import Foundation

func main() {
    // This tests whether a pattern matches a string.
    let match = try! NSRegularExpression(pattern: "p([a-z]+)ch").firstMatch(in: "peach", range: NSRange(location: 0, length: 5)) != nil
    print(match)

    // For other regex tasks, you'll need to create a NSRegularExpression object.
    let regex = try! NSRegularExpression(pattern: "p([a-z]+)ch")

    // Many methods are available on these objects. Here's a match test like we saw earlier.
    print(regex.firstMatch(in: "peach", range: NSRange(location: 0, length: 5)) != nil)

    // This finds the match for the regex.
    if let match = regex.firstMatch(in: "peach punch", range: NSRange(location: 0, length: 11)) {
        print(NSString(string: "peach punch").substring(with: match.range))
    }

    // This also finds the first match but returns the start and end indexes for the match instead of the matching text.
    if let match = regex.firstMatch(in: "peach punch", range: NSRange(location: 0, length: 11)) {
        print("idx:", match.range)
    }

    // The 'Submatch' variants include information about both the whole-pattern matches and the submatches within those matches.
    if let match = regex.firstMatch(in: "peach punch", range: NSRange(location: 0, length: 11)) {
        let wholeMatch = NSString(string: "peach punch").substring(with: match.range)
        let subMatch = NSString(string: "peach punch").substring(with: match.range(at: 1))
        print([wholeMatch, subMatch])
    }

    // To find all matches for a regex
    let matches = regex.matches(in: "peach punch pinch", range: NSRange(location: 0, length: 17))
    print(matches.map { NSString(string: "peach punch pinch").substring(with: $0.range) })

    // Providing a limit to the number of matches
    let limitedMatches = regex.matches(in: "peach punch pinch", range: NSRange(location: 0, length: 17), options: [], range: NSRange(location: 0, length: 17))
    print(limitedMatches.prefix(2).map { NSString(string: "peach punch pinch").substring(with: $0.range) })

    // We can also use Data instead of String
    if let match = regex.firstMatch(in: String(data: "peach".data(using: .utf8)!, encoding: .utf8)!, range: NSRange(location: 0, length: 5)) {
        print(match.range.length > 0)
    }

    // When creating global variables with regular expressions, you can use the try! variant of initialization.
    let globalRegex = try! NSRegularExpression(pattern: "p([a-z]+)ch")
    print("regex:", globalRegex.pattern)

    // The NSRegularExpression can also be used to replace subsets of strings with other values.
    let modifiedString = regex.stringByReplacingMatches(in: "a peach", range: NSRange(location: 0, length: 7), withTemplate: "<fruit>")
    print(modifiedString)

    // The 'enumerateMatches' method allows you to transform matched text with a given closure.
    var result = "a peach"
    regex.enumerateMatches(in: result, range: NSRange(location: 0, length: result.count)) { (match, _, _) in
        if let match = match {
            let range = Range(match.range, in: result)!
            result = result.replacingCharacters(in: range, with: result[range].uppercased())
        }
    }
    print(result)
}

main()