/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.index.seqno;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.support.ActionFilters;
import org.elasticsearch.action.support.ActiveShardCount;
import org.elasticsearch.action.support.replication.ReplicationRequest;
import org.elasticsearch.action.support.replication.ReplicationResponse;
import org.elasticsearch.action.support.replication.ReplicationTask;
import org.elasticsearch.action.support.replication.TransportReplicationAction;
import org.elasticsearch.cluster.action.shard.ShardStateAction;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.util.concurrent.ThreadContext;
import org.elasticsearch.index.shard.IndexShard;
import org.elasticsearch.index.shard.ShardId;
import org.elasticsearch.indices.IndicesService;
import org.elasticsearch.tasks.Task;
import org.elasticsearch.tasks.TaskId;
import org.elasticsearch.threadpool.ThreadPool;
import org.elasticsearch.transport.TransportException;
import org.elasticsearch.transport.TransportResponseHandler;
import org.elasticsearch.transport.TransportService;

import java.io.IOException;
import java.util.Map;
import java.util.Objects;

import static org.elasticsearch.core.Strings.format;
import static org.elasticsearch.index.seqno.RetentionLeaseSyncAction.getExceptionLogLevel;

/**
 * Replication action responsible for background syncing retention leases to replicas. This action is deliberately a replication action so
 * that if a replica misses a background retention lease sync then that shard will not be marked as stale. We have some tolerance for a
 * shard copy missing renewals of retention leases since the background sync interval is much smaller than the expected lifetime of
 * retention leases.
 */
public class RetentionLeaseBackgroundSyncAction extends TransportReplicationAction<
    RetentionLeaseBackgroundSyncAction.Request,
    RetentionLeaseBackgroundSyncAction.Request,
    ReplicationResponse> {

    public static final String ACTION_NAME = "indices:admin/seq_no/retention_lease_background_sync";
    private static final Logger LOGGER = LogManager.getLogger(RetentionLeaseSyncAction.class);

    protected static Logger getLogger() {
        return LOGGER;
    }

    @Inject
    public RetentionLeaseBackgroundSyncAction(
        final Settings settings,
        final TransportService transportService,
        final ClusterService clusterService,
        final IndicesService indicesService,
        final ThreadPool threadPool,
        final ShardStateAction shardStateAction,
        final ActionFilters actionFilters
    ) {
        super(
            settings,
            ACTION_NAME,
            transportService,
            clusterService,
            indicesService,
            threadPool,
            shardStateAction,
            actionFilters,
            Request::new,
            Request::new,
            ThreadPool.Names.MANAGEMENT
        );
    }

    @Override
    protected void doExecute(Task task, Request request, ActionListener<ReplicationResponse> listener) {
        assert false : "use RetentionLeaseBackgroundSyncAction#backgroundSync";
    }

    final void backgroundSync(ShardId shardId, String primaryAllocationId, long primaryTerm, RetentionLeases retentionLeases) {
        final ThreadContext threadContext = threadPool.getThreadContext();
        try (ThreadContext.StoredContext ignore = threadContext.stashContext()) {
            // we have to execute under the system context so that if security is enabled the sync is authorized
            threadContext.markAsSystemContext();
            final Request request = new Request(shardId, retentionLeases);
            try (var ignored = threadContext.newTraceContext()) {
                sendRetentionLeaseSyncAction(shardId, primaryAllocationId, primaryTerm, request);
            }
        }
    }

    private void sendRetentionLeaseSyncAction(ShardId shardId, String primaryAllocationId, long primaryTerm, Request request) {
        final ReplicationTask task = (ReplicationTask) taskManager.register("transport", "retention_lease_background_sync", request);
        transportService.sendChildRequest(
            clusterService.localNode(),
            transportPrimaryAction,
            new ConcreteShardRequest<>(request, primaryAllocationId, primaryTerm),
            task,
            transportOptions,
            new TransportResponseHandler<ReplicationResponse>() {
                @Override
                public ReplicationResponse read(StreamInput in) throws IOException {
                    return newResponseInstance(in);
                }

                @Override
                public void handleResponse(ReplicationResponse response) {
                    task.setPhase("finished");
                    taskManager.unregister(task);
                }

                @Override
                public void handleException(TransportException e) {
                    task.setPhase("finished");
                    taskManager.unregister(task);
                    LOGGER.log(getExceptionLogLevel(e), () -> format("%s retention lease background sync failed", shardId), e);
                }
            }
        );
    }

    @Override
    protected void shardOperationOnPrimary(
        final Request request,
        final IndexShard primary,
        ActionListener<PrimaryResult<Request, ReplicationResponse>> listener
    ) {
        ActionListener.completeWith(listener, () -> {
            assert request.waitForActiveShards().equals(ActiveShardCount.NONE) : request.waitForActiveShards();
            Objects.requireNonNull(request);
            Objects.requireNonNull(primary);
            primary.persistRetentionLeases();
            return new PrimaryResult<>(request, new ReplicationResponse());
        });
    }

    @Override
    protected void shardOperationOnReplica(Request request, IndexShard replica, ActionListener<ReplicaResult> listener) {
        ActionListener.completeWith(listener, () -> {
            Objects.requireNonNull(request);
            Objects.requireNonNull(replica);
            replica.updateRetentionLeasesOnReplica(request.getRetentionLeases());
            replica.persistRetentionLeases();
            return new ReplicaResult();
        });
    }

    public static final class Request extends ReplicationRequest<Request> {

        private final RetentionLeases retentionLeases;

        public RetentionLeases getRetentionLeases() {
            return retentionLeases;
        }

        public Request(StreamInput in) throws IOException {
            super(in);
            retentionLeases = new RetentionLeases(in);
        }

        public Request(final ShardId shardId, final RetentionLeases retentionLeases) {
            super(Objects.requireNonNull(shardId));
            this.retentionLeases = Objects.requireNonNull(retentionLeases);
            waitForActiveShards(ActiveShardCount.NONE);
        }

        @Override
        public void writeTo(final StreamOutput out) throws IOException {
            super.writeTo(Objects.requireNonNull(out));
            retentionLeases.writeTo(out);
        }

        @Override
        public Task createTask(long id, String type, String action, TaskId parentTaskId, Map<String, String> headers) {
            return new ReplicationTask(id, type, action, "retention_lease_background_sync shardId=" + shardId, parentTaskId, headers);
        }

        @Override
        public String toString() {
            return "RetentionLeaseBackgroundSyncAction.Request{"
                + "retentionLeases="
                + retentionLeases
                + ", shardId="
                + shardId
                + ", timeout="
                + timeout
                + ", index='"
                + index
                + '\''
                + ", waitForActiveShards="
                + waitForActiveShards
                + '}';
        }

    }

    @Override
    protected ReplicationResponse newResponseInstance(StreamInput in) throws IOException {
        return new ReplicationResponse(in);
    }

}
