// Word.java
// (C) 2008 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
// first published 26.03.2008 on http://yacy.net
//
// This is a part of YaCy, a peer-to-peer based web search engine
//
// $LastChangedDate$
// $LastChangedRevision$
// $LastChangedBy$
//
// 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 de.anomic.kelondro.text;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Locale;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;

import de.anomic.kelondro.order.Base64Order;
import de.anomic.kelondro.order.Bitfield;
import de.anomic.kelondro.order.Digest;
import de.anomic.yacy.yacySeedDB;

public class Word {

    private static final ConcurrentHashMap<String, String> hashCache = new ConcurrentHashMap<String, String>(1000);
    
    // object carries statistics for words and sentences
    public  int      count;       // number of occurrences
    public  int      posInText;   // unique handle, is initialized with word position (excluding double occurring words)
    public  int      posInPhrase; // position of word in phrase
    public  int      numOfPhrase; // number of phrase. 'normal' phrases begin with number 100
    HashSet<Integer> phrases;     // a set of handles to all phrases where this word appears
    public  Bitfield flags;       // the flag bits for each word

    public Word(final int handle, final int pip, final int nop) {
        this.count = 1;
        this.posInText = handle;
        this.posInPhrase = pip;
        this.numOfPhrase = nop;
        this.phrases = new HashSet<Integer>();
        this.flags = null;
    }

    public void inc() {
        count++;
    }
    
    public int occurrences() {
        return count;
    }

    public void check(final int i) {
        phrases.add(Integer.valueOf(i));
    }

    public Iterator<Integer> phrases() {
        // returns an iterator to handles of all phrases where the word appears
        return phrases.iterator();
    }
    
    // static methods

    // create a word hash
    public static final String word2hash(final String word) {
        String h = hashCache.get(word);
        if (h != null) return h;
        h = Base64Order.enhancedCoder.encode(Digest.encodeMD5Raw(word.toLowerCase(Locale.ENGLISH))).substring(0, yacySeedDB.commonHashLength);
        hashCache.put(word, h); // prevent expensive MD5 computation and encoding
        if (hashCache.size() > 20000) {
            // prevent memory leak
            hashCache.clear();
        }
        return h;
    }
    
    public static final Set<String> words2hashSet(final String[] words) {
        final TreeSet<String> hashes = new TreeSet<String>(Base64Order.enhancedComparator);
        for (int i = 0; i < words.length; i++) hashes.add(word2hash(words[i]));
        return hashes;
    }

    public static final String words2hashString(final String[] words) {
        final StringBuilder sb = new StringBuilder();
        for (int i = 0; i < words.length; i++) sb.append(word2hash(words[i]));
        return new String(sb);
    }

    public static final TreeSet<String> words2hashes(final Set<String> words) {
        final Iterator<String> i = words.iterator();
        final TreeSet<String> hashes = new TreeSet<String>(Base64Order.enhancedComparator);
        while (i.hasNext()) hashes.add(word2hash(i.next()));
        return hashes;
    }
}