package it.cavallium.dbengine.lucene;

import com.ibm.icu.text.Collator;
import com.ibm.icu.util.ULocale;
import it.cavallium.dbengine.client.CompositeSnapshot;
import it.cavallium.dbengine.client.IndicizerAnalyzers;
import it.cavallium.dbengine.client.IndicizerSimilarities;
import it.cavallium.dbengine.client.MultiSort;
import it.cavallium.dbengine.client.SearchResult;
import it.cavallium.dbengine.client.SearchResultItem;
import it.cavallium.dbengine.client.SearchResultKey;
import it.cavallium.dbengine.client.SearchResultKeys;
import it.cavallium.dbengine.database.LLKeyScore;
import it.cavallium.dbengine.database.LLSearchResultShard;
import it.cavallium.dbengine.database.LLUtils;
import it.cavallium.dbengine.database.collections.DatabaseMapDictionary;
import it.cavallium.dbengine.database.collections.DatabaseMapDictionaryDeep;
import it.cavallium.dbengine.database.collections.Joiner.ValueGetter;
import it.cavallium.dbengine.lucene.analyzer.NCharGramAnalyzer;
import it.cavallium.dbengine.lucene.analyzer.NCharGramEdgeAnalyzer;
import it.cavallium.dbengine.lucene.analyzer.TextFieldsAnalyzer;
import it.cavallium.dbengine.lucene.analyzer.TextFieldsSimilarity;
import it.cavallium.dbengine.lucene.analyzer.WordAnalyzer;
import it.cavallium.dbengine.lucene.searcher.LuceneStreamSearcher.HandleResult;
import it.cavallium.dbengine.lucene.searcher.LuceneStreamSearcher.ResultItemConsumer;
import it.cavallium.dbengine.lucene.similarity.NGramSimilarity;
import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.en.EnglishPossessiveFilter;
import org.apache.lucene.analysis.en.KStemFilter;
import org.apache.lucene.analysis.icu.ICUCollationKeyAnalyzer;
import org.apache.lucene.analysis.miscellaneous.ASCIIFoldingFilter;
import org.apache.lucene.analysis.miscellaneous.PerFieldAnalyzerWrapper;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.index.IndexableField;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.similarities.BooleanSimilarity;
import org.apache.lucene.search.similarities.ClassicSimilarity;
import org.apache.lucene.search.similarities.PerFieldSimilarityWrapper;
import org.apache.lucene.search.similarities.Similarity;
import org.jetbrains.annotations.Nullable;
import org.novasearch.lucene.search.similarities.BM25Similarity;
import org.novasearch.lucene.search.similarities.BM25Similarity.BM25Model;
import org.novasearch.lucene.search.similarities.LdpSimilarity;
import org.novasearch.lucene.search.similarities.LtcSimilarity;
import org.novasearch.lucene.search.similarities.RobertsonSimilarity;
import org.warp.commonutils.log.Logger;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

