List Converter — Kotlin source

// List Converter — split/trim/dedup/sort/join between separators — Kotlin port of the list-converter tool.

object ListConverter {

    /** Options mirror the TS ListOptions; defaults are from=newline, to=comma. */
    data class Options(
        val from: String = "newline",
        val to: String = "comma",
        val trim: Boolean = false,
        val removeEmpty: Boolean = false,
        val unique: Boolean = false,
        val sort: Boolean = false,
        val caseInsensitive: Boolean = false,
    )

    /** Resolve a TS-style separator name to its glue; unknown names pass
     *  through as a literal separator (the TS resolveSep behavior). */
    fun resolveSep(name: String): String = when (name) {
        "newline" -> "\n"
        "comma" -> ","
        "space" -> " "
        "pipe" -> "|"
        "semicolon" -> ";"
        "tab" -> "\t"
        else -> name
    }

    /** Convert a list between separators: split -> (trim) -> (drop empties) ->
     *  (dedup, first occurrence wins) -> (stable sort) -> join. Mirrors the Go twin. */
    fun convert(input: String, options: Options = Options()): String {
        val o = options
        // String.split keeps trailing empties, matching Go's strings.Split.
        var items = input.split(resolveSep(o.from))
        val to = resolveSep(o.to)

        if (o.trim) items = items.map { it.trim() }
        if (o.removeEmpty) items = items.filter { it.isNotEmpty() }
        if (o.unique) { // the set holds keys only; items keep their casing
            val seen = LinkedHashSet<String>()
            items = items.filter { seen.add(if (o.caseInsensitive) it.lowercase() else it) }
        }
        if (o.sort) { // sortedWith is documented stable; the key lowercases
            // only for comparison, leaving the stored values untouched.
            items = items.sortedWith(
                compareBy { if (o.caseInsensitive) it.lowercase() else it }
            )
        }
        return items.joinToString(to)
    }
}

fun main() {
    // "b\n a \nB\na\n\nc" -> trim, drop empties, case-insensitive dedup+sort
    val o = ListConverter.Options(
        trim = true, removeEmpty = true, unique = true,
        sort = true, caseInsensitive = true,
    )
    println(ListConverter.convert("b\n a \nB\na\n\nc", o)) // a,b,c
}