RegexKit.swift

//
//  RegexKit.swift
//  RegexKit
//
//  Created by Charlotte Tortorella on 3/7/17.
//  Copyright © 2017 Monadic Consulting. All rights reserved.
//

import Foundation

indirect enum Regex {
    case contains(String)
    case begins(with: String)
    case ends(with: String)
    case has(CharacterSet)
    case not(Regex)
    case or(Regex, Regex)
    case xor(Regex, Regex)
    case and(Regex, Regex)
    
    func evaluate(against target: String) -> Bool {
        switch self {
        case .contains(let string):
            return target.contains(string)
        case .begins(with: let string):
            return target.hasPrefix(string)
        case .ends(with: let string):
            return target.hasSuffix(string)
        case .has(let set):
            return target.unicodeScalars.contains(where: set.contains(_:))
        case .not(let regex):
            return !regex.evaluate(against: target)
        case .or(let lhs, let rhs):
            return lhs.evaluate(against: target) || rhs.evaluate(against: target)
        case .xor(let lhs, let rhs):
            return lhs.evaluate(against: target) != rhs.evaluate(against: target)
        case .and(let lhs, let rhs):
            return lhs.evaluate(against: target) && rhs.evaluate(against: target)
        }
    }
}

extension String {
    func match(regex: Regex) -> Bool {
        return regex.evaluate(against: self)
    }
}