Bound notification delivery and expansion

main.go

@@ -47,8 +47,10 @@ func do_list_devices() {
 	show_devs("Inputs:", idevs)
 }
 
+const notificationQueueSize = 32
+
 func setup_notify_runner(notify_command string) chan []string {
-	t := make(chan []string)
+	t := make(chan []string, notificationQueueSize)
 	var do_nothing = false
 	var err error
 	if err != nil {
@@ -57,23 +59,28 @@ func setup_notify_runner(notify_command string) chan []string {
 		do_nothing = true
 	}
 	go func(events chan []string, cmd_template string, dummy bool) {
-		for {
-			event := <-events
+		for event := range events {
 			if !dummy {
-				t := string(cmd_template)
-				t = strings.ReplaceAll(t, "%event", shellescape.Quote(event[0]))
-				t = strings.ReplaceAll(t, "%who", shellescape.Quote(event[1]))
-				t = strings.ReplaceAll(t, "%what", shellescape.Quote(event[2]))
 				cmd := "/bin/sh"
-				args := []string{"-c", t}
+				args := []string{"-c", expandNotification(cmd_template, event)}
 				x := exec.Command(cmd, args...)
 				x.Run()
-			} //if we actually have a command to run
-		} //for
+			}
+		}
 	}(t, notify_command, do_nothing)
 	return t
 }
 
+// expandNotification replaces placeholders in one pass so text supplied for
+// one field cannot cause another placeholder to be expanded recursively.
+func expandNotification(template string, event []string) string {
+	return strings.NewReplacer(
+		"%event", shellescape.Quote(event[0]),
+		"%who", shellescape.Quote(event[1]),
+		"%what", shellescape.Quote(event[2]),
+	).Replace(template)
+}
+
 func setup_fifo(fn string) (chan string, error) {
 	t := make(chan string)
 	if fn == "" {