/*
 * 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.action.admin.indices.create;

import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.SortedSetSelector;
import org.apache.lucene.search.SortedSetSortField;
import org.apache.lucene.search.join.ScoreMode;
import org.apache.lucene.util.Constants;
import org.elasticsearch.Version;
import org.elasticsearch.action.admin.cluster.state.ClusterStateRequest;
import org.elasticsearch.action.admin.cluster.state.ClusterStateResponse;
import org.elasticsearch.action.admin.indices.settings.get.GetSettingsResponse;
import org.elasticsearch.action.admin.indices.shrink.ResizeType;
import org.elasticsearch.action.admin.indices.stats.CommonStats;
import org.elasticsearch.action.admin.indices.stats.IndicesStatsResponse;
import org.elasticsearch.action.admin.indices.stats.ShardStats;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.index.IndexRequestBuilder;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.internal.Client;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.metadata.IndexMetadata;
import org.elasticsearch.cluster.metadata.MetadataCreateIndexService;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.routing.Murmur3HashFunction;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.index.Index;
import org.elasticsearch.index.IndexService;
import org.elasticsearch.index.IndexVersion;
import org.elasticsearch.index.engine.SegmentsStats;
import org.elasticsearch.index.query.TermsQueryBuilder;
import org.elasticsearch.index.seqno.SeqNoStats;
import org.elasticsearch.index.shard.IndexShard;
import org.elasticsearch.indices.IndicesService;
import org.elasticsearch.test.ESIntegTestCase;
import org.elasticsearch.test.VersionUtils;
import org.elasticsearch.xcontent.XContentType;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.function.BiFunction;
import java.util.stream.IntStream;

import static org.elasticsearch.action.admin.indices.create.ShrinkIndexIT.assertNoResizeSourceIndexSettings;
import static org.elasticsearch.index.query.QueryBuilders.nestedQuery;
import static org.elasticsearch.index.query.QueryBuilders.termQuery;
import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertHitCount;
import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertNoFailures;
import static org.elasticsearch.xcontent.XContentFactory.jsonBuilder;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.equalTo;

public class SplitIndexIT extends ESIntegTestCase {

    @Override
    protected boolean forbidPrivateIndexSettings() {
        return false;
    }

    public void testCreateSplitIndexToN() throws IOException {
        assumeFalse("https://github.com/elastic/elasticsearch/issues/33857", Constants.WINDOWS);

        int[][] possibleShardSplits = new int[][] { { 2, 4, 8 }, { 3, 6, 12 }, { 1, 2, 4 } };
        int[] shardSplits = randomFrom(possibleShardSplits);
        splitToN(shardSplits[0], shardSplits[1], shardSplits[2]);
    }

    public void testSplitFromOneToN() {
        assumeFalse("https://github.com/elastic/elasticsearch/issues/33857", Constants.WINDOWS);

        splitToN(1, 5, 10);
        indicesAdmin().prepareDelete("*").get();
        int randomSplit = randomIntBetween(2, 6);
        splitToN(1, randomSplit, randomSplit * 2);
    }

    private void splitToN(int sourceShards, int firstSplitShards, int secondSplitShards) {

        assertEquals(sourceShards, (sourceShards * firstSplitShards) / firstSplitShards);
        assertEquals(firstSplitShards, (firstSplitShards * secondSplitShards) / secondSplitShards);
        internalCluster().ensureAtLeastNumDataNodes(2);
        final boolean useRouting = randomBoolean();
        final boolean useNested = randomBoolean();
        final boolean useMixedRouting = useRouting ? randomBoolean() : false;
        CreateIndexRequestBuilder createInitialIndex = prepareCreate("source");
        Settings.Builder settings = Settings.builder().put(indexSettings()).put("number_of_shards", sourceShards);
        final boolean useRoutingPartition;
        if (randomBoolean()) {
            // randomly set the value manually
            int routingShards = secondSplitShards * randomIntBetween(1, 10);
            settings.put("index.number_of_routing_shards", routingShards);
            useRoutingPartition = false;
        } else {
            useRoutingPartition = randomBoolean();
        }
        if (useRouting && useMixedRouting == false && useRoutingPartition) {
            int numRoutingShards = MetadataCreateIndexService.calculateNumRoutingShards(secondSplitShards, IndexVersion.current()) - 1;
            settings.put("index.routing_partition_size", randomIntBetween(1, numRoutingShards));
            if (useNested) {
                createInitialIndex.setMapping("_routing", "required=true", "nested1", "type=nested");
            } else {
                createInitialIndex.setMapping("_routing", "required=true");
            }
        } else if (useNested) {
            createInitialIndex.setMapping("nested1", "type=nested");
        }
        logger.info("use routing {} use mixed routing {} use nested {}", useRouting, useMixedRouting, useNested);
        createInitialIndex.setSettings(settings).get();

        int numDocs = randomIntBetween(10, 50);
        String[] routingValue = new String[numDocs];

