/**
 *  Copyright 2005-2015 Red Hat, Inc.
 *
 *  Red Hat licenses this file to you 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 io.fabric8.insight.elasticsearch.discovery;

import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.google.common.base.Objects;
import io.fabric8.groups.Group;
import io.fabric8.groups.GroupFactory;
import io.fabric8.groups.GroupListener;
import io.fabric8.groups.NodeState;
import io.fabric8.groups.internal.ZooKeeperGroupFactory;
import org.apache.curator.framework.CuratorFramework;
import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.ElasticsearchIllegalStateException;
import org.elasticsearch.Version;
import org.elasticsearch.cluster.ClusterName;
import org.elasticsearch.cluster.ClusterService;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.ProcessedClusterStateUpdateTask;
import org.elasticsearch.cluster.block.ClusterBlocks;
import org.elasticsearch.cluster.metadata.IndexMetaData;
import org.elasticsearch.cluster.metadata.MetaData;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.node.DiscoveryNodeService;
import org.elasticsearch.cluster.node.DiscoveryNodes;
import org.elasticsearch.cluster.routing.allocation.AllocationService;
import org.elasticsearch.common.Base64;
import org.elasticsearch.common.Priority;
import org.elasticsearch.common.component.AbstractLifecycleComponent;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.inject.internal.Nullable;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.InetSocketTransportAddress;
import org.elasticsearch.common.transport.TransportAddress;
import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
import org.elasticsearch.discovery.Discovery;
import org.elasticsearch.discovery.DiscoverySettings;
import org.elasticsearch.discovery.InitialStateDiscoveryListener;
import org.elasticsearch.discovery.zen.DiscoveryNodesProvider;
import org.elasticsearch.discovery.zen.publish.PublishClusterStateAction;
import org.elasticsearch.node.service.NodeService;
import org.elasticsearch.node.settings.NodeSettingsService;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.transport.TransportService;
import org.osgi.framework.BundleContext;
import org.osgi.framework.FrameworkUtil;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;
import org.osgi.util.tracker.ServiceTrackerCustomizer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicBoolean;

public class FabricDiscovery extends AbstractLifecycleComponent<Discovery>
        implements Discovery,
        DiscoveryNodesProvider,
        ServiceTrackerCustomizer<CuratorFramework, CuratorFramework>,
        PublishClusterStateAction.NewClusterStateListener,
        GroupListener<FabricDiscovery.ESNode> {

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

    protected final ClusterName clusterName;
    protected final ThreadPool threadPool;
    protected final TransportService transportService;
    protected final ClusterService clusterService;
    protected final NodeSettingsService nodeSettingsService;
    protected final DiscoveryNodeService discoveryNodeService;
    protected final BundleContext context;
    protected final ServiceTracker<CuratorFramework, CuratorFramework> tracker;

    private DiscoveryNode localNode;
    private final CopyOnWriteArrayList<InitialStateDiscoveryListener> initialStateListeners = new CopyOnWriteArrayList<InitialStateDiscoveryListener>();
    @Nullable
    private NodeService nodeService;
    private AllocationService allocationService;
    private volatile DiscoveryNodes latestDiscoNodes;
    private final PublishClusterStateAction publishClusterState;
    private volatile Group<ESNode> singleton;
    private final AtomicBoolean initialStateSent = new AtomicBoolean();

    @Inject
    public FabricDiscovery(Settings settings,
                           ClusterName clusterName,
                           ThreadPool threadPool,
                           TransportService transportService,
                           ClusterService clusterService,
                           NodeSettingsService nodeSettingsService,
                           DiscoveryNodeService discoveryNodeService,
                           DiscoverySettings discoverySettings) {
        super(settings);
        this.clusterName = clusterName;
        this.threadPool = threadPool;
        this.clusterService = clusterService;
        this.transportService = transportService;
        this.nodeSettingsService = nodeSettingsService;
        this.discoveryNodeService = discoveryNodeService;
        this.publishClusterState = new PublishClusterStateAction(settings, transportService, this, this, discoverySettings);
        this.context = FrameworkUtil.getBundle(getClass()).getBundleContext();
        this.tracker = new ServiceTracker<>(context, CuratorFramework.class.getName(), this);
    }

