPeerRole);
            for (Map.Entry<PathArgument, AbstractRouteEntry> entry : this.routeEntries.entrySet()) {
                final AbstractRouteEntry routeEntry = entry.getValue();
                final PathArgument routeId = entry.getKey();
                final YangInstanceIdentifier routeTarget = getRouteTarget(rootPath, routeId);
                final NormalizedNode<?, ?> value = routeEntry.createValue(routeId);
                final PeerId routePeerId = RouterIds.createPeerId(routeEntry.getBestRouterId());
                final ContainerNode effectiveAttributes = peerGroup.effectiveAttributes(routePeerId, routeEntry.attributes());
                if (effectiveAttributes != null && value != null) {
                    LOG.debug("Write route {} to peer AdjRibsOut {}", value, peerIdOfNewPeer);
                    tx.put(LogicalDatastoreType.OPERATIONAL, routeTarget, value);
                    tx.put(LogicalDatastoreType.OPERATIONAL, routeTarget.node(this.attributesIdentifier), effectiveAttributes);
                }
            }
        }
    }

    private YangInstanceIdentifier getRouteTarget(final YangInstanceIdentifier rootPath, final PathArgument routeId) {
        return this.ribSupport.routePath(rootPath.node(AdjRibOut.QNAME).node(Tables.QNAME).node(this.tableKey).node(ROUTES_IDENTIFIER), routeId);
    }

    private void filterOutPeerRole(final PeerId peerId, final DataTreeCandidateNode rootNode, final YangInstanceIdentifier rootPath, final Map<YangInstanceIdentifier, PeerId> deletedPeers) {
        final DataTreeCandidateNode roleChange = rootNode.getModifiedChild(AbstractPeerRoleTracker.PEER_ROLE_NID);
        if (roleChange != null) {
            if (!rootNode.getModificationType().equals(ModificationType.DELETE)) {
                this.peerPolicyTracker.onDataTreeChanged(roleChange, IdentifierUtils.peerPath(rootPath));
            } else {
                deletedPeers.put(IdentifierUtils.peerPath(rootPath), peerId);
            }
        }
    }

    private void updateNodes(final DataTreeCandidateNode table, final PeerId peerId, final DOMDataWriteTransaction tx,
        final Map<RouteUpdateKey, AbstractRouteEntry> routes) {
        for (final DataTreeCandidateNode child : table.getChildNodes()) {
            LOG.debug("Modification type {}", child.getModificationType());
            if ((Attributes.QNAME).equals(child.getIdentifier().getNodeType())) {
                if (child.getDataAfter().isPresent()) {
                    // putting uptodate attribute in
                    LOG.trace("Uptodate found for {}", child.getDataAfter());
                    tx.put(LogicalDatastoreType.OPERATIONAL, this.locRibTarget.node(child.getIdentifier()), child.getDataAfter().get());
                }
                continue;
            }
            updateRoutesEntries(child, peerId, routes);
        }
    }

    private void updateRoutesEntries(final DataTreeCandidateNode child, final PeerId peerId, final Map<RouteUpdateKey, AbstractRouteEntry> routes) {
        final UnsignedInteger routerId = RouterIds.routerIdForPeerId(peerId);
        final Collection<DataTreeCandidateNode> modifiedRoutes = this.ribSupport.changedRoutes(child);
        for (final DataTreeCandidateNode route : modifiedRoutes) {
            final PathArgument routeId = route.getIdentifier();
            AbstractRouteEntry entry = this.routeEntries.get(routeId);

            final Optional<NormalizedNode<?, ?>> maybeData = route.getDataAfter();
            final RouteUpdateKey routeUpdateKey = new RouteUpdateKey(peerId, routeId);
            if (maybeData.isPresent()) {
                if (entry == null) {
                    entry = createEntry(routeId);
                }
                entry.addRoute(routerId, this.attributesIdentifier, maybeData.get());
            } else if (entry != null && entry.removeRoute(routerId)) {
                this.routeEntries.remove(routeId);
                LOG.trace("Removed route from {}", routerId);
                entry = null;
            }
            LOG.debug("Updated route {} entry {}", routeId, entry);
            routes.put(routeUpdateKey, entry);
        }
    }

