import cgi
import os
import wsgiref.handlers
from urlparse import urlparse
 
from google.appengine.api import users
from google.appengine.ext import webapp
from google.appengine.ext import db
 
class Kupify:
  def next(self, previous_pattern):
    if(previous_pattern == ''):
      return 'a'
    if(previous_pattern == 'z'):
      return 'aa'      
    if(previous_pattern.endswith("z")):
      return self.next(previous_pattern[0:-1]) + 'a'
    else:
      return previous_pattern[0:-1] + chr(ord(previous_pattern[-1]) + 1)
 
class URL(db.Model):
  url = db.StringProperty()
  url_id = db.IntegerProperty()
  pattern = db.StringProperty()
 
  def check_already_existing(self, url):
    u = False
    try:
      u = db.GqlQuery("SELECT * from URL WHERE url = :1", url)
      u = u[0]
      return u
    except (IndexError, AttributeError):
      return False
    
  def find_last_url(self):
    u = False
    try:
      u = db.GqlQuery("SELECT * from URL ORDER BY url_id DESC LIMIT 1")[0]
      return u
    except IndexError:
      return False
  
  def url_for_pattern(self, pattern):
    u = False
    try:
      u = db.GqlQuery("SELECT * from URL WHERE pattern = :1 LIMIT 1", pattern)[0]
      return u
    except IndexError:
      return False
 
class Index(webapp.RequestHandler):
  def get(self):
    template = file(os.path.join(os.path.dirname(__file__), 'index.html'))
    template = template.read()
    self.response.content_type = "text/html; charset=utf8"
    self.response.out.write(template)
 
class Redirect(webapp.RequestHandler):
  def get(self):
    pattern = self.request.environ['PATH_INFO'][1:].strip()
    
    u = URL()
    url = u.url_for_pattern(pattern)
    if(url):
      self.redirect(url.url)
    else:
      self.response.out.write("Can't find a URL to redirect!")
 
class Kup(webapp.RequestHandler):
  def post(self):
    u = URL()
    k = Kupify()
    
    next_url = self.request.get('url')
    
    #only if http or https
    scheme = urlparse(next_url)[0]
    if(not (scheme == 'http' or scheme == 'https')):
      self.response.out.write('ERROR')
      return
    
    #if already existing, return that record.
    b = u.check_already_existing(next_url)
    if(b):
      self.response.out.write('http://r.kup.in/' + b.pattern)
      return
      
    last_url = u.find_last_url()
    last_url_pattern = ''
    last_url_id = 0
    try:
      last_url_pattern = last_url.pattern
      last_url_id = last_url.url_id
    except AttributeError:
      pass
      
    next_url_pattern = k.next(last_url_pattern)
    
    u.url = self.request.get('url')
    u.url_id = last_url_id + 1
    u.pattern = next_url_pattern
    u.put()
        
    self.response.out.write('http://r.kup.in/' + next_url_pattern)
 
def main():
  application = webapp.WSGIApplication(
    [('/', Index),
    ('/_', Kup),
    ('/.*', Redirect)],
    debug=True)
  wsgiref.handlers.CGIHandler().run(application)
 
if __name__ == "__main__":
  main()