simple regex

Regex.swift

import Foundation

/// See also
// http://qiita.com/tsuruchika/items/9ca9c4811e1f28b9417c
// http://qiita.com/moaible/items/85d80173bb8ed7f64b74
// http://fromatom.hatenablog.com/entry/2015/07/15/192328

public struct Regex {

    private let pattern: String

    private let internalExpression: NSRegularExpression

    public init(_ pattern: String) {
        self.pattern = pattern
        do {
            self.internalExpression = try NSRegularExpression(pattern: pattern, options: [.CaseInsensitive])
        } catch let error as NSError {
            print(error.localizedDescription)
            self.internalExpression = NSRegularExpression()
        }
    }

    public func isMatch(input: String) -> Bool {
        let matches = internalExpression.matchesInString(input, options: [], range: NSRange(location: 0, length: input.characters.count))
        return matches.count > 0
    }

    public func matches(input: String) -> [String]? {
        guard isMatch(input) else { return nil }

        let matches = internalExpression.matchesInString(input, options: [], range: NSRange(location: 0, length: input.characters.count))
        return (0..<matches.count).reduce([]) { (acc: [String], n: Int) -> [String] in
            acc + [(input as NSString).substringWithRange(matches[n].range)]
        }
    }

    public func replace(input: String, after: String) -> String {
        guard let matches = matches(input) else { return input }

        return (0..<matches.count).reduce(input) { (acc: String, n: Int) -> String in
            acc.stringByReplacingOccurrencesOfString(matches[n], withString: after, options: [], range: nil)
        }
    }
}

infix operator =~ {}

public func =~ (input: String, pattern: String) -> Bool {
    return Regex(pattern).isMatch(input)
}