// 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
//
// Using this software in any meaning (reading, learning, copying, compiling,
// running) means that you agree that the Author(s) is (are) not responsible
// for cost, loss of data or any harm that may be caused directly or indirectly
// by usage of this softare or this documentation. The usage of this software
// is on your own risk. The installation and usage (starting/running) of this
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// (are) also not responsible for proper configuration and usage of the
// software, even if provoked by documentation provided together with
// the software.
//
// Any changes to this file according to the GPL as documented in the file
// gpl.txt aside this file in the shipment you received can be done to the
// lines that follows this copyright notice here, but changes must not be
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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.kelondroMergeIterator;
import de.anomic.kelondro.kelondroNaturalOrder;
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";
    private static final String indexAssortmentClusterPath = "ACLUSTER";
    private static final int assortmentCount = 64;
    private static final int ramCacheLimit = 200;

    // class variables
    private final File databaseRoot;
    private final plasmaWordIndexInterface backend;
    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;
    private final plasmaWordIndexAssortmentCluster assortmentCluster;
    private int assortmentBufferSize; //kb
    private final flush flushThread;

    // 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, plasmaWordIndexInterface backend, int assortmentbufferkb, serverLog log) {

        // create new assortment cluster path
        File assortmentClusterPath = new File(databaseRoot, indexAssortmentClusterPath);
        if (!(assortmentClusterPath.exists())) assortmentClusterPath.mkdirs();

        // create flushing thread
        flushThread = new flush();

        // 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.assortmentBufferSize = assortmentbufferkb;
        this.cache = new TreeMap();
        this.hashScore = new kelondroMScoreCluster();
        this.hashDate  = new kelondroMScoreCluster();
        this.startTime = System.currentTimeMillis();
        this.maxWordsLow  =  8000;
        this.maxWordsHigh = 10000;
        this.backend = backend;
        this.log = log;
        this.assortmentCluster = new plasmaWordIndexAssortmentCluster(assortmentClusterPath, assortmentCount, assortmentBufferSize, log);

        // read in dump of last session
        try {
            restore();
        } catch (IOException e){
            log.logSevere("unable to restore cache dump: " + e.getMessage(), e);
        }

        // start permanent flushing
        flushThread.start();
    }

    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(true).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;
    }

    public void intermission(long pause) {
        flushThread.intermission(pause);
    }

    // cache settings

    public int maxURLinWordCache() {
        return hashScore.getScore(hashScore.getMaxObject());
    }

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

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

    public int[] assortmentsSizes() {
        return assortmentCluster.sizes();
    }

    public int[] assortmentsCacheChunkSizeAvg() {
        return assortmentCluster.cacheChunkSizeAvg();
    }

    public int[] assortmentsCacheFillStatusCml() {
        return assortmentCluster.cacheFillStatusCml();
    }

    public int size() {
        return java.lang.Math.max(assortmentCluster.sizeTotal(), java.lang.Math.max(backend.size(), cache.size()));
    }

    public Iterator wordHashes(String startWordHash, boolean up) {
        // here we merge 3 databases into one view:
        // - the RAM Cache
        // - the assortmentCluster File Cache
        // - the backend
        if (!(up)) throw new RuntimeException("plasmaWordIndexCache.wordHashes can only count up");
        return new kelondroMergeIterator(
                        new kelondroMergeIterator(
                                 cache.tailMap(startWordHash).keySet().iterator(),
                                 assortmentCluster.hashConjunction(startWordHash, true),
                                 kelondroNaturalOrder.naturalOrder,
                                 true),
                        backend.wordHashes(startWordHash, true),
                        kelondroNaturalOrder.naturalOrder,
                        true);
    }

    private final class flush extends Thread {
        boolean terminate;
        long intermission;

        public flush() {
            terminate = false;
            intermission = 0;
            this.setName(this.getClass().getName());
        }

