Command line argument parsing function

main.swift

import Foundation

extension Array where Array.Element == String {
    func parseKeyValue(prefix: String = "--", suffix: String = "", valueSeparator: String = "=", removePrefix: Bool = true, removeSuffix: Bool = true, separateArguments: Bool = true, endIndicator: String = "--") -> Dictionary<String, String> {
        var unlabeled = [String]()
        return parseKeyValue(prefix: prefix, suffix: suffix, valueSeparator: valueSeparator, removePrefix: removePrefix, removeSuffix: removeSuffix, separateArguments: separateArguments, endIndicator: endIndicator, unlabeled: &unlabeled)
    }
    
    func parseKeyValue(prefix: String = "--", suffix: String = "", valueSeparator: String = "=", removePrefix: Bool = true, removeSuffix: Bool = true, separateArguments: Bool = true, endIndicator: String = "--", unlabeled: inout [String]) -> Dictionary<String, String> {
		var result = Dictionary<String, String>()
		var i = startIndex
		while i < count {
			var arg = self[i]
            if !endIndicator.isEmpty && arg == endIndicator {
                i += 1
                unlabeled.append(contentsOf: self[i ..< count])
                break
            }
			i += 1
			let key: String
			let value: String?
			var isArg = true
			if !prefix.isEmpty && !arg.hasPrefix(prefix) {
				isArg = false
			}
			if !suffix.isEmpty && !arg.hasSuffix(suffix) {
				isArg = false
			}
            if isArg {
                if removePrefix {
                    arg.removeFirst(prefix.count)
                }
                if removeSuffix {
                    arg.removeLast(suffix.count)
                }
            }
            
			if !isArg {
                unlabeled.append(arg)
			} else if !valueSeparator.isEmpty {
                let parts = arg.split(separator: valueSeparator.first!, maxSplits: 1, omittingEmptySubsequences: false)
				if parts.count > 1 {
					key = String(parts[0])
					value = String(parts[1])
                } else {
					key = arg
                    let possibleParam = (i < count) ? self[i] : ""
                    if separateArguments && (i < count) && (prefix.isEmpty || !possibleParam.hasPrefix(prefix)) {
						value = possibleParam
                        i += 1
					} else {
						value = ""
					}
				}
				result[key] = value
			} else {
				key = arg
                let possibleParam = (i < count) ? self[i] : ""
                if separateArguments && (i < count) && (prefix.isEmpty || !possibleParam.hasPrefix(prefix)) {
					value = possibleParam
                    i += 1
				} else {
					value = ""
				}
				result[key] = value
			}
		}
		return result
	}
}

print(CommandLine.arguments.parseKeyValue())
print("\(["--flag", "--key", "value", "--key2=value", "--flag2", "george"].parseKeyValue()) - [\"flag\": \"\", \"key\": \"value\", \"key2\": \"value\", \"flag2\": \"george\"]")
print("\(["--flag", "--key", "value", "--key2=value", "--flag2", "--george"].parseKeyValue()) - [\"flag\": \"\", \"key\": \"value\", \"key2\": \"value\", \"flag2\": \"\", \"george\": \"\"]")
var unlabeled = [String]()
print("\(["file.txt", "--flag", "--foo=bar=baz", "heyooo!", "--", "--notParam"].parseKeyValue(unlabeled: &unlabeled)) • \(unlabeled) - [\"flag\": \"\", \"foo\": \"bar=baz\"] • [\"file.txt\", \"heyooo!\", \"--notParam\"]")