/*
 * 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.engine;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.codecs.Codec;
import org.apache.lucene.index.LeafReader;
import org.apache.lucene.index.MergePolicy;
import org.apache.lucene.search.QueryCache;
import org.apache.lucene.search.QueryCachingPolicy;
import org.apache.lucene.search.ReferenceManager;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.similarities.Similarity;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Setting.Property;
import org.elasticsearch.common.unit.ByteSizeValue;
import org.elasticsearch.common.unit.MemorySizeValue;
import org.elasticsearch.core.Nullable;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.index.IndexSettings;
import org.elasticsearch.index.codec.CodecService;
import org.elasticsearch.index.seqno.RetentionLeases;
import org.elasticsearch.index.shard.ShardId;
import org.elasticsearch.index.store.Store;
import org.elasticsearch.index.translog.TranslogConfig;
import org.elasticsearch.indices.IndexingMemoryController;
import org.elasticsearch.indices.breaker.CircuitBreakerService;
import org.elasticsearch.plugins.IndexStorePlugin;
import org.elasticsearch.threadpool.ThreadPool;

import java.util.Comparator;
import java.util.List;
import java.util.Objects;
import java.util.function.LongSupplier;
import java.util.function.Supplier;

/*
 * Holds all the configuration that is used to create an {@link Engine}.
 * Once {@link Engine} has been created with this object, changes to this
 * object will affect the {@link Engine} instance.
 */
public final class EngineConfig {
    private final ShardId shardId;
    private final IndexSettings indexSettings;
    private final ByteSizeValue indexingBufferSize;
    private volatile boolean enableGcDeletes = true;
    private final TimeValue flushMergesAfter;
    private final String codecName;
    private final IndexStorePlugin.SnapshotCommitSupplier snapshotCommitSupplier;
    private final ThreadPool threadPool;
    private final Engine.Warmer warmer;
    private final Store store;
    private final MergePolicy mergePolicy;
    private final Analyzer analyzer;
    private final Similarity similarity;
    private final CodecService codecService;
    private final Engine.EventListener eventListener;
    private final QueryCache queryCache;
    private final QueryCachingPolicy queryCachingPolicy;
    @Nullable
    private final List<ReferenceManager.RefreshListener> externalRefreshListener;
    @Nullable
    private final List<ReferenceManager.RefreshListener> internalRefreshListener;
    @Nullable
    private final Sort indexSort;
    @Nullable
    private final CircuitBreakerService circuitBreakerService;
    private final LongSupplier globalCheckpointSupplier;
    private final Supplier<RetentionLeases> retentionLeasesSupplier;
    private final Comparator<LeafReader> leafSorter;

    /**
     * A supplier of the outstanding retention leases. This is used during merged operations to determine which operations that have been
     * soft deleted should be retained.
     *
     * @return a supplier of outstanding retention leases
     */
    public Supplier<RetentionLeases> retentionLeasesSupplier() {
        return retentionLeasesSupplier;
    }

    private final LongSupplier primaryTermSupplier;

    /**
     * Index setting to change the low level lucene codec used for writing new segments.
     * This setting is <b>not</b> realtime updateable.
     * This setting is also settable on the node and the index level, it's commonly used in hot/cold node archs where index is likely
     * allocated on both `kind` of nodes.
     */
    public static final Setting<String> INDEX_CODEC_SETTING = new Setting<>("index.codec", "default", s -> {
        switch (s) {
            case "default":
            case "best_compression":
            case "lucene_default":
                return s;
            default:
                if (Codec.availableCodecs().contains(s) == false) { // we don't error message the not officially supported ones
                    throw new IllegalArgumentException(
                        "unknown value for [index.codec] must be one of [default, best_compression] but was: " + s
                    );
                }
                return s;
        }
    }, Property.IndexScope, Property.NodeScope);

    /**
     * Legacy index setting, kept for 7.x BWC compatibility. This setting has no effect in 8.x. Do not use.
     * TODO: Remove in 9.0
     */
    @Deprecated
    public static final Setting<Boolean> INDEX_OPTIMIZE_AUTO_GENERATED_IDS = Setting.boolSetting(
        "index.optimize_auto_generated_id",
        true,
        Property.IndexScope,
        Property.Dynamic,
        Property.IndexSettingDeprecatedInV7AndRemovedInV8
    );

    private final TranslogConfig translogConfig;

    private final LongSupplier relativeTimeInNanosSupplier;

    @Nullable
    private final Engine.IndexCommitListener indexCommitListener;

    private final boolean promotableToPrimary;

