+# CLI frontend
+class CLIFrontend(QuestionFrontend):
+ def error(self, message):
+ print(message, file=sys.stderr)
+
+ def userChoose (self, title, choices, returns, fallback):
+ while True:
+ # print question
+ print(title)
+ for i in range(len(choices)):
+ print("%d. %s"%(i,choices[i]))
+ print("Enter 'c' to cancel.")
+ # handle input
+ answer = input("> ")
+ if answer == "c":
+ return None
+ #else
+ try:
+ answerint = int(answer)
+ if answerint >= 0 and answerint < len(choices):
+ return returns[answerint]
+ except ValueError:
+ pass
+ # if we are here something invalid was entered
+ print("INVALID ANSWER: '%s'" % answer)
+
+ @staticmethod
+ def isAvailable():
+ return True
+
+# list of available frontends
+frontends = collections.OrderedDict()
+frontends["qt"] = QtFrontend
+frontends["zenity"] = ZenityFrontend
+frontends["cli"] = CLIFrontend
+
+# get a frontend
+def getFrontend(name = None):
+ # by name
+ if name is not None:
+ if name in frontends:
+ if frontends[name].isAvailable():
+ return frontends[name]() # call constructor
+ else:
+ raise Exception("Frontend %s not available" % name)
+ # frontend not found
+ raise Exception("Frontend %s not found" % name)
+ # auto-detect
+ for frontend in frontends.values():
+ if frontend.isAvailable():
+ return frontend() # call constructor
+ raise Exception("No frontend is available - this should not happen")