module Logic

open System.Collections
open System.Threading

    type Blocking_Queue () =
        let mutable local_queue = Queue()

        let resetEvent = new AutoResetEvent(true)

        member this.add element =
            lock this (fun () -> if (Interlocked.CompareExchange(ref local_queue.Count, 0, 0) = 0)
                                 then resetEvent.Set() |> ignore
                                 local_queue.Enqueue(element))

        member this.getFirstElement =
            if (Interlocked.CompareExchange(ref local_queue.Count, 0, 0) = 0)
                then resetEvent.WaitOne() |> ignore
                     local_queue.Dequeue()
            else lock this (fun () -> local_queue.Dequeue())

        member this.getSize =
            lock this (fun () -> local_queue.Count)

        member this.firstElement =
            lock this (fun () -> local_queue.Peek)