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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.common.unit;
import org.elasticsearch.ElasticsearchParseException;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.ToXContentFragment;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParser;
import java.io.IOException;
import java.util.Locale;
import java.util.Objects;
/**
* A unit class that encapsulates all in-exact search
* parsing and conversion from similarities to edit distances
* etc.
*/
public final class Fuzziness implements ToXContentFragment, Writeable {
static final String X_FIELD_NAME = "fuzziness";
public static final ParseField FIELD = new ParseField(X_FIELD_NAME);
public static final Fuzziness ZERO = new Fuzziness("0");
public static final Fuzziness ONE = new Fuzziness("1");
public static final Fuzziness TWO = new Fuzziness("2");
public static final Fuzziness AUTO = new Fuzziness("AUTO");
static final int DEFAULT_LOW_DISTANCE = 3;
static final int DEFAULT_HIGH_DISTANCE = 6;
private final String fuzziness;
private int lowDistance = DEFAULT_LOW_DISTANCE;
private int highDistance = DEFAULT_HIGH_DISTANCE;
private Fuzziness(String fuzziness) {
this.fuzziness = fuzziness;
}
/**
* Creates a {@link Fuzziness} instance from an edit distance. The value must be one of {@code [0, 1, 2]}
* Note: Using this method only makes sense if the field you are applying Fuzziness to is some sort of string.
* @throws IllegalArgumentException if the edit distance is not in [0, 1, 2]
*/
public static Fuzziness fromEdits(int edits) {
return switch (edits) {
case 0 -> Fuzziness.ZERO;
case 1 -> Fuzziness.ONE;
case 2 -> Fuzziness.TWO;
default -> throw new IllegalArgumentException("Valid edit distances are [0, 1, 2] but was [" + edits + "]");
};
}
/**
* Creates a {@link Fuzziness} instance from a String representation. This can
* either be an edit distance where the value must be one of
* {@code ["0", "1", "2"]} or "AUTO" for a fuzziness that depends on the term
* length. Using the "AUTO" fuzziness, you can optionally supply low and high
* distance arguments in the format {@code "AUTO:[low],[high]"}. See the query
* DSL documentation for more information about how these values affect the
* fuzziness value.
* Note: Using this method only makes sense if the field you
* are applying Fuzziness to is some sort of string.
*/
public static Fuzziness fromString(String fuzzinessString) {
if (Strings.isEmpty(fuzzinessString)) {
throw new IllegalArgumentException("fuzziness cannot be null or empty.");
}
String upperCase = fuzzinessString.toUpperCase(Locale.ROOT);
// check if it is one of the "AUTO" variants
if (upperCase.equals("AUTO")) {
return Fuzziness.AUTO;
} else if (upperCase.startsWith("AUTO:")) {
return parseCustomAuto(upperCase);
} else {
// should be a float or int representing a valid edit distance, otherwise throw error
try {
float parsedFloat = Float.parseFloat(upperCase);
if (parsedFloat % 1 > 0) {
throw new IllegalArgumentException("fuzziness needs to be one of 0.0, 1.0 or 2.0 but was " + parsedFloat);
}
return fromEdits((int) parsedFloat);
} catch (NumberFormatException e) {
throw new IllegalArgumentException("fuzziness cannot be [" + fuzzinessString + "].", e);
}
}
}
/**
* Read from a stream.
*/
public Fuzziness(StreamInput in) throws IOException {
fuzziness = in.readString();
if (in.readBoolean()) {
lowDistance = in.readVInt();
highDistance = in.readVInt();
}
}
@Override
public void writeTo(StreamOutput out) throws IOException {
out.writeString(fuzziness);
// we cannot serialize the low/high bounds since the other node does not know about them.
// This is a best-effort to not fail queries in case the cluster is being upgraded and users
// start using features that are not available on all nodes.
if (isAutoWithCustomValues()) {
out.writeBoolean(true);
out.writeVInt(lowDistance);
out.writeVInt(highDistance);
} else {
out.writeBoolean(false);
}
}
private static Fuzziness parseCustomAuto(final String fuzzinessString) {
assert fuzzinessString.toUpperCase(Locale.ROOT).startsWith(AUTO.asString() + ":");
String[] fuzzinessLimit = fuzzinessString.substring(AUTO.asString().length() + 1).split(",");
if (fuzzinessLimit.length == 2) {
try {
int lowerLimit = Integer.parseInt(fuzzinessLimit[0]);
int highLimit = Integer.parseInt(fuzzinessLimit[1]);
if (lowerLimit < 0 || highLimit < 0 || lowerLimit > highLimit) {
throw new ElasticsearchParseException(
"fuzziness wrongly configured [{}]. Must be 0 < lower value <= higher value.",
fuzzinessString
);
}
Fuzziness fuzziness = new Fuzziness("AUTO");
fuzziness.lowDistance = lowerLimit;
fuzziness.highDistance = highLimit;
return fuzziness;
} catch (NumberFormatException e) {
throw new ElasticsearchParseException("failed to parse [{}] as a \"auto:int,int\"", e, fuzzinessString);
}
} else {
throw new ElasticsearchParseException("failed to find low and high distance values");
}
}
public static Fuzziness parse(XContentParser parser) throws IOException {
XContentParser.Token token = parser.currentToken();
return switch (token) {
case VALUE_STRING -> fromString(parser.text());
case VALUE_NUMBER -> fromEdits(parser.intValue());
default -> throw new IllegalArgumentException("Can't parse fuzziness on token: [" + token + "]");
};
}
@Override
public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
builder.field(X_FIELD_NAME, asString());
return builder;
}
public int asDistance() {
return asDistance(null);
}
public int asDistance(String text) {
if (this.equals(AUTO) || isAutoWithCustomValues()) { // AUTO
final int len = termLen(text);
if (len < lowDistance) {
return 0;
} else if (len < highDistance) {
return 1;
} else {
return 2;
}
}
return Math.min(2, (int) asFloat());
}
public float asFloat() {
if (this.equals(AUTO) || isAutoWithCustomValues()) {
return 1f;
}
return Float.parseFloat(fuzziness);
}
private static int termLen(String text) {
return text == null ? 5 : text.codePointCount(0, text.length()); // 5 avg term length in english
}
public String asString() {
if (isAutoWithCustomValues()) {
return fuzziness + ":" + lowDistance + "," + highDistance;
}
return fuzziness;
}
private boolean isAutoWithCustomValues() {
return fuzziness.equals("AUTO") && (lowDistance != DEFAULT_LOW_DISTANCE || highDistance != DEFAULT_HIGH_DISTANCE);
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null || getClass() != obj.getClass()) {
return false;
}
Fuzziness other = (Fuzziness) obj;
return Objects.equals(fuzziness, other.fuzziness) && lowDistance == other.lowDistance && highDistance == other.highDistance;
}
@Override
public int hashCode() {
return Objects.hash(fuzziness, lowDistance, highDistance);
}
}
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