shellSplit.swift

import Foundation

extension String {
    func quotedSplit(separator: String = " ", quote: String = "\"") -> [String] {
        let escapedQuote = "\\\(quote)"

        var parts: [String] = []

        var quotedPart: String? = nil

        for part in self.componentsSeparatedByString(separator) {
            var part = part

            if let quoted = quotedPart {
                var ending = false
                if part.hasSuffix(quote) && !part.hasSuffix(escapedQuote) {
                    part = part.substringToIndex(part.endIndex.predecessor())
                    ending = true
                }
                
                part = part.stringByReplacingOccurrencesOfString(escapedQuote, withString: quote)
                let newPart = "\(quoted) \(part)"
                
                if ending {
                    parts.append(newPart)
                    quotedPart = nil
                } else {
                    quotedPart = newPart
                }
            }
            else if part.hasPrefix(quote) {
                quotedPart = part.substringFromIndex(part.startIndex.successor())
                                 .stringByReplacingOccurrencesOfString(escapedQuote, withString: quote)
            }
            else {
                parts.append(part)
            }
        }

        return parts
    }
}

extension SequenceType where Generator.Element == String {
    func quotedJoin(separator: String = " ", quote: String = "\"") -> String {
        let escapedQuote = "\\\(quote)"

        return self.map { element in
            let element = element.stringByReplacingOccurrencesOfString(quote, withString: escapedQuote)

            if element.rangeOfString(separator) != nil {
                return "\(quote)\(element)\(quote)"
            } else {
                return element
            }
        }.joinWithSeparator(separator)
    }
}

// let tagList = "WRLD \"NEST \\\"HQ\\\" MiniMix\" \"NEST HQ\""

// tagList.quotedSplit().forEach { print($0) }
// 
let tags = ["WRLD", "NEST \"HQ\" MiniMix", "NEST HQ"]

print(tags.quotedJoin())