public class LuceneUtils {
	private static final Analyzer lucene4GramWordsAnalyzerEdgeInstance = new NCharGramEdgeAnalyzer(true, 4, 4);
	private static final Analyzer lucene4GramStringAnalyzerEdgeInstance = new NCharGramEdgeAnalyzer(false, 4, 4);
	private static final Analyzer lucene4GramWordsAnalyzerInstance = new NCharGramAnalyzer(true, 4, 4);
	private static final Analyzer lucene4GramStringAnalyzerInstance = new NCharGramAnalyzer(false, 4, 4);
	private static final Analyzer lucene3To5GramWordsAnalyzerEdgeInstance = new NCharGramEdgeAnalyzer(true, 3, 5);
	private static final Analyzer lucene3To5GramStringAnalyzerEdgeInstance = new NCharGramEdgeAnalyzer(false, 3, 5);
	private static final Analyzer lucene3To5GramWordsAnalyzerInstance = new NCharGramAnalyzer(true, 3, 5);
	private static final Analyzer lucene3To5GramStringAnalyzerInstance = new NCharGramAnalyzer(false, 3, 5);
	private static final Analyzer luceneStandardAnalyzerInstance = new StandardAnalyzer();
	private static final Analyzer luceneWordAnalyzerStopWordsAndStemInstance = new WordAnalyzer(false,true, true);
	private static final Analyzer luceneWordAnalyzerStopWordsInstance = new WordAnalyzer(false, true, false);
	private static final Analyzer luceneWordAnalyzerStemInstance = new WordAnalyzer(false, false, true);
	private static final Analyzer luceneWordAnalyzerSimpleInstance = new WordAnalyzer(false, false, false);
	private static final Analyzer luceneICUCollationKeyInstance = new WordAnalyzer(false, true, true);
	private static final Similarity luceneBM25ClassicSimilarityInstance = new BM25Similarity(BM25Model.CLASSIC);
	private static final Similarity luceneBM25PlusSimilarityInstance = new BM25Similarity(BM25Model.PLUS);
	private static final Similarity luceneBM25LSimilarityInstance = new BM25Similarity(BM25Model.L);
	private static final Similarity luceneBM15PlusSimilarityInstance = new BM25Similarity(1.2f, 0.0f, 0.5f, BM25Model.PLUS);
	private static final Similarity luceneBM11PlusSimilarityInstance = new BM25Similarity(1.2f, 1.0f, 0.5f, BM25Model.PLUS);
	private static final Similarity luceneBM25ClassicNGramSimilarityInstance = NGramSimilarity.bm25(BM25Model.CLASSIC);
	private static final Similarity luceneBM25PlusNGramSimilarityInstance = NGramSimilarity.bm25(BM25Model.PLUS);
	private static final Similarity luceneBM25LNGramSimilarityInstance = NGramSimilarity.bm25(BM25Model.L);
	private static final Similarity luceneBM15PlusNGramSimilarityInstance = NGramSimilarity.bm15(BM25Model.PLUS);
	private static final Similarity luceneBM11PlusNGramSimilarityInstance = NGramSimilarity.bm11(BM25Model.PLUS);
	private static final Similarity luceneClassicSimilarityInstance = new ClassicSimilarity();
	private static final Similarity luceneClassicNGramSimilarityInstance = NGramSimilarity.classic();
	private static final Similarity luceneLTCSimilarityInstance = new LtcSimilarity();
	private static final Similarity luceneLDPSimilarityInstance = new LdpSimilarity();
	private static final Similarity luceneLDPNoLengthSimilarityInstance = new LdpSimilarity(0, 0.5f);
	private static final Similarity luceneBooleanSimilarityInstance = new BooleanSimilarity();
	private static final Similarity luceneRobertsonSimilarityInstance = new RobertsonSimilarity();

	@SuppressWarnings("DuplicatedCode")
	public static Analyzer getAnalyzer(TextFieldsAnalyzer analyzer) {
		return switch (analyzer) {
			case N4GramPartialWords -> lucene4GramWordsAnalyzerInstance;
			case N4GramPartialString -> lucene4GramStringAnalyzerInstance;
			case N4GramPartialWordsEdge -> lucene4GramWordsAnalyzerEdgeInstance;
			case N4GramPartialStringEdge -> lucene4GramStringAnalyzerEdgeInstance;
			case N3To5GramPartialWords -> lucene3To5GramWordsAnalyzerInstance;
			case N3To5GramPartialString -> lucene3To5GramStringAnalyzerInstance;
			case N3To5GramPartialWordsEdge -> lucene3To5GramWordsAnalyzerEdgeInstance;
			case N3To5GramPartialStringEdge -> lucene3To5GramStringAnalyzerEdgeInstance;
			case Standard -> luceneStandardAnalyzerInstance;
			case FullText -> luceneWordAnalyzerStopWordsAndStemInstance;
			case WordWithStopwordsStripping -> luceneWordAnalyzerStopWordsInstance;
			case WordWithStemming -> luceneWordAnalyzerStemInstance;
			case WordSimple -> luceneWordAnalyzerSimpleInstance;
			case ICUCollationKey -> luceneICUCollationKeyInstance;
			//noinspection UnnecessaryDefault
			default -> throw new UnsupportedOperationException("Unknown analyzer: " + analyzer);
		};
	}

	@SuppressWarnings("DuplicatedCode")
	public static Similarity getSimilarity(TextFieldsSimilarity similarity) {
		return switch (similarity) {
			case BM25Classic -> luceneBM25ClassicSimilarityInstance;
			case NGramBM25Classic -> luceneBM25ClassicNGramSimilarityInstance;
			case BM25L -> luceneBM25LSimilarityInstance;
			case NGramBM25L -> luceneBM25LNGramSimilarityInstance;
			case Classic -> luceneClassicSimilarityInstance;
			case NGramClassic -> luceneClassicNGramSimilarityInstance;
			case BM25Plus -> luceneBM25PlusSimilarityInstance;
			case NGramBM25Plus -> luceneBM25PlusNGramSimilarityInstance;
			case BM15Plus -> luceneBM15PlusSimilarityInstance;
			case NGramBM15Plus -> luceneBM15PlusNGramSimilarityInstance;
			case BM11Plus -> luceneBM11PlusSimilarityInstance;
			case NGramBM11Plus -> luceneBM11PlusNGramSimilarityInstance;
			case LTC -> luceneLTCSimilarityInstance;
			case LDP -> luceneLDPSimilarityInstance;
			case LDPNoLength -> luceneLDPNoLengthSimilarityInstance;
			case Robertson -> luceneRobertsonSimilarityInstance;
			case Boolean -> luceneBooleanSimilarityInstance;
			//noinspection UnnecessaryDefault
			default -> throw new IllegalStateException("Unknown similarity: " + similarity);
		};
	}

