package org.xbib.elasticsearch.index.analysis.worddelimiter;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.core.WhitespaceTokenizer;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.util.ArrayUtil;
import java.io.IOException;
/**
* Splits words into subwords and performs optional transformations on subword
* groups. Words are split into subwords with the following rules:
* <ul>
* <li>split on intra-word delimiters (by default, all non alpha-numeric
* characters): <code>"Wi-Fi"</code> → <code>"Wi", "Fi"</code></li>
* <li>split on case transitions: <code>"PowerShot"</code> →
* <code>"Power", "Shot"</code></li>
* <li>split on letter-number transitions: <code>"SD500"</code> →
* <code>"SD", "500"</code></li>
* <li>leading and trailing intra-word delimiters on each subword are ignored:
* <code>"//hello---there, 'dude'"</code> →
* <code>"hello", "there", "dude"</code></li>
* <li>trailing "'s" are removed for each subword: <code>"O'Neil's"</code>
* → <code>"O", "Neil"</code>
* <ul>
* <li>Note: this step isn't performed in a separate filter because of possible
* subword combinations.</li>
* </ul>
* </li>
* </ul>
* The <b>combinations</b> parameter affects how subwords are combined:
* <ul>
* <li>combinations="0" causes no subword combinations: <code>"PowerShot"</code>
* → <code>0:"Power", 1:"Shot"</code> (0 and 1 are the token positions)</li>
* <li>combinations="1" means that in addition to the subwords, maximum runs of
* non-numeric subwords are catenated and produced at the same position of the
* last subword in the run:
* <ul>
* <li><code>"PowerShot"</code> →
* <code>0:"Power", 1:"Shot" 1:"PowerShot"</code></li>
* <li><code>"A's+B's&C's"</code> -gt; <code>0:"A", 1:"B", 2:"C", 2:"ABC"</code>
* </li>
* <li><code>"Super-Duper-XL500-42-AutoCoder!"</code> →
* <code>0:"Super", 1:"Duper", 2:"XL", 2:"SuperDuperXL", 3:"500" 4:"42", 5:"Auto", 6:"Coder", 6:"AutoCoder"</code>
* </li>
* </ul>
* </li>
* </ul>
* One use for {@link WordDelimiterFilter} is to help match words with different
* subword delimiters. For example, if the source text contained "wi-fi" one may
* want "wifi" "WiFi" "wi-fi" "wi+fi" queries to all match. One way of doing so
* is to specify combinations="1" in the analyzer used for indexing, and
* combinations="0" (the default) in the analyzer used for querying. Given that
* the current {@link StandardTokenizer} immediately removes many intra-word
* delimiters, it is recommended that this filter be used after a tokenizer that
* does not do this (such as {@link WhitespaceTokenizer}).
*/
public final class WordDelimiterFilter extends TokenFilter implements WordDelimiterFlags {
/**
* If not null is the set of tokens to protect from being delimited
*/
private final CharArraySet protWords;
private final int flags;
private final CharTermAttribute termAttribute = addAttribute(CharTermAttribute.class);
private final OffsetAttribute offsetAttribute = addAttribute(OffsetAttribute.class);
private final PositionIncrementAttribute posIncAttribute = addAttribute(PositionIncrementAttribute.class);
private final TypeAttribute typeAttribute = addAttribute(TypeAttribute.class);
// used for iterating word delimiter breaks
private final WordDelimiterIterator iterator;
// used for concatenating runs of similar typed subwords (word,number)
private final WordDelimiterConcatenation concat = new WordDelimiterConcatenation();
// used for catenate all
private final WordDelimiterConcatenation concatAll = new WordDelimiterConcatenation();
// number of subwords last output by concat.
private int lastConcatCount = 0;
// used for accumulating position increment gaps
private int accumPosInc = 0;
private char[] savedBuffer = new char[1024];
private int savedStartOffset;
private int savedEndOffset;
private String savedType;
private boolean hasSavedState = false;
// if length by start + end offsets doesn't match the term text then assume
// this is a synonym and don't adjust the offsets.
private boolean hasIllegalOffsets = false;
// for a run of the same subword type within a word, have we output anything?
private boolean hasOutputToken = false;
// when preserve original is on, have we output any token following it?
