term.hs

{-# language OverloadedStrings, NumericUnderscores, ImportQualifiedPost #-}

module Lib where
import Data.Typeable

import Control.Monad
import Prelude hiding (log)
import Data.Text (Text)
import Data.Text qualified as Text
import Say
import UnliftIO.Concurrent
import UnliftIO.Exception
import System.Posix.Process
import System.Posix.Signals qualified as Posix (Handler (Catch), installHandler, sigTERM)
import System.Exit (ExitCode(..))

log :: Text -> IO ()
log msg = do
    tid <- myThreadId
    say $ mconcat
        [ "[", Text.pack $ show tid, "]\t\t"
        , msg
        ]

tshow :: Show a => a -> Text
tshow = Text.pack . show

someFunc :: IO ()
someFunc = do
    log "Starting App"
    mainThread <- myThreadId
    void (Posix.installHandler Posix.sigTERM (Posix.Catch (shutdown mainThread)) Nothing)
    procId <- getProcessID
    log $ mconcat ["ProcessID: ", tshow procId]
    forkFinally (do
        tid <- myThreadId
        void (Posix.installHandler Posix.sigTERM (Posix.Catch (shutdown tid)) Nothing)
        forever loop
        ) $ \eerr ->
        case eerr of
            Left (SomeException err) -> do
                log $ mconcat ["Received exception: ", tshow err]
                log $ mconcat ["Exception type: ", tshow (typeOf err)]
            Right () ->
                log "Exited successfully"
    forever loop `finally` log "Exiting with Finally"
  where
    loop = do
        threadDelay 1_000_000
        log "Waiting . . ."

    shutdown tid = do
        log "Shutting down gracefully"
        throwTo tid ExitSuccess