// Fulltext.java
// (C) 2006 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 2006 as part of 'plasmaCrawlLURL.java' on http://yacy.net
//
// This is a part of YaCy, a peer-to-peer based web search engine
//
// LICENSE
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

package net.yacy.search.index;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.regex.Pattern;

import net.yacy.cora.date.GenericFormatter;
import net.yacy.cora.date.ISO8601Formatter;
import net.yacy.cora.document.encoding.ASCII;
import net.yacy.cora.document.id.DigestURL;
import net.yacy.cora.document.id.MultiProtocolURL;
import net.yacy.cora.federate.solr.connector.AbstractSolrConnector;
import net.yacy.cora.federate.solr.connector.EmbeddedSolrConnector;
import net.yacy.cora.federate.solr.connector.RemoteSolrConnector;
import net.yacy.cora.federate.solr.connector.ShardSelection;
import net.yacy.cora.federate.solr.connector.SolrConnector;
import net.yacy.cora.federate.solr.instance.EmbeddedInstance;
import net.yacy.cora.federate.solr.instance.InstanceMirror;
import net.yacy.cora.federate.solr.instance.RemoteInstance;
import net.yacy.cora.federate.solr.instance.ShardInstance;
import net.yacy.cora.order.CloneableIterator;
import net.yacy.cora.protocol.HeaderFramework;
import net.yacy.cora.sorting.ReversibleScoreMap;
import net.yacy.cora.sorting.ScoreMap;
import net.yacy.cora.sorting.WeakPriorityBlockingQueue;
import net.yacy.cora.storage.ZIPReader;
import net.yacy.cora.storage.ZIPWriter;
import net.yacy.cora.util.ConcurrentLog;
import net.yacy.document.parser.html.CharacterCoding;
import net.yacy.kelondro.data.meta.URIMetadataNode;
import net.yacy.kelondro.data.meta.URIMetadataRow;
import net.yacy.kelondro.data.word.WordReferenceVars;
import net.yacy.kelondro.index.Cache;
import net.yacy.kelondro.index.Index;
import net.yacy.kelondro.index.Row;
import net.yacy.kelondro.table.SplitTable;
import net.yacy.kelondro.util.MemoryControl;
import net.yacy.search.Switchboard;
import net.yacy.search.schema.CollectionConfiguration;
import net.yacy.search.schema.CollectionSchema;
import net.yacy.search.schema.WebgraphConfiguration;
import net.yacy.search.schema.WebgraphSchema;

import org.apache.solr.common.SolrDocument;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrInputDocument;
import org.apache.lucene.util.Version;

public final class Fulltext {

    private static final String SOLR_PATH = "solr_45"; // the number should be identical to the number in the property luceneMatchVersion in solrconfig.xml
    private static final String SOLR_OLD_PATH[] = new String[]{"solr_36", "solr_40", "solr_44"};
    
    // class objects
	private final File                    segmentPath;
    private       Index                   urlIndexFile;
    private       Export                  exportthread; // will have a export thread assigned if exporter is running
    private       String                  tablename;
    private       ArrayList<HostStat>     statsDump;
    private       InstanceMirror          solrInstances;
    private final CollectionConfiguration collectionConfiguration;
    private final WebgraphConfiguration   webgraphConfiguration;
    private       boolean                 writeWebgraph;

    protected Fulltext(final File segmentPath, final CollectionConfiguration collectionConfiguration, final WebgraphConfiguration webgraphConfiguration) {
        this.segmentPath = segmentPath;
        this.tablename = null;
        this.urlIndexFile = null;
        this.exportthread = null; // will have a export thread assigned if exporter is running
        this.statsDump = null;
        this.solrInstances = new InstanceMirror();
        this.collectionConfiguration = collectionConfiguration;
        this.webgraphConfiguration = webgraphConfiguration;
        this.writeWebgraph = false;
    }
    
    public void writeWebgraph(boolean check) {
        this.writeWebgraph = check;
    }
    
    public boolean writeToWebgraph() {
        return this.writeWebgraph;
    }

    /**
     * @deprecated
     * used only for migration
     * @return the connected URLDb

