/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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 org.elasticsearch.action.support.replication;

import org.elasticsearch.ElasticsearchException;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.ActionRequest;
import org.elasticsearch.action.ActionResponse;
import org.elasticsearch.action.support.TransportAction;
import org.elasticsearch.cluster.ClusterService;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.block.ClusterBlockException;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.transport.BaseTransportRequestHandler;
import org.elasticsearch.transport.TransportChannel;
import org.elasticsearch.transport.TransportService;

import java.util.Map;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;

/**
 */
public abstract class TransportIndicesReplicationOperationAction<Request extends IndicesReplicationOperationRequest, Response extends ActionResponse, IndexRequest extends IndexReplicationOperationRequest, IndexResponse extends ActionResponse,
        ShardRequest extends ShardReplicationOperationRequest, ShardReplicaRequest extends ActionRequest, ShardResponse extends ActionResponse>
        extends TransportAction<Request, Response> {

    protected final ClusterService clusterService;

    protected final TransportIndexReplicationOperationAction<IndexRequest, IndexResponse, ShardRequest, ShardReplicaRequest, ShardResponse> indexAction;


    final String transportAction;

    @Inject
    public TransportIndicesReplicationOperationAction(Settings settings, TransportService transportService, ClusterService clusterService, ThreadPool threadPool,
                                                      TransportIndexReplicationOperationAction<IndexRequest, IndexResponse, ShardRequest, ShardReplicaRequest, ShardResponse> indexAction) {
        super(settings, threadPool);
        this.clusterService = clusterService;
        this.indexAction = indexAction;

        this.transportAction = transportAction();

        transportService.registerHandler(transportAction, new TransportHandler());
    }


    protected abstract Map<String, Set<String>> resolveRouting(ClusterState clusterState, Request request) throws ElasticsearchException;

    @Override
    protected void doExecute(final Request request, final ActionListener<Response> listener) {
        ClusterState clusterState = clusterService.state();
        ClusterBlockException blockException = checkGlobalBlock(clusterState, request);
        if (blockException != null) {
            throw blockException;
        }
        // get actual indices
        String[] concreteIndices = clusterState.metaData().concreteIndices(request.indices(), request.indicesOptions());
        blockException = checkRequestBlock(clusterState, request, concreteIndices);
        if (blockException != null) {
            throw blockException;
        }

        final AtomicInteger indexCounter = new AtomicInteger();
        final AtomicInteger completionCounter = new AtomicInteger(concreteIndices.length);
        final AtomicReferenceArray<Object> indexResponses = new AtomicReferenceArray<Object>(concreteIndices.length);

        Map<String, Set<String>> routingMap = resolveRouting(clusterState, request);
        if (concreteIndices == null || concreteIndices.length == 0) {
            listener.onResponse(newResponseInstance(request, indexResponses));
        } else {
            for (final String index : concreteIndices) {
                Set<String> routing = null;
                if (routingMap != null) {
                    routing = routingMap.get(index);
                }
                IndexRequest indexRequest = newIndexRequestInstance(request, index, routing);
                // no threading needed, all is done on the index replication one
                indexRequest.listenerThreaded(false);
                indexAction.execute(indexRequest, new ActionListener<IndexResponse>() {
                    @Override
                    public void onResponse(IndexResponse result) {
                        indexResponses.set(indexCounter.getAndIncrement(), result);
                        if (completionCounter.decrementAndGet() == 0) {
                            listener.onResponse(newResponseInstance(request, indexResponses));
                        }
                    }
    
                    @Override
                    public void onFailure(Throwable e) {
                        int index = indexCounter.getAndIncrement();
                        if (accumulateExceptions()) {
                            indexResponses.set(index, e);
                        }
                        if (completionCounter.decrementAndGet() == 0) {
                            listener.onResponse(newResponseInstance(request, indexResponses));
                        }
                    }
                });
            }
        }
    }

    protected abstract Request newRequestInstance();

    protected abstract Response newResponseInstance(Request request, AtomicReferenceArray indexResponses);

    protected abstract String transportAction();

    protected abstract IndexRequest newIndexRequestInstance(Request request, String index, Set<String> routing);

    protected abstract boolean accumulateExceptions();

    protected abstract ClusterBlockException checkGlobalBlock(ClusterState state, Request request);

    protected abstract ClusterBlockException checkRequestBlock(ClusterState state, Request request, String[] concreteIndices);

    private class TransportHandler extends BaseTransportRequestHandler<Request> {

        @Override
        public Request newInstance() {
            return newRequestInstance();
        }

        @Override
        public String executor() {
            return ThreadPool.Names.SAME;
        }

        @Override
        public void messageReceived(final Request request, final TransportChannel channel) throws Exception {
            // no need for a threaded listener, since we just send a response
            request.listenerThreaded(false);
            execute(request, new ActionListener<Response>() {
                @Override
                public void onResponse(Response result) {
                    try {
                        channel.sendResponse(result);
                    } catch (Throwable e) {
                        onFailure(e);
                    }
                }

                @Override
                public void onFailure(Throwable e) {
                    try {
                        channel.sendResponse(e);
                    } catch (Exception e1) {
                        logger.warn("Failed to send error response for action [" + transportAction + "] and request [" + request + "]", e1);
                    }
                }
            });
        }
    }
}
