package luan.modules.lucene;

import java.io.Closeable;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Set;
import java.util.HashSet;
import java.util.Collections;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.zip.ZipOutputStream;
import java.util.zip.ZipEntry;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.core.KeywordAnalyzer;
import org.apache.lucene.analysis.en.EnglishAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.StoredField;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.document.IntField;
import org.apache.lucene.document.LongField;
import org.apache.lucene.document.DoubleField;
import org.apache.lucene.index.IndexableField;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.SnapshotDeletionPolicy;
import org.apache.lucene.index.IndexCommit;
import org.apache.lucene.index.AtomicReaderContext;
import org.apache.lucene.index.CheckIndex;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.NumericUtils;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.PrefixQuery;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.MatchAllDocsQuery;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.TotalHitCountCollector;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.Collector;
import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Explanation;
import org.apache.lucene.search.highlight.Formatter;
import org.apache.lucene.search.highlight.Highlighter;
import org.apache.lucene.search.highlight.InvalidTokenOffsetsException;
import org.apache.lucene.search.highlight.Fragmenter;
import org.apache.lucene.search.highlight.NullFragmenter;
import org.apache.lucene.search.highlight.SimpleSpanFragmenter;
import org.apache.lucene.search.highlight.QueryScorer;
import org.apache.lucene.search.highlight.TokenGroup;
import goodjava.lucene.analysis.LowercaseAnalyzer;
import goodjava.lucene.queryparser.GoodQueryParser;
import goodjava.lucene.queryparser.FieldParser;
import goodjava.lucene.queryparser.MultiFieldParser;
import goodjava.lucene.queryparser.StringFieldParser;
import goodjava.lucene.queryparser.NumberFieldParser;
import goodjava.lucene.api.GoodIndexWriter;
import goodjava.lucene.api.LuceneIndexWriter;
import goodjava.lucene.api.GoodIndexWriterConfig;
import goodjava.lucene.api.LuceneUtils;
import goodjava.lucene.logging.LoggingIndexWriter;
import goodjava.lucene.logging.OpDoer;
import goodjava.lucene.backup.BackupIndexWriter;
import goodjava.parser.ParseException;
import luan.modules.Utils;
import luan.Luan;
import luan.LuanTable;
import luan.LuanFunction;
import luan.LuanException;
import luan.LuanRuntimeException;
import luan.modules.parsers.LuanToString;
import goodjava.logging.Logger;
import goodjava.logging.LoggerFactory;


public final class LuceneIndex {
	private static final Logger logger = LoggerFactory.getLogger(LuceneIndex.class);

	private static Map<String,Reference<LuceneIndex>> indexes = new HashMap<String,Reference<LuceneIndex>>();

	public static LuceneIndex getLuceneIndex(Luan luan,File indexDir,LuanTable options)
		throws LuanException, IOException, ClassNotFoundException
	{
		String key = indexDir.getCanonicalPath();
		synchronized(indexes) {
			Reference<LuceneIndex> ref = indexes.get(key);
			if( ref != null ) {
				LuceneIndex li = ref.get();
				if( li != null ) {
					Object version = options.get(luan,"version");
					if( (version==null || version.equals(li.version)) && li.indexDir.exists() )
						return li;
					li.closeWriter();
				}
			}
			LuceneIndex li = new LuceneIndex(luan,indexDir,options);
			indexes.put(key, new WeakReference<LuceneIndex>(li));
			return li;
		}
	}

	private static final Version luceneVersion = Version.LUCENE_4_9;
	public static final StringFieldParser STRING_FIELD_PARSER = new StringFieldParser(new KeywordAnalyzer());
	public static final StringFieldParser LOWERCASE_FIELD_PARSER = new StringFieldParser(new LowercaseAnalyzer(luceneVersion));
	public static final StringFieldParser ENGLISH_FIELD_PARSER = new StringFieldParser(new EnglishAnalyzer(luceneVersion));
	private static final SortField ID_SORT = new SortField("id",SortField.Type.LONG);
	private static final SortField ID_DESC_SORT = new SortField("id",SortField.Type.LONG,true);

	private final Object version;

	private final ReentrantLock writeLock = new ReentrantLock();
	private final File indexDir;
	private GoodIndexWriter writer;
	private DirectoryReader reader;
	private IndexSearcher searcher;
	private final ThreadLocal<IndexSearcher> threadLocalSearcher = new ThreadLocal<IndexSearcher>();
	private final MultiFieldParser mfp;
	private final Analyzer analyzer;  // ???

