split text by limit in bytes

splitter.fsx

open System
open System.Globalization

type ISplitter =
    abstract member Split: string -> int -> string[]

type Splitter () =
    let folder (lim:int) (acc:string list)  (el:string) =
        match acc with
        | head::tail -> 
            match head.Length+el.Length>lim/2 with
            | true -> 
                el::acc
            | false -> 
                let newHead = head+el
                newHead::tail
        | _ -> [|el|] |> Array.toList


    interface ISplitter with
        member this.Split str len =
            let limitedFolder = folder len
            let strEnum = StringInfo.GetTextElementEnumerator str
            seq { while strEnum.MoveNext() do yield strEnum.GetTextElement() }
            |> Seq.fold limitedFolder list.Empty |> Seq.rev |> Seq.toArray