	/**
	 *
	 * @param stem Enable stem filters on words.
	 *              Pass false if it will be used with a n-gram filter
	 */
	public static TokenStream newCommonFilter(TokenStream tokenStream, boolean stem) {
		tokenStream = newCommonNormalizer(tokenStream);
		if (stem) {
			tokenStream = new KStemFilter(tokenStream);
			tokenStream = new EnglishPossessiveFilter(tokenStream);
		}
		return tokenStream;
	}

	public static TokenStream newCommonNormalizer(TokenStream tokenStream) {
		tokenStream = new ASCIIFoldingFilter(tokenStream);
		tokenStream = new LowerCaseFilter(tokenStream);
		return tokenStream;
	}

	/**
	 * Merge streams together maintaining absolute order
	 */
	public static <T> Flux<T> mergeStream(Flux<Flux<T>> mappedMultiResults,
			@Nullable MultiSort<T> sort,
			long offset,
			@Nullable Long limit) {
		if (limit != null && limit == 0) {
			return mappedMultiResults.flatMap(f -> f).ignoreElements().flux();
		} else {
			return mappedMultiResults.collectList().flatMapMany(mappedMultiResultsList -> {
				Flux<T> mergedFlux;
				if (sort == null) {
					mergedFlux = Flux.merge(mappedMultiResultsList);
				} else {
					//noinspection unchecked
					mergedFlux = Flux.mergeOrdered(32, sort.getResultSort(), mappedMultiResultsList.toArray(Flux[]::new));
				}
				Flux<T> offsetedFlux;
				if (offset > 0) {
					offsetedFlux = mergedFlux.skip(offset);
				} else {
					offsetedFlux = mergedFlux;
				}
				if (limit == null || limit == Long.MAX_VALUE) {
					return offsetedFlux;
				} else {
					return offsetedFlux.take(limit, true);
				}
			});
		}
	}

	public static HandleResult collectTopDoc(Logger logger,
			int docId,
			float score,
			Float minCompetitiveScore,
			IndexSearcher indexSearcher,
			String keyFieldName,
			ResultItemConsumer resultsConsumer) throws IOException {
		if (minCompetitiveScore == null || score >= minCompetitiveScore) {
			Document d = indexSearcher.doc(docId, Set.of(keyFieldName));
			if (d.getFields().isEmpty()) {
				logger.error("The document docId: {}, score: {} is empty.", docId, score);
				var realFields = indexSearcher.doc(docId).getFields();
				if (!realFields.isEmpty()) {
					logger.error("Present fields:");
					for (IndexableField field : realFields) {
						logger.error(" - {}", field.name());
					}
				}
			} else {
				var field = d.getField(keyFieldName);
				if (field == null) {
					logger.error("Can't get key of document docId: {}, score: {}", docId, score);
				} else {
					if (resultsConsumer.accept(new LLKeyScore(field.stringValue(), score)) == HandleResult.HALT) {
						return HandleResult.HALT;
					}
				}
			}
		}
		return HandleResult.CONTINUE;
	}

	public static <T> Mono<SearchResultKeys<T>> mergeSignalStreamKeys(Flux<SearchResultKeys<T>> mappedKeys,
			MultiSort<SearchResultKey<T>> sort,
			long offset,
			Long limit) {
		return mappedKeys.reduce(
				new SearchResultKeys<>(Flux.empty(), 0L),
				(a, b) -> new SearchResultKeys<>(LuceneUtils.mergeStream(Flux.just(a.results(), b.results()),
						sort,
						offset,
						limit
				), a.totalHitsCount() + b.totalHitsCount())
		);
	}