	private FSDirectory fsDir;
	private int writeCount;
	private AtomicInteger writeCounter = new AtomicInteger();
	private final GoodIndexWriterConfig config;

	private boolean wasCreated;
	private final File logDir;
	private final long logTime;
	private final String name;
	private final String domain;

	private LuceneIndex(Luan luan,File indexDir,LuanTable options)
		throws LuanException, IOException, ClassNotFoundException
	{
		options = new LuanTable(options);
		this.version = options.remove("version");
		FieldParser defaultFieldParser = (FieldParser)options.remove("default_type");
		LuanTable defaultFieldsTbl = Utils.removeTable(options,"default_fields");
		String[] defaultFields = defaultFieldsTbl==null ? null : (String[])defaultFieldsTbl.asList().toArray(new String[0]);
		LuanFunction supplementer = Utils.removeFunction(options,"supplementer");
		logDir = (File)options.remove("log_dir");
		logTime = (Long)options.remove("log_time");
		name = (String)options.remove("name");
		Utils.checkEmpty(options);

		{
			LuanTable module = (LuanTable)luan.require("luan:http/Http.luan");
			String domain = (String)module.get(luan,"domain");
			if( domain == null )
				domain = "localhost";
			this.domain = domain;
		}

		mfp = defaultFieldParser==null ? new MultiFieldParser() : new MultiFieldParser(defaultFieldParser,defaultFields);
		mfp.fields.put( "type", STRING_FIELD_PARSER );
		mfp.fields.put( "id", NumberFieldParser.LONG );
		this.indexDir = indexDir;
		Analyzer analyzer = STRING_FIELD_PARSER.analyzer;
		if( defaultFieldParser instanceof StringFieldParser ) {
			StringFieldParser sfp = (StringFieldParser)defaultFieldParser;
			analyzer = sfp.analyzer;
		}
		this.analyzer = analyzer;
		this.config = new SupplementingConfig(luceneVersion,mfp,supplementer);
		wasCreated = reopen();
	}

	public boolean reopen() throws IOException {
		fsDir = FSDirectory.open(indexDir);
		boolean wasCreated = !fsDir.getDirectory().exists();
		writer = new LuceneIndexWriter(fsDir,config);
		if( logDir != null ) {
			if( BackupIndexWriter.backupDomains == null ) {
				writer = new LoggingIndexWriter((LuceneIndexWriter)writer,logDir,logTime);
			} else {
				writer = BackupIndexWriter.newWithRestore((LuceneIndexWriter)writer,logDir,logTime,domain,name);
			}
		}
		reader = DirectoryReader.open(fsDir);
		searcher = new IndexSearcher(reader);
		initId();
		return wasCreated;
	}

	private void wrote() {
		writeCounter.incrementAndGet();
	}

	public void delete_all() throws IOException {
		boolean commit = !writeLock.isHeldByCurrentThread();
		writeLock.lock();
		try {
			writer.deleteAll();
			id = 0;
			if(commit) writer.commit();
		} finally {
			wrote();
			writeLock.unlock();
		}
	}

	private static Term term(String key,long value) {
		BytesRef br = new BytesRef();
		NumericUtils.longToPrefixCoded(value,0,br);
		return new Term(key,br);
	}

	public void delete(String queryStr)
		throws IOException, ParseException, LuanException
	{
		Query query = GoodQueryParser.parseQuery(mfp,queryStr);

		boolean commit = !writeLock.isHeldByCurrentThread();
		writeLock.lock();
		try {
			writer.deleteDocuments(query);
			if(commit) writer.commit();
		} finally {
			wrote();
			writeLock.unlock();
		}
	}

	public void reindex(String queryStr)
		throws IOException, ParseException
	{
		Query query = GoodQueryParser.parseQuery(mfp,queryStr);

		boolean commit = !writeLock.isHeldByCurrentThread();
		writeLock.lock();
		try {
			writer.reindexDocuments("id",query);
			if(commit) writer.commit();
		} finally {
			wrote();
			writeLock.unlock();
		}
	}

	public void save( Luan luan, LuanTable doc, LuanTable unstored, Map<String,Float> boosts )
		throws LuanException, IOException
	{
		Object obj = doc.get(luan,"id");
		Long id;
		try {
			id = (Long)obj;
		} catch(ClassCastException e) {
			throw new LuanException("id should be Long but is "+obj.getClass().getSimpleName());
		}