     */
    @Deprecated
    public Index getURLDb() {
        return this.urlIndexFile;
    }

    protected void connectUrlDb(final String tablename, final boolean useTailCache, final boolean exceed134217727) {
    	if (this.urlIndexFile != null) return;
        this.tablename = tablename;
    	this.urlIndexFile = new SplitTable(new File(this.segmentPath, "default"), tablename, URIMetadataRow.rowdef, useTailCache, exceed134217727);
        // SplitTable always returns != null, even if no file exists.
        // as old UrlDb should be null if not exist, check and close if empty
        // TODO: check if a SplitTable.open() returning null or error status on not existing file is preferable
        if (this.urlIndexFile.isEmpty()) {
            disconnectUrlDb();
        }
    }

    public void disconnectUrlDb() {
    	if (this.urlIndexFile == null) return;
    	this.urlIndexFile.close();
    	this.urlIndexFile = null;
    }

    public CollectionConfiguration getDefaultConfiguration() {
        return this.collectionConfiguration;
    }

    public WebgraphConfiguration getWebgraphConfiguration() {
        return this.webgraphConfiguration;
    }

    public boolean connectedLocalSolr() {
        return this.solrInstances.isConnected0();
    }

    public void connectLocalSolr() throws IOException {
        File solrLocation = new File(this.segmentPath, SOLR_PATH);
        // migrate old solr to new
        for (String oldVersion: SOLR_OLD_PATH) {
            File oldLocation = new File(this.segmentPath, oldVersion);
            if (oldLocation.exists()) oldLocation.renameTo(solrLocation);
        }
        
        EmbeddedInstance localCollectionInstance = new EmbeddedInstance(new File(new File(Switchboard.getSwitchboard().appPath, "defaults"), "solr"), solrLocation, CollectionSchema.CORE_NAME, new String[]{CollectionSchema.CORE_NAME, WebgraphSchema.CORE_NAME});
        EmbeddedSolrConnector localCollectionConnector = new EmbeddedSolrConnector(localCollectionInstance);

        Version luceneVersion = localCollectionConnector.getConfig().getLuceneVersion("luceneMatchVersion");
        String lvn = luceneVersion.name();
        ConcurrentLog.info("Fulltext", "using lucene version " + lvn);
        int p = lvn.indexOf('_');
        assert SOLR_PATH.endsWith(lvn.substring(p)) : "luceneVersion = " + lvn + ", solrPath = " + SOLR_PATH + ", p = " + p + ", check defaults/solr/solrconfig.xml";
        ConcurrentLog.info("Fulltext", "connected solr in " + solrLocation.toString() + ", lucene version " + lvn + ", default core size: " + localCollectionConnector.getSize());
        this.solrInstances.connect0(localCollectionInstance);
    }

    public void disconnectLocalSolr() {
        this.solrInstances.disconnect0();
    }

    public boolean connectedRemoteSolr() {
        return this.solrInstances.isConnected1();
    }

    public void connectRemoteSolr(final ArrayList<RemoteInstance> instances) {
        this.solrInstances.connect1(new ShardInstance(instances, ShardSelection.Method.MODULO_HOST_MD5));
    }

    public void disconnectRemoteSolr() {
        this.solrInstances.disconnect1();
    }

    public EmbeddedSolrConnector getDefaultEmbeddedConnector() {
        return this.solrInstances.getDefaultEmbeddedConnector();
    }

    public EmbeddedSolrConnector getEmbeddedConnector(String corename) {
        return this.solrInstances.getEmbeddedConnector(corename);
    }

    public RemoteSolrConnector getDefaultRemoteSolrConnector() {
        if (this.solrInstances.getSolr1() == null) return null;
        try {
            return new RemoteSolrConnector(this.solrInstances.getSolr1());
        } catch (final IOException e) {
            return null;
        }
    }
    
    public SolrConnector getDefaultConnector() {
        synchronized (this.solrInstances) {
            return this.solrInstances.getDefaultMirrorConnector();
        }
    }
    
    public SolrConnector getWebgraphConnector() {
        if (!this.writeWebgraph) return null;
        synchronized (this.solrInstances) {
            return this.solrInstances.getMirrorConnector(WebgraphSchema.CORE_NAME);
        }
    }

    public void clearCaches() {
        if (this.urlIndexFile != null && this.urlIndexFile instanceof Cache) ((Cache) this.urlIndexFile).clearCache();
        if (this.statsDump != null) this.statsDump.clear();
        this.solrInstances.clearCaches();
        this.statsDump = null;
    }

    public void clearURLIndex() throws IOException {
        if (this.exportthread != null) this.exportthread.interrupt();
        if (this.urlIndexFile == null) {
            SplitTable.delete(new File(this.segmentPath, "default"), this.tablename);
        } else {
            this.urlIndexFile.clear();
        }
        this.statsDump = null;
        this.commit(true);
    }

    public void clearLocalSolr() throws IOException {
        synchronized (this.solrInstances) {
            EmbeddedInstance instance = this.solrInstances.getSolr0();
            if (instance != null) {
                for (String name: instance.getCoreNames()) new EmbeddedSolrConnector(instance, name).clear();
            }
            this.commit(false);
            this.solrInstances.clearCaches();
        }
    }

    public void clearRemoteSolr() throws IOException {
        synchronized (this.solrInstances) {
            ShardInstance instance = this.solrInstances.getSolr1();
            if (instance != null) {
                for (String name: instance.getCoreNames()) new RemoteSolrConnector(instance, name).clear();
            }
            this.solrInstances.clearCaches();
        }
    }