    @Override
    protected void doStart() throws ElasticsearchException {
        logger.debug("Starting FabricDiscovery");
        Map<String, String> nodeAttributes = discoveryNodeService.buildAttributes();
        // note, we rely on the fact that its a new id each time we start, see FD and "kill -9" handling
        String nodeId = UUID.randomUUID().toString();
        String host = settings.get("discovery.publish.host");
        String port = settings.get("discovery.publish.port");
        if (host != null && port != null) {
            TransportAddress address = new InetSocketTransportAddress(host, Integer.parseInt(port));
            localNode = new DiscoveryNode(settings.get("name"), nodeId, address, nodeAttributes, Version.CURRENT);
        } else {
            localNode = new DiscoveryNode(settings.get("name"), nodeId, transportService.boundAddress().publishAddress(), nodeAttributes, Version.CURRENT);
        }
        tracker.open();
        logger.debug("FabricDiscovery started");
    }

    @Override
    protected void doStop() throws ElasticsearchException {
        logger.debug("Stopping FabricDiscovery");
        tracker.close();
        initialStateSent.set(false);
        logger.debug("FabricDiscovery stopped");
    }

    @Override
    protected void doClose() throws ElasticsearchException {
        logger.debug("Closing FabricDiscovery");
        tracker.close();
        publishClusterState.close();
        logger.debug("Closed FabricDiscovery");
    }

    @Override
    public DiscoveryNode localNode() {
        return localNode;
    }

    @Override
    public void addListener(InitialStateDiscoveryListener listener) {
        initialStateListeners.add(listener);
    }

    @Override
    public void removeListener(InitialStateDiscoveryListener listener) {
        initialStateListeners.remove(listener);
    }

    @Override
    public String nodeDescription() {
        return clusterName.value() + "/" + localNode.id();
    }

    @Override
    public void setNodeService(@Nullable NodeService nodeService) {
        this.nodeService = nodeService;
    }

    @Override
    public void setAllocationService(AllocationService allocationService) {
        this.allocationService = allocationService;
    }

    @Override
    public void publish(ClusterState clusterState, AckListener ackListener) {
        logger.debug("Publishing cluster state");
        if (!singleton.isMaster()) {
            throw new ElasticsearchIllegalStateException("Shouldn't publish state when not master");
        }
        latestDiscoNodes = clusterState.nodes();
        publishClusterState.publish(clusterState, ackListener);
        logger.debug("Cluster state published");
    }

    @Override
    public DiscoveryNodes nodes() {
        DiscoveryNodes latestNodes = this.latestDiscoNodes;
        if (latestNodes != null) {
            return latestNodes;
        }
        // have not decided yet, just send the local node
        return DiscoveryNodes.builder().put(localNode).localNodeId(localNode.id()).build();
    }

    @Override
    public NodeService nodeService() {
        return this.nodeService;
    }


    @Override
    public CuratorFramework addingService(ServiceReference<CuratorFramework> reference) {
        CuratorFramework curator = context.getService(reference);
        try {
            logger.debug("CuratorFramework found, starting group");
            GroupFactory factory = new ZooKeeperGroupFactory(curator);
            singleton = factory.createGroup("/fabric/registry/clusters/elasticsearch/" + clusterName.value(), ESNode.class);
            singleton.add(this);
            singleton.update(new ESNode(clusterName.value(), localNode, false));
            singleton.start();
        } catch (Exception e) {
            LOG.error("Error starting group", e);
        }
        return curator;
    }

    @Override
    public void modifiedService(ServiceReference<CuratorFramework> reference, CuratorFramework service) {
    }

    @Override
    public void removedService(ServiceReference<CuratorFramework> reference, CuratorFramework service) {
        logger.debug("CuratorFramework lost, closing group");
        try {
            singleton.close();
        } catch (IOException e) {
            LOG.error("Error stopping group", e);
        }
        context.ungetService(reference);
    }

    @Override
    public void groupEvent(Group<ESNode> group, GroupEvent event) {
        // We need to set the TCCL because elasticsearch Settings will grab the wrong classloader if not
        ClassLoader tccl = Thread.currentThread().getContextClassLoader();
        try {
            Thread.currentThread().setContextClassLoader(FabricDiscovery.class.getClassLoader());
            updateCluster();
        } finally {
            Thread.currentThread().setContextClassLoader(tccl);
        }
    }