// this token must have posInc=0!
private boolean hasOutputFollowingOriginal = false;
/**
* Creates a new WordDelimiterFilter
*
* @param in TokenStream to be filtered
* @param charTypeTable table containing character types
* @param configurationFlags Flags configuring the filter
* @param protWords If not null is the set of tokens to protect from being delimited
*/
public WordDelimiterFilter(TokenStream in, byte[] charTypeTable, int configurationFlags, CharArraySet protWords) {
super(in);
this.flags = configurationFlags;
this.protWords = protWords;
this.iterator = new WordDelimiterIterator(charTypeTable, has(SPLIT_ON_CASE_CHANGE), has(SPLIT_ON_NUMERICS), has(STEM_ENGLISH_POSSESSIVE));
}
/**
* Creates a new WordDelimiterFilter using {@link WordDelimiterIterator#DEFAULT_WORD_DELIM_TABLE}
* as its charTypeTable
*
* @param in TokenStream to be filtered
* @param configurationFlags Flags configuring the filter
* @param protWords If not null is the set of tokens to protect from being delimited
*/
public WordDelimiterFilter(TokenStream in, int configurationFlags, CharArraySet protWords) {
this(in, WordDelimiterIterator.DEFAULT_WORD_DELIM_TABLE, configurationFlags, protWords);
}
/**
* Checks if the given word type includes {@link #ALPHA}
*
* @param type Word type to check
* @return {@code true} if the type contains ALPHA, {@code false} otherwise
*/
static boolean isAlpha(int type) {
return (type & ALPHA) != 0;
}
/**
* Checks if the given word type includes {@link #DIGIT}
*
* @param type Word type to check
* @return {@code true} if the type contains DIGIT, {@code false} otherwise
*/
static boolean isDigit(int type) {
return (type & DIGIT) != 0;
}
/**
* Checks if the given word type includes {@link #SUBWORD_DELIM}
*
* @param type Word type to check
* @return {@code true} if the type contains SUBWORD_DELIM, {@code false} otherwise
*/
static boolean isSubwordDelim(int type) {
return (type & SUBWORD_DELIM) != 0;
}
/**
* Checks if the given word type includes {@link #UPPER}
*
* @param type Word type to check
* @return {@code true} if the type contains UPPER, {@code false} otherwise
*/
static boolean isUpper(int type) {
return (type & UPPER) != 0;
}
@Override
public boolean incrementToken() throws IOException {
while (true) {
if (!hasSavedState) {
// process a new input word
if (!input.incrementToken()) {
return false;
}
int termLength = termAttribute.length();
char[] termBuffer = termAttribute.buffer();
accumPosInc += posIncAttribute.getPositionIncrement();
iterator.setText(termBuffer, termLength);
iterator.next();
// word of no delimiters, or protected word: just return it
if ((iterator.current == 0 && iterator.end == termLength) ||
(protWords != null && protWords.contains(termBuffer, 0, termLength))) {
posIncAttribute.setPositionIncrement(accumPosInc);
accumPosInc = 0;
return true;
}
// word of simply delimiters
if (iterator.end == WordDelimiterIterator.DONE && !has(PRESERVE_ORIGINAL)) {
// if the posInc is 1, simply ignore it in the accumulation
if (posIncAttribute.getPositionIncrement() == 1) {
accumPosInc--;
}
continue;
}
saveState();
hasOutputToken = false;
hasOutputFollowingOriginal = !has(PRESERVE_ORIGINAL);
lastConcatCount = 0;
if (has(PRESERVE_ORIGINAL)) {
posIncAttribute.setPositionIncrement(accumPosInc);
accumPosInc = 0;
return true;
}
}
// at the end of the string, output any concatenations
if (iterator.end == WordDelimiterIterator.DONE) {
if (!concat.isEmpty() && flushConcatenation(concat)) {
return true;
}
if (!concatAll.isEmpty()) {
// only if we haven't output this same combo above!
