/**
* WordCache
* Copyright 2009 by Michael Peter Christen; mc@yacy.net, Frankfurt a. M., Germany
* first published 01.10.2009 on http://yacy.net
*
* 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.document;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ConcurrentModificationException;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.zip.GZIPInputStream;
import net.yacy.cora.storage.OrderedScoreMap;
import net.yacy.kelondro.logging.Log;
import net.yacy.kelondro.util.MemoryControl;
/**
* provide a completion library for the did-you-mean class
*
*/
public class WordCache {
// common word cache
private static final int commonWordsMaxSize = 100000; // maximum size of common word cache
private static final int commonWordsMinLength = 5; // words must have that length at minimum
private OrderedScoreMap<String> commonWords = new OrderedScoreMap<String>(String.CASE_INSENSITIVE_ORDER);
// dictionaries
private final File dictionaryPath;
private TreeSet<String> dict; // the word dictionary
private TreeSet<String> tcid; // the dictionary of reverse words
/**
* create a new dictionary
* This loads all files that ends with '.words'
* The files must have one word per line
* Comment lines may be given and are encoded as line starting with '#'
* @param dictionaryPath path to a directory with library files
*/
public WordCache(final File dictionaryPath) {
this.dictionaryPath = dictionaryPath;
reload();
}
/**
* add a word to the generic dictionary
* @param word
*/
public void learn(String word) {
if (word == null) return;
if (word.length() < commonWordsMinLength) return;
if (MemoryControl.shortStatus()) commonWords.clear();
commonWords.inc(word);
if (!(commonWords.sizeSmaller(commonWordsMaxSize))) {
commonWords.shrinkToMaxSize(commonWordsMaxSize / 2);
}
}
/**
* scan the input directory and load all dictionaries (again)
*/
public void reload() {
this.dict = new TreeSet<String>();
this.tcid = new TreeSet<String>();
if (dictionaryPath == null || !dictionaryPath.exists()) return;
final String[] files = dictionaryPath.list();
for (final String f: files) {
if (f.endsWith(".words")) try {
inputStream(new File(dictionaryPath, f));
} catch (IOException e) {
Log.logException(e);
}
}
}
private void inputStream(final File file) throws IOException {
InputStream is = new FileInputStream(file);
if (file.getName().endsWith(".gz")) {
is = new GZIPInputStream(is);
}
final BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
String l;
try {
while ((l = reader.readLine()) != null) {
if (l.length() == 0 || l.charAt(0) == '#') continue;
l = l.trim().toLowerCase();
this.dict.add(l);
this.tcid.add(reverse(l));
}
} catch (IOException e) {
// finish
}
}
private static String reverse(final String s) {
StringBuilder sb = new StringBuilder(s.length());
for (int i = s.length() - 1; i >= 0; i--) {
sb.append(s.charAt(i));
}
return sb.toString();
}
/**
* read the dictionary and construct a set of recommendations to a given string
* @param s input value that is used to match recommendations
* @return set that contains all words that start or end with the input value
*/
public Set<String> recommend(final String s) {
final Set<String> ret = new HashSet<String>();
String string = s.trim().toLowerCase();
SortedSet<String> t = this.dict.tailSet(string);
for (final String r: t) {
if (r.startsWith(string) && r.length() > string.length()) ret.add(r); else break;
}
SortedMap<String, AtomicInteger> u = this.commonWords.tailMap(string);
String vv;
try {
for (final Map.Entry<String, AtomicInteger> v: u.entrySet()) {
vv = v.getKey();
if (vv.startsWith(string) && vv.length() > string.length()) ret.add(vv); else break;
}
} catch (ConcurrentModificationException e) {}
string = reverse(string);
t = this.tcid.tailSet(string);
for (final String r: t) {
if (r.startsWith(string) && r.length() > string.length()) ret.add(reverse(r)); else break;
}
return ret;
}
/**
* check if the library contains the given word
* @param s the given word
* @return true if the library contains the word
*/
public boolean contains(final String s) {
return this.dict.contains(s.trim().toLowerCase());
// if the above case is true then it is also true for this.tcid and vice versa
// that means it does not need to be tested as well
}
/**
* check if the library supports the given word
* A word is supported, if the library contains a word
* that starts or ends with the given word
* @param s the given word
* @return true if the library supports the word
*/
public boolean supports(final String s) {
String string = s.trim().toLowerCase();
SortedSet<String> t = this.dict.tailSet(string);
for (final String r: t) {
if (string.startsWith(r)) return true; else break;
}
string = reverse(string);
t = this.tcid.tailSet(string);
for (final String r: t) {
if (string.startsWith(r)) return true; else break;
}
return false;
}
/**
* the size of the dictionay
* @return the number of words in the dictionary
*/
public int size() {
return this.dict.size();
}
/**
* a property that is used during the construction of recommendation:
* if the dictionary is too small, then the non-existence of constructed words
* is not relevant for the construction of artificially constructed words
* If this property returns true, all other words must be in the dictionary
* @param minimumWords
* @return
*/
public boolean isRelevant(final int minimumWords) {
return this.dict.size() >= minimumWords;
}
}