        BiFunction<String, Integer, IndexRequestBuilder> indexFunc = (index, id) -> {
            try {
                return client().prepareIndex(index)
                    .setId(Integer.toString(id))
                    .setSource(
                        jsonBuilder().startObject()
                            .field("foo", "bar")
                            .field("i", id)
                            .startArray("nested1")
                            .startObject()
                            .field("n_field1", "n_value1_1")
                            .field("n_field2", "n_value2_1")
                            .endObject()
                            .startObject()
                            .field("n_field1", "n_value1_2")
                            .field("n_field2", "n_value2_2")
                            .endObject()
                            .endArray()
                            .endObject()
                    );
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        };
        for (int i = 0; i < numDocs; i++) {
            IndexRequestBuilder builder = indexFunc.apply("source", i);
            if (useRouting) {
                String routing = randomRealisticUnicodeOfCodepointLengthBetween(1, 10);
                if (useMixedRouting && randomBoolean()) {
                    routingValue[i] = null;
                } else {
                    routingValue[i] = routing;
                }
                builder.setRouting(routingValue[i]);
            }
            builder.get();
        }

        if (randomBoolean()) {
            for (int i = 0; i < numDocs; i++) { // let's introduce some updates / deletes on the index
                if (randomBoolean()) {
                    IndexRequestBuilder builder = indexFunc.apply("source", i);
                    if (useRouting) {
                        builder.setRouting(routingValue[i]);
                    }
                    builder.get();
                }
            }
        }

        ensureYellow();
        updateIndexSettings(Settings.builder().put("index.blocks.write", true), "source");
        ensureGreen();
        Settings.Builder firstSplitSettingsBuilder = indexSettings(firstSplitShards, 0).putNull("index.blocks.write");
        if (sourceShards == 1 && useRoutingPartition == false && randomBoolean()) { // try to set it if we have a source index with 1 shard
            firstSplitSettingsBuilder.put("index.number_of_routing_shards", secondSplitShards);
        }
        assertAcked(
            indicesAdmin().prepareResizeIndex("source", "first_split")
                .setResizeType(ResizeType.SPLIT)
                .setSettings(firstSplitSettingsBuilder.build())
                .get()
        );
        ensureGreen();
        assertHitCount(client().prepareSearch("first_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        assertNoResizeSourceIndexSettings("first_split");

        for (int i = 0; i < numDocs; i++) { // now update
            IndexRequestBuilder builder = indexFunc.apply("first_split", i);
            if (useRouting) {
                builder.setRouting(routingValue[i]);
            }
            builder.get();
        }
        flushAndRefresh();
        assertHitCount(client().prepareSearch("first_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        assertHitCount(client().prepareSearch("source").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        for (int i = 0; i < numDocs; i++) {
            GetResponse getResponse = client().prepareGet("first_split", Integer.toString(i)).setRouting(routingValue[i]).get();
            assertTrue(getResponse.isExists());
        }

        updateIndexSettings(Settings.builder().put("index.blocks.write", true), "first_split");
        ensureGreen();
        // now split source into a new index
        assertAcked(
            indicesAdmin().prepareResizeIndex("first_split", "second_split")
                .setResizeType(ResizeType.SPLIT)
                .setSettings(indexSettings(secondSplitShards, 0).putNull("index.blocks.write").build())
                .get()
        );
        ensureGreen();
        assertHitCount(client().prepareSearch("second_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        assertNoResizeSourceIndexSettings("second_split");

