/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.recovery;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.opensearch.action.admin.indices.refresh.RefreshResponse;
import org.opensearch.action.admin.indices.stats.IndicesStatsResponse;
import org.opensearch.action.admin.indices.stats.ShardStats;
import org.opensearch.action.get.GetResponse;
import org.opensearch.action.search.SearchResponse;
import org.opensearch.cluster.ClusterState;
import org.opensearch.cluster.routing.ShardRouting;
import org.opensearch.cluster.service.ClusterService;
import org.opensearch.common.Priority;
import org.opensearch.common.settings.Setting;
import org.opensearch.common.settings.Settings;
import org.opensearch.common.unit.TimeValue;
import org.opensearch.core.common.util.CollectionUtils;
import org.opensearch.core.index.shard.ShardId;
import org.opensearch.index.IndexService;
import org.opensearch.index.IndexSettings;
import org.opensearch.index.shard.DocsStats;
import org.opensearch.index.translog.Translog;
import org.opensearch.plugins.Plugin;
import org.opensearch.search.sort.SortOrder;
import org.opensearch.test.BackgroundIndexer;
import org.opensearch.test.OpenSearchIntegTestCase;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_REPLICAS;
import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_SHARDS;
import static org.opensearch.index.query.QueryBuilders.matchAllQuery;
import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAllSuccessful;
import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertHitCount;
import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertNoTimeout;

public class RecoveryWhileUnderLoadIT extends OpenSearchIntegTestCase {
    private final Logger logger = LogManager.getLogger(RecoveryWhileUnderLoadIT.class);

    public static final class RetentionLeaseSyncIntervalSettingPlugin extends Plugin {

        @Override
        public List<Setting<?>> getSettings() {
            return Collections.singletonList(IndexService.RETENTION_LEASE_SYNC_INTERVAL_SETTING);
        }

    }

    @Override
    protected Collection<Class<? extends Plugin>> nodePlugins() {
        return Stream.concat(super.nodePlugins().stream(), Stream.of(RetentionLeaseSyncIntervalSettingPlugin.class))
            .collect(Collectors.toList());
    }

    public void testRecoverWhileUnderLoadAllocateReplicasTest() throws Exception {
        logger.info("--> creating test index ...");
        int numberOfShards = numberOfShards();
        assertAcked(
            prepareCreate(
                "test",
                1,
                Settings.builder()
                    .put(SETTING_NUMBER_OF_SHARDS, numberOfShards)
                    .put(SETTING_NUMBER_OF_REPLICAS, 1)
                    .put(IndexSettings.INDEX_TRANSLOG_DURABILITY_SETTING.getKey(), Translog.Durability.ASYNC)
            )
        );

        final int totalNumDocs = scaledRandomIntBetween(200, 10000);
        int waitFor = totalNumDocs / 10;
        int extraDocs = waitFor;
        try (BackgroundIndexer indexer = new BackgroundIndexer("test", "type", client(), extraDocs)) {
            logger.info("--> waiting for {} docs to be indexed ...", waitFor);
            waitForDocs(waitFor, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", waitFor);

            extraDocs = totalNumDocs / 10;
            waitFor += extraDocs;
            indexer.continueIndexing(extraDocs);
            logger.info("--> flushing the index ....");
            // now flush, just to make sure we have some data in the index, not just translog
            client().admin().indices().prepareFlush().execute().actionGet();

            logger.info("--> waiting for {} docs to be indexed ...", waitFor);
            waitForDocs(waitFor, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", waitFor);

            extraDocs = totalNumDocs - waitFor;
            indexer.continueIndexing(extraDocs);

            logger.info("--> allow 2 nodes for index [test] ...");
            // now start another node, while we index
            allowNodes("test", 2);

            logger.info("--> waiting for GREEN health status ...");
            // make sure the cluster state is green, and all has been recovered
            assertNoTimeout(
                client().admin().cluster().prepareHealth().setWaitForEvents(Priority.LANGUID).setTimeout("5m").setWaitForGreenStatus()
            );

            logger.info("--> waiting for {} docs to be indexed ...", totalNumDocs);
            waitForDocs(totalNumDocs, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", totalNumDocs);

            logger.info("--> marking and waiting for indexing threads to stop ...");
            indexer.stopAndAwaitStopped();
            logger.info("--> indexing threads stopped");