    /**
     * get the size of the default index
     * @return
     */
    private long collectionSizeLastAccess = 0;
    private long collectionSizeLastValue = 0;
    public long collectionSize() {
        long t = System.currentTimeMillis();
        if (t - this.collectionSizeLastAccess < 1000) return this.collectionSizeLastValue;
        long size = this.urlIndexFile == null ? 0 : this.urlIndexFile.size();
        size += this.solrInstances.getDefaultMirrorConnector().getSize();
        this.collectionSizeLastAccess = t;
        this.collectionSizeLastValue = size;
        return size;
    }
    
    /**
     * get the size of the webgraph index
     * @return
     */
    public long webgraphSize() {
        return this.writeWebgraph ? this.getWebgraphConnector().getSize() : 0;
    }

    public void close() {
        this.statsDump = null;
        if (this.urlIndexFile != null) {
            this.urlIndexFile.close();
            this.urlIndexFile = null;
        }
        this.solrInstances.close();
    }
    
    private long lastCommit = 0;
    public void commit(boolean softCommit) {
        long t = System.currentTimeMillis();
        if (lastCommit + 10000 > t) return;
        lastCommit = t;
        getDefaultConnector().commit(softCommit);
        if (this.writeWebgraph) getWebgraphConnector().commit(softCommit);
    }

    public Date getLoadDate(final String urlHash) {
        if (urlHash == null) return null;
        Date x;
        try {
            String d = this.getDefaultConnector().getFieldById(urlHash, CollectionSchema.load_date_dt.getSolrFieldName());
            if (d == null) return null;
            x = new Date(Long.parseLong(d));
        } catch (final IOException e) {
            return null;
        }
        return x;
    }

    public DigestURL getURL(final byte[] urlHash) {
        if (urlHash == null || this.getDefaultConnector() == null) return null;
        
        String x;
        try {
            x = this.getDefaultConnector().getFieldById(ASCII.String(urlHash), CollectionSchema.sku.getSolrFieldName());
        } catch (final IOException e) {
            return null;
        }
        if (x == null) return null;
        try {
            DigestURL uri = new DigestURL(x, urlHash);
            return uri;
        } catch (final MalformedURLException e) {
            return null;
        }
    }
    
    public URIMetadataNode getMetadata(final WeakPriorityBlockingQueue.Element<WordReferenceVars> element) {
        if (element == null) return null;
        WordReferenceVars wre = element.getElement();        
        if (wre == null) return null; // all time was already wasted in takeRWI to get another element
        long weight = element.getWeight();
        URIMetadataNode node = getMetadata(wre.urlhash(), wre, weight);
        return node;
    }

    public URIMetadataNode getMetadata(final byte[] urlHash) {
        if (urlHash == null) return null;
        return getMetadata(urlHash, null, 0);
    }
    
    private URIMetadataNode getMetadata(final byte[] urlHash, final WordReferenceVars wre, final long weight) {
        String u = ASCII.String(urlHash);
        
        // get the metadata from Solr
        try {
            SolrDocument doc = this.getDefaultConnector().getDocumentById(u);
            if (doc != null) {
            	if (this.urlIndexFile != null) this.urlIndexFile.remove(urlHash); // migration
            	return new URIMetadataNode(doc, wre, weight);
            }
        } catch (final IOException e) {
            ConcurrentLog.logException(e);
        }

        // get the metadata from the old metadata index
        if (this.urlIndexFile != null) try {
    		// slow migration to solr
    		final Row.Entry entry = this.urlIndexFile.remove(urlHash);
            if (entry == null) return null;
			URIMetadataRow row = new URIMetadataRow(entry, wre);
			SolrInputDocument solrInput = this.collectionConfiguration.metadata2solr(row);
			this.putDocument(solrInput);
			SolrDocument sd = this.collectionConfiguration.toSolrDocument(solrInput);
			return new URIMetadataNode(sd, wre, weight);
        } catch (final IOException e) {
            ConcurrentLog.logException(e);
        }