	public static <T, U> Mono<SearchResult<T, U>> mergeSignalStreamItems(Flux<SearchResult<T, U>> mappedKeys,
			MultiSort<SearchResultItem<T, U>> sort,
			long offset,
			Long limit) {
		return mappedKeys.reduce(
				new SearchResult<>(Flux.empty(), 0L),
				(a, b) -> new SearchResult<>(LuceneUtils.mergeStream(Flux.just(a.results(), b.results()),
						sort,
						offset,
						limit
				), a.totalHitsCount() + b.totalHitsCount())
		);
	}

	public static Mono<LLSearchResultShard> mergeSignalStreamRaw(Flux<LLSearchResultShard> mappedKeys,
			MultiSort<LLKeyScore> mappedSort,
			long offset,
			Long limit) {
		return mappedKeys.reduce(
				new LLSearchResultShard(Flux.empty(), 0),
				(s1, s2) -> new LLSearchResultShard(
						LuceneUtils.mergeStream(Flux.just(s1.results(), s2.results()), mappedSort, offset, limit),
						s1.totalHitsCount() + s2.totalHitsCount()
				)
		);
	}

	public static <T, U, V> ValueGetter<Entry<T, U>, V> getAsyncDbValueGetterDeep(
			CompositeSnapshot snapshot,
			DatabaseMapDictionaryDeep<T, Map<U, V>, DatabaseMapDictionary<U, V>> dictionaryDeep) {
		return entry -> dictionaryDeep
				.at(snapshot, entry.getKey())
				.flatMap(sub -> sub.getValue(snapshot, entry.getValue()).doAfterTerminate(sub::release));
	}

	public static PerFieldAnalyzerWrapper toPerFieldAnalyzerWrapper(IndicizerAnalyzers indicizerAnalyzers) {
		HashMap<String, Analyzer> perFieldAnalyzer = new HashMap<>();
		indicizerAnalyzers
				.fieldAnalyzer()
				.forEach((key, value) -> perFieldAnalyzer.put(key, LuceneUtils.getAnalyzer(value)));
		return new PerFieldAnalyzerWrapper(LuceneUtils.getAnalyzer(indicizerAnalyzers.defaultAnalyzer()), perFieldAnalyzer);
	}

	public static PerFieldSimilarityWrapper toPerFieldSimilarityWrapper(IndicizerSimilarities indicizerSimilarities) {
		HashMap<String, Similarity> perFieldSimilarity = new HashMap<>();
		indicizerSimilarities
				.fieldSimilarity()
				.forEach((key, value) -> perFieldSimilarity.put(key, LuceneUtils.getSimilarity(value)));
		var defaultSimilarity = LuceneUtils.getSimilarity(indicizerSimilarities.defaultSimilarity());
		return new PerFieldSimilarityWrapper() {

			@Override
			public Similarity get(String name) {
				return perFieldSimilarity.getOrDefault(name, defaultSimilarity);
			}
		};
	}

	public static int alignUnsigned(int number, boolean expand) {
		if (number % 4096 != 0) {
			if (expand) {
				return number + (4096 - (number % 4096));
			} else {
				return number - (number % 4096);
			}
		} else {
			return number;
		}
	}

	public static long alignUnsigned(long number, boolean expand) {
		if (number % 4096L != 0) {
			if (expand) {
				return number + (4096L - (number % 4096L));
			} else {
				return number - (number % 4096L);
			}
		} else {
			return number;
		}
	}

	public static void readInternalAligned(Object ref, FileChannel channel, long pos, ByteBuffer b, int readLength, int usefulLength, long end) throws IOException {
		int startBufPosition = b.position();
		int readData = 0;
		int i;
		for(; readLength > 0; readLength -= i) {
			int toRead = readLength;
			b.limit(b.position() + toRead);

			assert b.remaining() == toRead;

			var beforeReadBufPosition = b.position();
			channel.read(b, pos);
			b.limit(Math.min(startBufPosition + usefulLength, b.position() + toRead));
			var afterReadBufPosition = b.position();
			i = (afterReadBufPosition - beforeReadBufPosition);
			readData += i;

			if (i < toRead && i > 0) {
				if (readData < usefulLength) {
					throw new EOFException("read past EOF: " + ref + " buffer: " + b + " chunkLen: " + toRead + " end: " + end);
				}
				if (readData == usefulLength) {
					b.limit(b.position());
					// File end reached
					return;
				}
			}

			if (i < 0) {
				throw new EOFException("read past EOF: " + ref + " buffer: " + b + " chunkLen: " + toRead + " end: " + end);
			}

			assert i > 0 : "FileChannel.read with non zero-length bb.remaining() must always read at least one byte (FileChannel is in blocking mode, see spec of ReadableByteChannel)";

			pos += (long)i;
		}

		assert readLength == 0;
	}
}