/*=============================================================================#
 # Copyright (c) 2018, 2019 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.internal.rhelp.core.index;

import java.io.IOException;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.highlight.DefaultEncoder;
import org.apache.lucene.search.highlight.Encoder;
import org.apache.lucene.search.vectorhighlight.FastVectorHighlighter;
import org.apache.lucene.search.vectorhighlight.FieldFragList;
import org.apache.lucene.search.vectorhighlight.FieldFragList.WeightedFragInfo;
import org.apache.lucene.search.vectorhighlight.FieldPhraseList;
import org.apache.lucene.search.vectorhighlight.FieldPhraseList.WeightedPhraseInfo;
import org.apache.lucene.search.vectorhighlight.FieldPhraseList.WeightedPhraseInfo.Toffs;
import org.apache.lucene.search.vectorhighlight.FieldQuery;
import org.apache.lucene.search.vectorhighlight.FieldTermStack;
import org.apache.lucene.search.vectorhighlight.FragListBuilder;
import org.apache.lucene.search.vectorhighlight.FragmentsBuilder;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;


@NonNullByDefault
public class Highlighter extends FastVectorHighlighter {
	
	
	public static final Encoder DEFAULT_ENCODER= new DefaultEncoder();
	
	
	private static String getTag(final String[] tags, final int num) {
		return tags[num % tags.length];
	}
	
	private static int countMatches(final List<WeightedFragInfo> fragInfos) {
		int matchCount= 0;
		for (int j = 0; j < fragInfos.size(); j++) {
			matchCount+= fragInfos.get(j).getSubInfos().size();
		}
		return matchCount;
	}
	
	
	private final FragListBuilder fragListBuilder;
	private final FragmentsBuilder fragmentsBuilder;
	
	
	public Highlighter(final boolean phraseHighlight, final boolean fieldMatch,
			final FragListBuilder fragListBuilder, final FragmentsBuilder fragmentsBuilder) {
		super(phraseHighlight, fieldMatch, fragListBuilder, fragmentsBuilder);
		this.fragListBuilder= fragListBuilder;
		this.fragmentsBuilder= fragmentsBuilder;
	}
	
	
	public String getComplete(final FieldQuery fieldQuery, final IndexReader reader, final int docId,
			final String fieldName,
			final String[] preTags, final String[] postTags, final Encoder encoder) throws IOException {
		final FieldTermStack fieldTermStack= new FieldTermStack(reader, docId, fieldName, fieldQuery);
		final FieldPhraseList fieldPhraseList= new FieldPhraseList(fieldTermStack, fieldQuery);
		final String src= reader.document(docId).get(fieldName);
		int srcIndex= 0;
		final StringBuilder sb= new StringBuilder(src.length() + fieldPhraseList.getPhraseList().size() * 32);
		for (final WeightedPhraseInfo phraseInfo : fieldPhraseList.getPhraseList()) {
			for (final Toffs to : phraseInfo.getTermsOffsets()) {
				sb.append(encoder.encodeText(src.substring(srcIndex, to.getStartOffset())));
				sb.append(getTag(preTags, phraseInfo.getSeqnum()));
				sb.append(encoder.encodeText(src.substring(to.getStartOffset(), to.getEndOffset())));
				sb.append(getTag(postTags, phraseInfo.getSeqnum()));
				srcIndex= to.getEndOffset();
			}
		}
		sb.append(encoder.encodeText(src.substring(srcIndex)));
		return sb.toString();
	}
	
	public final String @Nullable [] getBestFragments(final FieldQuery fieldQuery, final IndexReader reader, final int docId,
			final String fieldName, final int fragCharSize, final int maxNumFragments,
			final String[] preTags, final String[] postTags, final Encoder encoder,
			final @Nullable AtomicInteger counter) throws IOException {
		final FieldTermStack fieldTermStack= new FieldTermStack(reader, docId, fieldName, fieldQuery);
		final FieldPhraseList fieldPhraseList= new FieldPhraseList(fieldTermStack, fieldQuery,
				getPhraseLimit() );
		final FieldFragList fieldFragList= this.fragListBuilder.createFieldFragList(
				fieldPhraseList, fragCharSize );
		
		if (counter != null) {
			final int matchCount= countMatches(fieldFragList.getFragInfos());
			if (matchCount == 0) {
				return null;
			}
			counter.addAndGet(matchCount);
		}
		
		return this.fragmentsBuilder.createFragments(reader, docId, fieldName,
				fieldFragList, maxNumFragments,
				preTags, postTags, encoder );
	}
	
}