package it.cavallium.dbengine.client;

import it.cavallium.dbengine.client.Hits.CloseableHits;
import it.cavallium.dbengine.client.Hits.LuceneHits;
import it.cavallium.dbengine.client.query.ClientQueryParams;
import it.cavallium.dbengine.client.query.current.data.Query;
import it.cavallium.dbengine.client.query.current.data.TotalHitsCount;
import it.cavallium.dbengine.database.DiscardingCloseable;
import it.cavallium.dbengine.database.LLKeyScore;
import it.cavallium.dbengine.database.LLLuceneIndex;
import it.cavallium.dbengine.database.LLSearchResultShard;
import it.cavallium.dbengine.database.LLSearchResultShard.LuceneLLSearchResultShard;
import it.cavallium.dbengine.database.LLSearchResultShard.ResourcesLLSearchResultShard;
import it.cavallium.dbengine.database.LLSnapshot;
import it.cavallium.dbengine.database.LLTerm;
import it.cavallium.dbengine.database.LLUpdateDocument;
import it.cavallium.dbengine.database.LLUtils;
import it.cavallium.dbengine.database.SafeCloseable;
import it.cavallium.dbengine.lucene.LuceneCloseable;
import it.cavallium.dbengine.lucene.LuceneUtils;
import it.cavallium.dbengine.lucene.collector.Buckets;
import it.cavallium.dbengine.lucene.searcher.BucketParams;
import it.unimi.dsi.fastutil.objects.ObjectArrayList;
import java.time.Duration;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
import java.util.logging.Level;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.publisher.SignalType;

public class LuceneIndexImpl<T, U> implements LuceneIndex<T, U> {

	private static final Duration MAX_COUNT_TIME = Duration.ofSeconds(30);
	private static final Logger LOG = LogManager.getLogger(LuceneIndex.class);
	private final LLLuceneIndex luceneIndex;
	private final Indicizer<T,U> indicizer;

	public LuceneIndexImpl(LLLuceneIndex luceneIndex, Indicizer<T, U> indicizer) {
		this.luceneIndex = luceneIndex;
		this.indicizer = indicizer;
	}

	private LLSnapshot resolveSnapshot(CompositeSnapshot snapshot) {
		if (snapshot == null) {
			return null;
		} else {
			return snapshot.getSnapshot(luceneIndex);
		}
	}

	@Override
	public Mono<Void> addDocument(T key, U value) {
		return indicizer
				.toDocument(key, value)
				.flatMap(doc -> luceneIndex.addDocument(indicizer.toIndex(key), doc));
	}

	@Override
	public Mono<Long> addDocuments(boolean atomic, Flux<Entry<T, U>> entries) {
		return luceneIndex.addDocuments(atomic, entries.flatMap(entry -> indicizer
				.toDocument(entry.getKey(), entry.getValue())
				.map(doc -> Map.entry(indicizer.toIndex(entry.getKey()), doc))));
	}

	@Override
	public Mono<Void> deleteDocument(T key) {
		LLTerm id = indicizer.toIndex(key);
		return luceneIndex.deleteDocument(id);
	}

	@Override
	public Mono<Void> updateDocument(T key, @NotNull U value) {
		return indicizer
				.toIndexRequest(key, value)
				.flatMap(doc -> luceneIndex.update(indicizer.toIndex(key), doc));
	}

	@Override
	public Mono<Long> updateDocuments(Flux<Entry<T, U>> entries) {
		Flux<Entry<LLTerm, LLUpdateDocument>> mappedEntries = entries
				.flatMap(entry -> Mono
						.zip(Mono.just(indicizer.toIndex(entry.getKey())),
								indicizer.toDocument(entry.getKey(), entry.getValue()).single(),
								Map::entry
						)
						.single()
				)
				.log("impl-update-documents", Level.FINEST, false, SignalType.ON_NEXT, SignalType.ON_COMPLETE);
		return luceneIndex.updateDocuments(mappedEntries);
	}

	@Override
	public Mono<Void> deleteAll() {
		return luceneIndex.deleteAll();
	}

	@Override
	public Mono<Hits<HitKey<T>>> moreLikeThis(ClientQueryParams queryParams,
			T key,
			U mltDocumentValue) {
		var mltDocumentFields
				= indicizer.getMoreLikeThisDocumentFields(key, mltDocumentValue);

		return luceneIndex
				.moreLikeThis(resolveSnapshot(queryParams.snapshot()),
						queryParams.toQueryParams(),
						indicizer.getKeyFieldName(),
						mltDocumentFields
				)
				.collectList()
				.mapNotNull(shards -> mergeResults(queryParams, shards))
				.map(llSearchResult -> mapResults(llSearchResult))
				.defaultIfEmpty(Hits.empty())
				.doOnDiscard(DiscardingCloseable.class, LLUtils::onDiscard);
	}

