{-# OPTIONS_GHC -fno-warn-unused-do-bind #-}

module Core.Program.Signal (
    setupSignalHandlers,
) where

import Control.Concurrent.MVar (MVar, modifyMVar_, putMVar)
import Core.Program.Context
import Foreign.C.Types (CInt)
import System.Exit (ExitCode (..))
import System.IO (hFlush, hPutStrLn, stdout)
import System.Posix.Signals (
    Handler (Catch),
    installHandler,
    sigINT,
    sigTERM,
    sigUSR1,
 )

{- |
Make a non-zero exit code which is 0b1000000 + the number of the signal.
Probably never need this (especaially given our attempt to write out a human
readable name for the signal caught) but it's a convention we're happy to
observe.
-}
code :: CInt -> ExitCode
code :: CInt -> ExitCode
code CInt
signal = Int -> ExitCode
ExitFailure (Int
128 forall a. Num a => a -> a -> a
+ forall a b. (Integral a, Num b) => a -> b
fromIntegral CInt
signal)

{-
    Technique to have a blocking MVar and signal handlers to set it
    adapted from code in vaultaire-common package's Vaultaire.Program,
    BSD3 licenced.
-}

interruptHandler :: MVar ExitCode -> Handler
interruptHandler :: MVar ExitCode -> Handler
interruptHandler MVar ExitCode
quit = IO () -> Handler
Catch forall a b. (a -> b) -> a -> b
$ do
    Handle -> String -> IO ()
hPutStrLn Handle
stdout String
"\nInterrupt"
    Handle -> IO ()
hFlush Handle
stdout
    forall a. MVar a -> a -> IO ()
putMVar MVar ExitCode
quit (CInt -> ExitCode
code CInt
sigINT)

terminateHandler :: MVar ExitCode -> Handler
terminateHandler :: MVar ExitCode -> Handler
terminateHandler MVar ExitCode
quit = IO () -> Handler
Catch forall a b. (a -> b) -> a -> b
$ do
    Handle -> String -> IO ()
hPutStrLn Handle
stdout String
"Terminating"
    Handle -> IO ()
hFlush Handle
stdout
    forall a. MVar a -> a -> IO ()
putMVar MVar ExitCode
quit (CInt -> ExitCode
code CInt
sigTERM)

logLevelHandler :: MVar Verbosity -> Handler
logLevelHandler :: MVar Verbosity -> Handler
logLevelHandler MVar Verbosity
v = IO () -> Handler
Catch forall a b. (a -> b) -> a -> b
$ do
    Handle -> String -> IO ()
hPutStrLn Handle
stdout String
"Signal"
    Handle -> IO ()
hFlush Handle
stdout
    forall a. MVar a -> (a -> IO a) -> IO ()
modifyMVar_
        MVar Verbosity
v
        ( \Verbosity
level -> case Verbosity
level of
            Verbosity
Output -> forall (f :: * -> *) a. Applicative f => a -> f a
pure Verbosity
Debug
            Verbosity
Verbose -> forall (f :: * -> *) a. Applicative f => a -> f a
pure Verbosity
Debug
            Verbosity
Debug -> forall (f :: * -> *) a. Applicative f => a -> f a
pure Verbosity
Output
            Verbosity
Internal -> forall (f :: * -> *) a. Applicative f => a -> f a
pure Verbosity
Output
        )

--

{- |
Install signal handlers for SIGINT and SIGTERM that set the exit
semaphore so that a Program's [minimal] cleanup can occur.
-}
setupSignalHandlers :: MVar ExitCode -> MVar Verbosity -> IO ()
setupSignalHandlers :: MVar ExitCode -> MVar Verbosity -> IO ()
setupSignalHandlers MVar ExitCode
quit MVar Verbosity
level = do
    CInt -> Handler -> Maybe SignalSet -> IO Handler
installHandler CInt
sigINT (MVar ExitCode -> Handler
interruptHandler MVar ExitCode
quit) forall a. Maybe a
Nothing
    CInt -> Handler -> Maybe SignalSet -> IO Handler
installHandler CInt
sigTERM (MVar ExitCode -> Handler
terminateHandler MVar ExitCode
quit) forall a. Maybe a
Nothing
    CInt -> Handler -> Maybe SignalSet -> IO Handler
installHandler CInt
sigUSR1 (MVar Verbosity -> Handler
logLevelHandler MVar Verbosity
level) forall a. Maybe a
Nothing
    forall (m :: * -> *) a. Monad m => a -> m a
return ()