(ns ird.async
  "Macro half of ird.async: `<?` and `go-try`. Loaded automatically when a
  ClojureScript namespace requires ird.async (it self-requires this file), so
  consumers write (:require [ird.async :refer [<? go-try]]).")

(defmacro <?
  "Take from CH inside a go block. When the delivered value is an error
  (any js/Error, including ExceptionInfo) it is thrown right there instead
  of being returned — turning ird's error-as-value channels back into
  ordinary try/catch flow."
  [ch]
  `(ird.async/throw-err (cljs.core.async/<! ~ch)))

(defmacro go-try
  "A go block whose body may throw: the exception is delivered on the
  returned channel as a value instead of escaping (an exception escaping a
  plain go block closes its channel and surfaces as an uncaught Node
  exception). Returns a promise-chan, so the single result can be taken any
  number of times; a nil result closes the channel."
  [& body]
  `(let [out# (cljs.core.async/promise-chan)]
     (cljs.core.async/go
       (let [v# (try ~@body (catch :default e# e#))]
         (if (nil? v#)
           (cljs.core.async/close! out#)
           (cljs.core.async/put! out# v#))))
     out#))