if (concatAll.subwordCount > lastConcatCount) {
concatAll.writeAndClear();
return true;
}
concatAll.clear();
}
// no saved concatenations, on to the next input word
hasSavedState = false;
continue;
}
// word surrounded by delimiters: always output
if (iterator.isSingleWord()) {
generatePart(true);
iterator.next();
return true;
}
int wordType = iterator.type();
// do we already have queued up incompatible concatenations?
if (!concat.isEmpty() && (concat.type & wordType) == 0) {
if (flushConcatenation(concat)) {
hasOutputToken = false;
return true;
}
hasOutputToken = false;
}
// add subwords depending upon options
if (shouldConcatenate(wordType)) {
if (concat.isEmpty()) {
concat.type = wordType;
}
concatenate(concat);
}
// add all subwords (catenateAll)
if (has(CATENATE_ALL)) {
concatenate(concatAll);
}
// if we should output the word or number part
if (shouldGenerateParts(wordType)) {
generatePart(false);
iterator.next();
return true;
}
iterator.next();
}
}
/**
* {@inheritDoc}
*/
@Override
public void reset() throws IOException {
super.reset();
hasSavedState = false;
concat.clear();
concatAll.clear();
accumPosInc = 0;
}
/**
* Saves the existing attribute states
*/
private void saveState() {
// otherwise, we have delimiters, save state
savedStartOffset = offsetAttribute.startOffset();
savedEndOffset = offsetAttribute.endOffset();
// if length by start + end offsets doesn't match the term text then assume this is a synonym and don't adjust the offsets.
hasIllegalOffsets = savedEndOffset - savedStartOffset != termAttribute.length();
savedType = typeAttribute.type();
if (savedBuffer.length < termAttribute.length()) {
savedBuffer = new char[ArrayUtil.oversize(termAttribute.length(), Character.BYTES)];
}
System.arraycopy(termAttribute.buffer(), 0, savedBuffer, 0, termAttribute.length());
iterator.text = savedBuffer;
hasSavedState = true;
}
/**
* Flushes the given WordDelimiterConcatenation by either writing its concat and then clearing, or just clearing.
*
* @param concatenation WordDelimiterConcatenation that will be flushed
* @return {@code true} if the concatenation was written before it was cleared, {@code false} otherwise
*/
private boolean flushConcatenation(WordDelimiterConcatenation concatenation) {
lastConcatCount = concatenation.subwordCount;
if (concatenation.subwordCount != 1 || !shouldGenerateParts(concatenation.type)) {
concatenation.writeAndClear();
return true;
}
concatenation.clear();
return false;
}
/**
* Determines whether to concatenate a word or number if the current word is the given type
*
* @param wordType Type of the current word used to determine if it should be concatenated
* @return {@code true} if concatenation should occur, {@code false} otherwise
*/
private boolean shouldConcatenate(int wordType) {
return (has(CATENATE_WORDS) && isAlpha(wordType)) || (has(CATENATE_NUMBERS) && isDigit(wordType));
}
/**
* Determines whether a word/number part should be generated for a word of the given type
*
* @param wordType Type of the word used to determine if a word/number part should be generated
* @return {@code true} if a word/number part should be generated, {@code false} otherwise
*/
private boolean shouldGenerateParts(int wordType) {
return (has(GENERATE_WORD_PARTS) && isAlpha(wordType)) || (has(GENERATE_NUMBER_PARTS) && isDigit(wordType));
}
/**
* Concatenates the saved buffer to the given WordDelimiterConcatenation
*
* @param concatenation WordDelimiterConcatenation to concatenate the buffer to
*/
private void concatenate(WordDelimiterConcatenation concatenation) {
if (concatenation.isEmpty()) {
concatenation.startOffset = savedStartOffset + iterator.current;
}
concatenation.append(savedBuffer, iterator.current, iterator.end - iterator.current);
