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// Copyright (C) 2011 The Android Open Source Project
//
// Licensed 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
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package com.google.gerrit.server.util;

import com.google.gerrit.entities.AccessSection;
import com.google.gerrit.server.project.RefPattern;
import java.util.Comparator;
import org.apache.commons.text.similarity.LevenshteinDistance;

/**
 * Order the Ref Pattern by the most specific. This sort is done by:
 *
 * 
    *
  • 1 - The minor value of Levenshtein string distance between the branch name and the regex * string shortest example. A shorter distance is a more specific match. *
  • 2 - Finites first, infinities after. *
  • 3 - Number of transitions. More transitions is more specific. *
  • 4 - Length of the expression text. *
* * Levenshtein distance is a measure of the similarity between two strings. The distance is the * number of deletions, insertions, or substitutions required to transform one string into another. * *

For example, if given refs/heads/m* and refs/heads/*, the distances are 5 and 6. It means that * refs/heads/m* is more specific because it's closer to refs/heads/master than refs/heads/*. * *

Another example could be refs/heads/* and refs/heads/[a-zA-Z]*, the distances are both 6. Both * are infinite, but refs/heads/[a-zA-Z]* has more transitions, which after all turns it more * specific. */ public final class MostSpecificComparator implements Comparator { private final String refName; public MostSpecificComparator(String refName) { this.refName = refName; } @Override public int compare(AccessSection a, AccessSection b) { return compare(a.getName(), b.getName()); } public int compare(String pattern1, String pattern2) { int cmp = distance(pattern1) - distance(pattern2); if (cmp == 0) { boolean p1_finite = finite(pattern1); boolean p2_finite = finite(pattern2); if (p1_finite && !p2_finite) { cmp = -1; } else if (!p1_finite && p2_finite) { cmp = 1; } else /* if (f1 == f2) */ { cmp = 0; } } if (cmp == 0) { cmp = transitions(pattern2) - transitions(pattern1); } if (cmp == 0) { cmp = pattern2.length() - pattern1.length(); } return cmp; } private int distance(String pattern) { String example; if (RefPattern.isRE(pattern)) { example = RefPattern.shortestExample(pattern); } else if (pattern.endsWith("/*")) { example = pattern; } else if (pattern.equals(refName)) { return 0; } else { return Math.max(pattern.length(), refName.length()); } return LevenshteinDistance.getDefaultInstance().apply(example, refName); } private boolean finite(String pattern) { if (RefPattern.isRE(pattern)) { return RefPattern.toRegExp(pattern).toAutomaton().isFinite(); } else if (pattern.endsWith("/*")) { return false; } else { return true; } } private int transitions(String pattern) { if (RefPattern.isRE(pattern)) { return RefPattern.toRegExp(pattern).toAutomaton().getNumberOfTransitions(); } else if (pattern.endsWith("/*")) { return pattern.length(); } else { return pattern.length(); } } }





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