/*
 * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
 * License v3.0 only", or the "Server Side Public License, v 1".
 */

package org.elasticsearch.cluster.metadata;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.ExceptionsHelper;
import org.elasticsearch.action.ActionListener;
import org.elasticsearch.action.admin.indices.settings.put.UpdateSettingsClusterStateUpdateRequest;
import org.elasticsearch.action.support.master.AcknowledgedResponse;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.ClusterStateAckListener;
import org.elasticsearch.cluster.ClusterStateTaskListener;
import org.elasticsearch.cluster.block.ClusterBlock;
import org.elasticsearch.cluster.block.ClusterBlockLevel;
import org.elasticsearch.cluster.block.ClusterBlocks;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.routing.IndexRoutingTable;
import org.elasticsearch.cluster.routing.RoutingTable;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.ShardRoutingState;
import org.elasticsearch.cluster.routing.UnassignedInfo;
import org.elasticsearch.cluster.routing.allocation.AllocationService;
import org.elasticsearch.cluster.routing.allocation.allocator.AllocationActionMultiListener;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.cluster.service.MasterServiceTaskQueue;
import org.elasticsearch.common.Priority;
import org.elasticsearch.common.regex.Regex;
import org.elasticsearch.common.settings.IndexScopedSettings;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.index.Index;
import org.elasticsearch.index.IndexSettings;
import org.elasticsearch.indices.IndicesService;
import org.elasticsearch.indices.ShardLimitValidator;
import org.elasticsearch.threadpool.ThreadPool;

import java.io.IOException;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import java.util.Set;
import java.util.function.BiFunction;
import java.util.function.Function;

import static org.elasticsearch.cluster.metadata.MetadataIndexStateService.VERIFIED_READ_ONLY_SETTING;
import static org.elasticsearch.index.IndexSettings.same;

/**
 * Service responsible for submitting update index settings requests
 */
public class MetadataUpdateSettingsService {
    private static final Logger logger = LogManager.getLogger(MetadataUpdateSettingsService.class);

    private final AllocationService allocationService;
    private final IndexScopedSettings indexScopedSettings;
    private final IndicesService indicesService;
    private final ShardLimitValidator shardLimitValidator;
    private final MasterServiceTaskQueue<UpdateSettingsTask> taskQueue;

    public MetadataUpdateSettingsService(
        ClusterService clusterService,
        AllocationService allocationService,
        IndexScopedSettings indexScopedSettings,
        IndicesService indicesService,
        ShardLimitValidator shardLimitValidator,
        ThreadPool threadPool
    ) {
        this.allocationService = allocationService;
        this.indexScopedSettings = indexScopedSettings;
        this.indicesService = indicesService;
        this.shardLimitValidator = shardLimitValidator;
        this.taskQueue = clusterService.createTaskQueue("update-settings", Priority.URGENT, batchExecutionContext -> {
            var listener = new AllocationActionMultiListener<AcknowledgedResponse>(threadPool.getThreadContext());
            var state = batchExecutionContext.initialState();
            for (final var taskContext : batchExecutionContext.taskContexts()) {
                try {
                    final var task = taskContext.getTask();
                    try (var ignored = taskContext.captureResponseHeaders()) {
                        state = task.execute(state);
                    }
                    taskContext.success(task.getAckListener(listener));
                } catch (Exception e) {
                    taskContext.onFailure(e);
                }

            }
            if (state != batchExecutionContext.initialState()) {
                // reroute in case things change that require it (like number of replicas)
                try (var ignored = batchExecutionContext.dropHeadersContext()) {
                    state = allocationService.reroute(state, "settings update", listener.reroute());
                }
            } else {
                listener.noRerouteNeeded();
            }
            return state;
        });
    }

    private final class UpdateSettingsTask implements ClusterStateTaskListener {
        private final UpdateSettingsClusterStateUpdateRequest request;
        private final ActionListener<AcknowledgedResponse> listener;

        private UpdateSettingsTask(UpdateSettingsClusterStateUpdateRequest request, ActionListener<AcknowledgedResponse> listener) {
            this.request = request;
            this.listener = listener;
        }

        private ClusterStateAckListener getAckListener(AllocationActionMultiListener<AcknowledgedResponse> multiListener) {
            return new ClusterStateAckListener() {
                @Override
                public boolean mustAck(DiscoveryNode discoveryNode) {
                    return true;
                }

