# Using our JSON service from Python with cache

import json
import urllib2
import time
import os.path

# Get an object from a service if we don't have a recent local copy
# How long ago ago was the local file [or, later, record] modified?

# see if the local file exists too - if it doesn't set "out of date"

try:
        cachetime = os.path.getmtime("cachedrecord.txt")
except:
        cachetime = 0

if time.time() - cachetime > 20:

        # local copy is old - grab it afresh

        response = urllib2.urlopen('http://www.wellho.net/services/pix.json')
        stuff = response.read()
        source = "from remote server"

        # store the fresh copy (we are using a file ..
        # but could use memcached or another database with similar principles
        # -- that will let us cache multiple / keyed records! --

        # Trap issues if the file won't open for overwrite

        try:
                fho = open("cachedrecord.txt","w")
                fho.write(stuff)
                fho.close()
        except:
                pass
                # source = " ... CANNOT STORE TO CACHE"

else:

        # local copy is quite new. Get it our of fridge and re-serve it ;-)

        stuff = open("cachedrecord.txt","r").read()
        source = "from cache"

# We now have it as a serialised stream - in JSON format.
# turn it into an object (type dict)

memory = json.loads(stuff)

# A top level look (so the trainee can see what's happening!)

print " ---- Here is what we have ---- "
for itemname in memory.keys():
        print itemname
print "For your training info, the data is",source
print " ------------------------------- "

# or in more detail

toby = time.gmtime(memory["timedat"])
print "This was generated at",memory["timedat"],time.strftime("%c",toby)

if memory["lookfor"]:
        print "Searching only for",memory["lookfor"]
else:
        print "All available records requested"

# And look at the detailed stuff within the response too!

for record in memory["acc"]:
        print record["when"], record["which"]