// plasmaWordIndexCache.java
// -------------------------
// part of YACY
// (C) by Michael Peter Christen; mc@anomic.de
// first published on http://www.anomic.de
// Frankfurt, Germany, 2005
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// 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
//
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// running) means that you agree that the Author(s) is (are) not responsible
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package de.anomic.plasma;

import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
import de.anomic.kelondro.kelondroArray;
import de.anomic.kelondro.kelondroException;
import de.anomic.kelondro.kelondroMScoreCluster;
import de.anomic.kelondro.kelondroRecords;
import de.anomic.server.logging.serverLog;
import de.anomic.yacy.yacySeedDB;

public final class plasmaWordIndexCache implements plasmaWordIndexInterface {

    // environment constants
    private static final String indexArrayFileName = "indexDump1.array";
    public static final int  ramCacheReferenceLimit = 50;
    public static final long ramCacheAgeLimit       = 60 * 60 * 2 * 1000; // milliseconds; 2 Hours

    // class variables
    private final File databaseRoot;
    private final TreeMap cache;
    private final kelondroMScoreCluster hashScore;
    private final kelondroMScoreCluster hashDate;
    private long  startTime;
    private int   maxWordsLow, maxWordsHigh; // we have 2 cache limits for different priorities
    private final serverLog log;

    // calculated constants
    private static String maxKey;
    static {
        maxKey = ""; for (int i = 0; i < yacySeedDB.commonHashLength; i++) maxKey += 'z';
        //minKey = ""; for (int i = 0; i < yacySeedDB.commonHashLength; i++) maxKey += '-';
    }

    public plasmaWordIndexCache(File databaseRoot, serverLog log) {

        // creates a new index cache
        // the cache has a back-end where indexes that do not fit in the cache are flushed
        this.databaseRoot = databaseRoot;
        this.cache = new TreeMap();
        this.hashScore = new kelondroMScoreCluster();
        this.hashDate  = new kelondroMScoreCluster();
        this.startTime = System.currentTimeMillis();
        this.maxWordsLow  =  8000;
        this.maxWordsHigh = 10000;
        this.log = log;
        
        // read in dump of last session
        try {
            restore();
        } catch (IOException e){
            log.logSevere("unable to restore cache dump: " + e.getMessage(), e);
        }
    }

    private void dump(int waitingSeconds) throws IOException {
        log.logConfig("creating dump for index cache, " + cache.size() + " words (and much more urls)");
        File indexDumpFile = new File(databaseRoot, indexArrayFileName);
        if (indexDumpFile.exists()) indexDumpFile.delete();
        kelondroArray dumpArray = null;
            dumpArray = new kelondroArray(indexDumpFile, plasmaWordIndexAssortment.bufferStructureBasis, 0, false);
            long startTime = System.currentTimeMillis();
            long messageTime = System.currentTimeMillis() + 5000;
            long wordsPerSecond = 0, wordcount = 0, urlcount = 0;
            synchronized (cache) {
                Iterator i = cache.entrySet().iterator();
                Map.Entry entry;
                String wordHash;
                plasmaWordIndexEntryContainer container;
                long updateTime;
                plasmaWordIndexEntry wordEntry;
                byte[][] row = new byte[5][];
                while (i.hasNext()) {
                    // get entries
                    entry = (Map.Entry) i.next();
                    wordHash = (String) entry.getKey();
                    updateTime = getUpdateTime(wordHash);
                    container = (plasmaWordIndexEntryContainer) entry.getValue();

                    // put entries on stack
                    if (container != null) {
                        Iterator ci = container.entries();
                        while (ci.hasNext()) {
                            wordEntry = (plasmaWordIndexEntry) ci.next();
                            row[0] = wordHash.getBytes();
                            row[1] = kelondroRecords.long2bytes(container.size(), 4);
                            row[2] = kelondroRecords.long2bytes(updateTime, 8);
                            row[3] = wordEntry.getUrlHash().getBytes();
                            row[4] = wordEntry.toEncodedForm().getBytes();
                            dumpArray.set((int) urlcount++, row);
                        }
                    }
                    wordcount++;
                    i.remove(); // free some mem

