List Converter — C# source

// List Converter — split/trim/dedup/sort/join between separators — C# (.NET 8) port of the list-converter tool.

using System;
using System.Linq;

namespace CosmoDev.ListConverter;

public static class ListConverter
{
    // Resolve a TS-style separator name to its glue; unknown names pass
    // through as a literal separator (the TS resolveSep behavior).
    static string ResolveSep(string? name, string fallback) => name switch
    {
        "newline" => "\n",
        "comma" => ",",
        "space" => " ",
        "pipe" => "|",
        "semicolon" => ";",
        "tab" => "\t",
        null => fallback,
        _ => name,
    };

    // Options mirror the TS ListOptions; defaults are from=newline, to=comma.
    public sealed record Options
    {
        public string? From { get; init; } = "newline";
        public string? To { get; init; } = "comma";
        public bool Trim { get; init; }
        public bool RemoveEmpty { get; init; }
        public bool Unique { get; init; }
        public bool Sort { get; init; }
        public bool CaseInsensitive { get; init; }
    }

    // Convert a list between separators: split -> (trim) -> (drop empties) ->
    // (dedup, first occurrence wins) -> (stable sort) -> join. Mirrors the Go twin.
    public static string Convert(string input, Options? options = null)
    {
        var o = options ?? new Options();
        var items = input.Split(ResolveSep(o.From, "\n"));
        string to = ResolveSep(o.To, ",");

        if (o.Trim) items = items.Select(s => s.Trim()).ToArray();
        if (o.RemoveEmpty) items = items.Where(s => s.Length != 0).ToArray();
        if (o.Unique) // GroupBy yields groups in first-seen order; First()
            // keeps the first occurrence's original casing.
            items = items
                .GroupBy(s => o.CaseInsensitive ? s.ToLowerInvariant() : s)
                .Select(g => g.First())
                .ToArray();
        if (o.Sort) // OrderBy is documented stable; the key lowercases only
            // for comparison, leaving the stored values untouched.
            items = items
                .OrderBy(s => o.CaseInsensitive ? s.ToLowerInvariant() : s,
                         StringComparer.Ordinal)
                .ToArray();
        return string.Join(to, items);
    }

    public static void Main()
    {
        // "b\n a \nB\na\n\nc" -> trim, drop empties, case-insensitive dedup+sort
        var o = new Options
        {
            Trim = true,
            RemoveEmpty = true,
            Unique = true,
            Sort = true,
            CaseInsensitive = true,
        };
        Console.WriteLine(Convert("b\n a \nB\na\n\nc", o)); // a,b,c
    }
}