#!/usr/bin/env python

import sys
import imp
import urllib
import os
import popen2

def abort(s):
	sys.stderr.write("%s\n" % s)
	sys.exit(1)

def usage():
	abort("Usage: %s configFile" % sys.argv[0])

def importModule(name):
	try:
		return sys.modules[name]
	except KeyError:
		pass
	try:
		fp,pathname,description=imp.find_module(name)
	except:
		raise "Cannot find module '%s'" % name
	try:
		return imp.load_module(name, fp, pathname, description)
	except:
		if fp:
			fp.close()
		raise "Cannot load module '%s'" % name
	else:
		fp.close()

def urlFile(url):
	for c in "/:":
		url=url.replace(c,"_")
	return url

def pipeNoInput(cmd,get_stdout=1,get_stderr=1):
	(stdout,stdin,stderr)=popen2.popen3(cmd)
	stdin.close()
	if get_stdout:
		out=stdout.read()
	else:
		out=None
	stdout.close()
	if get_stderr:
		err=stderr.read()
	else:
		err=None
	stderr.close()
	return (out,err)

def makeDiff(old,new):
	files=[]
	s=(old,new)
	names=("old","new")
	for i in range(2):
		fileName=names[i]
		file=open(fileName,"w")
		file.write(s[i])
		file.close()
	command="diff -s -B %s %s" % names
	(out,err)=pipeNoInput(command,get_stderr=0)
	if out.find("Files %s and %s are identical" % names)==-1:
		return out
	else:
		return None

def mail(fromAddress,toAddress,subject,body):
	messagebody="To: %s\nReply-To: %s\nFrom: %s\nSubject:%s\n%s\n" % (toAddress,toAddress,fromAddress,subject,body)
	f=os.popen("/usr/sbin/sendmail -F%s %s" % (fromAddress,toAddress),"w")
	f.write(messagebody)
	f.close()

def checkUrl(url):
	sys.stdout.write("Checking url %s ... " % url)
	f=urllib.urlopen(url)
	new=f.read()
	f.close()
	file="%s/%s" % (cacheDir,urlFile(url))
	try:
		fold=open(file)
		old=fold.read()
		fold.close()
	except:
		old=None
	if old==None:
		sys.stdout.write("first check\n")
	else:
		diff=makeDiff(old,new)
		if diff:
			sys.stdout.write("differs\n")
			mail(fromAddress,toAddress,"Webtrack change: %s" % url,diff)
		else:
			sys.stdout.write("unchanged\n")
			return
	fold=open(file,"w")
	fold.write(new)
	fold.close()


try:
	configFile=sys.argv[1]
except:
	usage()

if "/" in configFile:
	path="/".join(configFile.split("/")[:-1])
	sys.path.append(path)
	configFile=configFile.split("/")[-1]

config=importModule(configFile)

fromAddress=config.fromAddress
toAddress=config.toAddress
cacheDir=config.cacheDir
tmpDir=config.tmpDir

os.chdir(tmpDir)

try:
	urls=config.urls
except:
	abort("Missing directive 'urls' in the configuration file")

for url in urls:
	checkUrl(url)