open System
open System.Net
open System.Text
open System.Reactive.Concurrency
open System.Reactive.Subjects
open System.Reactive.Linq
open FSharp.Control.Reactive

let makeObservableListener url =
    let listener = new HttpListener()
    listener.Prefixes.Add url
    listener.Start()
    let makeObservable =
        Observable.FromAsync(listener.GetContextAsync)
        |> Observable.repeat
        |> Observable.retry
        |> Observable.publish
        |> Observable.refCount
    (listener, makeObservable)

let handleRequest obs =
    obs
    |> Observable.filter (fun (ctx : HttpListenerContext) -> ctx.Request.Url.AbsolutePath.EndsWith("/hello"))
    |> Observable.subscribe (fun ctx ->
            let b = Encoding.UTF8.GetBytes("world")
            ctx.Response.OutputStream.Write(b, 0, b.Length)
            ctx.Response.Close())

[<EntryPoint>]
let main argv =
    let (lst, obs) = makeObservableListener "http://localhost:55555/"
    handleRequest obs |> ignore
    Console.ReadKey() |> ignore
    lst.Close()
    0