    private void walkThrough(final DOMDataWriteTransaction tx, final Map<RouteUpdateKey, AbstractRouteEntry> toUpdate,
        final Map<YangInstanceIdentifier, PeerId> deletedPeers) {
        for (final Entry<RouteUpdateKey, AbstractRouteEntry> e : toUpdate.entrySet()) {
            LOG.trace("Walking through {}", e);
            final AbstractRouteEntry entry = e.getValue();
            final RouteUpdateKey key = e.getKey();
            final NormalizedNode<?, ?> value;
            final PathArgument routeId = key.getRouteId();
            PeerId routePeerId = key.getPeerId();
            if (entry != null) {
                if (!entry.selectBest(this.ourAs)) {
                    // Best path has not changed, no need to do anything else. Proceed to next route.
                    LOG.trace("Continuing");
                    continue;
                }
                routePeerId = RouterIds.createPeerId(entry.getBestRouterId());
                value = entry.createValue(routeId);
                LOG.trace("Selected best value {}", value);
            } else {
                value = null;
            }
            fillLocRib(tx, entry, value, routeId);
            fillAdjRibsOut(tx, entry, value, routeId, routePeerId, deletedPeers);
        }
    }

    private void fillLocRib(final DOMDataWriteTransaction tx, final AbstractRouteEntry entry, final NormalizedNode<?, ?> value, final PathArgument routeId) {
        final YangInstanceIdentifier writePath = this.ribSupport.routePath(this.locRibTarget.node(ROUTES_IDENTIFIER), routeId);
        if (value != null) {
            LOG.debug("Write route to LocRib {}", value);
            tx.put(LogicalDatastoreType.OPERATIONAL, writePath, value);
        } else {
            LOG.debug("Delete route from LocRib {}", entry);
            tx.delete(LogicalDatastoreType.OPERATIONAL, writePath);
        }
    }

    @VisibleForTesting
    private void fillAdjRibsOut(final DOMDataWriteTransaction tx, final AbstractRouteEntry entry, final NormalizedNode<?, ?> value,
        final PathArgument routeId, final PeerId routePeerId, final Map<YangInstanceIdentifier, PeerId> deletedPeers) {
        /*
         * We need to keep track of routers and populate adj-ribs-out, too. If we do not, we need to
         * expose from which client a particular route was learned from in the local RIB, and have
         * the listener perform filtering.
         *
         * We walk the policy set in order to minimize the amount of work we do for multiple peers:
         * if we have two eBGP peers, for example, there is no reason why we should perform the translation
         * multiple times.
         */
        final ContainerNode attributes = entry == null ? null : entry.attributes();
        for (final PeerRole role : PeerRole.values()) {
            final PeerExportGroup peerGroup = this.peerPolicyTracker.getPeerGroup(role);
            if (peerGroup != null) {
                final ContainerNode effectiveAttributes = peerGroup.effectiveAttributes(routePeerId, attributes);
                for (final Entry<PeerId, YangInstanceIdentifier> pid : peerGroup.getPeers()) {
                    final PeerId peerDestiny = pid.getKey();
                    if (!routePeerId.equals(peerDestiny) && isTableSupported(peerDestiny) && !deletedPeers.containsValue(peerDestiny)) {
                        final YangInstanceIdentifier routeTarget = getRouteTarget(pid.getValue(), routeId);
                        if (value != null && effectiveAttributes != null) {
                            LOG.debug("Write route {} to peers AdjRibsOut {}", value, peerDestiny);
                            tx.put(LogicalDatastoreType.OPERATIONAL, routeTarget, value);
                            tx.put(LogicalDatastoreType.OPERATIONAL, routeTarget.node(this.attributesIdentifier), effectiveAttributes);
                        } else {
                            LOG.trace("Removing {} from transaction for peer {}", routeTarget, peerDestiny);
                            tx.delete(LogicalDatastoreType.OPERATIONAL, routeTarget);
                        }
                    }
                }
            }
        }
    }

    private boolean isTableSupported(final PeerId key) {
        if (!this.peerPolicyTracker.isTableSupported(key, this.localTablesKey)) {
            LOG.trace("Route rejected, peer {} does not support this table type {}", key, this.localTablesKey);
            return false;
        }
        return true;
    }
}