import System.Directory
import System.IO
import Control.Monad
import System.Posix.Signals
import System.Posix.Types
import Control.Monad.Error.Class
import Control.Exception (throw)
import System.Posix.Process
import Data.Maybe

import System.INotify
import UTmp
import FGConsole

jid user host rsrc = user ++ "@" ++ host ++ "/" ++ rsrc

toJabberId :: String -> (String,String,t) -> Maybe String
toJabberId host (user,tty,_) = 
    if take 3 tty == "tty"
      then Just (jid user host tty)
      else Nothing

utmp_event e = do
    -- print e
    putStrLn "---"
    us <- users
    let ids = mapMaybe (toJabberId "localhost") us
        ids :: [String]
    forM_ ids putStrLn

on_chvt vtnum = do
    putStrLn $ "changed vt to "++ show vtnum

start :: IO ()
start = do
    installHandler sigUSR1 (Catch (utmp_event (userError "signaled"))) Nothing
    inotify <- initINotify
    print inotify
    wd <- addWatch
            inotify
            [CloseWrite] -- [Open,Close,Access,Modify,Move]
            utmp_file
            utmp_event
    print wd
    mtty <- monitorTTY on_chvt
    putStrLn "Hit enter to terminate..."
    getLine
    unmonitorTTY mtty
    removeWatch wd

sendUSR1 pid = do
    signalProcess sigUSR1 pid

getStartupAction []     = throw (userError "pid file?") >> return (Right "")
getStartupAction (p:ps) = do
    catch
        ( do
            pid <- fmap CPid (readFile p >>= readIO)
            -- signal pid
            return (Left pid) )
        onEr
 where
    onEr e = do
        pid <- getProcessID
        putStrLn $ "starting pid = "++show pid
        catch (do 
                writeFile p (show pid)
                putStrLn $ "writing "++show p
                -- start daemon
                return (Right p) )
              (\_ -> getStartupAction ps)

runOnce ps run notify = getStartupAction ps >>= doit
 where
    doit (Left pid      ) = notify pid
    doit (Right pidfile ) = do 
        run
        removeFile pidfile


main = do
    runOnce ["/var/run/presence.pid","/tmp/presence.pid"] start sendUSR1