/**
 *  AccessTracker
 *  an interface for Adaptive Replacement Caches
 *  Copyright 2009 by Michael Peter Christen, mc@yacy.net, Frankfurt a. M., Germany
 *  First released 29.08.2009 at http://yacy.net
 *
 * $LastChangedDate$
 * $LastChangedRevision$
 * $LastChangedBy$
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program in the file lgpl21.txt
 *  If not, see <http://www.gnu.org/licenses/>.
 */

package net.yacy.search.query;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import net.yacy.cora.date.GenericFormatter;
import net.yacy.cora.document.WordCache;
import net.yacy.cora.document.encoding.UTF8;
import net.yacy.cora.util.ConcurrentLog;
import net.yacy.kelondro.util.MemoryControl;
import net.yacy.search.EventTracker;

public class AccessTracker {

    private final static long DUMP_PERIOD = 60000L;

    private static final int minSize = 100;
    private static final int maxSize = 1000;
    private static final int maxAge = 24 * 60 * 60 * 1000;
    
    public static class QueryEvent {
        final public String address;
        final public String userAgent;
        final public String query;
        final public Date date;
        final public short offset;
        final public short requestedResults;
        final public short returnedResults;
        final public short knownResults;
        final public short executionTime;
        
        public QueryEvent(
                final String address, final String userAgent,
                final String query, final Date date,
                final short offset, final short requestedResults,
                final short returnedResults, final short knownResults,
                final short executionTime) {
            this.address = address;
            this.userAgent = userAgent;
            this.query = query;
            this.date = date;
            this.offset = offset;
            this.requestedResults = requestedResults;
            this.returnedResults = returnedResults;
            this.knownResults = knownResults;
            this.executionTime = executionTime;
        }
    }
    
    public enum Location {local, remote}

    private static final LinkedList<QueryParams> localSearches = new LinkedList<QueryParams>();
    private static final LinkedList<QueryParams> remoteSearches = new LinkedList<QueryParams>();
    private static final ArrayList<String> log = new ArrayList<String>();
    private static long lastLogDump = System.currentTimeMillis();
    private static File dumpFile = null;

    public static void setDumpFile(File f) {
        dumpFile = f;
    }

    public static File getDumpFile() {
        return dumpFile;
    }

    public static void add(final Location location, final QueryParams query, int resultCount) {
        if (location == Location.local) synchronized (localSearches) {add(localSearches, query, resultCount);}
        if (location == Location.remote) synchronized (remoteSearches) {add(remoteSearches, query, resultCount);}
    }

    private static void add(final LinkedList<QueryParams> list, final QueryParams query, int resultCount) {
        // learn that this word can be a word completion for the DidYouMeanLibrary
        String queryString = query.getQueryGoal().getQueryString(false);
        if (resultCount > 10 && queryString != null && queryString.length() > 0) {
            final StringBuilder sb = new StringBuilder(queryString);
            sb.append(queryString);
            WordCache.learn(sb);
        }

        // add query to statistics list
        list.add(query);

        // shrink dump list but keep essentials in dump
        while (list.size() > maxSize || (!list.isEmpty() && MemoryControl.shortStatus())) {
            synchronized (list) {
                if (!list.isEmpty()) addToDump(list.removeFirst(), resultCount); else break;
            }
        }

        // if the list is small we can terminate
        if (list.size() <= minSize) return;

        // if the list is large we look for too old entries
        final long timeout = System.currentTimeMillis() - maxAge;
        while (!list.isEmpty()) {
            final QueryParams q = list.getFirst();
            if (q.starttime > timeout) break;
            addToDump(list.removeFirst(), resultCount);
        }
    }

    public static Iterator<QueryParams> get(final Location location) {
        if (location == Location.local) return localSearches.descendingIterator();
        if (location == Location.remote) return remoteSearches.descendingIterator();
        return null;
    }

    public static int size(final Location location) {
        if (location == Location.local) synchronized (localSearches) {return localSearches.size();}
        if (location == Location.remote) synchronized (remoteSearches) {return remoteSearches.size();}
        return 0;
    }

    private static void addToDump(final QueryParams query, int resultCount) {
        String queryString = query.getQueryGoal().getQueryString(false);
        if (queryString == null || queryString.isEmpty()) return;
        addToDump(queryString, Integer.toString(resultCount), new Date(query.starttime));
    }

    public static void addToDump(String querystring, String resultcount) {
        addToDump(querystring, resultcount, new Date());
        if (lastLogDump + DUMP_PERIOD < System.currentTimeMillis()) {
            lastLogDump = System.currentTimeMillis();
            dumpLog();
        }
    }

    public static void addToDump(String querystring, String resultcount, Date d) {
        //if (query.resultcount == 0) return;
        if (querystring == null || querystring.isEmpty()) return;
        final StringBuilder sb = new StringBuilder(40);
        sb.append(GenericFormatter.SHORT_SECOND_FORMATTER.format(d));
        sb.append(' ');
        sb.append(resultcount);
        sb.append(' ');
        sb.append(querystring);
        synchronized (log) {
            log.add(sb.toString());
        }
    }

    public static void dumpLog() {
        while (!localSearches.isEmpty()) {
            addToDump(localSearches.removeFirst(), 0);
        }
        Thread t = new Thread() {
            @Override
            public void run() {
                ArrayList<String> logCopy = new ArrayList<String>();
                synchronized (log) {
                    logCopy.addAll(log);
                    log.clear();
                }
                RandomAccessFile raf = null;
                try {
                    raf = new RandomAccessFile(dumpFile, "rw");
                    raf.seek(raf.length());
                    for (final String s: logCopy) {
                        raf.write(UTF8.getBytes(s));
                        raf.writeByte(10);
                    }
                    logCopy.clear();
                } catch (final FileNotFoundException e) {
                    ConcurrentLog.logException(e);
                } catch (final IOException e) {
                    ConcurrentLog.logException(e);
                } finally {
                    if (raf != null) try {raf.close();} catch (final IOException e) {}
                }
            }
        };
        t.start();
    }
    
