irealpro_unobfuscate.swift

// Unobfuscate the iRealPro data format
//
// information and test data taken from:
//   https://github.com/ironss/accompaniser/blob/master/irealb_parser.lua
//   https://github.com/ironss/accompaniser/blob/59fd4cfb45447ac77ae7cc2bfca2e25bc9ce218d/test/test_irealb_parser.lua

// ********

import Darwin

func flatten<T>(a: [[T]]) -> [T] {
    return reduce(a, [] as [T]) { $0 + $1 }
}

func partition<S: SequenceType>(seq: S, count: Int, partial: Bool = false) -> SequenceOf<[S.Generator.Element]> {
    typealias ResultType = [S.Generator.Element]
    return SequenceOf { ()->GeneratorOf<ResultType> in
        var generator = seq.generate()
        let range = 0..<count
        return GeneratorOf {
            var result: ResultType = []
            for _ in range {
                let elem = generator.next()
                if let elem = elem {
                    result.append(elem)
                } else {
                    return partial && result.count > 0 ? result : nil
                }
            }
            return result
        }
    }
}

// ********

func obfusc50(a: [Character]) -> [Character] {
    let slices = [
        a[45...49].reverse(),
        a[5...9],
        a[26...39].reverse(),
        a[24...25],
        a[10...23].reverse(),
        a[40...44],
        a[0...4].reverse()
    ]
    return flatten( slices.map { Array($0) })
}

func obfusc(s: String) -> String {
    let p1 = map(partition(s, 50, partial: true)) { Array($0) }
    
    let p2 = dropFirst(p1.map { $0.count > 1 } + [false])
    
    return join("", map(Zip2(p1,p2)) { (a: [Character], obfuscated: Bool) in String( obfuscated ? obfusc50(a) : a) })
}

func unobfusc(s: String) -> String {
    return obfusc(s)
}

// ********

func unobfusc(# test: String, # tune: String, # expected: String) {
    if unobfusc(tune) != expected {
        println("unobfusc fail \(test)")
    }
    if obfusc(expected) != tune {
        println("obfusc fail \(test)")
    }
}

unobfusc(test:"50", tune: "[T44A BLZC DLZE FLZG, ALZA BLZC DLZE FLZG ALZA B | ", expected: "[T44A BLZC DLZE FLZG, ALZA BLZC DLZE FLZG ALZA B | ")

unobfusc(test:"51", tune:"| B A BLZCZLF EZLD CZLB ZALA ,GZLF EZLD G ALZA44T[C ", expected: "[T44A BLZC DLZE FLZG, ALZA BLZC DLZE FLZG ALZA B |C ")

unobfusc(test:"100", tune: "ZLB A BLZCZLF EZLD CZLB ZALA ,GZLF EZLD G ALZA44T[C- DLZE FLZG A,LZA BLZC DLZE FLZG ALZA BLZC- D |E ", expected: "[T44A BLZC DLZE FLZG, ALZA BLZC DLZE FLZG ALZA BLZC- DLZE FLZG A,LZA BLZC DLZE FLZG ALZA BLZC- D |E ")

unobfusc(test:"101", tune: "ZLB A BLZCZLF EZLD CZLB ZALA ,GZLF EZLD G ALZA44T[ EZLDZE FLB AZLA GZLF EZDL CZLB AZL,A GZLZC- LD -CF ", expected: "[T44A BLZC DLZE FLZG, ALZA BLZC DLZE FLZG ALZA BLZC- DLZE FLZG A,LZA BLZC DLZE FLZG ALZA BLZC- DLZE F ")