| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.sling.mailarchiveserver.impl; |
| |
| import static java.lang.Character.isLetterOrDigit; |
| import static org.apache.sling.mailarchiveserver.impl.MessageStoreImpl.makeJcrFriendly; |
| import static org.apache.sling.mailarchiveserver.impl.MessageStoreImpl.removeRe; |
| |
| import org.apache.felix.scr.annotations.Component; |
| import org.apache.felix.scr.annotations.Service; |
| import org.apache.james.mime4j.dom.Message; |
| import org.apache.sling.mailarchiveserver.api.ThreadKeyGenerator; |
| |
| @Component |
| @Service(ThreadKeyGenerator.class) |
| public class ThreadKeyGeneratorImpl implements ThreadKeyGenerator { |
| |
| /** |
| * These constants are gotten by sampling around 1500 messages |
| * from some open source projects using SubjectLettersEntropy class. |
| * |
| * Entropy of each letter position of the subject was calculated. And two letter positions |
| * with biggest entropy and occurrence in at least 90% of the messages were chosen. |
| * |
| * In order to {@link #getThreadKey(Message)} works correctly, following invariant should hold: LETTER_POS_WITH_BIGGEST_ENTROPY < LETTER_POS_WITH_2ND_BIGGEST_ENTROPY |
| */ |
| private static final int LETTER_POS_WITH_BIGGEST_ENTROPY = 9; |
| private static final int LETTER_POS_WITH_2ND_BIGGEST_ENTROPY = 40; |
| private static final String UNADDRESSABLE_SUBJECT = "unaddressable subject"; |
| |
| public String getThreadKey(String subject) { |
| String wordCharsSubj; |
| String noReSubj; |
| if (subject != null) { |
| noReSubj = removeRe(subject); |
| wordCharsSubj = noReSubj.replaceAll("\\W", "_"); |
| if (!isAddressable(wordCharsSubj)) { |
| noReSubj = wordCharsSubj = UNADDRESSABLE_SUBJECT; |
| } |
| } else { |
| noReSubj = wordCharsSubj = UNADDRESSABLE_SUBJECT; |
| } |
| |
| char prefix1; |
| char prefix2; |
| prefix1 = assignPrefix(wordCharsSubj, LETTER_POS_WITH_BIGGEST_ENTROPY); |
| prefix2 = assignPrefix(wordCharsSubj, LETTER_POS_WITH_2ND_BIGGEST_ENTROPY); |
| return ""+prefix1+"/"+prefix1+prefix2+"/"+ makeJcrFriendly(noReSubj); |
| } |
| |
| private static boolean isAddressable(String subject) { |
| for (char c : subject.toCharArray()) { |
| if (isLetterOrDigit(c)) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| private static char assignPrefix(String subject, int length) { |
| char prefix; |
| if (subject.length() > length) { |
| |
| int i = length; |
| while (i > -1 && !isLetterOrDigit(subject.charAt(i))) |
| i--; |
| if (i > -1) |
| prefix = subject.charAt(i); |
| else { |
| i = length; |
| while (i<subject.length() && !isLetterOrDigit(subject.charAt(i))) |
| i++; |
| if (i<subject.length()) |
| prefix = subject.charAt(i); |
| else |
| throw new IllegalArgumentException(); |
| } |
| |
| } else { |
| |
| int i = subject.length()-1; |
| while (i > -1 && !isLetterOrDigit(subject.charAt(i))) |
| i--; |
| if (i > -1) |
| prefix = subject.charAt(i); |
| else |
| throw new IllegalArgumentException(); |
| |
| } |
| |
| return prefix; |
| } |
| |
| } |