        public void intermission(long pause) {
            this.intermission = System.currentTimeMillis() + pause;
        }

        public void run() {
            long pausetime;
            while (!terminate) {
                if (intermission > 0) {
                    if (this.intermission > System.currentTimeMillis()) {
                        try {sleep(this.intermission - System.currentTimeMillis());} catch (InterruptedException e) {}
                    }
                    this.intermission = 0;
                }
                flushFromMem();
                pausetime = 1 + java.lang.Math.min(1000, 5 * maxWordsHigh / (cache.size() + 1));
                if (cache.size() == 0) pausetime = 2000;
                try { sleep(pausetime); } catch (InterruptedException e) { }
            }
        }

        public void terminate() {
            terminate = true;
        }
    }

    private void flushFromMem() {
        // 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;
        try {
            synchronized (cache) {
                String hash = (String) hashScore.getMaxObject();
                if (hash == null) return;
                int count = hashScore.getMaxScore();
                long time = longTime(hashDate.getScore(hash));
                if ((count > ramCacheLimit) || ((count > assortmentCount) && (System.currentTimeMillis() - time > 10000))) {
                    // flush high-score entries
                    flushFromMem(hash);
                } else {
                    // flush oldest entries
                    hash = (String) hashDate.getMinObject();
                    flushFromMem(hash);
                }
            }
        } catch (Exception e) {
            log.logSevere("flushFromMem: " + e.getMessage(), e);
        }
    }

    private int flushFromMem(String key) {
        // this method flushes indexes out from the ram to the disc.
        plasmaWordIndexEntryContainer container = null;
        long time;
        synchronized (cache) {
            // get the container
            container = (plasmaWordIndexEntryContainer) cache.get(key);
            if (container == null) return 0; // flushing of nonexisting key
            time = getUpdateTime(key);

            // remove it from the cache
            cache.remove(key);
            hashScore.deleteScore(key);
            hashDate.deleteScore(key);
        }
        
        // now decide where to flush that container
        plasmaWordIndexEntryContainer feedback = assortmentCluster.storeTry(key, container);
        if (feedback == null) {
            return container.size();
        } else {
            // *** should care about another option here ***
            return backend.addEntries(feedback, time, true);
        }
    }

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

    private long longTime(int intTime) {
        return ((long) intTime) * ((long) 1000) + startTime;
    }

    private boolean flushFromAssortmentCluster(String key, long maxTime) {
        // this should only be called if the assortment shall be deleted or returned in an index entity
        maxTime = 8 * maxTime / 10; // reserve time for later adding to backend
        plasmaWordIndexEntryContainer container = assortmentCluster.removeFromAll(key, maxTime);
        if (container == null) {
            return false;
        } else {
            // we have a non-empty entry-container
            // integrate it to the backend
            return backend.addEntries(container, container.updated(), true) > 0;
        }
    }

    public plasmaWordIndexEntity getIndex(String wordHash, boolean deleteIfEmpty, long maxTime) {
        // this possibly creates an index file in the back-end
        // the index file is opened and returned as entity object
        long start = System.currentTimeMillis();
        synchronized (cache) {
            flushFromMem(wordHash);
            if (maxTime < 0) {
                flushFromAssortmentCluster(wordHash, -1);
            } else {
                long remaining = maxTime - (System.currentTimeMillis() - start);
                if (remaining > 0)
                    flushFromAssortmentCluster(wordHash, remaining);
            }
        }
        long r = maxTime - (System.currentTimeMillis() - start);
        return backend.getIndex(wordHash, deleteIfEmpty, (r < 0) ? 0 : r);
    }

    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 void deleteIndex(String wordHash) {
        synchronized (cache) {
            cache.remove(wordHash);
            hashScore.deleteScore(wordHash);
            hashDate.deleteScore(wordHash);
        }
        assortmentCluster.removeFromAll(wordHash, -1);
        backend.deleteIndex(wordHash);
    }

    public synchronized int removeEntries(String wordHash, String[] urlHashes, boolean deleteComplete) {
        flushFromMem(wordHash);
        flushFromAssortmentCluster(wordHash, -1);
        int removed = backend.removeEntries(wordHash, urlHashes, deleteComplete);
        return removed;
    }

