//
//  Roman.swift
//  RegexInSwift : use regex to parse a string with a Roman number and returns its decimal value
//
//  Created by Guy Lapalme on 2024-07-26.
//

let romanRE = #/
    (M{1,3})?                  # thousands
    (C(?:M|D|C{,2})|DC{,3})?   # hundreds
    (X(?:C|L|X{,2})|LX{,3})?   # tens
    (I(?:X|V|I{,2})|VI{,3})?   # units
/#

let romanVals = [
    "C": 100, "CC": 200, "CCC": 300, "CD": 400, "CM": 900,
    "D": 500, "DC": 600, "DCC": 700, "DCCC": 800,
    "I": 1, "II": 2, "III": 3, "IV": 4, "IX": 9,
    "L": 50, "LX": 60, "LXX": 70, "LXXX": 80,
    "M": 1000, "MM": 2000, "MMM": 3000,
    "V": 5, "VI": 6, "VII": 7, "VIII": 8,
    "X": 10, "XC": 90, "XL": 40, "XX": 20, "XXX": 30
]

func parseRomanRE(_ s:String)->Int? {
    if let m = s.wholeMatch(of: romanRE){
        var res = 0
        let out = m.output
        if out.1 != nil {res += romanVals[String(out.1!)]!}
        if out.2 != nil {res += romanVals[String(out.2!)]!}
        if out.3 != nil {res += romanVals[String(out.3!)]!}
        if out.4 != nil {res += romanVals[String(out.4!)]!}
        return res
    }
    print("Invalid Roman number:\(s)")
    return nil
}

// ////////////////////////////////////////////////
//        using a RegexBuilder
//
import RegexBuilder

func makeRB(_ i: String,_ v:String, _ x:String)->Capture<(Substring, Int)>{
    return Capture {
                ChoiceOf {
                    Regex {i ; ChoiceOf { x; v ; Repeat(...2) { i }}}
                    Regex { v; Repeat(...3) { i }}
                }
            } transform:{str in romanVals[String(str)]!}
}

let romanRB = Regex {
    Optionally {Capture { Repeat(1...3){"M"} } transform: {str in 1000*str.count}}
    Optionally {makeRB("C","D","M")}
    Optionally {makeRB("X","L","C")}
    Optionally {makeRB("I","V","X")}
}

func parseRomanRB(_ s:String)->Int? {
    if let m = s.wholeMatch(of: romanRB){
        let out = m.output
        return (out.1 ?? 0) + (out.2 ?? 0) + (out.3 ?? 0) + (out.4 ?? 0)
    }
    print("Invalid Roman number:\(s)")
    return nil
}

// a few tests, not at all exhaustive!
func runRoman(){
    print("** parseRomanRE tests")
    print(parseRomanRE("VII")!)
    print(parseRomanRE("XM") ?? 0)
    print(parseRomanRE("MMCDLXXVI")!)

    print("** parseRomanRB tests")
    print(parseRomanRB("VIII")!)
    print(parseRomanRB("DM") ?? 0)
    print(parseRomanRB("MMMDCCCLXVII")!)
}