    /**
     * Creates a new {@link org.elasticsearch.index.engine.EngineConfig}
     */
    public EngineConfig(
        ShardId shardId,
        ThreadPool threadPool,
        IndexSettings indexSettings,
        Engine.Warmer warmer,
        Store store,
        MergePolicy mergePolicy,
        Analyzer analyzer,
        Similarity similarity,
        CodecService codecService,
        Engine.EventListener eventListener,
        QueryCache queryCache,
        QueryCachingPolicy queryCachingPolicy,
        TranslogConfig translogConfig,
        TimeValue flushMergesAfter,
        List<ReferenceManager.RefreshListener> externalRefreshListener,
        List<ReferenceManager.RefreshListener> internalRefreshListener,
        Sort indexSort,
        CircuitBreakerService circuitBreakerService,
        LongSupplier globalCheckpointSupplier,
        Supplier<RetentionLeases> retentionLeasesSupplier,
        LongSupplier primaryTermSupplier,
        IndexStorePlugin.SnapshotCommitSupplier snapshotCommitSupplier,
        Comparator<LeafReader> leafSorter,
        LongSupplier relativeTimeInNanosSupplier,
        Engine.IndexCommitListener indexCommitListener,
        boolean promotableToPrimary
    ) {
        this.shardId = shardId;
        this.indexSettings = indexSettings;
        this.threadPool = threadPool;
        this.warmer = warmer == null ? (a) -> {} : warmer;
        this.store = store;
        this.mergePolicy = mergePolicy;
        this.analyzer = analyzer;
        this.similarity = similarity;
        this.codecService = codecService;
        this.eventListener = eventListener;
        codecName = indexSettings.getValue(INDEX_CODEC_SETTING);
        // We need to make the indexing buffer for this shard at least as large
        // as the amount of memory that is available for all engines on the
        // local node so that decisions to flush segments to disk are made by
        // IndexingMemoryController rather than Lucene.
        // Add an escape hatch in case this change proves problematic - it used
        // to be a fixed amound of RAM: 256 MB.
        // TODO: Remove this escape hatch in 8.x
        final String escapeHatchProperty = "es.index.memory.max_index_buffer_size";
        String maxBufferSize = System.getProperty(escapeHatchProperty);
        if (maxBufferSize != null) {
            indexingBufferSize = MemorySizeValue.parseBytesSizeValueOrHeapRatio(maxBufferSize, escapeHatchProperty);
        } else {
            indexingBufferSize = IndexingMemoryController.INDEX_BUFFER_SIZE_SETTING.get(indexSettings.getNodeSettings());
        }
        this.queryCache = queryCache;
        this.queryCachingPolicy = queryCachingPolicy;
        this.translogConfig = translogConfig;
        this.flushMergesAfter = flushMergesAfter;
        this.externalRefreshListener = externalRefreshListener;
        this.internalRefreshListener = internalRefreshListener;
        this.indexSort = indexSort;
        this.circuitBreakerService = circuitBreakerService;
        this.globalCheckpointSupplier = globalCheckpointSupplier;
        this.retentionLeasesSupplier = Objects.requireNonNull(retentionLeasesSupplier);
        this.primaryTermSupplier = primaryTermSupplier;
        this.snapshotCommitSupplier = snapshotCommitSupplier;
        this.leafSorter = leafSorter;
        this.relativeTimeInNanosSupplier = relativeTimeInNanosSupplier;
        this.indexCommitListener = indexCommitListener;
        this.promotableToPrimary = promotableToPrimary;
    }

    /**
     * Enables / disables gc deletes
     *
     * @see #isEnableGcDeletes()
     */
    public void setEnableGcDeletes(boolean enableGcDeletes) {
        this.enableGcDeletes = enableGcDeletes;
    }

    /**
     * Returns the initial index buffer size. This setting is only read on startup and otherwise controlled
     * by {@link IndexingMemoryController}
     */
    public ByteSizeValue getIndexingBufferSize() {
        return indexingBufferSize;
    }

    /**
     * Returns <code>true</code> iff delete garbage collection in the engine should be enabled. This setting is updateable
     * in realtime and forces a volatile read. Consumers can safely read this value directly go fetch it's latest value.
     * The default is <code>true</code>
     * <p>
     *     Engine GC deletion if enabled collects deleted documents from in-memory realtime data structures after a certain amount of
     *     time ({@link IndexSettings#getGcDeletesInMillis()} if enabled. Before deletes are GCed they will cause re-adding the document
     *     that was deleted to fail.
     * </p>
     */
    public boolean isEnableGcDeletes() {
        return enableGcDeletes;
    }

    /**
     * Returns the {@link Codec} used in the engines {@link org.apache.lucene.index.IndexWriter}
     * <p>
     *     Note: this settings is only read on startup.
     * </p>
     */
    public Codec getCodec() {
        return codecService.codec(codecName);
    }

    /**
     * @return the {@link CodecService}
     */
    public CodecService getCodecService() {
        return codecService;
    }

