63 lines
2.2 KiB
Swift
63 lines
2.2 KiB
Swift
//
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// FuzzyMatcher.swift
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// TuskerComponents
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//
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// Created by Shadowfacts on 10/10/20.
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// Copyright © 2020 Shadowfacts. All rights reserved.
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//
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import Foundation
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public struct FuzzyMatcher {
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private init() {}
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/// Rudimentary string fuzzy matching algorithm.
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///
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/// Operates on UTF-8 code points, so attempting to match strings which include characters composed of
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/// multiple code points may produce unexpected results.
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///
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/// Scoring is as follows:
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/// +2 points for every char in `pattern` that occurs in `str` sequentially
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/// -2 points for every char in `pattern` that does not occur in `str` sequentially
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/// -1 point for every char in `str` skipped between matching chars from the `pattern`
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public static func match(pattern: String, str: String) -> (matched: Bool, score: Int) {
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let pattern = pattern.lowercased()
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let str = str.lowercased()
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var patternIndex = pattern.utf8.startIndex
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var lastStrMatchIndex: String.UTF8View.Index?
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var strIndex = str.utf8.startIndex
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var score = 0
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while patternIndex < pattern.utf8.endIndex && strIndex < str.utf8.endIndex {
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let patternChar = pattern.utf8[patternIndex]
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let strChar = str.utf8[strIndex]
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if patternChar == strChar {
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let distance = str.utf8.distance(from: lastStrMatchIndex ?? str.utf8.startIndex, to: strIndex)
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if distance > 1 {
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score -= distance - 1
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}
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patternIndex = pattern.utf8.index(after: patternIndex)
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lastStrMatchIndex = strIndex
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strIndex = str.utf8.index(after: strIndex)
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score += 2
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} else {
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strIndex = str.utf8.index(after: strIndex)
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if strIndex >= str.utf8.endIndex {
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patternIndex = pattern.utf8.index(after: patternIndex)
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strIndex = str.utf8.index(after: lastStrMatchIndex ?? str.utf8.startIndex)
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score -= 2
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}
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}
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}
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return (score > 0, score)
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}
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}
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