filebot/source/net/sourceforge/filebot/similarity/CommonSequenceMatcher.java

package net.sourceforge.filebot.similarity;


import static java.util.Arrays.*;
import static java.util.Collections.*;

import java.text.CollationKey;
import java.text.Collator;
import java.util.Locale;
import java.util.Map;
import java.util.WeakHashMap;


public class CommonSequenceMatcher {
	
	public static Collator getLenientCollator(Locale locale) {
		// use maximum strength collator by default
		Collator collator = Collator.getInstance(locale);
		collator.setDecomposition(Collator.FULL_DECOMPOSITION);
		collator.setStrength(Collator.PRIMARY);
		return collator;
	}
	
	
	protected final Collator collator;
	protected final int commonSequenceMaxStartIndex;
	
	
	public CommonSequenceMatcher(Collator collator, int commonSequenceMaxStartIndex) {
		this.collator = collator;
		this.commonSequenceMaxStartIndex = commonSequenceMaxStartIndex;
	}
	
	
	public Collator getCollator() {
		return collator;
	}
	
	
	public String matchFirstCommonSequence(String... names) {
		CollationKey[] common = null;
		
		for (String it : names) {
			CollationKey[] words = split(it);
			
			if (common == null) {
				// initialize common with current word array
				common = words;
			} else {
				// find common sequence
				common = firstCommonSequence(common, words, commonSequenceMaxStartIndex);
				
				if (common == null) {
					// no common sequence
					return null;
				}
			}
		}
		
		if (common == null)
			return null;
		
		return synth(common);
	}
	
	
	protected String synth(CollationKey[] keys) {
		StringBuilder sb = new StringBuilder();
		for (CollationKey it : keys) {
			if (sb.length() > 0) {
				sb.append(' ');
			}
			sb.append(it.getSourceString());
		}
		return sb.toString();
	}
	
	
	protected CollationKey[] split(String sequence) {
		return getCollationKeys(sequence.split("\\s+"));
	}
	
	
	private final Map<String, CollationKey> collationKeyDictionary = synchronizedMap(new WeakHashMap<String, CollationKey>(256));
	
	
	protected CollationKey[] getCollationKeys(String[] words) {
		CollationKey[] keys = new CollationKey[words.length];
		for (int i = 0; i < keys.length; i++) {
			keys[i] = collationKeyDictionary.get(words[i]);
			if (keys[i] == null) {
				keys[i] = collator.getCollationKey(words[i]);
				collationKeyDictionary.put(words[i], keys[i]);
			}
		}
		return keys;
	}
	
	
	protected <E extends Comparable<E>> E[] firstCommonSequence(E[] seq1, E[] seq2, int maxStartIndex) {
		for (int i = 0; i < seq1.length && i <= maxStartIndex; i++) {
			for (int j = 0; j < seq2.length && j <= maxStartIndex; j++) {
				// common sequence length
				int len = 0;
				
				// iterate over common sequence
				while ((i + len < seq1.length) && (j + len < seq2.length) && (seq1[i + len].compareTo(seq2[j + len]) == 0)) {
					len++;
				}
				
				// check if a common sequence was found
				if (len > 0) {
					if (i == 0 && len == seq1.length)
						return seq1;
					
					return copyOfRange(seq1, i, i + len);
				}
			}
		}
		
		// no intersection at all
		return null;
	}
}