        return null;
    }

    public void putDocument(final SolrInputDocument doc) throws IOException {
        SolrConnector connector = this.getDefaultConnector();
        if (connector == null) return;
        String id = (String) doc.getFieldValue(CollectionSchema.id.getSolrFieldName());
        String url = (String) doc.getFieldValue(CollectionSchema.sku.getSolrFieldName());
        ConcurrentLog.info("Fulltext", "indexing: " + id + " " + url);
        byte[] idb = ASCII.getBytes(id);
        try {
            if (this.urlIndexFile != null) this.urlIndexFile.remove(idb);
            //Date sdDate = (Date) connector.getFieldById(id, CollectionSchema.last_modified.getSolrFieldName());
            //Date docDate = null;
            //if (sdDate == null || (docDate = SchemaConfiguration.getDate(doc, CollectionSchema.last_modified)) == null || sdDate.before(docDate)) {
            connector.add(doc);
            //}
        } catch (final SolrException e) {
            throw new IOException(e.getMessage(), e);
        }
        this.statsDump = null;
        if (MemoryControl.shortStatus()) clearCaches();
    }

    public void putEdges(final Collection<SolrInputDocument> edges) throws IOException {
        if (!this.writeToWebgraph()) return;
        if (edges == null || edges.size() == 0) return;
        try {
            this.getWebgraphConnector().add(edges);
        } catch (final SolrException e) {
            throw new IOException(e.getMessage(), e);
        }
        this.statsDump = null;
        if (MemoryControl.shortStatus()) clearCaches();
    }

    /**
     * deprecated method to store document metadata, use Solr documents wherever possible
     */
    public void putMetadata(final URIMetadataRow entry) throws IOException {
        byte[] idb = entry.hash();
        String id = ASCII.String(idb);
        try {
            if (this.urlIndexFile != null) this.urlIndexFile.remove(idb);
            // because node entries are richer than metadata entries we must check if they exist to prevent that they are overwritten
            SolrDocument sd = this.getDefaultConnector().getDocumentById(id);
            if (sd == null || (new URIMetadataNode(sd)).isOlder(entry)) {
                putDocument(getDefaultConfiguration().metadata2solr(entry));
            }
        } catch (final SolrException e) {
            throw new IOException(e.getMessage(), e);
        }
        this.statsDump = null;
        if (MemoryControl.shortStatus()) clearCaches();
    }

    /**
     * using a fragment of the url hash (6 bytes: bytes 6 to 11) it is possible to address all urls from a specific domain
     * here such a fragment can be used to delete all these domains at once
     * @param hosthash the hash of the host to be deleted
     * @param freshdate either NULL or a date in the past which is the limit for deletion. Only documents older than this date are deleted
     * @throws IOException
     */
    public void deleteStaleDomainHashes(final Set<String> hosthashes, Date freshdate) {
        // delete in solr
        Date now = new Date();
        deleteDomainWithConstraint(this.getDefaultConnector(), CollectionSchema.host_id_s.getSolrFieldName(), hosthashes,
                (freshdate == null || freshdate.after(now)) ? null :
                (CollectionSchema.load_date_dt.getSolrFieldName() + ":[* TO " + ISO8601Formatter.FORMATTER.format(freshdate) + "]"));
        if (this.writeWebgraph) deleteDomainWithConstraint(this.getWebgraphConnector(), WebgraphSchema.source_host_id_s.getSolrFieldName(), hosthashes,
                (freshdate == null || freshdate.after(now)) ? null :
                (WebgraphSchema.load_date_dt.getSolrFieldName() + ":[* TO " + ISO8601Formatter.FORMATTER.format(freshdate) + "]"));

        // delete in old metadata structure
        if (Fulltext.this.urlIndexFile != null) {
            final ArrayList<String> l = new ArrayList<String>();
            CloneableIterator<byte[]> i;
            try {
                i = Fulltext.this.urlIndexFile.keys(true, null);
                String hash;
                while (i != null && i.hasNext()) {
                    hash = ASCII.String(i.next());
                    if (hosthashes.contains(hash.substring(6))) l.add(hash);
                }
                
                // then delete the urls using this list
                for (final String h: l) Fulltext.this.urlIndexFile.delete(ASCII.getBytes(h));
            } catch (final IOException e) {}
        }

        // finally remove the line with statistics
        if (Fulltext.this.statsDump != null) {
            final Iterator<HostStat> hsi = Fulltext.this.statsDump.iterator();
            HostStat hs;
            while (hsi.hasNext()) {
                hs = hsi.next();
                if (hosthashes.contains(hs.hosthash)) hsi.remove();
            }
        }
    }

    public void deleteStaleDomainNames(final Set<String> hostnames, Date freshdate) {

        Date now = new Date();
        deleteDomainWithConstraint(this.getDefaultConnector(), CollectionSchema.host_s.getSolrFieldName(), hostnames,
                (freshdate == null || freshdate.after(now)) ? null :
                (CollectionSchema.load_date_dt.getSolrFieldName() + ":[* TO " + ISO8601Formatter.FORMATTER.format(freshdate) + "]"));
        if (this.writeWebgraph) deleteDomainWithConstraint(this.getWebgraphConnector(), WebgraphSchema.source_host_s.getSolrFieldName(), hostnames,
                (freshdate == null || freshdate.after(now)) ? null :
                (WebgraphSchema.load_date_dt.getSolrFieldName() + ":[* TO " + ISO8601Formatter.FORMATTER.format(freshdate) + "]"));
        
