(ns pixie.async

(:require [pixie.stacklets :as st]))

(deftype Promise [val pending-callbacks delivered?]

IDeref

(-deref [self]

(if delivered?

val

(do

(st/call-cc (fn [k]

(swap! pending-callbacks conj

(fn [v]

(st/-run-later (partial st/run-and-process k v)))))))))

IFn

(-invoke [self v]

(assert (not delivered?) "Can only deliver a promise once")

(set-field! self :val v)

(set-field! self :delivered? true)

(doseq [f @pending-callbacks]

(f v))

(reset! pending-callbacks nil)

nil))

(defn promise []

(->Promise nil (atom []) false))

(defmacro future [& body]

`(let [p# (promise)]

(st/spawn (p# (do ~@body)))

p#))