		boolean commit = !writeLock.isHeldByCurrentThread();
		writeLock.lock();
		try {
			if( unstored!=null || boosts!=null ) {
				if( unstored == null )
					throw new LuanException("unstored required with boosts");
				if( boosts == null )
					throw new LuanException("boosts required with unstored");
				if( id != null )
					throw new LuanException("update not supported");
				if( !(writer instanceof LuceneIndexWriter) )
					throw new LuanException("not supported with index logging");
				id = ++this.id;
				doc.put(luan,"id",id);
				LuceneIndexWriter liw = (LuceneIndexWriter)writer;
				liw.addDocument( toLucene(doc), toLucene(unstored), boosts );
			} else if( id == null ) {
				id = ++this.id;
				doc.put(luan,"id",id);
				writer.addDocument(toLucene(doc));
			} else {
				writer.updateDocument( "id", toLucene(doc) );
			}
			if(commit) writer.commit();
		} finally {
			wrote();
			writeLock.unlock();
		}
	}

	public boolean is_in_transaction() {
		return writeLock.isHeldByCurrentThread();
	}

	public Object run_in_transaction(Luan luan,LuanFunction fn)
		throws IOException, LuanException
	{
		boolean commit = !writeLock.isHeldByCurrentThread();
		writeLock.lock();
		boolean ok = false;
		try {
			Object rtn = fn.call(luan);
			ok = true;
			if(commit) {
				writer.commit();
			}
			return rtn;
		} finally {
			if( !ok && commit ) {
				writer.rollback();
				reopen();
			}
			wrote();
			writeLock.unlock();
		}
	}

	// ???
	public Object run_in_lock(Luan luan,LuanFunction fn) throws IOException, LuanException {
		if( writeLock.isHeldByCurrentThread() )
			throw new RuntimeException();
		writeLock.lock();
		try {
			synchronized(this) {
				return fn.call(luan);
			}
		} finally {
			wrote();
			writeLock.unlock();
		}
	}


	private long id;

	private void initId() throws IOException {
		TopDocs td = searcher.search(new MatchAllDocsQuery(),1,new Sort(ID_DESC_SORT));
		switch(td.scoreDocs.length) {
		case 0:
			id = 0;
			break;
		case 1:
			id = (Long)searcher.doc(td.scoreDocs[0].doc).getField("id").numericValue();
			break;
		default:
			throw new RuntimeException();
		}
	}

/*
	public void backup(String zipFile) throws LuanException, IOException {
		if( !zipFile.endsWith(".zip") )
			throw new LuanException("file "+zipFile+" doesn't end with '.zip'");
		IndexCommit ic = snapshotDeletionPolicy.snapshot();
		try {
			ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipFile));
			for( String fileName : ic.getFileNames() ) {
				out.putNextEntry(new ZipEntry(fileName));
				FileInputStream in = new FileInputStream(new File(indexDir,fileName));
				Utils.copyAll(in,out);
				in.close();
				out.closeEntry();
			}
			out.close();
		} finally {
			snapshotDeletionPolicy.release(ic);
		}
	}
*/
	public SnapshotDeletionPolicy snapshotDeletionPolicy() {
		return (SnapshotDeletionPolicy)writer.getLuceneIndexWriter().getConfig().getIndexDeletionPolicy();
	}

	public Object snapshot(Luan luan,LuanFunction fn) throws LuanException, IOException {
		SnapshotDeletionPolicy snapshotDeletionPolicy = snapshotDeletionPolicy();
		IndexCommit ic = snapshotDeletionPolicy.snapshot();
		try {
			String dir = fsDir.getDirectory().toString();
			LuanTable fileNames = new LuanTable(new ArrayList(ic.getFileNames()));
			return fn.call(luan,dir,fileNames);
		} finally {
			snapshotDeletionPolicy.release(ic);
		}
	}

	public void tag(String tag) throws IOException {
		boolean commit = !writeLock.isHeldByCurrentThread();
		writeLock.lock();
		try {
			writer.tag(tag);
			if(commit) writer.commit();
		} finally {
			writeLock.unlock();
		}
	}



	public String to_string() {
		return writer.getLuceneIndexWriter().getDirectory().toString();
	}

	protected void finalize() throws Throwable {
		close();
		super.finalize();
	}

	public void close() throws IOException {
		closeWriter();
		reader.close();
	}

	private void closeWriter() throws IOException {
		writeLock.lock();
		try {
			writer.close();
		} finally {
			writeLock.unlock();
		}
	}


	private static class DocFn extends LuanFunction {
		final IndexSearcher searcher;
		final Query query;
		int docID;

		DocFn(IndexSearcher searcher,Query query) {
			this.searcher = searcher;
			this.query = query;
		}

