openClose(path: Text) (ok: Bool) {
  file = dever.io.open(path)
  alias = file
  dever.io.close(alias)
  ok = true
}

readBytes(path: Text, limit: Int) (bytes: Bytes) {
  file = dever.io.open(path)
  bytes = unpack(dever.io.read(file, limit))
  dever.io.close(file)
}

unpack(state: dever.io.ReadState.Read(value)) (bytes: Bytes) { bytes = value }
unpack(state: dever.io.ReadState.End) (bytes: Bytes) { bytes = dever.bytes.fromText("") }

consume(path: Text, limit: Int) (total: Int) {
  file = dever.io.open(path)
  stream = dever.io.chunks(file, limit)
  total = reduce(count, stream, 0)
  dever.io.close(file)
}

resume(path: Text, limit: Int) (total: Int) {
  file = dever.io.open(path)
  stream = dever.io.chunks(file, limit)
  alias = stream
  head = reduceUntil(take, stream, 0)
  total = reduce(count, alias, head)
  close(stream)
  close(alias)
  dever.io.close(file)
}

closedStream(path: Text) (total: Int) {
  file = dever.io.open(path)
  stream = dever.io.chunks(file, 64)
  dever.io.close(file)
  total = reduce(count, stream, 0)
}

count(event: dever.io.ReadEvent.Chunk(bytes), state: Int) (total: Int) {
  total = reduce(add, bytes, state)
}
count(event: dever.io.ReadEvent.Failed(message), state: Int) (total: Int) {
  fail(dever.io.ReadEvent.Failed(message))
}

add(item: Int, state: Int) (total: Int) { total = state + item }

take(event: dever.io.ReadEvent, state: Int) (total: Int, stop: Bool) {
  total = count(event, state)
  stop = true
}