#
# Add special methods to ZipCode class so code looks cleaner
#

_cache = None

def find_zip(zipcode):
	"""Return town and information for "zipcode" by querying uszip.com"""
	global _cache
	if _cache is None:
		import shelve
		_cache = shelve.open("uszip_cache")
	try:
		return _cache[zipcode]
	except KeyError:
		print "Not in cache"
		pass
	import urllib
	zip = ZipCode(zipcode)
	conn = urllib.urlopen("http://www.uszip.com/zip/%s" % zipcode)
	for line in conn:
		if "is the zip code of " in line:
			zip.town = _get_town(line)
		else:
			_check_info(line, zip.info)
	conn.close()
	if zip.town:
		_cache[zipcode] = zip
	return zip

class ZipCode(object):
	def __init__(self, zipcode):
		self.zipcode = zipcode
		self.town = "unknown"
		self.info = dict()

	def __str__(self):
		if self.town is None:
			town = "unknown"
		else:
			town = self.town
		return "%s -> %s" % (self.zipcode, town)

def _get_town(line):
	"""Extract town name if present"""
	line = _strip_tags(line)
	key_string = "is the zip code of "
	try:
		n = line.index(key_string)
	except ValueError:
		return "unknown"
	else:
		return line[n + len(key_string):]

# Info_map is map of dictionary key
# to label for information available from uszip.com
_Info_map = {
	"population":	"Population:",
	"housing":	"Housing Units:",
	"land_area":	"Land Area:",
	"water_area":	"Water Area:",
	"latitude":	"Latitude:",
	"longitude":	"Longitude:",
}
def _check_info(line, info):
	"""Extract information if present"""
	line = _strip_tags(line)
	for key, label in _Info_map.iteritems():
		try:
			n = line.index(label)
		except ValueError:
			continue
		else:
			start = n + len(label)
			stop = start + 1
			while stop < len(line):
				if line[stop].isspace():
					break
				stop += 1
			info[key] = line[start:stop].strip()
			break

def print_info(zip):
	for key, value in zip.info.iteritems():
		print "\t%s\t%s" % (_Info_map[key], value)

def _strip_tags(line):
	"""Remove HTML tags from string, leaving only "real" text"""
	keep = []
	in_tag = False
	for c in line:
		if in_tag:
			if c == '>':
				in_tag = False
		else:
			if c == '<':
				in_tag = True
			else:
				keep.append(c)
	return ''.join(keep).strip()