        // finally remove the line with statistics
        if (Fulltext.this.statsDump != null) {
            final Iterator<HostStat> hsi = Fulltext.this.statsDump.iterator();
            HostStat hs;
            while (hsi.hasNext()) {
                hs = hsi.next();
                if (hostnames.contains(hs.hostname)) hsi.remove();
            }
        }
    }
    
    /**
     * delete all documents within a domain that are registered as error document
     * @param hosthashes
     */
    public void deleteDomainErrors(final Set<String> hosthashes) {
        deleteDomainWithConstraint(this.getDefaultConnector(), CollectionSchema.host_id_s.getSolrFieldName(), hosthashes, CollectionSchema.failreason_s.getSolrFieldName() + ":[* TO *]");
    }
    
    private static void deleteDomainWithConstraint(SolrConnector connector, String fieldname, final Set<String> hosthashes, String constraintQuery) {
        if (hosthashes == null || hosthashes.size() == 0) return;
        int subsetscount = 1 + (hosthashes.size() / 255); // if the list is too large, we get a "too many boolean clauses" exception
        int c = 0;
        @SuppressWarnings("unchecked")
        List<String>[] subsets = new ArrayList[subsetscount];
        for (int i = 0; i < subsetscount; i++) subsets[i] = new ArrayList<String>();
        for (String hosthash: hosthashes) subsets[c++ % subsetscount].add(hosthash);
        for (List<String> subset: subsets) {
            try {
                StringBuilder query = new StringBuilder();
                for (String hosthash: subset) {
                    if (query.length() > 0) query.append(" OR ");
                    //query.append(CollectionSchema.host_id_s.getSolrFieldName()).append(":\"").append(hosthash).append(":\"");
                    query.append("({!raw f=").append(fieldname).append('}').append(hosthash).append(")");
                }
                if (constraintQuery == null) connector.deleteByQuery(query.toString()); else connector.deleteByQuery("(" + query.toString() + ") AND " + constraintQuery);
            } catch (final IOException e) {
            }
        }
    }

    /**
     * remove a full subpath from the index
     * @param subpath the left path of the url; at least until the end of the host
     * @param freshdate either NULL or a date in the past which is the limit for deletion. Only documents older than this date are deleted
     * @param concurrently if true, then the method returnes immediately and runs concurrently
     */
    public int remove(final String basepath, Date freshdate) {
        DigestURL uri;
        try {uri = new DigestURL(basepath);} catch (final MalformedURLException e) {return 0;}
        final String host = uri.getHost();
        final String collectionQuery = CollectionSchema.host_s.getSolrFieldName() + ":\"" + host + "\"" +
                ((freshdate != null && freshdate.before(new Date())) ? (" AND " + CollectionSchema.load_date_dt.getSolrFieldName() + ":[* TO " + ISO8601Formatter.FORMATTER.format(freshdate) + "]") : "");
        final AtomicInteger count = new AtomicInteger(0);
        final BlockingQueue<SolrDocument> docs = Fulltext.this.getDefaultConnector().concurrentDocumentsByQuery(collectionQuery, 0, 1000000, 600000, -1, CollectionSchema.id.getSolrFieldName(), CollectionSchema.sku.getSolrFieldName());
        try {
            SolrDocument doc;
            while ((doc = docs.take()) != AbstractSolrConnector.POISON_DOCUMENT) {
                String u = (String) doc.getFieldValue(CollectionSchema.sku.getSolrFieldName());
                if (u.startsWith(basepath)) {
                    remove(ASCII.getBytes((String) doc.getFieldValue(CollectionSchema.id.getSolrFieldName())));
                    count.incrementAndGet();
                }
            }
            if (count.get() > 0) Fulltext.this.commit(true);
        } catch (final InterruptedException e) {}
        return count.get();
    }
    