	@Override
	public Mono<Hits<HitKey<T>>> search(ClientQueryParams queryParams) {
		return luceneIndex
				.search(resolveSnapshot(queryParams.snapshot()),
						queryParams.toQueryParams(),
						indicizer.getKeyFieldName()
				)
				.collectList()
				.mapNotNull(shards -> mergeResults(queryParams, shards))
				.map(llSearchResult -> mapResults(llSearchResult))
				.defaultIfEmpty(Hits.empty())
				.doOnDiscard(DiscardingCloseable.class, LLUtils::onDiscard);
	}

	@Override
	public Mono<Buckets> computeBuckets(@Nullable CompositeSnapshot snapshot,
			@NotNull List<Query> query,
			@Nullable Query normalizationQuery,
			BucketParams bucketParams) {
		return luceneIndex.computeBuckets(resolveSnapshot(snapshot), query,
				normalizationQuery, bucketParams).single();
	}

	private Hits<HitKey<T>> mapResults(LLSearchResultShard llSearchResult) {
		Flux<HitKey<T>> scoresWithKeysFlux = llSearchResult.results()
				.map(hit -> new HitKey<>(indicizer.getKey(hit.key()), hit.score()));

		if (llSearchResult instanceof LuceneCloseable luceneCloseable) {
			return new LuceneHits<>(scoresWithKeysFlux, llSearchResult.totalHitsCount(), luceneCloseable);
		} else {
			return new CloseableHits<>(scoresWithKeysFlux, llSearchResult.totalHitsCount(), llSearchResult);
		}
	}

	@Override
	public Mono<TotalHitsCount> count(@Nullable CompositeSnapshot snapshot, Query query) {
		return luceneIndex
				.count(resolveSnapshot(snapshot), query, MAX_COUNT_TIME)
				.doOnDiscard(DiscardingCloseable.class, LLUtils::onDiscard);
	}

	@Override
	public boolean isLowMemoryMode() {
		return luceneIndex.isLowMemoryMode();
	}

	@Override
	public void close() {
		luceneIndex.close();
	}

	/**
	 * Flush writes to disk
	 */
	@Override
	public Mono<Void> flush() {
		return luceneIndex.flush();
	}

	@Override
	public Mono<Void> waitForMerges() {
		return luceneIndex.waitForMerges();
	}

	@Override
	public Mono<Void> waitForLastMerges() {
		return luceneIndex.waitForLastMerges();
	}

	/**
	 * Refresh index searcher
	 */
	@Override
	public Mono<Void> refresh(boolean force) {
		return luceneIndex.refresh(force);
	}

	@Override
	public Mono<LLSnapshot> takeSnapshot() {
		return luceneIndex.takeSnapshot();
	}

	@Override
	public Mono<Void> releaseSnapshot(LLSnapshot snapshot) {
		return luceneIndex.releaseSnapshot(snapshot);
	}

	@SuppressWarnings({"unchecked", "rawtypes"})
	@Nullable
	private static LLSearchResultShard mergeResults(ClientQueryParams queryParams, List<LLSearchResultShard> shards) {
		if (shards.size() == 0) {
			return null;
		} else if (shards.size() == 1) {
			return shards.get(0);
		}
		TotalHitsCount count = null;
		ObjectArrayList<Flux<LLKeyScore>> results = new ObjectArrayList<>(shards.size());
		ObjectArrayList resources = new ObjectArrayList(shards.size());
		boolean luceneResources = false;
		for (LLSearchResultShard shard : shards) {
			if (!luceneResources && shard instanceof LuceneCloseable) {
				luceneResources = true;
			}
			if (count == null) {
				count = shard.totalHitsCount();
			} else {
				count = LuceneUtils.sum(count, shard.totalHitsCount());
			}
			var maxLimit = queryParams.offset() + queryParams.limit();
			results.add(shard.results().take(maxLimit, true));
			resources.add(shard);
		}
		Objects.requireNonNull(count);
		Flux<LLKeyScore> resultsFlux;
		if (results.size() == 0) {
			resultsFlux = Flux.empty();
		} else if (results.size() == 1) {
			resultsFlux = results.get(0);
		} else {
			resultsFlux = Flux.merge(results);
		}
		if (luceneResources) {
			return new LuceneLLSearchResultShard(resultsFlux, count, (List<LuceneCloseable>) resources);
		} else {
			return new ResourcesLLSearchResultShard(resultsFlux, count, (List<SafeCloseable>) resources);
		}
	}

}