import time
class BasicNotebook:
	def __init__(self):
		self.messages = {}

	def _addToNotes(self,touser,msgformat):
		if touser in self.messages:
			self.messages[touser].append(msgformat)
		else:
			self.messages[touser]=[msgformat]

	def addNote(self,touser,fromuser,msg):
		self._addToNotes(touser,[fromuser,msg])

	def _readNotes(self,user,fmtstr):
		if not self.checkNotes(user):
			return []
		ret = []
		for messageI in self.messages[user]:
			ret.append(fmtstr.format(*messageI))
		del self.messages[user]
		return ret

	def readNotes(self,user):
		return self._readNotes(user,"{0} left a message: {1}")

	def checkNotes(self,user):
		return user in self.messages.keys()

class DatedNotebook(BasicNotebook):
	def addNote(self,touser,fromuser,msg):
		self._addToNotes(touser,[fromuser,msg,time.strftime("%H:%M:%S"),time.strftime("%A, %B %d, %Y")])

	def readNotes(self,user):
		return self._readNotes(user,"{0} left a message at {2} on {3}: {1}")