    /**
     * remove a list of id's from the index
     * @param deleteIDs a list of urlhashes; each denoting a document
     * @param concurrently if true, then the method returnes immediately and runs concurrently
     */
    public void remove(final Collection<String> deleteIDs) {
        if (deleteIDs == null || deleteIDs.size() == 0) return;
        try {
            this.getDefaultConnector().deleteByIds(deleteIDs);
            if (this.writeWebgraph) this.getWebgraphConnector().deleteByIds(deleteIDs);
        } catch (final Throwable e) {
            ConcurrentLog.logException(e);
        }
        if (Fulltext.this.urlIndexFile != null) try {
            for (String id: deleteIDs) {
                final Row.Entry r = Fulltext.this.urlIndexFile.remove(ASCII.getBytes(id));
                if (r != null) Fulltext.this.statsDump = null;
            }
        } catch (final IOException e) {}
    }
    
    public boolean remove(final byte[] urlHash) {
        if (urlHash == null) return false;
        try {
            String id = ASCII.String(urlHash);
            this.getDefaultConnector().deleteById(id);
            if (this.writeWebgraph) this.getWebgraphConnector().deleteById(id);
        } catch (final Throwable e) {
            ConcurrentLog.logException(e);
        }
        if (this.urlIndexFile != null) try {
            final Row.Entry r = this.urlIndexFile.remove(urlHash);
            if (r != null) this.statsDump = null;
            return r != null;
        } catch (final IOException e) {
            return false;
        }
        return false;
    }

    @Deprecated
    public boolean exists(final String urlHash) {
        if (urlHash == null) return false;
        if (this.urlIndexFile != null && this.urlIndexFile.has(ASCII.getBytes(urlHash))) return true;
        try {
            if (this.getDefaultConnector().existsById(urlHash)) return true;
        } catch (final Throwable e) {
            ConcurrentLog.logException(e);
        }
        return false;
    }
    
    /**
     * Multiple-test for existing url hashes in the search index.
     * All given ids are tested and a subset of the given ids are returned.
     * @param ids
     * @return a set of ids which exist in the database
     */
    public Set<String> exists(Set<String> ids) {
        HashSet<String> e = new HashSet<String>();
        if (ids == null || ids.size() == 0) return e;
        if (ids.size() == 1) return exists(ids.iterator().next()) ? ids : e;
        Set<String> idsC = new HashSet<String>();
        idsC.addAll(ids);
        if (this.urlIndexFile != null) {
            Iterator<String> idsi = idsC.iterator();
            String h;
            while (idsi.hasNext()) {
                h = idsi.next();
                if (this.urlIndexFile.has(ASCII.getBytes(h))) {
                    idsi.remove();
                    e.add(h);
                }
            }
        }
        try {
            Set<String> e1 = this.getDefaultConnector().existsByIds(idsC);
            e.addAll(e1);
        } catch (final Throwable ee) {
            ConcurrentLog.logException(ee);
        }
        return e;
    }

    public String failReason(final String urlHash) throws IOException {
        if (urlHash == null) return null;
        String reason = this.getDefaultConnector().getFieldById(urlHash, CollectionSchema.failreason_s.getSolrFieldName());
        if (reason == null) return null;
        return reason.length() == 0 ? null : reason;
    }
    
    public List<File> dumpFiles() {
        EmbeddedInstance esc = this.solrInstances.getSolr0();
        ArrayList<File> zips = new ArrayList<File>();
        if (esc == null) {
            ConcurrentLog.warn("Fulltext", "HOT DUMP selected solr0 == NULL, no dump list!");
            return zips;
        }
        if (esc.getContainerPath() == null) {
            ConcurrentLog.warn("Fulltext", "HOT DUMP selected solr0.getStoragePath() == NULL, no dump list!");
            return zips;
        }
        File storagePath = esc.getContainerPath().getParentFile();
        if (storagePath == null) {
            ConcurrentLog.warn("Fulltext", "HOT DUMP selected esc.getStoragePath().getParentFile() == NULL, no dump list!");
            return zips;
        }
        ConcurrentLog.info("Fulltext", "HOT DUMP dump path = " + storagePath.toString());
        for (String p: storagePath.list()) {
            if (p.endsWith("zip")) zips.add(new File(storagePath, p));
        }
        return zips;
    }
    
    /**
     * create a dump file from the current solr directory
     * @return
     */
    public File dumpSolr() {
        EmbeddedInstance esc = this.solrInstances.getSolr0();
        File storagePath = esc.getContainerPath();
        File zipOut = new File(storagePath.toString() + "_" + GenericFormatter.SHORT_DAY_FORMATTER.format() + ".zip");
        synchronized (this.solrInstances) {
            this.disconnectLocalSolr();
            this.solrInstances.close();
            try {
                ZIPWriter.zip(storagePath, zipOut);
            } catch (final IOException e) {
                ConcurrentLog.logException(e);
            } finally {
                this.solrInstances = new InstanceMirror();
                try {
                    this.connectLocalSolr();
                } catch (final IOException e) {
                    ConcurrentLog.logException(e);
                }
            }
        }
        return zipOut;
    }
    