                @Override
                public void onAllNodesAcked() {
                    multiListener.delay(listener).onResponse(AcknowledgedResponse.of(true));
                }

                @Override
                public void onAckFailure(Exception e) {
                    multiListener.delay(listener).onFailure(e);
                }

                @Override
                public void onAckTimeout() {
                    multiListener.delay(listener).onResponse(AcknowledgedResponse.of(false));
                }

                @Override
                public TimeValue ackTimeout() {
                    return request.ackTimeout();
                }
            };
        }

        @Override
        public void onFailure(Exception e) {
            listener.onFailure(e);
        }

        ClusterState execute(ClusterState currentState) {
            final Settings normalizedSettings = Settings.builder()
                .put(request.settings())
                .normalizePrefix(IndexMetadata.INDEX_SETTING_PREFIX)
                .build();
            Settings.Builder settingsForClosedIndices = Settings.builder();
            Settings.Builder settingsForOpenIndices = Settings.builder();
            final Set<String> skippedSettings = new HashSet<>();

            indexScopedSettings.validate(
                normalizedSettings.filter(s -> Regex.isSimpleMatchPattern(s) == false), // don't validate wildcards
                false, // don't validate values here we check it below never allow to change the number of shards
                true
            ); // validate internal or private index settings
            for (String key : normalizedSettings.keySet()) {
                Setting<?> setting = indexScopedSettings.get(key);
                boolean isWildcard = setting == null && Regex.isSimpleMatchPattern(key);
                assert setting != null // we already validated the normalized settings
                    || (isWildcard && normalizedSettings.hasValue(key) == false)
                    : "unknown setting: " + key + " isWildcard: " + isWildcard + " hasValue: " + normalizedSettings.hasValue(key);
                settingsForClosedIndices.copy(key, normalizedSettings);
                if (isWildcard || setting.isDynamic()) {
                    settingsForOpenIndices.copy(key, normalizedSettings);
                } else {
                    skippedSettings.add(key);
                }
            }
            final Settings closedSettings = settingsForClosedIndices.build();
            final Settings openSettings = settingsForOpenIndices.build();
            final boolean preserveExisting = request.onExisting() == UpdateSettingsClusterStateUpdateRequest.OnExisting.PRESERVE;

            final var currentRoutingTable = currentState.routingTable(request.projectId());
            RoutingTable.Builder routingTableBuilder = null;
            final Metadata currentMetadata = currentState.metadata();
            final ProjectMetadata currentProject = currentMetadata.getProject(request.projectId());
            ProjectMetadata.Builder metadataBuilder = ProjectMetadata.builder(currentProject);
            final var minSupportedIndexVersion = currentState.nodes().getMinSupportedIndexVersion();

            // allow to change any settings to a closed index, and only allow dynamic settings to be changed
            // on an open index
            Set<Index> openIndices = new HashSet<>();
            Set<Index> closedIndices = new HashSet<>();
            Set<Index> readOnlyIndices = null;

            final String[] actualIndices = new String[request.indices().length];
            for (int i = 0; i < request.indices().length; i++) {
                Index index = request.indices()[i];
                actualIndices[i] = index.getName();
                final IndexMetadata metadata = currentProject.getIndexSafe(index);

                if (metadata.getState() == IndexMetadata.State.OPEN) {
                    openIndices.add(index);
                } else {
                    closedIndices.add(index);
                }
                if (metadata.getCompatibilityVersion().before(minSupportedIndexVersion)) {
                    if (readOnlyIndices == null) {
                        readOnlyIndices = new HashSet<>();
                    }
                    readOnlyIndices.add(index);
                }
            }

