From 23399ceab6ca3fe9938cf97b7aa726258512be98 Mon Sep 17 00:00:00 2001
From: jao <jao@gnu.org>
Date: Sat, 29 Jan 2022 01:59:17 +0000
Subject: Refactoring of the previous patch and its surroundings

---
 src/Xmobar/App/CommandThreads.hs | 82 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 76 insertions(+), 6 deletions(-)

(limited to 'src/Xmobar/App/CommandThreads.hs')

diff --git a/src/Xmobar/App/CommandThreads.hs b/src/Xmobar/App/CommandThreads.hs
index 1de2936..931a072 100644
--- a/src/Xmobar/App/CommandThreads.hs
+++ b/src/Xmobar/App/CommandThreads.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 ------------------------------------------------------------------------------
 -- |
 -- Module: Xmobar.App.CommandThreads
@@ -14,18 +16,29 @@
 --
 ------------------------------------------------------------------------------
 
-module Xmobar.App.CommandThreads ( startCommand
+module Xmobar.App.CommandThreads ( initLoop
+                                 , loop
                                  , newRefreshLock
-                                 , refreshLock
-                                 , refreshLockT) where
+                                 , refreshLock) where
 
+import Control.Concurrent (forkIO)
+import Control.Exception (bracket_, bracket, handle, SomeException(..))
 import Control.Concurrent.STM
-import Control.Concurrent.Async (Async, async)
-import Control.Exception (bracket_)
+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 (SignalType)
+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.App.Timer (withTimer)
+
+#ifdef DBUS
+import Xmobar.System.DBus
+#endif
 
 newRefreshLock :: IO (TMVar ())
 newRefreshLock = newTMVarIO ()
@@ -43,6 +56,45 @@ refreshLockT var action = do
     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
@@ -59,3 +111,21 @@ startCommand sig (com,s,ss)
                                                  (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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