clean_arch.fs

// F# version of https://twitter.com/gsferreira/status/1516827091127394309/

open System
open System.IO

type PotentialProcessingError = StringMissing | StringTooShort

let application (str: string) =
    match str with
    | str when str.Length < 5 -> Error StringTooShort
    | str -> Ok str

let infrastructure text =
    let path = Path.Combine(Path.GetTempPath(), "my-text.txt")
    printfn $"Storing at {path}"
    File.WriteAllText(path, text)

let console () =
    printfn "What message do you want to store?"
    match Console.ReadLine() with
    | null | "" -> None
    | str -> Some str

console ()
|> Option.map application
|> Option.defaultValue (Error StringMissing)
|> Result.map infrastructure
|> printfn "Stored successfully? %A"

Actually, figured that Ctrl-Z on Windows (EOF) makes the string null, so console would return Some null...

let console () =
    printfn "What message do you want to store?"
    match Console.ReadLine() with
    | null -> None
    | "" -> None
    | str -> Some str