callbackWithFallback

callback_with_fallback.coffee

# Takes: a callback function and a fallback function
# Returns: a callback function.
# Also: sets up a timeout, so that if the callback function is not called, the fallback function will be run

callbackWithFallback = (callback, fallback, waitSeconds) ->
  waitSeconds = waitSeconds || 15

  callbackHappened = false

  robustCallback = () ->
    if callbackHappened
      console.warn "Waited so long to call "+getSimpleFunctionString(callback)+" that we called the fallback "+getSimpleFunctionString(fallback)
      return   # Don't call the callback if we've already called the fallback
    callbackHappened = true
    callback.apply(this,arguments)

  checkForFailure = () ->
    if !callbackHappened
      console.log "Callback did not happen within assigned time.  Calling fallback."
      callbackHappened = true
      fallback()

  setTimeout checkForFailure, waitSeconds*1000
  return robustCallback   # Use this immediately!

# CONSIDER: Should our scripts assume the existence of console.warn() or just
# warn()?  We can implement either of them!