            if (skippedSettings.isEmpty() == false && openIndices.isEmpty() == false) {
                if (request.onStaticSetting() == UpdateSettingsClusterStateUpdateRequest.OnStaticSetting.REOPEN_INDICES) {
                    // We have non-dynamic settings and open indices. We will unassign all of the shards in these indices so that the new
                    // changed settings are applied when the shards are re-assigned.
                    routingTableBuilder = RoutingTable.builder(allocationService.getShardRoutingRoleStrategy(), currentRoutingTable);
                    for (Index index : new HashSet<>(openIndices)) {
                        // We only want to take on the expense of reopening all shards for an index if the setting is really changing
                        Settings existingSettings = currentProject.index(index).getSettings();
                        boolean needToReopenIndex = false;
                        for (String setting : skippedSettings) {
                            String newValue = request.settings().get(setting);
                            if (Objects.equals(newValue, existingSettings.get(setting)) == false) {
                                needToReopenIndex = true;
                                break;
                            }
                        }
                        if (needToReopenIndex) {
                            List<ShardRouting> shardRoutingList = currentRoutingTable.allShards(index.getName());
                            IndexRoutingTable.Builder indexRoutingTableBuilder = IndexRoutingTable.builder(index);
                            for (ShardRouting shardRouting : shardRoutingList) {
                                if (ShardRoutingState.UNASSIGNED.equals(shardRouting.state()) == false) {
                                    indexRoutingTableBuilder.addShard(
                                        shardRouting.moveToUnassigned(
                                            new UnassignedInfo(
                                                UnassignedInfo.Reason.INDEX_REOPENED,
                                                "Unassigning shards to update static settings"
                                            )
                                        )
                                    );
                                } else {
                                    indexRoutingTableBuilder.addShard(shardRouting);
                                }
                            }
                            routingTableBuilder.add(indexRoutingTableBuilder.build());
                            openIndices.remove(index);
                            closedIndices.add(index);
                        }
                    }
                } else {
                    throw new IllegalArgumentException(
                        String.format(
                            Locale.ROOT,
                            "Can't update non dynamic settings [%s] for open indices %s unless the `reopen` query parameter is set to "
                                + "true. Alternatively, close the indices, apply the settings changes, and reopen the indices",
                            skippedSettings,
                            openIndices
                        )
                    );
                }
            }

            if (IndexMetadata.INDEX_NUMBER_OF_REPLICAS_SETTING.exists(openSettings)) {
                final int updatedNumberOfReplicas = IndexMetadata.INDEX_NUMBER_OF_REPLICAS_SETTING.get(openSettings);
                if (preserveExisting == false) {
                    // Verify that this won't take us over the cluster shard limit.
                    shardLimitValidator.validateShardLimitOnReplicaUpdate(
                        currentState.nodes(),
                        currentMetadata,
                        request.indices(),
                        updatedNumberOfReplicas
                    );

                    /*
                     * We do not update the in-sync allocation IDs as they will be removed upon the first index operation
                     * which makes these copies stale.
                     *
                     * TODO: should we update the in-sync allocation IDs once the data is deleted by the node?
                     */
                    if (routingTableBuilder == null) {
                        routingTableBuilder = RoutingTable.builder(allocationService.getShardRoutingRoleStrategy(), currentRoutingTable);
                    }
                    routingTableBuilder.updateNumberOfReplicas(updatedNumberOfReplicas, actualIndices);
                    metadataBuilder.updateNumberOfReplicas(updatedNumberOfReplicas, actualIndices);
                    logger.info("updating number_of_replicas to [{}] for indices {}", updatedNumberOfReplicas, actualIndices);
                }
            }

            updateIndexSettings(
                openIndices,
                metadataBuilder,
                (index, indexSettings) -> indexScopedSettings.updateDynamicSettings(
                    openSettings,
                    indexSettings,
                    Settings.builder(),
                    index.getName()
                ),
                preserveExisting,
                indexScopedSettings
            );

            updateIndexSettings(
                closedIndices,
                metadataBuilder,
                (index, indexSettings) -> indexScopedSettings.updateSettings(
                    closedSettings,
                    indexSettings,
                    Settings.builder(),
                    index.getName()
                ),
                preserveExisting,
                indexScopedSettings
            );

