From 45fd6dc4dd71f752e25628d07a666aadc2e26e17 Mon Sep 17 00:00:00 2001
From: jao <jao@gnu.org>
Date: Fri, 4 Feb 2022 00:07:54 +0000
Subject: Xmobar.App.CommandThreads -> Xmobar.Run.Loop

---
 src/Xmobar/Run/Loop.hs | 128 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 src/Xmobar/Run/Loop.hs

(limited to 'src/Xmobar/Run/Loop.hs')

diff --git a/src/Xmobar/Run/Loop.hs b/src/Xmobar/Run/Loop.hs
new file mode 100644
index 0000000..30ee112
--- /dev/null
+++ b/src/Xmobar/Run/Loop.hs
@@ -0,0 +1,128 @@
+{-# LANGUAGE CPP #-}
+
+------------------------------------------------------------------------------
+-- |
+-- Module: Xmobar.Run.Loop
+-- Copyright: (c) 2022 Jose Antonio Ortega Ruiz
+-- License: BSD3-style (see LICENSE)
+--
+-- Maintainer: jao@gnu.org
+-- Stability: unstable
+-- Portability: unportable
+-- Created: Fri Jan 28, 2022 03:20
+--
+--
+-- Running a thread for each defined Command in a loop
+--
+------------------------------------------------------------------------------
+
+module Xmobar.Run.Loop (initLoop, loop) where
+
+import Control.Concurrent (forkIO)
+import Control.Exception (bracket_, bracket, handle, SomeException(..))
+import Control.Concurrent.STM
+import Control.Concurrent.Async (Async, async, cancel)
+import Control.Monad (guard, void, unless)
+import Data.Maybe (isJust)
+import Data.Foldable (for_)
+
+import Xmobar.System.Signal
+import Xmobar.Config.Types
+import Xmobar.Run.Runnable (Runnable)
+import Xmobar.Run.Exec (start, trigger, alias)
+import Xmobar.Run.Template
+import Xmobar.Run.Timer (withTimer)
+
+#ifdef DBUS
+import Xmobar.System.DBus
+#endif
+
+newRefreshLock :: IO (TMVar ())
+newRefreshLock = newTMVarIO ()
+
+refreshLock :: TMVar () -> IO a -> IO a
+refreshLock var = bracket_ lock unlock
+    where
+        lock = atomically $ takeTMVar var
+        unlock = atomically $ putTMVar var ()
+
+refreshLockT :: TMVar () -> STM a -> STM a
+refreshLockT var action = do
+    takeTMVar var
+    r <- action
+    putTMVar var ()
+    return r
+
+type StartFunction = TMVar SignalType
+                     -> TMVar ()
+                     -> [[([Async ()], TVar String)]]
+                     -> IO ()
+
+loop :: Config -> StartFunction -> IO ()
+loop conf starter = withDeferSignals $ do
+  cls <- mapM (parseTemplate (commands conf) (sepChar conf))
+                (splitTemplate (alignSep conf) (template conf))
+  let confSig = unSignalChan (signal conf)
+  sig <- maybe newEmptyTMVarIO pure confSig
+  unless (isJust confSig) $ setupSignalHandler sig
+  refLock <- newRefreshLock
+  withTimer (refreshLock refLock) $
+    bracket (mapM (mapM $ startCommand sig) cls)
+            cleanupThreads
+            $ \vars -> do
+      starter sig refLock vars
+
+cleanupThreads :: [[([Async ()], a)]] -> IO ()
+cleanupThreads vars =
+  for_ (concat vars) $ \(asyncs, _) ->
+    for_ asyncs cancel
+
+-- | Initialises context for an event loop, returning a TVar that
+-- will hold the current list of values computed by commands.
+initLoop :: TMVar SignalType -> TMVar () -> [[([Async ()], TVar String)]]
+         -> IO (TVar [String])
+initLoop sig lock vs = do
+  tv <- newTVarIO ([] :: [String])
+  _ <- forkIO (handle (handler "checker") (checker tv [] vs sig lock))
+#ifdef DBUS
+  runIPC sig
+#endif
+  return tv
+  where
+    handler thing (SomeException e) =
+      void $ putStrLn ("Thread " ++ thing ++ " failed: " ++ show e)
+
+-- | Runs a command as an independent thread and returns its Async handles
+-- and the TVar the command will be writing to.
+startCommand :: TMVar SignalType
+             -> (Runnable,String,String)
+             -> IO ([Async ()], TVar String)
+startCommand sig (com,s,ss)
+    | alias com == "" = do var <- newTVarIO is
+                           atomically $ writeTVar var (s ++ ss)
+                           return ([], var)
+    | otherwise = do var <- newTVarIO is
+                     let cb str = atomically $ writeTVar var (s ++ str ++ ss)
+                     a1 <- async $ start com cb
+                     a2 <- async $ trigger com $ maybe (return ())
+                                                 (atomically . putTMVar sig)
+                     return ([a1, a2], var)
+    where is = s ++ "Updating..." ++ ss
+
+-- | Send signal to eventLoop every time a var is updated
+checker :: TVar [String]
+           -> [String]
+           -> [[([Async ()], TVar String)]]
+           -> TMVar SignalType
+           -> TMVar ()
+           -> IO ()
+checker tvar ov vs sig pauser = do
+      nval <- atomically $ refreshLockT pauser $ do
+              nv <- mapM concatV vs
+              guard (nv /= ov)
+              writeTVar tvar nv
+              return nv
+      atomically $ putTMVar sig Wakeup
+      checker tvar nval vs sig pauser
+    where
+      concatV = fmap concat . mapM (readTVar . snd)
-- 
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