concatenation.endOffset = savedStartOffset + iterator.end;
}
/**
* Generates a word/number part, updating the appropriate attributes
*
* @param isSingleWord {@code true} if the generation is occurring from a single word, {@code false} otherwise
*/
private void generatePart(boolean isSingleWord) {
clearAttributes();
termAttribute.copyBuffer(savedBuffer, iterator.current, iterator.end - iterator.current);
int startOffset = savedStartOffset + iterator.current;
int endOffset = savedStartOffset + iterator.end;
if (hasIllegalOffsets) {
// historically this filter did this regardless for 'isSingleWord',
// but we must do a sanity check:
if (isSingleWord && startOffset <= savedEndOffset) {
offsetAttribute.setOffset(startOffset, savedEndOffset);
} else {
offsetAttribute.setOffset(savedStartOffset, savedEndOffset);
}
} else {
offsetAttribute.setOffset(startOffset, endOffset);
}
posIncAttribute.setPositionIncrement(position(false));
typeAttribute.setType(savedType);
}
/**
* Get the position increment gap for a subword or concatenation
*
* @param inject true if this token wants to be injected
* @return position increment gap
*/
private int position(boolean inject) {
int posInc = accumPosInc;
if (hasOutputToken) {
accumPosInc = 0;
return inject ? 0 : Math.max(1, posInc);
}
hasOutputToken = true;
if (!hasOutputFollowingOriginal) {
// the first token following the original is 0 regardless
hasOutputFollowingOriginal = true;
return 0;
}
// clear the accumulated position increment
accumPosInc = 0;
return Math.max(1, posInc);
}
/**
* Determines whether the given flag is set
*
* @param flag Flag to see if set
* @return {@code true} if flag is set
*/
private boolean has(int flag) {
return (flags & flag) != 0;
}
@Override
public boolean equals(Object object) {
return object instanceof WordDelimiterFilter &&
iterator.equals(((WordDelimiterFilter)object).iterator);
}
@Override
public int hashCode() {
return iterator.hashCode();
}
/**
* A WDF concatenated 'run'
*/
final class WordDelimiterConcatenation {
final StringBuilder buffer = new StringBuilder();
int startOffset;
int endOffset;
int type;
int subwordCount;
/**
* Appends the given text of the given length, to the concetenation at the given offset
*
* @param text Text to append
* @param offset Offset in the concetenation to add the text
* @param length Length of the text to append
*/
void append(char[] text, int offset, int length) {
buffer.append(text, offset, length);
subwordCount++;
}
/**
* Writes the concatenation to the attributes
*/
void write() {
clearAttributes();
if (termAttribute.length() < buffer.length()) {
termAttribute.resizeBuffer(buffer.length());
}
char[] termbuffer = termAttribute.buffer();
buffer.getChars(0, buffer.length(), termbuffer, 0);
termAttribute.setLength(buffer.length());
if (hasIllegalOffsets) {
offsetAttribute.setOffset(savedStartOffset, savedEndOffset);
} else {
offsetAttribute.setOffset(startOffset, endOffset);
}
posIncAttribute.setPositionIncrement(position(true));
typeAttribute.setType(savedType);
accumPosInc = 0;
}
/**
* Determines if the concatenation is empty
*
* @return {@code true} if the concatenation is empty, {@code false} otherwise
*/
boolean isEmpty() {
return buffer.length() == 0;
}
/**
* Clears the concatenation and resets its state
*/
void clear() {
buffer.setLength(0);
startOffset = endOffset = type = subwordCount = 0;
}
/**
* Convenience method for the common scenario of having to write the concetenation and then clearing its state
*/
void writeAndClear() {
write();
clear();
}
}
// questions:
// negative numbers? -42 indexed as just 42?
// dollar sign? $42
// percent sign? 33%
// downsides: if source text is "powershot" then a query of "PowerShot" won't match!
}