/*
 * 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.cluster.routing.GroupShardsIterator;
import org.elasticsearch.cluster.routing.ShardIterator;
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.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;

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

    protected final ClusterService clusterService;

    protected final TransportShardReplicationOperationAction<ShardRequest, ShardReplicaRequest, ShardResponse> shardAction;

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

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

    @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;
        }
        // update to concrete index
        request.index(clusterState.metaData().concreteIndex(request.index()));
        blockException = checkRequestBlock(clusterState, request);
        if (blockException != null) {
            throw blockException;
        }

        GroupShardsIterator groups;
        try {
            groups = shards(request);
        } catch (Throwable e) {
            listener.onFailure(e);
            return;
        }
        final AtomicInteger indexCounter = new AtomicInteger();
        final AtomicInteger completionCounter = new AtomicInteger(groups.size());
        final AtomicReferenceArray<Object> shardsResponses = new AtomicReferenceArray<Object>(groups.size());

        for (final ShardIterator shardIt : groups) {
            ShardRequest shardRequest = newShardRequestInstance(request, shardIt.shardId().id());

            // TODO for now, we fork operations on shardIt of the index
            shardRequest.beforeLocalFork(); // optimize for local fork
            shardRequest.operationThreaded(true);

            // no need for threaded listener, we will fork when its done based on the index request
            shardRequest.listenerThreaded(false);
            shardAction.execute(shardRequest, new ActionListener<ShardResponse>() {
                @Override
                public void onResponse(ShardResponse result) {
                    shardsResponses.set(indexCounter.getAndIncrement(), result);
                    if (completionCounter.decrementAndGet() == 0) {
                        listener.onResponse(newResponseInstance(request, shardsResponses));
                    }
                }

                @Override
                public void onFailure(Throwable e) {
                    int index = indexCounter.getAndIncrement();
                    if (accumulateExceptions()) {
                        shardsResponses.set(index, e);
                    }
                    if (completionCounter.decrementAndGet() == 0) {
                        listener.onResponse(newResponseInstance(request, shardsResponses));
                    }
                }
            });
        }
    }

    protected abstract Request newRequestInstance();

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

    protected abstract String transportAction();

    protected abstract GroupShardsIterator shards(Request request) throws ElasticsearchException;

    protected abstract ShardRequest newShardRequestInstance(Request request, int shardId);

    protected abstract boolean accumulateExceptions();

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

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

    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 to use 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);
                    }
                }
            });
        }
    }
}