    private void updateCluster() {
        try {
            singleton.update(new ESNode(clusterName.value(), localNode, singleton.isMaster()));
        } catch (Exception e) {
            // Ignore if not joined
        }
        if (singleton.isMaster()) {
            if (logger.isDebugEnabled()) {
                String master = singleton.master() != null ? singleton.master().node.name() : null;
                List<String> slaves = new ArrayList<>();
                for (ESNode s : singleton.slaves()) {
                    slaves.add(s.node.name());
                }
                logger.debug("Updating cluster: master {}, slaves {}", master, slaves);
            }
            clusterService.submitStateUpdateTask("fabric-discovery-master", Priority.URGENT, new ProcessedClusterStateUpdateTask() {
                @Override
                public ClusterState execute(ClusterState currentState) {
                    // Rebuild state
                    ClusterState.Builder stateBuilder = ClusterState.builder(currentState);
                    // Rebuild nodes
                    DiscoveryNodes.Builder nodesBuilder = DiscoveryNodes.builder()
                            .localNodeId(localNode.id())
                            .masterNodeId(singleton.master().getNode().id())
                            .put(singleton.master().getNode());
                    for (ESNode node : singleton.slaves()) {
                        nodesBuilder.put(node.getNode());
                    }
                    latestDiscoNodes = nodesBuilder.build();
                    stateBuilder.nodes(latestDiscoNodes);
                    for (DiscoveryNode node : latestDiscoNodes) {
                        if (!currentState.nodes().nodeExists(node.id())) {
                            transportService.connectToNode(node);
                        }
                    }
                    // update the fact that we are the master...
                    if (!localNode().id().equals(currentState.nodes().masterNodeId())) {
                        ClusterBlocks clusterBlocks = ClusterBlocks.builder().blocks(currentState.blocks()).removeGlobalBlock(NO_MASTER_BLOCK).build();
                        stateBuilder.blocks(clusterBlocks);
                    }
                    return stateBuilder.build();
                }

                @Override
                public void clusterStateProcessed(String source, ClusterState oldState, ClusterState newState) {
                    logger.debug("Cluster updated");
                    sendInitialStateEventIfNeeded();
                }

                @Override
                public void onFailure(String source, Throwable t) {
                    logger.error("unexpected failure during [{}]", t, source);
                }
            });
        } else if (singleton.master() != null) {
            DiscoveryNode masterNode = singleton.master().getNode();
            try {
                // first, make sure we can connect to the master
                transportService.connectToNode(masterNode);
            } catch (Exception e) {
                logger.warn("failed to connect to master [{}], retrying...", e, masterNode);
            }
        }

    }

    static class ProcessClusterState {
        final ClusterState clusterState;
        final PublishClusterStateAction.NewClusterStateListener.NewStateProcessed newStateProcessed;
        volatile boolean processed;

        ProcessClusterState(ClusterState clusterState, PublishClusterStateAction.NewClusterStateListener.NewStateProcessed newStateProcessed) {
            this.clusterState = clusterState;
            this.newStateProcessed = newStateProcessed;
        }
    }

    private final BlockingQueue<ProcessClusterState> processNewClusterStates = ConcurrentCollections.newBlockingQueue();

    @Override
    public void onNewClusterState(final ClusterState newState, final NewStateProcessed newStateProcessed) {
        if (singleton.isMaster()) {
            logger.warn("master should not receive new cluster state from [{}]", newState.nodes().masterNode());
        } else {
            if (newState.nodes().localNode() == null) {
                logger.warn("received a cluster state from [{}] and not part of the cluster, should not happen", newState.nodes().masterNode());
            } else {
                if (logger.isDebugEnabled()) {
                    String master = singleton.master() != null ? singleton.master().node.name() : null;
                    List<String> slaves = new ArrayList<String>();
                    for (ESNode s : singleton.slaves()) {
                        slaves.add(s.node.name());
                    }
                    logger.debug("Cluster state received: master {}, slaves {}", master, slaves);
                }
                final ProcessClusterState processClusterState = new ProcessClusterState(newState, newStateProcessed);
                processNewClusterStates.add(processClusterState);
                clusterService.submitStateUpdateTask("fabric-discovery-slave", new ProcessedClusterStateUpdateTask() {
                    @Override
                    public ClusterState execute(ClusterState currentState) {
                        // we already processed it in a previous event
                        if (processClusterState.processed) {
                            return currentState;
                        }

                        // try and get the state with the highest version out of all the ones with the same master node id
                        ProcessClusterState stateToProcess = processNewClusterStates.poll();
                        if (stateToProcess == null) {
                            return currentState;
                        }
                        stateToProcess.processed = true;
                        while (true) {
                            ProcessClusterState potentialState = processNewClusterStates.peek();
                            // nothing else in the queue, bail
                            if (potentialState == null) {
                                break;
                            }
                            // if its not from the same master, then bail
                            if (!Objects.equal(stateToProcess.clusterState.nodes().masterNodeId(), potentialState.clusterState.nodes().masterNodeId())) {
                                break;
                            }

                            // we are going to use it for sure, poll (remove) it
                            potentialState = processNewClusterStates.poll();
                            potentialState.processed = true;

                            if (potentialState.clusterState.version() > stateToProcess.clusterState.version()) {
                                // we found a new one
                                stateToProcess = potentialState;
                            }
                        }

