Kotlin: Parsing of enum-based application linux-like arguments (--name[=value])

OptionsParsingUtils.kt

object OptionsParsingUtils {

   private inline fun <reified T : OptionEnum> tryParseEnumOption(enumArgumentDefault: T, arg: String): T? {
        val optionIntro = "--${enumArgumentDefault.optionName}"

        if (!arg.startsWith(optionIntro))
            return null

        if (arg.endsWith(optionIntro) || arg.endsWith("=${enumArgumentDefault.optionValue}"))
            return enumArgumentDefault

        val valueStr = arg.substringAfter(optionIntro)

        val enumConstants = T::class.java.enumConstants
        return enumConstants.firstOrNull { it.optionName == valueStr }
            ?: throw IllegalArgumentException("Unknown value for ${enumArgumentDefault.optionName}: $arg Try one of ${enumConstants.map { it.optionValue }}")
    }
}

usage.kt

fun main(args: List<String>) {
    for (arg in args) {
        
        // Tries to match an option starting "--sortInputPaths", 
        // matching the enum value after, or PARAMS_ORDER as default if no value after "=".
        
        val order = tryParseEnumOption(SortInputPaths.PARAMS_ORDER, arg)
        val combine = tryParseEnumOption(CombineInputFiles.CONCAT, arg)
        
    }
    
    // If you have many options, the enums could be put to a list and tried in another loop:
    
    val optionEnums = listOf<OptionEnum>(SortInputPaths.PARAMS_ORDER, CombineInputFiles.CONCAT, ...)
    val appOptions = Map<Class<OptionEnum>, OptionEnum>>
    
    for (arg in args)
       for (enumDefault in optionEnums) {
           val choice = tryParseEnumOption(enumDefault, arg)
           if (choice != null)
               appOptions[enumDefault.javaClass] = choice
           
       }
    }
}

enum class SortInputPaths(override val optionValue: String) : OptionEnum {
    PARAMS_ORDER("paramOrder"),
    ALPHA("alpha"),
    TIME("time");

    // A little trick: The name is defined on all members, not on the class.
    override val optionName: String by lazy { "sortInputPaths" }
}

interface OptionEnum {
    val optionName: String
    val optionValue: String?
}