#!/usr/bin/env python

import re, urllib

r_json = re.compile(r'^[,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]+$')
r_string = re.compile(r'"(\\.|[^"\\])*"')
 
def json(text): 
   """Evaluate JSON text safely (we hope)."""
   if r_json.match(r_string.sub('', text)): 
      return eval(text, {'__builtins__': None}, {})
   print text
   raise ValueError('Input must be serialised JSON.')

def sparql(query): 
   service = 'http://www.sparql.org/sparql'
   qstring = 'query=%s&default-graph-uri=&stylesheet=&output=json'
   uri = service + '?' + (qstring % urllib.quote(query))
   u = urllib.urlopen(uri)
   bytes = u.read()
   u.close()
   return json(bytes)

query = """\
PREFIX : <http://purl.org/ns/meteo#>

SELECT ?time ?cloud ?temperature ?precipitation
FROM <http://infomesh.net/forecast/%s.rdf>
WHERE { [ :time ?time; :cloudCover [ :percent ?cloud ]; 
          :temperature [ :celsius ?temperature ]; 
          :precipitation [ :inches ?precipitation ] ] }
"""

def convert(place): 
   results = sparql(query % place)

   data = []
   for bindings in results['results']['bindings']: 
      w3cdtf = bindings['time']['value']
      cloudCover = bindings['cloud']['value']
      temperature = bindings['temperature']['value']
      precipitation = bindings['precipitation']['value']
      data.append((w3cdtf, cloudCover, temperature, precipitation))

   f = open('%s.forecast.txt' % place, 'w')
   for (w3cdtf, cloudCover, temperature, precipitation) in sorted(data): 
      print >> f, w3cdtf, temperature, cloudCover, precipitation
   f.close()

def main(argv=None): 
   if argv is None: 
      argv = __import__('sys').argv

   if len(argv) == 2: 
      place = argv[1]
      convert(place)
   else: Exception('usage: %prog <place>')

if __name__ == '__main__': 
   main()