    /**
     * restore a solr dump to the current solr directory
     * @param solrDumpZipFile
     */
    public void restoreSolr(File solrDumpZipFile) {
        EmbeddedInstance esc = this.solrInstances.getSolr0();
        File storagePath = esc.getContainerPath();
        synchronized (this.solrInstances) {
            this.disconnectLocalSolr();
            this.solrInstances.close();
            try {
                ZIPReader.unzip(solrDumpZipFile, storagePath);
            } catch (final IOException e) {
                ConcurrentLog.logException(e);
            } finally {
                this.solrInstances = new InstanceMirror();
                try {
                    this.connectLocalSolr();
                } catch (final IOException e) {
                    ConcurrentLog.logException(e);
                }
            }
        }
    }

    /**
     * optimize solr (experimental to check resource management)
     * @param size
     */
    public void optimize(final int size) {
        if (size < 1) return;
        getDefaultConnector().optimize(size);
        if (this.writeWebgraph) getWebgraphConnector().optimize(size);
    }
    
    /**
     * reboot solr (experimental to check resource management)
     */
    public void rebootSolr() {
        synchronized (this.solrInstances) {
            this.disconnectLocalSolr();
            this.solrInstances.close();
            this.solrInstances = new InstanceMirror();
            try {
                this.connectLocalSolr();
            } catch (final IOException e) {
                ConcurrentLog.logException(e);
            }
        }
    }
    
    // export methods
    public Export export(final File f, final String filter, final String query, final int format, final boolean dom) {
        if ((this.exportthread != null) && (this.exportthread.isAlive())) {
            ConcurrentLog.warn("LURL-EXPORT", "cannot start another export thread, already one running");
            return this.exportthread;
        }
        this.exportthread = new Export(f, filter, query, format, dom);
        this.exportthread.start();
        return this.exportthread;
    }

    public Export export() {
        return this.exportthread;
    }

    public class Export extends Thread {
        private final File f;
        private final Pattern pattern;
        private int count;
        private String failure, query;
        private final int format;
        private final boolean dom;

        private Export(final File f, final String filter, final String query, final int format, boolean dom) {
            // format: 0=text, 1=html, 2=rss/xml
            this.f = f;
            this.pattern = filter == null ? null : Pattern.compile(filter);
            this.query = query == null? "*:*" : query;
            this.count = 0;
            this.failure = null;
            this.format = format;
            this.dom = dom;
            //if ((dom) && (format == 2)) dom = false;
        }

        @Override
        public void run() {
            try {
                final File parentf = this.f.getParentFile();
                if (parentf != null) parentf.mkdirs();
                final PrintWriter pw = new PrintWriter(new BufferedOutputStream(new FileOutputStream(this.f)));
                if (this.format == 1) {
                    pw.println("<html><head></head><body>");
                }
                if (this.format == 2) {
                    pw.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
                    pw.println("<?xml-stylesheet type='text/xsl' href='/yacysearch.xsl' version='1.0'?>");
                    pw.println("<rss version=\"2.0\" xmlns:yacy=\"http://www.yacy.net/\" xmlns:opensearch=\"http://a9.com/-/spec/opensearch/1.1/\" xmlns:atom=\"http://www.w3.org/2005/Atom\">");
                    pw.println("<channel>");
                    pw.println("<title>YaCy Peer-to-Peer - Web-Search URL Export</title>");
                    pw.println("<description></description>");
                    pw.println("<link>http://yacy.net</link>");
                }
                