		@Override public Object call(Luan luan,Object[] args) throws LuanException {
			try {
				LuanTable doc = toTable(searcher.doc(docID));
				if( args.length > 0 && "explain".equals(args[0]) ) {
					Explanation explanation = searcher.explain(query,docID);
					return new Object[]{doc,explanation};
				} else {
					return doc;
				}
			} catch(IOException e) {
				throw new LuanException(e);
			}
		}
	}

	private static abstract class MyCollector extends Collector {
		int docBase;
		int i = 0;

		@Override public void setScorer(Scorer scorer) {}
		@Override public void setNextReader(AtomicReaderContext context) {
			this.docBase = context.docBase;
		}
		@Override public boolean acceptsDocsOutOfOrder() {
			return true;
		}
	}

	private synchronized IndexSearcher openSearcher() throws IOException {
		int gwc = writeCounter.get();
		if( writeCount != gwc ) {
			writeCount = gwc;
			DirectoryReader newReader = DirectoryReader.openIfChanged(reader);
//			DirectoryReader newReader = DirectoryReader.openIfChanged(reader,writer.getLuceneIndexWriter(),true);
			if( newReader != null ) {
				reader.decRef();
				reader = newReader;
				searcher = new IndexSearcher(reader);
			}
		}
		reader.incRef();
		return searcher;
	}

	// call in finally block
	private static void close(IndexSearcher searcher) throws IOException {
		searcher.getIndexReader().decRef();
	}

	public void ensure_open() throws IOException {
		close(openSearcher());
	}

	public int advanced_search( final Luan luan, String queryStr, LuanFunction fn, Integer n, String sortStr )
		throws LuanException, IOException, ParseException
	{
		Utils.checkNotNull(queryStr);
		Query query = GoodQueryParser.parseQuery(mfp,queryStr);
		IndexSearcher searcher = threadLocalSearcher.get();
		boolean inTransaction = searcher != null;
		if( !inTransaction )
			searcher = openSearcher();
		try {
			if( fn!=null && n==null ) {
				if( sortStr != null )
					throw new LuanException("sort must be nil when n is nil");
				final DocFn docFn = new DocFn(searcher,query);
				MyCollector col = new MyCollector() {
					@Override public void collect(int doc) {
						try {
							docFn.docID = docBase + doc;
							fn.call(luan,++i,docFn);
						} catch(LuanException e) {
							throw new LuanRuntimeException(e);
						}
					}
				};
				try {
					searcher.search(query,col);
				} catch(LuanRuntimeException e) {
					throw (LuanException)e.getCause();
				}
				return col.i;
			}
			if( fn==null || n==0 ) {
				TotalHitCountCollector thcc = new TotalHitCountCollector();
				searcher.search(query,thcc);
				return thcc.getTotalHits();
			}
			Sort sort = sortStr==null ? null : GoodQueryParser.parseSort(mfp,sortStr);
			TopDocs td = sort==null ? searcher.search(query,n) : searcher.search(query,n,sort);
			final ScoreDoc[] scoreDocs = td.scoreDocs;
			DocFn docFn = new DocFn(searcher,query);
			for( int i=0; i<scoreDocs.length; i++ ) {
				ScoreDoc scoreDoc = scoreDocs[i];
				docFn.docID = scoreDoc.doc;
				fn.call(luan,i+1,docFn,scoreDoc.score);
			}
			return td.totalHits;
		} finally {
			if( !inTransaction )
				close(searcher);
		}
	}

	public Object search_in_transaction(Luan luan,LuanFunction fn) throws LuanException, IOException {
		if( threadLocalSearcher.get() != null )
			throw new LuanException("can't nest search_in_transaction calls");
		IndexSearcher searcher = openSearcher();
		threadLocalSearcher.set(searcher);
		try {
			return fn.call(luan);
		} finally {
			threadLocalSearcher.set(null);
			close(searcher);
		}
	}


	public FieldParser getIndexedFieldParser(String field) {
		return mfp.fields.get(field);
	}

	public void setIndexedFieldParser(String field,FieldParser fp) {
		if( fp==null ) {  // delete
			mfp.fields.remove(field);
			return;
		}
		mfp.fields.put( field, fp );
	}

	static Map<String,Object> toLucene(LuanTable table) throws LuanException {
		return SupplementingConfig.toLucene(table);
	}

	private static LuanTable toTable(Document doc) throws LuanException {
		return doc==null ? null : SupplementingConfig.toTable(LuceneUtils.toMap(doc));
	}


	private static final Formatter nullFormatter = new Formatter() {
		public String highlightTerm(String originalText,TokenGroup tokenGroup) {
			return originalText;
		}
	};