            if (IndexSettings.INDEX_TRANSLOG_RETENTION_AGE_SETTING.exists(normalizedSettings)
                || IndexSettings.INDEX_TRANSLOG_RETENTION_SIZE_SETTING.exists(normalizedSettings)) {
                for (String index : actualIndices) {
                    final Settings settings = metadataBuilder.get(index).getSettings();
                    MetadataCreateIndexService.validateTranslogRetentionSettings(settings);
                    MetadataCreateIndexService.validateStoreTypeSetting(settings);
                }
            }
            boolean changed = false;
            // increment settings versions
            for (final String index : actualIndices) {
                if (same(currentProject.index(index).getSettings(), metadataBuilder.get(index).getSettings()) == false) {
                    changed = true;
                    final IndexMetadata.Builder builder = IndexMetadata.builder(metadataBuilder.get(index));
                    builder.settingsVersion(1 + builder.settingsVersion());
                    metadataBuilder.put(builder);
                }
            }

            final Function<String, Boolean> verifiedReadOnly = indexName -> VERIFIED_READ_ONLY_SETTING.get(
                currentProject.index(indexName).getSettings()
            );
            final ClusterBlocks.Builder blocks = ClusterBlocks.builder().blocks(currentState.blocks());
            boolean changedBlocks = false;
            for (IndexMetadata.APIBlock block : IndexMetadata.APIBlock.values()) {
                changedBlocks |= maybeUpdateClusterBlock(
                    request.projectId(),
                    actualIndices,
                    blocks,
                    block.block,
                    block.setting,
                    openSettings,
                    metadataBuilder,
                    verifiedReadOnly
                );
            }
            changed |= changedBlocks;

            if (changed == false) {
                return currentState;
            }

            ClusterState updatedState = ClusterState.builder(currentState)
                .putProjectMetadata(metadataBuilder)
                .putRoutingTable(request.projectId(), routingTableBuilder == null ? currentRoutingTable : routingTableBuilder.build())
                .blocks(changedBlocks ? blocks.build() : currentState.blocks())
                .build();

            try {
                final var updatedProject = updatedState.metadata().getProject(request.projectId());
                for (Index index : openIndices) {
                    final IndexMetadata currentIndexMetadata = currentProject.getIndexSafe(index);
                    final IndexMetadata updatedIndexMetadata = updatedProject.getIndexSafe(index);
                    indicesService.verifyIndexMetadata(currentIndexMetadata, updatedIndexMetadata);
                }
                for (Index index : closedIndices) {
                    final IndexMetadata currentIndexMetadata = currentProject.getIndexSafe(index);
                    final IndexMetadata updatedIndexMetadata = updatedProject.getIndexSafe(index);
                    // Verifies that the current index settings can be updated with the updated dynamic settings.
                    indicesService.verifyIndexMetadata(currentIndexMetadata, updatedIndexMetadata);
                    // Now check that we can create the index with the updated settings (dynamic and non-dynamic).
                    // This step is mandatory since we allow to update non-dynamic settings on closed indices.
                    indicesService.verifyIndexMetadata(updatedIndexMetadata, updatedIndexMetadata);
                }
                verifyReadOnlyIndices(request.projectId(), readOnlyIndices, updatedState.blocks());
            } catch (IOException ex) {
                throw ExceptionsHelper.convertToElastic(ex);
            }

            return updatedState;
        }

        @Override
        public String toString() {
            return request.toString();
        }
    }

    public void updateSettings(final UpdateSettingsClusterStateUpdateRequest request, final ActionListener<AcknowledgedResponse> listener) {
        taskQueue.submitTask(
            "update-settings " + Arrays.toString(request.indices()),
            new UpdateSettingsTask(request, listener),
            request.masterNodeTimeout()
        );
    }

