Utility.hs

module RawFilePath.Process.Utility (
  callProcess,
  readProcessWithExitCode,
) where

-- base modules

-- extra modules

import qualified Data.ByteString as B
import qualified Data.ByteString.Builder as B
import qualified Data.ByteString.Lazy as LB
import RawFilePath.Import
-- local modules

import RawFilePath.Process.Basic
import RawFilePath.Process.Common


-- | Create a new process with the given configuration, and wait for it to
-- finish. Note that this will set all streams to `NoStream`, so the process
-- will be completely silent. If you need the output data from the process, use
-- `readProcessWithExitCode` instead.
callProcess :: ProcessConf stdin stdout stderr -> IO ExitCode
callProcess conf = start >>= waitForProcess
 where
  start =
    startProcess
      conf
        { cfgStdin = NoStream
        , cfgStdout = NoStream
        , cfgStderr = NoStream
        }


-- | Fork an external process, read its standard output and standard error
-- strictly, blocking until the process terminates, and return them with the
-- process exit code.
readProcessWithExitCode
  :: ProcessConf stdin stdout stderr
  -> IO (ExitCode, ByteString, ByteString)
readProcessWithExitCode conf = do
  process <-
    startProcess
      conf
        { cfgStdin = NoStream
        , cfgStdout = CreatePipe
        , cfgStderr = CreatePipe
        }
  stdoutB <- hGetAll (processStdout process)
  stderrB <- hGetAll (processStderr process)
  exitCode <- waitForProcess process
  return (exitCode, stdoutB, stderrB)


-- utility functions

-- Read from Handle until IOError
hGetAll :: Handle -> IO ByteString
hGetAll h = LB.toStrict . B.toLazyByteString <$> hGetAll' mempty h
 where
  hGetAll' acc h' =
    tryIOError (B.hGetContents h) >>= \case
      Left _ -> return acc
      Right b -> hGetAll' (acc <> B.byteString b) h'