            logger.info("--> refreshing the index");
            refreshAndAssert();
            logger.info("--> verifying indexed content");
            iterateAssertCount(numberOfShards, 10, indexer.getIds());
        }
    }

    public void testRecoverWhileUnderLoadAllocateReplicasRelocatePrimariesTest() throws Exception {
        logger.info("--> creating test index ...");
        int numberOfShards = numberOfShards();
        assertAcked(
            prepareCreate(
                "test",
                1,
                Settings.builder()
                    .put(SETTING_NUMBER_OF_SHARDS, numberOfShards)
                    .put(SETTING_NUMBER_OF_REPLICAS, 1)
                    .put(IndexSettings.INDEX_TRANSLOG_DURABILITY_SETTING.getKey(), Translog.Durability.ASYNC)
            )
        );

        final int totalNumDocs = scaledRandomIntBetween(200, 10000);
        int waitFor = totalNumDocs / 10;
        int extraDocs = waitFor;
        try (BackgroundIndexer indexer = new BackgroundIndexer("test", "type", client(), extraDocs)) {
            logger.info("--> waiting for {} docs to be indexed ...", waitFor);
            waitForDocs(waitFor, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", waitFor);

            extraDocs = totalNumDocs / 10;
            waitFor += extraDocs;
            indexer.continueIndexing(extraDocs);
            logger.info("--> flushing the index ....");
            // now flush, just to make sure we have some data in the index, not just translog
            client().admin().indices().prepareFlush().execute().actionGet();

            logger.info("--> waiting for {} docs to be indexed ...", waitFor);
            waitForDocs(waitFor, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", waitFor);

            extraDocs = totalNumDocs - waitFor;
            indexer.continueIndexing(extraDocs);
            logger.info("--> allow 4 nodes for index [test] ...");
            allowNodes("test", 4);

            logger.info("--> waiting for GREEN health status ...");
            assertNoTimeout(
                client().admin().cluster().prepareHealth().setWaitForEvents(Priority.LANGUID).setTimeout("5m").setWaitForGreenStatus()
            );

            logger.info("--> waiting for {} docs to be indexed ...", totalNumDocs);
            waitForDocs(totalNumDocs, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", totalNumDocs);

            logger.info("--> marking and waiting for indexing threads to stop ...");
            indexer.stopAndAwaitStopped();
            logger.info("--> indexing threads stopped");

            logger.info("--> refreshing the index");
            refreshAndAssert();
            logger.info("--> verifying indexed content");
            iterateAssertCount(numberOfShards, 10, indexer.getIds());
        }
    }

    public void testRecoverWhileUnderLoadWithReducedAllowedNodes() throws Exception {
        logger.info("--> creating test index ...");
        int numberOfShards = numberOfShards();
        assertAcked(
            prepareCreate(
                "test",
                2,
                Settings.builder()
                    .put(SETTING_NUMBER_OF_SHARDS, numberOfShards)
                    .put(SETTING_NUMBER_OF_REPLICAS, 1)
                    .put(IndexSettings.INDEX_TRANSLOG_DURABILITY_SETTING.getKey(), Translog.Durability.ASYNC)
            )
        );

        final int totalNumDocs = scaledRandomIntBetween(200, 10000);
        int waitFor = totalNumDocs / 10;
        int extraDocs = waitFor;
        try (BackgroundIndexer indexer = new BackgroundIndexer("test", "type", client(), extraDocs)) {
            logger.info("--> waiting for {} docs to be indexed ...", waitFor);
            waitForDocs(waitFor, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", waitFor);

            extraDocs = totalNumDocs / 10;
            waitFor += extraDocs;
            indexer.continueIndexing(extraDocs);
            logger.info("--> flushing the index ....");
            // now flush, just to make sure we have some data in the index, not just translog
            client().admin().indices().prepareFlush().execute().actionGet();

            logger.info("--> waiting for {} docs to be indexed ...", waitFor);
            waitForDocs(waitFor, indexer);
            indexer.assertNoFailures();
            logger.info("--> {} docs indexed", waitFor);

