Purescript Node Streams

foo.txt

Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec hendrerit tempor
tellus. Donec pretium posuere tellus. Proin quam nisl, tincidunt et, mattis
eget, convallis nec, purus. Cum sociis natoque penatibus et magnis dis
parturient montes, nascetur ridiculus mus. Nulla posuere. Donec vitae dolor.
Nullam tristique diam non turpis. Cras placerat accumsan nulla. Nullam rutrum.
Nam vestibulum accumsan nisl.

output.txt

╭─mmyrseth@set  ~/projects/capture ‹master*› 
╰─$ pulp run -m StreamTest
* Building project in /home/mmyrseth/projects/capture
* Build successful.
log: Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Donec hendrerit tempor
tellus. Donec pretium posuere tellus. Proin quam nisl, tincidunt et, mattis
eget, convallis nec, purus. Cum sociis natoque penatibus et magnis dis
parturient montes, nascetur ridiculus mus. Nulla posuere. Donec vitae dolor.
Nullam tristique diam non turpis. Cras placerat accumsan nulla. Nullam rutrum.
Nam vestibulum accumsan nisl.


Done!

readStream.purs

module StreamTest where

import Prelude

import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)
import Control.Monad.Eff.Exception (EXCEPTION, message)
import Node.Encoding (Encoding(..))
import Node.FS (FS)
import Node.FS.Stream (createReadStream)
import Node.Stream (Readable, onDataString, onEnd, onError)


readStream :: forall eff
            . Readable () (console :: CONSOLE, exception :: EXCEPTION | eff)
           -> Eff (console :: CONSOLE, exception :: EXCEPTION | eff) Unit
readStream stream = do
  onDataString stream UTF8 handleOutput
  onEnd stream handleEnd
  onError stream handleError
  where
    handleError err = log $ "error: " <> (message err)
    handleOutput out = log $ "log: " <> out
    handleEnd = log "Done!"


main :: forall eff. Eff (console :: CONSOLE, exception :: EXCEPTION, fs :: FS | eff) Unit
main = do
  stream <- createReadStream "foo.txt"
  readStream stream