        // let it be allocated anywhere and bump replicas
        setReplicaCount(1, "second_split");
        ensureGreen();
        assertHitCount(client().prepareSearch("second_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);

        for (int i = 0; i < numDocs; i++) { // now update
            IndexRequestBuilder builder = indexFunc.apply("second_split", i);
            if (useRouting) {
                builder.setRouting(routingValue[i]);
            }
            builder.get();
        }
        flushAndRefresh();
        for (int i = 0; i < numDocs; i++) {
            GetResponse getResponse = client().prepareGet("second_split", Integer.toString(i)).setRouting(routingValue[i]).get();
            assertTrue(getResponse.isExists());
        }
        assertHitCount(client().prepareSearch("second_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        assertHitCount(client().prepareSearch("first_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        assertHitCount(client().prepareSearch("source").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
        if (useNested) {
            assertNested("source", numDocs);
            assertNested("first_split", numDocs);
            assertNested("second_split", numDocs);
        }
        assertAllUniqueDocs(
            client().prepareSearch("second_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(),
            numDocs
        );
        assertAllUniqueDocs(
            client().prepareSearch("first_split").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(),
            numDocs
        );
        assertAllUniqueDocs(client().prepareSearch("source").setSize(100).setQuery(new TermsQueryBuilder("foo", "bar")).get(), numDocs);
    }

    public void assertNested(String index, int numDocs) {
        // now, do a nested query
        SearchResponse searchResponse = client().prepareSearch(index)
            .setQuery(nestedQuery("nested1", termQuery("nested1.n_field1", "n_value1_1"), ScoreMode.Avg))
            .get();
        assertNoFailures(searchResponse);
        assertThat(searchResponse.getHits().getTotalHits().value, equalTo((long) numDocs));
    }

    public void assertAllUniqueDocs(SearchResponse response, int numDocs) {
        Set<String> ids = new HashSet<>();
        for (int i = 0; i < response.getHits().getHits().length; i++) {
            String id = response.getHits().getHits()[i].getId();
            assertTrue("found ID " + id + " more than once", ids.add(id));
        }
        assertEquals(numDocs, ids.size());
    }

    public void testSplitIndexPrimaryTerm() throws Exception {
        int numberOfTargetShards = randomIntBetween(2, 20);
        int numberOfShards = randomValueOtherThanMany(n -> numberOfTargetShards % n != 0, () -> between(1, numberOfTargetShards - 1));
        internalCluster().ensureAtLeastNumDataNodes(2);
        prepareCreate("source").setSettings(
            Settings.builder()
                .put(indexSettings())
                .put("number_of_shards", numberOfShards)
                .put("index.number_of_routing_shards", numberOfTargetShards)
        ).get();
        ensureGreen(TimeValue.timeValueSeconds(120)); // needs more than the default to allocate many shards

        // fail random primary shards to force primary terms to increase
        final Index source = resolveIndex("source");
        final int iterations = scaledRandomIntBetween(0, 16);
        for (int i = 0; i < iterations; i++) {
            final String node = randomSubsetOf(1, internalCluster().nodesInclude("source")).get(0);
            final IndicesService indexServices = internalCluster().getInstance(IndicesService.class, node);
            final IndexService indexShards = indexServices.indexServiceSafe(source);
            for (final Integer shardId : indexShards.shardIds()) {
                final IndexShard shard = indexShards.getShard(shardId);
                if (shard.routingEntry().primary() && randomBoolean()) {
                    disableAllocation("source");
                    shard.failShard("test", new Exception("test"));
                    // this can not succeed until the shard is failed and a replica is promoted
                    int id = 0;
                    while (true) {
                        // find an ID that routes to the right shard, we will only index to the shard that saw a primary failure
                        final String s = Integer.toString(id);
                        final int hash = Math.floorMod(Murmur3HashFunction.hash(s), numberOfShards);
                        if (hash == shardId) {
                            final IndexRequest request = new IndexRequest("source").id(s)
                                .source("{ \"f\": \"" + s + "\"}", XContentType.JSON);
                            client().index(request).get();
                            break;
                        } else {
                            id++;
                        }
                    }
                    enableAllocation("source");
                    ensureGreen();
                }
            }
        }

        updateIndexSettings(Settings.builder().put("index.blocks.write", true), "source");
        ensureYellow();

        final IndexMetadata indexMetadata = indexMetadata(client(), "source");
        final long beforeSplitPrimaryTerm = IntStream.range(0, numberOfShards).mapToLong(indexMetadata::primaryTerm).max().getAsLong();