            // now start more nodes, while we index
            extraDocs = totalNumDocs - waitFor;
            indexer.continueIndexing(extraDocs);
            logger.info("--> allow 4 nodes for index [test] ...");
            allowNodes("test", 4);

            logger.info("--> waiting for GREEN health status ...");
            assertNoTimeout(
                client().admin()
                    .cluster()
                    .prepareHealth()
                    .setWaitForEvents(Priority.LANGUID)
                    .setTimeout("5m")
                    .setWaitForGreenStatus()
                    .setWaitForNoRelocatingShards(true)
            );

            logger.info("--> waiting for {} docs to be indexed ...", totalNumDocs);
            waitForDocs(totalNumDocs, indexer);
            indexer.assertNoFailures();

            logger.info("--> {} docs indexed", totalNumDocs);
            // now, shutdown nodes
            logger.info("--> allow 3 nodes for index [test] ...");
            allowNodes("test", 3);
            logger.info("--> waiting for relocations ...");
            assertNoTimeout(
                client().admin()
                    .cluster()
                    .prepareHealth()
                    .setWaitForEvents(Priority.LANGUID)
                    .setTimeout("5m")
                    .setWaitForNoRelocatingShards(true)
            );

            logger.info("--> allow 2 nodes for index [test] ...");
            allowNodes("test", 2);
            logger.info("--> waiting for relocations ...");
            assertNoTimeout(
                client().admin()
                    .cluster()
                    .prepareHealth()
                    .setWaitForEvents(Priority.LANGUID)
                    .setTimeout("5m")
                    .setWaitForNoRelocatingShards(true)
            );

            logger.info("--> allow 1 nodes for index [test] ...");
            allowNodes("test", 1);
            logger.info("--> waiting for relocations ...");
            assertNoTimeout(
                client().admin()
                    .cluster()
                    .prepareHealth()
                    .setWaitForEvents(Priority.LANGUID)
                    .setTimeout("5m")
                    .setWaitForNoRelocatingShards(true)
            );

            logger.info("--> marking and waiting for indexing threads to stop ...");
            indexer.stopAndAwaitStopped();
            logger.info("--> indexing threads stopped");

            assertNoTimeout(
                client().admin()
                    .cluster()
                    .prepareHealth()
                    .setWaitForEvents(Priority.LANGUID)
                    .setTimeout("5m")
                    .setWaitForNoRelocatingShards(true)
            );

            logger.info("--> refreshing the index");
            refreshAndAssert();
            logger.info("--> verifying indexed content");
            iterateAssertCount(numberOfShards, 10, indexer.getIds());
        }
    }

    public void testRecoverWhileRelocating() throws Exception {
        final int numShards = between(2, 5);
        final int numReplicas = 0;
        logger.info("--> creating test index ...");
        int allowNodes = 2;
        assertAcked(
            prepareCreate(
                "test",
                3,
                Settings.builder()
                    .put(SETTING_NUMBER_OF_SHARDS, numShards)
                    .put(SETTING_NUMBER_OF_REPLICAS, numReplicas)
                    .put(IndexSettings.INDEX_TRANSLOG_DURABILITY_SETTING.getKey(), Translog.Durability.ASYNC)
                    .put(IndexService.RETENTION_LEASE_SYNC_INTERVAL_SETTING.getKey(), randomFrom("100ms", "1s", "5s", "30s", "60s"))
            )
        );

        final int numDocs = scaledRandomIntBetween(200, 9999);

        try (BackgroundIndexer indexer = new BackgroundIndexer("test", "type", client(), numDocs)) {

            for (int i = 0; i < numDocs; i += scaledRandomIntBetween(100, Math.min(1000, numDocs))) {
                indexer.assertNoFailures();
                logger.info("--> waiting for {} docs to be indexed ...", i);
                waitForDocs(i, indexer);
                logger.info("--> {} docs indexed", i);
                allowNodes = 2 / allowNodes;
                allowNodes("test", allowNodes);
                logger.info("--> waiting for GREEN health status ...");
                ensureGreen(TimeValue.timeValueMinutes(5));
            }

            logger.info("--> marking and waiting for indexing threads to stop ...");
            indexer.stopAndAwaitStopped();

            logger.info("--> indexing threads stopped");
            logger.info("--> bump up number of replicas to 1 and allow all nodes to hold the index");
            allowNodes("test", 3);
            assertAcked(
                client().admin().indices().prepareUpdateSettings("test").setSettings(Settings.builder().put("number_of_replicas", 1)).get()
            );
            ensureGreen(TimeValue.timeValueMinutes(5));

