let cts = new CancellationTokenSource()

let inline decode<'a> x = x |> unbox<string> |> JsonConvert.DeserializeObject<'a>
let buildWsSender (ws:WebSocket) : WsSender =
    fun (message:WebSocketClientMessage) ->
        let message = {| Topic = ""; Ref = ""; Payload = message |}
        let message = JsonConvert.SerializeObject(message)
        let byteMessage = System.Text.Encoding.UTF8.GetBytes(message)
        let segmnet = new ArraySegment<byte>(byteMessage)

        ws.SendAsync(segmnet, WebSocketMessageType.Text, true, cts.Token).Wait()

let subscription f _ =
    let sub dispatch =
        let cts = new CancellationTokenSource()
        let mutable ws = new ClientWebSocket()

        /// Continually tries to connect to the server websocket.
        let connect () =
            Task.Factory.StartNew(fun () ->
                while true do
                    try
                        if ws.State <> WebSocketState.Open
                        then ws.ConnectAsync(new Uri("ws://10.0.1.3:8085"), cts.Token).Wait()
                             dispatch (f (ConnectionChange (ConnectedToServer (buildWsSender ws))))

                        let message = new ArraySegment<byte>(Array.zeroCreate 4096)
                        let mutable foo = true
                        while foo do
                            let result = ws.ReceiveAsync(message, cts.Token).Result
                            let messageBytes = message.Skip(message.Offset).Take(result.Count).ToArray()
                            let serialisedMessage = System.Text.Encoding.UTF8.GetString(messageBytes)
                            try
                                let msg = decode<WebSocketServerMessage>(serialisedMessage)
                                dispatch (f (ReceivedFromServer msg))
                                foo <- false
                            with | e -> 
                                dispatch (f (ConnectionError e))
                                Thread.Sleep 5000
                    with e -> dispatch (f (ConnectionError e))
                              ws.Dispose()
                              Console.WriteLine e.StackTrace
                              ws <- new ClientWebSocket()
                              Thread.Sleep 5000
            ,cts.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default).Start()
        connect()

    Cmd.ofSub sub