        // now split source into target
        final Settings splitSettings = indexSettings(numberOfTargetShards, 0).putNull("index.blocks.write").build();
        assertAcked(indicesAdmin().prepareResizeIndex("source", "target").setResizeType(ResizeType.SPLIT).setSettings(splitSettings).get());

        ensureGreen(TimeValue.timeValueSeconds(120)); // needs more than the default to relocate many shards

        final IndexMetadata aftersplitIndexMetadata = indexMetadata(client(), "target");
        for (int shardId = 0; shardId < numberOfTargetShards; shardId++) {
            assertThat(aftersplitIndexMetadata.primaryTerm(shardId), equalTo(beforeSplitPrimaryTerm + 1));
        }
        assertNoResizeSourceIndexSettings("target");
    }

    private static IndexMetadata indexMetadata(final Client client, final String index) {
        final ClusterStateResponse clusterStateResponse = client.admin().cluster().state(new ClusterStateRequest()).actionGet();
        return clusterStateResponse.getState().metadata().index(index);
    }

    public void testCreateSplitIndex() throws Exception {
        Version version = VersionUtils.randomIndexCompatibleVersion(random());
        prepareCreate("source").setSettings(
            Settings.builder().put(indexSettings()).put("number_of_shards", 1).put("index.version.created", version)
        ).get();
        final int docs = randomIntBetween(0, 128);
        for (int i = 0; i < docs; i++) {
            client().prepareIndex("source").setSource("{\"foo\" : \"bar\", \"i\" : " + i + "}", XContentType.JSON).get();
        }
        internalCluster().ensureAtLeastNumDataNodes(2);
        // ensure all shards are allocated otherwise the ensure green below might not succeed since we require the merge node
        // if we change the setting too quickly we will end up with one replica unassigned which can't be assigned anymore due
        // to the require._name below.
        ensureGreen();
        // relocate all shards to one node such that we can merge it.
        updateIndexSettings(Settings.builder().put("index.blocks.write", true), "source");
        ensureGreen();

        final IndicesStatsResponse sourceStats = indicesAdmin().prepareStats("source").setSegments(true).get();

        // disable rebalancing to be able to capture the right stats. balancing can move the target primary
        // making it hard to pin point the source shards.
        updateClusterSettings(Settings.builder().put(EnableAllocationDecider.CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), "none"));
        try {

            final boolean createWithReplicas = randomBoolean();
            assertAcked(
                indicesAdmin().prepareResizeIndex("source", "target")
                    .setResizeType(ResizeType.SPLIT)
                    .setSettings(indexSettings(2, createWithReplicas ? 1 : 0).putNull("index.blocks.write").build())
                    .get()
            );
            ensureGreen();
            assertNoResizeSourceIndexSettings("target");

            final ClusterState state = clusterAdmin().prepareState().get().getState();
            DiscoveryNode mergeNode = state.nodes().get(state.getRoutingTable().index("target").shard(0).primaryShard().currentNodeId());
            logger.info("split node {}", mergeNode);

            final long maxSeqNo = Arrays.stream(sourceStats.getShards())
                .filter(shard -> shard.getShardRouting().currentNodeId().equals(mergeNode.getId()))
                .map(ShardStats::getSeqNoStats)
                .mapToLong(SeqNoStats::getMaxSeqNo)
                .max()
                .getAsLong();
            final long maxUnsafeAutoIdTimestamp = Arrays.stream(sourceStats.getShards())
                .filter(shard -> shard.getShardRouting().currentNodeId().equals(mergeNode.getId()))
                .map(ShardStats::getStats)
                .map(CommonStats::getSegments)
                .mapToLong(SegmentsStats::getMaxUnsafeAutoIdTimestamp)
                .max()
                .getAsLong();

            final IndicesStatsResponse targetStats = indicesAdmin().prepareStats("target").get();
            for (final ShardStats shardStats : targetStats.getShards()) {
                final SeqNoStats seqNoStats = shardStats.getSeqNoStats();
                final ShardRouting shardRouting = shardStats.getShardRouting();
                assertThat("failed on " + shardRouting, seqNoStats.getMaxSeqNo(), equalTo(maxSeqNo));
                assertThat("failed on " + shardRouting, seqNoStats.getLocalCheckpoint(), equalTo(maxSeqNo));
                assertThat(
                    "failed on " + shardRouting,
                    shardStats.getStats().getSegments().getMaxUnsafeAutoIdTimestamp(),
                    equalTo(maxUnsafeAutoIdTimestamp)
                );
            }