            logger.info("--> refreshing the index");
            refreshAndAssert();
            logger.info("--> verifying indexed content");
            iterateAssertCount(numShards, 10, indexer.getIds());
        }
    }

    private void iterateAssertCount(final int numberOfShards, final int iterations, final Set<String> ids) throws Exception {
        final long numberOfDocs = ids.size();
        SearchResponse[] iterationResults = new SearchResponse[iterations];
        boolean error = false;
        for (int i = 0; i < iterations; i++) {
            SearchResponse searchResponse = client().prepareSearch()
                .setSize((int) numberOfDocs)
                .setQuery(matchAllQuery())
                .setTrackTotalHits(true)
                .addSort("id", SortOrder.ASC)
                .get();
            logSearchResponse(numberOfShards, numberOfDocs, i, searchResponse);
            iterationResults[i] = searchResponse;
            if (searchResponse.getHits().getTotalHits().value != numberOfDocs) {
                error = true;
            }
        }

        if (error) {
            // Printing out shards and their doc count
            IndicesStatsResponse indicesStatsResponse = client().admin().indices().prepareStats().get();
            for (ShardStats shardStats : indicesStatsResponse.getShards()) {
                DocsStats docsStats = shardStats.getStats().docs;
                logger.info(
                    "shard [{}] - count {}, primary {}",
                    shardStats.getShardRouting().id(),
                    docsStats.getCount(),
                    shardStats.getShardRouting().primary()
                );
            }

            ClusterService clusterService = clusterService();
            final ClusterState state = clusterService.state();
            for (int shard = 0; shard < numberOfShards; shard++) {
                for (String id : ids) {
                    ShardId docShard = clusterService.operationRouting().shardId(state, "test", id, null);
                    if (docShard.id() == shard) {
                        for (ShardRouting shardRouting : state.routingTable().shardRoutingTable("test", shard)) {
                            GetResponse response = client().prepareGet("test", id)
                                .setPreference("_only_nodes:" + shardRouting.currentNodeId())
                                .get();
                            if (response.isExists()) {
                                logger.info("missing id [{}] on shard {}", id, shardRouting);
                            }
                        }
                    }
                }
            }

            // if there was an error we try to wait and see if at some point it'll get fixed
            logger.info("--> trying to wait");
            assertBusy(() -> {
                boolean errorOccurred = false;
                for (int i = 0; i < iterations; i++) {
                    SearchResponse searchResponse = client().prepareSearch()
                        .setTrackTotalHits(true)
                        .setSize(0)
                        .setQuery(matchAllQuery())
                        .get();
                    if (searchResponse.getHits().getTotalHits().value != numberOfDocs) {
                        errorOccurred = true;
                    }
                }
                assertFalse("An error occurred while waiting", errorOccurred);
            }, 5, TimeUnit.MINUTES);
            assertEquals(numberOfDocs, ids.size());
        }

        // lets now make the test fail if it was supposed to fail
        for (int i = 0; i < iterations; i++) {
            assertHitCount(iterationResults[i], numberOfDocs);
        }
    }

    private void logSearchResponse(int numberOfShards, long numberOfDocs, int iteration, SearchResponse searchResponse) {
        logger.info(
            "iteration [{}] - successful shards: {} (expected {})",
            iteration,
            searchResponse.getSuccessfulShards(),
            numberOfShards
        );
        logger.info("iteration [{}] - failed shards: {} (expected 0)", iteration, searchResponse.getFailedShards());
        if (CollectionUtils.isEmpty(searchResponse.getShardFailures()) == false) {
            logger.info("iteration [{}] - shard failures: {}", iteration, Arrays.toString(searchResponse.getShardFailures()));
        }
        logger.info(
            "iteration [{}] - returned documents: {} (expected {})",
            iteration,
            searchResponse.getHits().getTotalHits().value,
            numberOfDocs
        );
    }

    private void refreshAndAssert() throws Exception {
        assertBusy(() -> {
            RefreshResponse actionGet = client().admin().indices().prepareRefresh().get();
            assertAllSuccessful(actionGet);
        }, 5, TimeUnit.MINUTES);
    }
}