    /**
     * read the log and return a list of lines which are equal or greater than
     * the from-date and smaller than the to-date
     * @param f the dump file
     * @param from the left boundary of the sequence to search for (included)
     * @param to the right boundary of the sequence to search for (excluded)
     * @return a list of lines within the given dates
     */
    public static List<EventTracker.Event> readLog(File f, Date from, Date to) {
        List<EventTracker.Event> events = new ArrayList<>();
        RandomAccessFile raf = null;
        try {
            raf = new RandomAccessFile(f, "r");
            Date fd = readDate(raf, 0);
            if (fd.after(from)) from = fd;
            long seekFrom = binarySearch(raf, from, 0, raf.length());
            long seekTo = binarySearch(raf, to, seekFrom, raf.length());
            //Date eDate = readDate(raf, seekTo);
            //if (eDate.before(to)) seekTo = raf.length();
            raf.seek(seekFrom);
            byte[] buffer = new byte[(int) (seekTo - seekFrom)];
            raf.readFully(buffer); // we make a copy because that dramatically speeds up reading lines; RandomAccessFile.readLine is very slow
            raf.close();
            ByteArrayInputStream bais = new ByteArrayInputStream(buffer);
            BufferedReader reader = new BufferedReader(new InputStreamReader(bais, "UTF-8"));
            String line;
            while ((line = reader.readLine()) != null) {
                // parse the line
                if (line.length() < GenericFormatter.PATTERN_SHORT_SECOND.length() + 3 ||
                    line.charAt(GenericFormatter.PATTERN_SHORT_SECOND.length()) != ' ') continue;
                String dateStr = line.substring(0, GenericFormatter.PATTERN_SHORT_SECOND.length());
                int countEnd = -1;
                for (int i = GenericFormatter.PATTERN_SHORT_SECOND.length() + 2; i < line.length(); i++) {
                    if (line.charAt(i) == ' ') { countEnd = i; break; }
                }
                if (countEnd == -1) continue;
                String countStr = line.substring(GenericFormatter.PATTERN_SHORT_SECOND.length() + 1, countEnd);
                if (countStr.length() > 5) continue;
                int hits = countStr.length() == 1 ? (countStr.charAt(0)) - 48 : Integer.parseInt(countStr);
                EventTracker.Event event;
                try {
                    event = new EventTracker.Event(dateStr, 0, "query", line.substring(dateStr.length() + countStr.length() + 2), hits);
                    events.add(event);
                } catch (NumberFormatException e) {
                    continue;
                } catch (Throwable e) {
                    continue;
                }
            }
            reader.close();
            bais.close();
            buffer = null;
        } catch (final FileNotFoundException e) {
            ConcurrentLog.logException(e);
        } catch (final IOException e) {
            ConcurrentLog.logException(e);
        } finally {
            if (raf != null) try {raf.close();} catch (final IOException e) {}
        }
        return events;
    }

    /**
     * recursively search for a the smallest date which is equal or greater than the given date
     * @param raf the random access file
     * @param date the given date
     * @param l first seek position to look (included, we expect a date there or after the position l)
     * @param r last seek position to look (excluded, we do not expect that there is a date)
     * @return the first position where a date appears that is equal or greater than the given one
     */
    private static long binarySearch(RandomAccessFile raf, Date date, long l, long r) throws IOException {
        if (r <= l) return l;
        long m = seekLB(raf, (l + r) / 2);
        if (m <= l) return m;
        Date mDate = readDate(raf, m);
        if (mDate.after(date)) return binarySearch(raf, date, l, m);
        return binarySearch(raf, date, m, r);
    }
    
    /**
     * find the beginning of a line
     * @param raf the random access file
     * @param x any seek position in the file
     * @return the seek position of the beginning of a line smaller or equal to x
     * @throws IOException
     */
    private static long seekLB(RandomAccessFile raf, long x) throws IOException {
        if (x <= 0) return x;
        raf.seek(x);
        while (x > 0 && raf.read() >= 32) {x--; raf.seek(x);}
        if (x == 0) return 0;
        raf.seek(x);
        return raf.read() >= 32 ? x : x + 1;
    }
    
    /**
     * read a date at the seek position; the seek position must be exactly at the date start
     * @param raf the random access file
     * @param x the seek position of the date string start position
     * @return the date at position x
     * @throws IOException
     */
    private static Date readDate(RandomAccessFile raf, long x) throws IOException {
        raf.seek(x);
        byte[] b = new byte[GenericFormatter.PATTERN_SHORT_SECOND.length()];
        raf.readFully(b);
        try {
            return GenericFormatter.SHORT_SECOND_FORMATTER.parse(UTF8.String(b), 0).getTime();
        } catch (ParseException e) {
            throw new IOException(e.getMessage());
        }
    }
    
    public static void main(String[] args) {
        // i.e. /Users/admin/git/rc1/DATA/LOG/queries.log 20140522135156 20140614223118
        String file = args[0];
        Date from;
        try {
            from = GenericFormatter.SHORT_SECOND_FORMATTER.parse(args[1], 0).getTime();
            Date to = GenericFormatter.SHORT_SECOND_FORMATTER.parse(args[2], 0).getTime();
            List<EventTracker.Event> dump = readLog(new File(file), from, to);
            for (EventTracker.Event s: dump) System.out.println(s.toString());
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}