- added a directory callback

- updated the template (fixes #11)

over/callback.py

@@ -3,6 +3,10 @@
 
 # --------------------------------------------------
 
+import os
+
+# --------------------------------------------------
+
 def boolean(arg):
 	"""
 	Converts
@@ -48,3 +52,29 @@ def strings(*args):
 		out.append(str(arg))
 	
 	return out
+
+def directory(exists=False, writable=False, gio=False):
+	"""
+	Returns a directory callback that raises hell if:
+	- the supplied directory doesn't exist and `exists` is True
+	- isn't writable and `writable` is True
+	- isn't a valid Gio path and `gio` is True
+	
+	@while generating a callback
+	"""
+	
+	if gio:
+		raise NotImplementedError("Gio support is not yet here")
+	
+	def cb(arg):
+		path = os.path.abspath(os.path.expanduser(arg))
+		
+		if not os.path.isdir(path) and exists:
+			raise FileNotFoundError("%s (%s) does not exist" %(arg, path))
+		
+		if writable and not os.access(path, os.W_OK | os.X_OK):
+			raise PermissionError("%s exists but is not writable" %(arg))
+		
+		return path
+	
+	return cb