package it.cavallium.dbengine.lucene.searcher;

import static it.cavallium.dbengine.client.UninterruptibleScheduler.uninterruptibleScheduler;
import static it.cavallium.dbengine.database.LLUtils.singleOrClose;

import io.netty5.buffer.api.Send;
import it.cavallium.dbengine.database.LLKeyScore;
import it.cavallium.dbengine.database.LLUtils;
import it.cavallium.dbengine.database.disk.LLIndexSearchers;
import it.cavallium.dbengine.database.disk.LLTempHugePqEnv;
import it.cavallium.dbengine.lucene.LuceneUtils;
import it.cavallium.dbengine.lucene.FullDocs;
import it.cavallium.dbengine.lucene.LLScoreDoc;
import it.cavallium.dbengine.lucene.hugepq.search.HugePqFullScoreDocCollector;
import java.io.IOException;
import java.io.UncheckedIOException;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.lucene.search.IndexSearcher;
import org.jetbrains.annotations.Nullable;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.scheduler.Schedulers;

public class SortedByScoreFullMultiSearcher implements MultiSearcher {

	protected static final Logger LOG = LogManager.getLogger(SortedByScoreFullMultiSearcher.class);

	private final LLTempHugePqEnv env;

	public SortedByScoreFullMultiSearcher(LLTempHugePqEnv env) {
		this.env = env;
	}

	@Override
	public Mono<LuceneSearchResult> collectMulti(Mono<LLIndexSearchers> indexSearchersMono,
			LocalQueryParams queryParams,
			@Nullable String keyFieldName,
			GlobalQueryRewrite transformer) {
		return singleOrClose(indexSearchersMono, indexSearchers -> {
			Mono<LocalQueryParams> queryParamsMono;
			if (transformer == GlobalQueryRewrite.NO_REWRITE) {
				queryParamsMono = Mono.just(queryParams);
			} else {
				queryParamsMono = Mono
						.fromCallable(() -> transformer.rewrite(indexSearchers, queryParams))
						.subscribeOn(uninterruptibleScheduler(Schedulers.boundedElastic()));
			}

			return queryParamsMono.flatMap(queryParams2 -> {
				if (queryParams2.isSorted() && !queryParams2.isSortedByScore()) {
					throw new IllegalArgumentException(SortedByScoreFullMultiSearcher.this.getClass().getSimpleName()
							+ " doesn't support sorted queries");
				}

				return this
						// Search results
						.search(indexSearchers.shards(), queryParams2)
						// Compute the results
						.transform(fullDocsMono -> this.computeResults(fullDocsMono, indexSearchers, keyFieldName, queryParams2))
						// Ensure that one LuceneSearchResult is always returned
						.single();
			});
		});
	}

	/**
	 * Search effectively the raw results
	 */
	private Mono<FullDocs<LLScoreDoc>> search(Iterable<IndexSearcher> indexSearchers,
			LocalQueryParams queryParams) {
		return Mono
				.fromCallable(() -> {
					LLUtils.ensureBlocking();
					var totalHitsThreshold = queryParams.getTotalHitsThresholdLong();
					return HugePqFullScoreDocCollector.createSharedManager(env, queryParams.limitLong(), totalHitsThreshold);
				})
				.flatMap(sharedManager -> Flux
						.fromIterable(indexSearchers)
						.flatMap(shard -> Mono.fromCallable(() -> {
							LLUtils.ensureBlocking();

							var collector = sharedManager.newCollector();
							try {
								assert queryParams.computePreciseHitsCount() == null ||
										queryParams.computePreciseHitsCount() == collector.scoreMode().isExhaustive();

								shard.search(queryParams.query(), collector);
								return collector;
							} catch (Throwable ex) {
								collector.close();
								throw ex;
							}
						}))
						.collectList()
						.flatMap(collectors -> Mono.fromCallable(() -> {
							try {
								LLUtils.ensureBlocking();
								return sharedManager.reduce(collectors);
							} catch (Throwable ex) {
								for (HugePqFullScoreDocCollector collector : collectors) {
									collector.close();
								}
								throw ex;
							}
						}))
				);
	}

	/**
	 * Compute the results, extracting useful data
	 */
	private Mono<LuceneSearchResult> computeResults(Mono<FullDocs<LLScoreDoc>> dataMono,
			LLIndexSearchers indexSearchers,
			String keyFieldName,
			LocalQueryParams queryParams) {
		return dataMono.map(data -> {
			var totalHitsCount = LuceneUtils.convertTotalHitsCount(data.totalHits());

			Flux<LLKeyScore> hitsFlux = LuceneUtils
					.convertHits(data.iterate(queryParams.offsetLong()).map(LLScoreDoc::toScoreDoc),
							indexSearchers.shards(), keyFieldName, true)
					.take(queryParams.limitLong(), true);

			return new LuceneSearchResult(totalHitsCount, hitsFlux, () -> {
				try {
					indexSearchers.close();
				} catch (UncheckedIOException e) {
					LOG.error("Can't close index searchers", e);
				}
				try {
					data.close();
				} catch (Exception e) {
					LOG.error("Failed to discard data", e);
				}
			});
		});
	}

	@Override
	public String getName() {
		return "sorted by score full multi";
	}
}