    public static void updateIndexSettings(
        Set<Index> indices,
        ProjectMetadata.Builder metadataBuilder,
        BiFunction<Index, Settings.Builder, Boolean> settingUpdater,
        Boolean preserveExisting,
        IndexScopedSettings indexScopedSettings
    ) {
        for (Index index : indices) {
            IndexMetadata indexMetadata = metadataBuilder.getSafe(index);
            // We validate the settings for removed deprecated settings, since we have the indexMetadata now.
            indexScopedSettings.validate(indexMetadata.getSettings(), true, true, true);
            Settings.Builder indexSettings = Settings.builder().put(indexMetadata.getSettings());
            if (settingUpdater.apply(index, indexSettings)) {
                if (preserveExisting) {
                    indexSettings.put(indexMetadata.getSettings());
                }
                /*
                 * The setting index.number_of_replicas is special; we require that this setting has a value
                 * in the index. When creating the index, we ensure this by explicitly providing a value for
                 * the setting to the default (one) if there is a not value provided on the source of the
                 * index creation. A user can update this setting though, including updating it to null,
                 * indicating that they want to use the default value. In this case, we again have to
                 * provide an explicit value for the setting to the default (one).
                 */
                if (IndexMetadata.INDEX_NUMBER_OF_REPLICAS_SETTING.exists(indexSettings) == false) {
                    indexSettings.put(
                        IndexMetadata.SETTING_NUMBER_OF_REPLICAS,
                        IndexMetadata.INDEX_NUMBER_OF_REPLICAS_SETTING.get(Settings.EMPTY)
                    );
                }
                Settings finalSettings = indexSettings.build();
                indexScopedSettings.validate(finalSettings.filter(k -> indexScopedSettings.isPrivateSetting(k) == false), true);
                metadataBuilder.put(IndexMetadata.builder(indexMetadata).settings(finalSettings));
            }
        }
    }

    /**
     * Verifies that read-only compatible indices always have a write block.
     *
     * @param projectId the project ID
     * @param readOnlyIndices the read-only compatible indices
     * @param blocks the updated cluster state blocks
     */
    private static void verifyReadOnlyIndices(ProjectId projectId, @Nullable Set<Index> readOnlyIndices, ClusterBlocks blocks) {
        if (readOnlyIndices != null) {
            for (Index readOnlyIndex : readOnlyIndices) {
                if (blocks.hasIndexBlockLevel(projectId, readOnlyIndex.getName(), ClusterBlockLevel.WRITE) == false) {
                    throw new IllegalArgumentException(
                        String.format(Locale.ROOT, "Can't remove the write block on read-only compatible index %s", readOnlyIndex)
                    );
                }
            }
        }
    }

    /**
     * Updates the cluster block only iff the setting exists in the given settings
     */
    private static boolean maybeUpdateClusterBlock(
        ProjectId projectId,
        String[] actualIndices,
        ClusterBlocks.Builder blocks,
        ClusterBlock block,
        Setting<Boolean> setting,
        Settings openSettings,
        ProjectMetadata.Builder metadataBuilder,
        Function<String, Boolean> verifiedReadOnlyBeforeBlockChanges
    ) {
        boolean changed = false;
        if (setting.exists(openSettings)) {
            final boolean updateBlock = setting.get(openSettings);
            for (String index : actualIndices) {
                if (updateBlock) {
                    if (blocks.hasIndexBlock(projectId, index, block) == false) {
                        blocks.addIndexBlock(projectId, index, block);
                        changed = true;
                        if (block.contains(ClusterBlockLevel.WRITE)) {
                            var isVerifiedReadOnly = verifiedReadOnlyBeforeBlockChanges.apply(index);
                            if (isVerifiedReadOnly) {
                                var indexMetadata = metadataBuilder.get(index);
                                metadataBuilder.put(
                                    IndexMetadata.builder(indexMetadata)
                                        .settings(
                                            Settings.builder()
                                                .put(indexMetadata.getSettings())
                                                .put(VERIFIED_READ_ONLY_SETTING.getKey(), true)
                                        )
                                );
                            }
                        }
                    }
                } else {
                    if (blocks.hasIndexBlock(projectId, index, block)) {
                        blocks.removeIndexBlock(projectId, index, block);
                        changed = true;
                        if (block.contains(ClusterBlockLevel.WRITE)) {
                            if (blocks.hasIndexBlockLevel(projectId, index, ClusterBlockLevel.WRITE) == false) {
                                var indexMetadata = metadataBuilder.get(index);
                                var indexSettings = Settings.builder().put(indexMetadata.getSettings());
                                indexSettings.remove(VERIFIED_READ_ONLY_SETTING.getKey());
                                metadataBuilder.put(IndexMetadata.builder(indexMetadata).settings(indexSettings));
                            }
                        }
                    }
                }
            }
        }
        return changed;
    }
}