import os
import stat
import time

# create global variables for message timestamps:
#        Timestamp contains the last time a message of this type was seen
#        WarningTime contains the last time a warning was sent for
#                    messages of this type
def startMessageChecking(paramMessageNames):
	global MessageNames
	global Timestamp
	global MessageCount
	global WarningTime
	MessageNames = paramMessageNames
	try:
    		Timestamp
	except NameError:
		# the following statements are needed to define the dictionaries;
		# otherwise, Python will flag this as an error
		Timestamp = {}
		MessageCount = {}
		WarningTime = {}
		# now that the dictionaries are defined, they can be initialized
		for MessageName in MessageNames:
			Timestamp[MessageName] = time.time()
			MessageCount[MessageName] = 0
			WarningTime[MessageName] = 0

# update the timestamp for this message and increment message counter
def touchMessage(MessageName):
	global Timestamp
	global MessageCount
    	Timestamp[MessageName] = time.time()
    	MessageCount[MessageName] += 1

# check each message type to see whether there is message activity
def checkForInactivity(InactivityTime, WarningFrequency):
	global MessageNames
	global Timestamp
	global MessageCount
	global WarningTime
    	CurrentTime = time.time()
    	for MessageName in MessageNames:
        	# check whether messages of this type have arrived recently
        	LastTime = Timestamp[MessageName]
        	Delta = int(CurrentTime - LastTime)
		if Delta > InactivityTime:
	   		# no message of this type has arrived recently; channel
	   		# inactivity has been detected
	   		#
           		# check whether a warning message has been sent recently
           		LastWarningTime = WarningTime[MessageName]
           		WarningDelta = int(CurrentTime - LastWarningTime)
           		if WarningDelta > WarningFrequency:
				# no warning message has been sent recently, so send one
				print "CHANNEL INACTIVITY WARNING:"
				if MessageCount[MessageName] > 0:
					LastString = time.strftime( '%Y-%m-%d %H:%M', \
							time.localtime(LastTime))
					print "No %s messages since %s" % \
							(MessageName, LastString)
				else:
					print "No %s messages ever" % MessageName
					# update the timestamp for warning messages
				WarningTime[MessageName] = CurrentTime