foami.clj

(ns foami.core
  "FOreign Asynchronous Mechanism Interop"
  (:require [clojure.core.async :as async]))

(defn put! 
  "Takes a `ch`, a `msg`, a single arg function that when passed `true` enables backpressure
   and when passed `false` disables it, and a no-arg function which, when invoked, closes the
   upstream source."
  [ch msg backpressure! close!]
  (let [status (atom :sending]
    (async/put! ch msg
      (fn [result]
        (if-not result
          (close!)
          (cond 
            (compare-and-set! status :sending :sent)
            nil
            
            (compare-and-set! status :paused  :sent) 
            (backpressure! false)))))
    (when (compare-and-set! status :sending :paused)
      (backpressure! true))
    nil))