Porting bacon.js

baconrod.nim

type
  TBaconRet* = enum
    BaconMore,
    BaconEnd

  TBaconEventType* = enum
    BaconEventNext,
    BaconEventEnd,
    BaconEventError,
    BaconEventInitial

  TBaconEvent*[T] = object
    case kind: tbaconeventtype
    of BaconEventNext, BaconEventInitial:
      value: T
    of BaconEventEnd:
      nil
    of BaconEventError:
      error: string

  TValueProc*[T] = proc(value: T): TBaconRet {.nimcall.}
  TEventProc*[T] = proc(value: TBaconEvent[T]): TBaconRet {.nimcall.}

  TBaconPusher[T] = object
    pushTo: seq[TValueProc[T]]
    subs: seq[TEventProc[T]]

  TEventStream*[T] = object
    pusher: TBaconPusher[T]
    values: seq[T]

proc initialEvent*[T](value: T): TBaconEvent[T] =
  return TBaconEvent[T](kind: BaconEventInitial, value: value)
proc nextEvent*[T](value: T): TBaconEvent[T] =
  return TBaconEvent[T](kind: BaconEventNext, value: value)
proc endEvent*[T](): TBaconEvent[T] =
  return TBaconEvent[T](kind: BaconEventEnd)
proc errorEvent*[T](error: string): TBaconEvent[T] =
  return TBaconEvent[T](kind: BaconEventError, error: error)

proc isNext*(e: TBaconEvent): bool =
  result = e.kind == BaconEventNext
proc isInitial*(e: TBaconEvent): bool =
  result = e.kind == BaconEventInitial
proc isError*(e: TBaconEvent): bool =
  result = e.kind == BaconEventError
proc isEnd*(e: TBaconEvent): bool =
  result = e.kind == BaconEventEnd

proc push[T](pusher: TBaconPusher, value: T) =
  for f in pusher.pushTo:
    discard f(value)
  for f in pusher.subs:
    discard f(nextEvent[T](value))

proc drain[T](stream: var TEventStream[T]) =
  for v in stream.values:
    #stream.pusher.push(v)
    push(stream.pusher, v)
  stream.values = @[]

proc fromSeq*[T](values: seq[T]): TEventStream[T] =
  TEventStream[T](pusher: TBaconPusher[T](pushTo: @[], subs: @[]), values: values)

proc onValue*[T](stream: var TEventStream[T], f: TValueProc[T]) =
  stream.pusher.pushTo.add(f)
  stream.drain()

when isMainModule:
  let nextTest = nextEvent[int](10)
  echo($nextTest)
  if not nextTest.isNext:
    echo("nextTest: does not detect next correctly")
  elif nextTest.value != 10:
    echo("nextTest: did not store value correctly")
  else:
    echo("nextTest: ran correctly")

  let endTest = endEvent[int]()
  echo($endTest)

  let fromSeqTest = fromSeq[int](@[1, 2, 3])
  #fromSeqTest.onValue(proc(val: int): TBaconEvent =
  onValue[int](fromSeqTest, proc(val: int): TBaconEvent =
    echo("onValue: ", $val)
    return BaconMore)