            final int size = docs > 0 ? 2 * docs : 1;
            assertHitCount(client().prepareSearch("target").setSize(size).setQuery(new TermsQueryBuilder("foo", "bar")).get(), docs);

            if (createWithReplicas == false) {
                // bump replicas
                setReplicaCount(1, "target");
                ensureGreen();
                assertHitCount(client().prepareSearch("target").setSize(size).setQuery(new TermsQueryBuilder("foo", "bar")).get(), docs);
            }

            for (int i = docs; i < 2 * docs; i++) {
                client().prepareIndex("target").setSource("{\"foo\" : \"bar\", \"i\" : " + i + "}", XContentType.JSON).get();
            }
            flushAndRefresh();
            assertHitCount(
                client().prepareSearch("target").setSize(2 * size).setQuery(new TermsQueryBuilder("foo", "bar")).get(),
                2 * docs
            );
            assertHitCount(client().prepareSearch("source").setSize(size).setQuery(new TermsQueryBuilder("foo", "bar")).get(), docs);
            GetSettingsResponse target = indicesAdmin().prepareGetSettings("target").get();
            assertEquals(version, target.getIndexToSettings().get("target").getAsVersion("index.version.created", null));
        } finally {
            // clean up
            updateClusterSettings(
                Settings.builder().put(EnableAllocationDecider.CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), (String) null)
            );
        }

    }

    public void testCreateSplitWithIndexSort() throws Exception {
        SortField expectedSortField = new SortedSetSortField("id", true, SortedSetSelector.Type.MAX);
        expectedSortField.setMissingValue(SortedSetSortField.STRING_FIRST);
        Sort expectedIndexSort = new Sort(expectedSortField);
        internalCluster().ensureAtLeastNumDataNodes(2);
        prepareCreate("source").setSettings(
            Settings.builder()
                .put(indexSettings())
                .put("sort.field", "id")
                .put("sort.order", "desc")
                .put("number_of_shards", 2)
                .put("number_of_replicas", 0)
        ).setMapping("id", "type=keyword,doc_values=true").get();
        for (int i = 0; i < 20; i++) {
            client().prepareIndex("source")
                .setId(Integer.toString(i))
                .setSource("{\"foo\" : \"bar\", \"id\" : " + i + "}", XContentType.JSON)
                .get();
        }
        // ensure all shards are allocated otherwise the ensure green below might not succeed since we require the merge node
        // if we change the setting too quickly we will end up with one replica unassigned which can't be assigned anymore due
        // to the require._name below.
        ensureGreen();

        flushAndRefresh();
        assertSortedSegments("source", expectedIndexSort);

        updateIndexSettings(Settings.builder().put("index.blocks.write", true), "source");
        ensureYellow();

        // check that index sort cannot be set on the target index
        IllegalArgumentException exc = expectThrows(
            IllegalArgumentException.class,
            () -> indicesAdmin().prepareResizeIndex("source", "target")
                .setResizeType(ResizeType.SPLIT)
                .setSettings(indexSettings(4, 0).put("index.sort.field", "foo").build())
                .get()
        );
        assertThat(exc.getMessage(), containsString("can't override index sort when resizing an index"));

        // check that the index sort order of `source` is correctly applied to the `target`
        assertAcked(
            indicesAdmin().prepareResizeIndex("source", "target")
                .setResizeType(ResizeType.SPLIT)
                .setSettings(indexSettings(4, 0).putNull("index.blocks.write").build())
                .get()
        );
        ensureGreen();
        flushAndRefresh();
        GetSettingsResponse settingsResponse = indicesAdmin().prepareGetSettings("target").execute().actionGet();
        assertEquals(settingsResponse.getSetting("target", "index.sort.field"), "id");
        assertEquals(settingsResponse.getSetting("target", "index.sort.order"), "desc");
        assertSortedSegments("target", expectedIndexSort);

        // ... and that the index sort is also applied to updates
        for (int i = 20; i < 40; i++) {
            client().prepareIndex("target").setSource("{\"foo\" : \"bar\", \"i\" : " + i + "}", XContentType.JSON).get();
        }
        flushAndRefresh();
        assertSortedSegments("target", expectedIndexSort);
        assertNoResizeSourceIndexSettings("target");
    }
}
