commands: implement a no-quit mode

Add a mode that prevents aerc from quitting normally when an important
task is performed, i.e. when sending a message. The no-quit mode will be
ignored when quit is used with the -f option to force an exit.

Suggested-by: ph14nix[m]
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

commands/mode/noquit.go

@@ -0,0 +1,26 @@
+package mode
+
+import "sync/atomic"
+
+// noquit is a counter for goroutines that requested the no-quit mode
+var noquit int32
+
+// NoQuit enters no-quit mode where aerc cannot be exited (unless the force
+// option is used)
+func NoQuit() {
+	atomic.AddInt32(&noquit, 1)
+}
+
+// NoQuitDone leaves the no-quit mode
+func NoQuitDone() {
+	atomic.AddInt32(&noquit, -1)
+}
+
+// QuitAllowed checks if aerc can exit normally (only when all goroutines that
+// requested a no-quit mode were done and called the NoQuitDone() function)
+func QuitAllowed() bool {
+	if atomic.LoadInt32(&noquit) > 0 {
+		return false
+	}
+	return true
+}