                    // write a log
                    if (System.currentTimeMillis() > messageTime) {
                        // System.gc(); // for better statistic
                        wordsPerSecond = wordcount * 1000 / (1 + System.currentTimeMillis() - startTime);
                        log.logInfo("dumping status: " + wordcount + " words done, " + (cache.size() / (wordsPerSecond + 1)) + " seconds remaining, free mem = " + (Runtime.getRuntime().freeMemory() / 1024 / 1024) + "MB");
                        messageTime = System.currentTimeMillis() + 5000;
                    }
                }
            }
            dumpArray.close();
            dumpArray = null;
            log.logConfig("dumped " + urlcount + " word/URL relations in " + ((System.currentTimeMillis() - startTime) / 1000) + " seconds");
    }

    private long restore() throws IOException {
        File indexDumpFile = new File(databaseRoot, indexArrayFileName);
        if (!(indexDumpFile.exists())) return 0;
        kelondroArray dumpArray = new kelondroArray(indexDumpFile);
        log.logConfig("restore array dump of index cache, " + dumpArray.size() + " word/URL relations");
        long startTime = System.currentTimeMillis();
        long messageTime = System.currentTimeMillis() + 5000;
        long urlCount = 0, urlsPerSecond = 0;
        try {
            synchronized (cache) {
                int i = dumpArray.size();
                String wordHash;
                long creationTime;
                plasmaWordIndexEntry wordEntry;
                byte[][] row;
                //Runtime rt = Runtime.getRuntime();
                while (i-- > 0) {
                    // get out one entry
                    row = dumpArray.get(i);
                    if ((row[0] == null) || (row[1] == null) || (row[2] == null) || (row[3] == null) || (row[4] == null)) continue;
                    wordHash = new String(row[0], "UTF-8");
                    creationTime = kelondroRecords.bytes2long(row[2]);
                    wordEntry = new plasmaWordIndexEntry(new String(row[3], "UTF-8"), new String(row[4], "UTF-8"));
                    // store to cache
                    addEntry(wordHash, wordEntry, creationTime);
                    urlCount++;
                    // protect against memory shortage
                    //while (rt.freeMemory() < 1000000) {flushFromMem(); java.lang.System.gc();}
                    // write a log
                    if (System.currentTimeMillis() > messageTime) {
                        System.gc(); // for better statistic
                        urlsPerSecond = 1 + urlCount * 1000 / (1 + System.currentTimeMillis() - startTime);
                        log.logInfo("restoring status: " + urlCount + " urls done, " + (i / urlsPerSecond) + " seconds remaining, free mem = " + (Runtime.getRuntime().freeMemory() / 1024 / 1024) + "MB");
                        messageTime = System.currentTimeMillis() + 5000;
                    }
                }
            }

            dumpArray.close();
            log.logConfig("restored " + cache.size() + " words in " + ((System.currentTimeMillis() - startTime) / 1000) + " seconds");
        } catch (kelondroException e) {
            // restore failed
            log.logSevere("restore of indexCache array dump failed: " + e.getMessage(), e);
        } finally {
            if (dumpArray != null) try {dumpArray.close();}catch(Exception e){}
        }
        return urlCount;
    }

    // cache settings

    public int maxURLinWordCache() {
        return hashScore.getMaxScore();
    }

    public long maxAgeOfWordCache() {
        return System.currentTimeMillis() - longEmit(hashDate.getMinScore());
    }

    public int wordCacheRAMSize() {
        return cache.size();
    }

    public void setMaxWords(int maxWordsLow, int maxWordsHigh) {
        this.maxWordsLow = maxWordsLow;
        this.maxWordsHigh = maxWordsHigh;
    }
    
    public int getMaxWordsLow() {
        return this.maxWordsLow;
    }

    public int getMaxWordsHigh() {
        return this.maxWordsHigh;
    }
    
    public int size() {
        return cache.size();
    }

    public int indexSize(String wordHash) {
        int size = 0;
        plasmaWordIndexEntryContainer cacheIndex = (plasmaWordIndexEntryContainer) cache.get(wordHash);
        if (cacheIndex != null) size += cacheIndex.size();
        return size;
    }
    
    public Iterator wordHashes(String startWordHash, boolean rot) {
        if (rot) throw new UnsupportedOperationException("plasmaWordIndexCache cannot rotate");
        return cache.tailMap(startWordHash).keySet().iterator();
    }