                        ClusterState updatedState = stateToProcess.clusterState;

                        // if the new state has a smaller version, and it has the same master node, then no need to process it
                        if (updatedState.version() < currentState.version() && Objects.equal(updatedState.nodes().masterNodeId(), currentState.nodes().masterNodeId())) {
                            return currentState;
                        }

                        latestDiscoNodes = updatedState.nodes();

                        ClusterState.Builder builder = ClusterState.builder(updatedState);
                        // if the routing table did not change, use the original one
                        if (updatedState.routingTable().version() == currentState.routingTable().version()) {
                            builder.routingTable(currentState.routingTable());
                        }
                        // same for metadata
                        if (updatedState.metaData().version() == currentState.metaData().version()) {
                            builder.metaData(currentState.metaData());
                        } else {
                            // if its not the same version, only copy over new indices or ones that changed the version
                            MetaData.Builder metaDataBuilder = MetaData.builder(updatedState.metaData()).removeAllIndices();
                            for (IndexMetaData indexMetaData : updatedState.metaData()) {
                                IndexMetaData currentIndexMetaData = currentState.metaData().index(indexMetaData.index());
                                if (currentIndexMetaData == null || currentIndexMetaData.version() != indexMetaData.version()) {
                                    metaDataBuilder.put(indexMetaData, false);
                                } else {
                                    metaDataBuilder.put(currentIndexMetaData, false);
                                }
                            }
                            builder.metaData(metaDataBuilder);
                        }

                        return builder.build();
                    }

                    @Override
                    public void clusterStateProcessed(String s, ClusterState clusterState, ClusterState clusterState2) {
                        logger.debug("Cluster state processed");
                        sendInitialStateEventIfNeeded();
                        newStateProcessed.onNewClusterStateProcessed();
                    }

                    @Override
                    public void onFailure(String source, Throwable t) {
                        logger.error("unexpected failure during [{}]", t, source);
                        newStateProcessed.onNewClusterStateFailed(t);
                    }
                });
            }
        }
    }

    private void sendInitialStateEventIfNeeded() {
        if (initialStateSent.compareAndSet(false, true)) {
            logger.debug("Sending initial state event");
            for (InitialStateDiscoveryListener listener : initialStateListeners) {
                listener.initialStateProcessed();
            }
        }
    }

    @JsonSerialize(using = NodeSerializer.class)
    @JsonDeserialize(using = NodeDeserializer.class)
    static class ESNode extends NodeState {
        private final DiscoveryNode node;
        private final boolean master;

        ESNode(String id, DiscoveryNode node, boolean master) {
            super(id, node.getName());
            this.node = node;
            this.master = master;
        }

        public DiscoveryNode getNode() {
            return node;
        }

        public boolean isMaster() {
            return master;
        }
    }

    static class NodeSerializer extends JsonSerializer<ESNode> {

        @Override
        public void serialize(ESNode value, com.fasterxml.jackson.core.JsonGenerator jgen, SerializerProvider provider) throws IOException {
            jgen.writeStartObject();
            jgen.writeStringField("id", value.getId());
            jgen.writeStringField("agent", System.getProperty("runtime.id"));
            if (value.isMaster()) {
                jgen.writeArrayFieldStart("services");
                jgen.writeString("elasticsearch");
                jgen.writeEndArray();
            }
            jgen.writeStringField("nodeName", value.getNode().name());
            jgen.writeStringField("nodeId", value.getNode().id());
            jgen.writeStringField("address", value.getNode().address().toString());
            jgen.writeStringField("version", value.getNode().version().toString());
            jgen.writeFieldName("attributes");
            jgen.writeStartObject();
            for (Map.Entry<String, String> entry : value.getNode().attributes().entrySet()) {
                jgen.writeStringField(entry.getKey(), entry.getValue());
            }
            jgen.writeEndObject();
            jgen.writeStringField("binary", Base64.encodeObject(value.getNode()));
            jgen.writeEndObject();
        }
    }

    static class NodeDeserializer extends JsonDeserializer<ESNode> {

        @Override
        public ESNode deserialize(com.fasterxml.jackson.core.JsonParser jp, DeserializationContext ctxt) throws IOException {
            try {
                Map map = jp.readValueAs(Map.class);
                String id = map.get("id").toString();
                DiscoveryNode node = (DiscoveryNode) Base64.decodeToObject(map.get("binary").toString(), Base64.NO_OPTIONS, DiscoveryNode.class.getClassLoader());
                return new ESNode(id, node, false);
            } catch (ClassNotFoundException e) {
                throw new IllegalStateException(e);
            }
        }

    }

}