From 67462dcf04fe703c49fbc8514cbc3b0d6cdf1e81 Mon Sep 17 00:00:00 2001
From: Aaron Fischer <mail@aaron-fischer.net>
Date: Thu, 21 Jul 2016 23:51:25 +0200
Subject: [PATCH] Fix the "vim swaps files" bug

---
 agent.go | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/agent.go b/agent.go
index c7c8de7..7acc8cd 100644
--- a/agent.go
+++ b/agent.go
@@ -58,24 +58,32 @@ func watchForConfigChanges(configFile string) {
 				// The file is changed. This is the only event we are interested
 				// in. If the file is renamed, removed or something else, we drop
 				// an error to the user.
-				if event.Op&fsnotify.Write == fsnotify.Write {
-					log.Println("Reload the config file ...")
-					// TODO: Parse the config file
-					// TODO: Handle errors in the config file
-					// TODO: Write a mapping for the mapping of the keys to the binary format the avr wants.
-					// TODO: Establish a connection to the device
-					// TODO: Transfer the new key mappings
-					// TODO: Close the connection?
+				if event.Op&fsnotify.Write == fsnotify.Write ||
+					event.Op&fsnotify.Remove == fsnotify.Remove {
+
+					if _, err := os.Stat(event.Name); err == nil {
+						log.Println("Reload the config file ...")
+						// TODO: Parse the config file
+						// TODO: Handle errors in the config file
+						// TODO: Write a mapping for the mapping of the keys to the binary format the avr wants.
+						// TODO: Establish a connection to the device
+						// TODO: Transfer the new key mappings
+						// TODO: Close the connection?
+					}
 				}
 
-				// TODO: vim has a very strange behaviour to save a file. There is
-				// no WRITE event triggered. Instead: RENAME -> CHMOD -> REMOVE is
-				// called on that file and after that, this mechanism lost track of
-				// the file. Why is that tha case? Cant find a valid answer to that.
-				if event.Op&fsnotify.Rename == fsnotify.Rename ||
-					event.Op&fsnotify.Remove == fsnotify.Remove {
-					log.Println("The configuration file is renamed or removed. We cant do any further changes without the config file. So create the file or rename it back and restart the agent.")
-					stop()
+				// Some editors have a feature calles "swap save" (like vim), which
+				// will trigger a simple WRITE event, instead it wil trigger RENAME
+				// -> CHMOD -> REMOVE in that order. So we lost track of the file.
+				// To prevent this, we add the file again, if it exist after a
+				// REMOVE event.
+				if event.Op&fsnotify.Remove == fsnotify.Remove {
+					if _, err := os.Stat(event.Name); err == nil {
+						watcher.Add(event.Name)
+					} else {
+						log.Fatal("Lost the configuration file. We stop now.")
+						stop()
+					}
 				}
 			case err := <-watcher.Errors:
 				log.Println("We have the following problem with the configuration file: ", err)