    public String bestFlushWordHash() {
        // select appropriate hash
        // we have 2 different methods to find a good hash:
        // - the oldest entry in the cache
        // - the entry with maximum count
        if (cache.size() == 0) return null;
        try {
            synchronized (cache) {
                String hash = null;
                int count = hashScore.getMaxScore();
                if ((count > ramCacheReferenceLimit) &&
                    ((hash = (String) hashScore.getMaxObject()) != null)) {
                    // flush high-score entries
                    return hash;
                }
                long oldestTime = longEmit(hashDate.getMinScore());
                if (((System.currentTimeMillis() - oldestTime) > ramCacheAgeLimit) &&
                    ((hash = (String) hashDate.getMinObject()) != null)) {
                    // flush out-dated entries
                    return hash;
                }
                // not an urgent case
                if (Runtime.getRuntime().freeMemory() < 10000000) {
                    // low-memory case
                    hash = (String) hashScore.getMaxObject(); // flush high-score entries (saves RAM)
                } else {
                    // not-efficient-so-far case
                    hash = (String) hashDate.getMinObject(); // flush oldest entries (makes indexing faster)
                }
                return hash;
            }
        } catch (Exception e) {
            log.logSevere("flushFromMem: " + e.getMessage(), e);
        }
        return null;
    }

    private int intTime(long longTime) {
        return (int) ((longTime - startTime) / 1000);
    }

    private long longEmit(int intTime) {
        return (((long) intTime) * (long) 1000) + startTime;
    }
    
    /*
    private long longTime(int intTime) {
        return ((long) intTime) * ((long) 1000) + startTime;
    }
    */
    
    public plasmaWordIndexEntryContainer getContainer(String wordHash, boolean deleteIfEmpty) {
        return (plasmaWordIndexEntryContainer) cache.get(wordHash);
    }

    public long getUpdateTime(String wordHash) {
        plasmaWordIndexEntryContainer entries = (plasmaWordIndexEntryContainer) cache.get(wordHash);
        if (entries == null) return 0;
        return entries.updated();
        /*
        Long time = new Long(longTime(hashDate.getScore(wordHash)));
        if (time == null) return 0;
        return time.longValue();
        */
    }

    public plasmaWordIndexEntryContainer deleteContainer(String wordHash) {
        // returns the index that had been deleted
        synchronized (cache) {
            plasmaWordIndexEntryContainer container = (plasmaWordIndexEntryContainer) cache.remove(wordHash);
            hashScore.deleteScore(wordHash);
            hashDate.deleteScore(wordHash);
            return container;
        }
    }

    public int removeEntries(String wordHash, String[] urlHashes, boolean deleteComplete) {
        if (urlHashes.length == 0) return 0;
        int count = 0;
        synchronized (cache) {
            plasmaWordIndexEntryContainer c = (plasmaWordIndexEntryContainer) deleteContainer(wordHash);
            if (c != null) {
                count = c.removeEntries(wordHash, urlHashes, deleteComplete);
                if (c.size() != 0) this.addEntries(c, System.currentTimeMillis(), false);
            }
        }
        return count;
    }

    public int addEntries(plasmaWordIndexEntryContainer container, long updateTime, boolean highPriority) {
        // this puts the entries into the cache, not into the assortment directly

        int added = 0;
        // check cache space

        //serverLog.logDebug("PLASMA INDEXING", "addEntryToIndexMem: cache.size=" + cache.size() + "; hashScore.size=" + hashScore.size());

        // put new words into cache
        String wordHash = container.wordHash();
        plasmaWordIndexEntryContainer entries = null;
        synchronized (cache) {
            // put container into cache
            entries = (plasmaWordIndexEntryContainer) cache.get(wordHash); // null pointer exception? wordhash != null! must be cache==null
            if (entries == null) entries = new plasmaWordIndexEntryContainer(wordHash);
            added = entries.add(container);
            if (added > 0) {
                cache.put(wordHash, entries);
                hashScore.addScore(wordHash, added);
                hashDate.setScore(wordHash, intTime(updateTime));
            }
        }
        entries = null;
        return added;
    }

    public boolean addEntry(String wordHash, plasmaWordIndexEntry newEntry, long updateTime) {
        plasmaWordIndexEntryContainer container = null;
        plasmaWordIndexEntry[] entries = null;
        synchronized (cache) {
            container = (plasmaWordIndexEntryContainer) cache.get(wordHash);
            if (container == null) container = new plasmaWordIndexEntryContainer(wordHash);
            entries = new plasmaWordIndexEntry[] { newEntry };
            if (container.add(entries, updateTime) > 0) {
                cache.put(wordHash, container);
                hashScore.incScore(wordHash);
                hashDate.setScore(wordHash, intTime(updateTime));
                return true;
            }
        }
        container = null;
        entries = null;
        return false;
    }

    public void close(int waitingSeconds) {
        // dump cache
        try {
            dump(waitingSeconds);
        } catch (IOException e){
            log.logSevere("unable to dump cache: " + e.getMessage(), e);
        }
    }
}