    /**
     * Returns a thread-pool mainly used to get estimated time stamps from
     * {@link org.elasticsearch.threadpool.ThreadPool#relativeTimeInMillis()} and to schedule
     * async force merge calls on the {@link org.elasticsearch.threadpool.ThreadPool.Names#FORCE_MERGE} thread-pool
     */
    public ThreadPool getThreadPool() {
        return threadPool;
    }

    /**
     * Returns an {@link org.elasticsearch.index.engine.Engine.Warmer} used to warm new searchers before they are used for searching.
     */
    public Engine.Warmer getWarmer() {
        return warmer;
    }

    /**
     * Returns the {@link org.elasticsearch.index.store.Store} instance that provides access to the
     * {@link org.apache.lucene.store.Directory} used for the engines {@link org.apache.lucene.index.IndexWriter} to write it's index files
     * to.
     * <p>
     * Note: In order to use this instance the consumer needs to increment the stores reference before it's used the first time and hold
     * it's reference until it's not needed anymore.
     * </p>
     */
    public Store getStore() {
        return store;
    }

    /**
     * Returns the global checkpoint tracker
     */
    public LongSupplier getGlobalCheckpointSupplier() {
        return globalCheckpointSupplier;
    }

    /**
     * Returns the {@link org.apache.lucene.index.MergePolicy} for the engines {@link org.apache.lucene.index.IndexWriter}
     */
    public MergePolicy getMergePolicy() {
        return mergePolicy;
    }

    /**
     * Returns a listener that should be called on engine failure
     */
    public Engine.EventListener getEventListener() {
        return eventListener;
    }

    /**
     * Returns the index settings for this index.
     */
    public IndexSettings getIndexSettings() {
        return indexSettings;
    }

    /**
     * Returns the engines shard ID
     */
    public ShardId getShardId() {
        return shardId;
    }

    /**
     * Returns the analyzer as the default analyzer in the engines {@link org.apache.lucene.index.IndexWriter}
     */
    public Analyzer getAnalyzer() {
        return analyzer;
    }

    /**
     * Returns the {@link org.apache.lucene.search.similarities.Similarity} used for indexing and searching.
     */
    public Similarity getSimilarity() {
        return similarity;
    }

    /**
     * Return the cache to use for queries.
     */
    public QueryCache getQueryCache() {
        return queryCache;
    }

    /**
     * Return the policy to use when caching queries.
     */
    public QueryCachingPolicy getQueryCachingPolicy() {
        return queryCachingPolicy;
    }

    /**
     * Returns the translog config for this engine
     */
    public TranslogConfig getTranslogConfig() {
        return translogConfig;
    }

    /**
     * Returns a {@link TimeValue} at what time interval after the last write modification to the engine finished merges
     * should be automatically flushed. This is used to free up transient disk usage of potentially large segments that
     * are written after the engine became inactive from an indexing perspective.
     */
    public TimeValue getFlushMergesAfter() {
        return flushMergesAfter;
    }

    /**
     * The refresh listeners to add to Lucene for externally visible refreshes
     */
    public List<ReferenceManager.RefreshListener> getExternalRefreshListener() {
        return externalRefreshListener;
    }

    /**
     * The refresh listeners to add to Lucene for internally visible refreshes. These listeners will also be invoked on external refreshes
     */
    public List<ReferenceManager.RefreshListener> getInternalRefreshListener() {
        return internalRefreshListener;
    }

    /**
     * Return the sort order of this index, or null if the index has no sort.
     */
    public Sort getIndexSort() {
        return indexSort;
    }

    /**
     * Returns the circuit breaker service for this engine, or {@code null} if none is to be used.
     */
    @Nullable
    public CircuitBreakerService getCircuitBreakerService() {
        return this.circuitBreakerService;
    }

    /**
     * Returns a supplier that supplies the latest primary term value of the associated shard.
     */
    public LongSupplier getPrimaryTermSupplier() {
        return primaryTermSupplier;
    }

    public IndexStorePlugin.SnapshotCommitSupplier getSnapshotCommitSupplier() {
        return snapshotCommitSupplier;
    }

    /**
     * Returns how segments should be sorted for reading or @null if no sorting should be applied.
     */
    @Nullable
    public Comparator<LeafReader> getLeafSorter() {
        return leafSorter;
    }

    public LongSupplier getRelativeTimeInNanosSupplier() {
        return relativeTimeInNanosSupplier;
    }

    @Nullable
    public Engine.IndexCommitListener getIndexCommitListener() {
        return indexCommitListener;
    }

    /**
     * @return whether the engine should be configured so that it can be promoted to primary in future
     */
    public boolean isPromotableToPrimary() {
        return promotableToPrimary;
    }
}