    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
        /*
        if (cache.size() > 0) try {
            // pause to get space in the cache (while it is flushed)
            long pausetime;
            if (highPriority) {
                if (cache.size() + 1000 >= this.maxWordsHigh) Thread.sleep(java.lang.Math.min(1000, cache.size() - this.maxWordsHigh + 1000));
                pausetime = java.lang.Math.min(10, 2 * cache.size() / (maxWordsHigh + 1));
            } else {
                if (cache.size() + 1000 >= this.maxWordsLow) Thread.sleep(java.lang.Math.min(1000, cache.size() - this.maxWordsLow + 1000));
                pausetime = java.lang.Math.min(10, 2 * cache.size() / (maxWordsLow + 1));
            }

            // slow down if we reach cache limit
            Thread.sleep(pausetime);
        } catch (InterruptedException e) {}
        */
        //serverLog.logDebug("PLASMA INDEXING", "addEntryToIndexMem: cache.size=" + cache.size() + "; hashScore.size=" + hashScore.size());

        // put new words into cache
        String wordHash = container.wordHash();
        synchronized (cache) {
            // put container into cache
            plasmaWordIndexEntryContainer 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;
            
            // force flush (sometimes)
            if (System.currentTimeMillis() % 7 == 4) flushFromMem();
        }
        return added;
    }

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

    public void close(int waitingSeconds) {
        // stop permanent flushing
        flushThread.terminate();
        try {flushThread.join(5000);} catch (InterruptedException e) {}

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

    public Object migrateWords2Assortment(String wordhash) throws IOException {
        // returns the number of entries that had been added to the assortments
        // can be negative if some assortments have been moved to the backend
        File db = plasmaWordIndexEntity.wordHash2path(databaseRoot, wordhash);
        if (!(db.exists())) return "not available";
        plasmaWordIndexEntity entity = null;
        try {
            entity =  new plasmaWordIndexEntity(databaseRoot, wordhash, true);
            int size = entity.size();
            if (size > assortmentCluster.clusterCapacity) {
                // this will be too big to integrate it
                entity.close(); entity = null;
                return "too big";
            } else {
                // take out all words from the assortment to see if it fits
                // together with the extracted assortment
                plasmaWordIndexEntryContainer container = assortmentCluster.removeFromAll(wordhash, -1);
                if (size + container.size() > assortmentCluster.clusterCapacity) {
                    // this will also be too big to integrate, add to entity
                    entity.addEntries(container);
                    entity.close(); entity = null;
                    return new Integer(-container.size());
                } else {
                    // the combined container will fit, read the container
                    try {
                        Iterator entries = entity.elements(true);
                        plasmaWordIndexEntry entry;
                        while (entries.hasNext()) {
                            entry = (plasmaWordIndexEntry) entries.next();
                            // System.out.println("ENTRY = " + entry.getUrlHash());
                            container.add(new plasmaWordIndexEntry[]{entry}, System.currentTimeMillis());
                        }
                        // we have read all elements, now delete the entity
                        entity.deleteComplete();
                        entity.close(); entity = null;
                        // integrate the container into the assortments; this will work
                        assortmentCluster.storeTry(wordhash, container);
                        return new Integer(size);
                    } catch (kelondroException e) {
                        // database corrupted, we simply give up the database and delete it
                        try {entity.close();} catch (Exception ee) {} entity = null;
                        try {db.delete();} catch (Exception ee) {}
                        return "database corrupted; deleted";                        
                    }
                }
            }
        } finally {
            if (entity != null) try {entity.close();}catch(Exception e){}
        }
    }

}