	public LuanFunction highlighter(final Luan luan,String queryStr,final LuanFunction formatter,final Integer fragmentSize,String dotdotdot)
		throws ParseException
	{
		Query query = GoodQueryParser.parseQuery(mfp,queryStr);
		Formatter fmt = new Formatter() {
			public String highlightTerm(String originalText,TokenGroup tokenGroup) {
				if( tokenGroup.getTotalScore() <= 0 )
					return originalText;
				try {
					return (String)Luan.first(formatter.call(luan,originalText));
				} catch(LuanException e) {
					throw new LuanRuntimeException(e);
				}
			}
		};
		QueryScorer queryScorer = new QueryScorer(query);
		final Highlighter chooser = fragmentSize==null ? null : new Highlighter(nullFormatter,queryScorer);
		if( chooser != null )
			chooser.setTextFragmenter( new SimpleSpanFragmenter(queryScorer,fragmentSize) );
		final Highlighter hl = new Highlighter(fmt,queryScorer);
		hl.setTextFragmenter( new NullFragmenter() );
		return new LuanFunction() {
			@Override public String call(Luan luan,Object[] args) throws LuanException {
				String text = (String)args[0];
				try {
					if( chooser != null ) {
						String s = chooser.getBestFragment(analyzer,null,text);
						if( s != null ) {
							if( dotdotdot != null ) {
								boolean atStart = text.startsWith(s);
								boolean atEnd = text.endsWith(s);
								if( !atStart )
									s = dotdotdot + s;
								if( !atEnd )
									s = s + dotdotdot;
							}
							text = s;
						} else if( text.length() > fragmentSize ) {
							text = text.substring(0,fragmentSize);
							if( dotdotdot != null )
								text += "...";
						}
					}
					String s = hl.getBestFragment(analyzer,null,text);
					return s!=null ? s : text;
				} catch(LuanRuntimeException e) {
					throw (LuanException)e.getCause();
				} catch(IOException e) {
					throw new RuntimeException(e);
				} catch(InvalidTokenOffsetsException e) {
					throw new RuntimeException(e);
				}
			}
		};
	}

	public int count_tokens(String text)
		throws IOException
	{
		int n = 0;
		TokenStream ts = analyzer.tokenStream(null,text);
		ts.reset();
		while( ts.incrementToken() ) {
			n++;
		}
		ts.close();
		return n;
	}


	void restore(LuanTable doc)
		throws LuanException, IOException
	{
		writer.addDocument(toLucene(doc));
	}

	public void relog()
		throws IOException, LuanException
	{
		logger.info("start relog");
		writeLock.lock();
		try {
			LoggingIndexWriter loggingWriter = (LoggingIndexWriter)writer;
			loggingWriter.logLucene();
		} finally {
			writeLock.unlock();
		}
		logger.info("end relog");
	}

	public void restore_from_log(Luan luan,LuanFunction handler)
		throws IOException, LuanException, ParseException
	{
		LoggingIndexWriter loggingWriter = (LoggingIndexWriter)writer;
		if( wasCreated && !loggingWriter.wasCreated ) {
			logger.error("restoring from log");
			force_restore_from_log(luan,handler);
		}
	}

	public void force_restore_from_log(Luan luan,LuanFunction handler)
		throws IOException
	{
		logger.warn("start force_restore_from_log");
		if( writeLock.isHeldByCurrentThread() )
			throw new RuntimeException();
		OpDoer opDoer = handler==null ? null : new LuanOpDoer(writer,luan,handler);
		writeLock.lock();
		boolean ok = false;
		try {
			LoggingIndexWriter loggingWriter = (LoggingIndexWriter)writer;
			loggingWriter.playLogs(opDoer);
			ok = true;
			wrote();
			ensure_open();  // refresh searcher
			initId();
			wasCreated = false;
		} finally {
			if( !ok ) {
				writer.rollback();
				reopen();
			}
			wrote();
			writeLock.unlock();
		}
		logger.warn("end force_restore_from_log");
	}

	public void check() throws IOException, LuanException, ParseException {
		String msg = "start check";
		logger.info(msg);
		CheckIndex.Status status = new CheckIndex(fsDir).checkIndex();
		if( !status.clean )
			logger.error("index not clean");
		if( writer instanceof LoggingIndexWriter ) {
			LoggingIndexWriter loggingWriter = (LoggingIndexWriter)writer;
			logger.info("log check");
			boolean ok = loggingWriter.check(ID_SORT);
		}
		logger.info("end check");
	}

}