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/*
This source file is part of the Swift.org open source project
Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
Licensed under Apache License v2.0 with Runtime Library Exception
See http://swift.org/LICENSE.txt for license information
See http://swift.org/CONTRIBUTORS.txt for Swift project authors
*/
/// Computes the number of edits needed to transform source string to target.
///
/// - Complexity: O(_n*m_), where *n* is the length of the source String and
/// *m* is the length of the target one.
public func editDistance(_ source: String, _ target: String) -> Int {
// FIXME: We should use the new `CollectionDifference` API once the
// deployment target is bumped.
if #available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *) {
return collectionDiffEditDistance(source, target)
}
else {
return internalEditDistance(source, target)
}
}
@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
func collectionDiffEditDistance(_ source: String, _ target: String) -> Int {
let difference = target.difference(from: source)
return max(difference.insertions.count, difference.removals.count)
}
func internalEditDistance(_ first: String, _ second: String) -> Int {
let a = Array(first.utf16)
let b = Array(second.utf16)
var distance = [[Int]](repeating: [Int](repeating: 0, count: b.count + 1), count: a.count + 1)
for i in 0...a.count {
for j in 0...b.count {
if i == 0 {
distance[i][j] = j
} else if j == 0 {
distance[i][j] = i
} else if a[i - 1] == b[j - 1] {
distance[i][j] = distance[i - 1][j - 1]
} else {
let insertion = distance[i][ j - 1]
let deletion = distance[i - 1][j]
let replacement = distance[i - 1][j - 1]
distance[i][j] = 1 + min(insertion, deletion, replacement)
}
}
}
return distance[a.count][b.count]
}
/// Finds the "best" match for a `String` from an array of possible options.
///
/// - Parameters:
/// - input: The input `String` to match.
/// - options: The available options for `input`.
///
/// - Returns: The best match from the given `options`, or `nil` if none were sufficiently close.
public func bestMatch(for input: String, from options: [String]) -> String? {
return options
.map { ($0, editDistance(input, $0)) }
// Filter out unreasonable edit distances. Based on:
// https://github.com/apple/swift/blob/37daa03b7dc8fb3c4d91dc560a9e0e631c980326/lib/Sema/TypeCheckNameLookup.cpp#L606
.filter { $0.1 <= ($0.0.count + 2) / 3 }
// Sort by edit distance
.sorted { $0.1 < $1.1 }
.first?.0
}
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