import Foundation

struct Regex {
    let pattern: String
}

protocol Matchable : StringProtocol {
    var regex: Regex { get }
    func matches(regex: Regex, options: NSRegularExpression.Options) -> [String]
    func captureGroups(regex: Regex, options: NSRegularExpression.Options) -> [String]
}

extension Matchable {
     var regex: Regex { return  Regex(pattern: String(self)) }
}

extension String: Matchable {

    func capturedGroups(regex: Regex, options: NSRegularExpression.Options = []) -> [String] {
        return Array(matches(regex: regex, options: options)[1...])
    }

    func matches(regex: Regex, options: NSRegularExpression.Options = []) -> [String] {
        guard let match = (try? NSRegularExpression(pattern: regex.pattern, options: options))?.firstMatch(in: self, options: [], range: NSRange(startIndex..., in: self)) else { return [] }
        return (0..<match.numberOfRanges).flatMap {
            return match.range(at: $0).location == NSNotFound ? nil : Range(match.range(at: $0), in: self).flatMap { String(self[$0]) }
        }

    }
}

"hi hello".capturedGroups(regex: "(\\w*)\\s(\\w*)".regex) // ["hi", "hello"]
"hi hello".matches(regex: "(\\w*)\\s(\\w*)".regex)        // ["hi hello", "hi", "hello"]