#!/usr/bin/python

# Name: aws_ip_ranges
# Written by: Jim Cameron
# Created: 2017-02-21
# Last updated: 2017-02-21
# Version: 1.0
#
# Purpose: Parse a JSON file downloaded from 
# https://ip-ranges.amazonaws.com/ip-ranges.json that contains a list of the
# IP address ranges used by Amazon Web Services (AWS). See
# http://support.moonpoint.com/languages/python/aws for example output.

import getopt, json, os.path, urllib2, sys

inputfile = ""

# Print usage information
def usage():
   print 'Usage: aws_ip_ranges [-hd] [-i inputfile]'
   print
   print '-h --help                print this message'
   print '-d --download            download the current JSON data from Amazon'
   print '-i, --input input_file   use input file'

# Download current JSON data from Amazon
def downloadJSONdata():

    url = "https://ip-ranges.amazonaws.com/ip-ranges.json"
    outfile = "ip-ranges.json"
    page = urllib2.urlopen(url)
    source=page.read()
    f=open(outfile, 'w')
    f.write(source)
    f.close()

try:
    opts, args = getopt.getopt(sys.argv[1:], "hdi:", ["help","download","input="])
except getopt.GetoptError as err:
    # print help information and exit
    print str(err)
    usage()
    sys.exit(2)

for o, a in opts:
    if o in ('-h', '--help'):
       usage()
       sys.exit()
    elif o in ('-d', '--download'):
       downloadJSONdata()
    elif o in ('-i', '--input'):
         inputfile = a
    else:
         assert False, "unhandled option"

# if the input file isn't specified assume it is a file named ip-ranges.json
# in the current directory
if not inputfile:
   inputfile = 'ip-ranges.json'
if not os.path.isfile(inputfile):
   print "Input file ", inputfile, "not found"
   print "Use", sys.argv[0], "-d or --download to download ip-ranges.json"
   sys.exit(2)
else: 
    data = json.load(open(inputfile))

# Print the data left-justified in 3 columns of 20 characters in length
print "IP Prefix".ljust(20) + "Region".ljust(20) + "Service".ljust(20)
for d in data["prefixes"]:
    print d["ip_prefix"].ljust(20) + d["region"].ljust(20) + d["service"].ljust(20)