sirh3e/Rust

namespace Sirh3e.Rust.Result;

public static partial class ResultExtension
{
    /// <summary>
    /// Transposes a Result of an Option into an Option of a Result.
    /// Ok(None) will be mapped to None. Ok(Some(_)) and Err(_) will be mapped to Some(Ok(_)) and Some(Err(_)). 
    /// </summary>
    /// <param name="result"></param>
    /// <typeparam name="TOk"></typeparam>
    /// <typeparam name="TErr"></typeparam>
    /// <returns></returns>
    public static Option<Result<TOk, TErr>> Transpose<TOk, TErr>(this Result<Option<TOk>, TErr> result)
        => result.Match(ok =>
                        {
                            return ok.Match(
                                            some => Option<Result<TOk, TErr>>.Some(Ok(some)),
                                            () => Option<Result<TOk, TErr>>.None
                                           );
                        },
                        err => Option<Result<TOk, TErr>>.Some(Result<TOk, TErr>.Err(err)));
}