               
                if (this.dom) {
                    Map<String, ReversibleScoreMap<String>> scores = Fulltext.this.getDefaultConnector().getFacets(this.query + " AND " + CollectionSchema.httpstatus_i.getSolrFieldName() + ":200", 100000000, CollectionSchema.host_s.getSolrFieldName());
                    ReversibleScoreMap<String> stats = scores.get(CollectionSchema.host_s.getSolrFieldName());
                    for (final String host: stats) {
                        if (this.pattern != null && !this.pattern.matcher(host).matches()) continue;
                        if (this.format == 0) pw.println(host);
                        if (this.format == 1) pw.println("<a href=\"http://" + host + "\">" + host + "</a><br>");
                        this.count++;
                    }
                } else {
                    BlockingQueue<SolrDocument> docs = Fulltext.this.getDefaultConnector().concurrentDocumentsByQuery(this.query + " AND " + CollectionSchema.httpstatus_i.getSolrFieldName() + ":200", 0, 100000000, 10 * 60 * 60 * 1000, 100,
                            CollectionSchema.id.getSolrFieldName(), CollectionSchema.sku.getSolrFieldName(), CollectionSchema.title.getSolrFieldName(),
                            CollectionSchema.author.getSolrFieldName(), CollectionSchema.description_txt.getSolrFieldName(), CollectionSchema.size_i.getSolrFieldName(), CollectionSchema.last_modified.getSolrFieldName());
                    SolrDocument doc;
                    String url, hash, title, author, description;
                    Integer size;
                    Date date;
                    while ((doc = docs.take()) != AbstractSolrConnector.POISON_DOCUMENT) {
                        hash = getStringFrom(doc.getFieldValue(CollectionSchema.id.getSolrFieldName()));
                        url = getStringFrom(doc.getFieldValue(CollectionSchema.sku.getSolrFieldName()));
                        title = getStringFrom(doc.getFieldValue(CollectionSchema.title.getSolrFieldName()));
                        author = getStringFrom(doc.getFieldValue(CollectionSchema.author.getSolrFieldName()));
                        description = getStringFrom(doc.getFieldValue(CollectionSchema.description_txt.getSolrFieldName()));
                        size = (Integer) doc.getFieldValue(CollectionSchema.size_i.getSolrFieldName());
                        date = (Date) doc.getFieldValue(CollectionSchema.last_modified.getSolrFieldName());
                        if (this.pattern != null && !this.pattern.matcher(url).matches()) continue;
                        if (this.format == 0) {
                            pw.println(url);
                        }
                        if (this.format == 1) {
                            if (title != null) pw.println("<a href=\"" + MultiProtocolURL.escape(url) + "\">" + CharacterCoding.unicode2xml(title, true) + "</a>");
                        }
                        if (this.format == 2) {
                            pw.println("<item>");
                            if (title != null) pw.println("<title>" + CharacterCoding.unicode2xml(title, true) + "</title>");
                            pw.println("<link>" + MultiProtocolURL.escape(url) + "</link>");
                            if (author != null && !author.isEmpty()) pw.println("<author>" + CharacterCoding.unicode2xml(author, true) + "</author>");
                            if (description != null && !description.isEmpty()) pw.println("<description>" + CharacterCoding.unicode2xml(description, true) + "</description>");
                            if (date != null) pw.println("<pubDate>" + HeaderFramework.formatRFC1123(date) + "</pubDate>");
                            if (size != null) pw.println("<yacy:size>" + size.intValue() + "</yacy:size>");
                            pw.println("<guid isPermaLink=\"false\">" + hash + "</guid>");
                            pw.println("</item>");
                        }
                        this.count++;
                    }
                }
                if (this.format == 1) {
                    pw.println("</body></html>");
                }
                if (this.format == 2) {
                    pw.println("</channel>");
                    pw.println("</rss>");
                }
                pw.close();
            } catch (final IOException e) {
                ConcurrentLog.logException(e);
                this.failure = e.getMessage();
            } catch (final Exception e) {
                ConcurrentLog.logException(e);
                this.failure = e.getMessage();
            }
            // terminate process
        }

        public File file() {
            return this.f;
        }

        public String failed() {
            return this.failure;
        }

        public int count() {
            return this.count;
        }
        
        @SuppressWarnings("unchecked")
		private String getStringFrom(final Object o) {
        	if (o == null) return "";
        	if (o instanceof ArrayList) return ((ArrayList<String>) o).get(0);
        	return (String) o;
        }

    }
    
    public Iterator<HostStat> statistics(int count, final ScoreMap<String> domainScore) {
        // prevent too heavy IO.
        if (this.statsDump != null && count <= this.statsDump.size()) return this.statsDump.iterator();

        // fetch urls from the database to determine the host in clear text
        final Iterator<String> j = domainScore.keys(false); // iterate urlhash-examples in reverse order (biggest first)
        String urlhash;
        count += 10; // make some more to prevent that we have to do this again after deletions too soon.
        if (count < 0 || domainScore.sizeSmaller(count)) count = domainScore.size();
        this.statsDump = new ArrayList<HostStat>();
        DigestURL url;
        while (j.hasNext()) {
            urlhash = j.next();
            if (urlhash == null) continue;
            url = this.getURL(ASCII.getBytes(urlhash));
            if (url == null || url.getHost() == null) continue;
            if (this.statsDump == null) return new ArrayList<HostStat>().iterator(); // some other operation has destroyed the object
            this.statsDump.add(new HostStat(url.getHost(), url.getPort(), urlhash.substring(6), domainScore.get(urlhash)));
            count--;
            if (count == 0) break;
        }
        // finally return an iterator for the result array
        return (this.statsDump == null) ? new ArrayList<HostStat>().iterator() : this.statsDump.iterator();
    }

    public static class HostStat {
        public String hostname, hosthash;
        public int port;
        public int count;
        private HostStat(final String host, final int port, final String urlhashfragment, final int count) {
            assert urlhashfragment.length() == 6;
            this.hostname = host;
            this.port = port;
            this.hosthash = urlhashfragment;
            this.count = count;
        }
    }
}