Untitled

# -*- coding: utf-8 -*-
from google.appengine.ext import db, webapp
from google.appengine.api import users
from google.appengine.ext.webapp.util import run_wsgi_app
import logging

STATE_START = 0
STATE_HALF = 1
STATE_FINISHED = 2

class User(db.Model):
  name = db.StringProperty(required=True)
  sum = db.IntegerProperty(required=True,default=1000)
  def start_trans(self, trans):
    def txn():
      self.sum = self.sum - trans.amount
      self.put()
      log = TransactionLog(parent=self, transaction=trans, amount=trans.amount)
      log.put()
    log = TransactionLog.all().filter('transaction =', trans
                                      ).ancestor(self).get()
    if log is None:
      db.run_in_transaction(txn)
    trans.state = STATE_HALF
    trans.put()

  def accept_trans(self, trans):
    def txn():
      self.sum = self.sum + trans.amount
      self.put()
      log = TransactionLog(parent=self, transaction=trans, amount=trans.amount*-1)
      log.put()
    log = TransactionLog.all().filter('transaction =', trans
                                      ).ancestor(self).get()
    if log is None:
      db.run_in_transaction(txn)
    trans.state = STATE_FINISHED
    trans.put()

  def delete_log(self, trans):
    log = TransactionLog.all().filter('transaction =', trans
                                      ).ancestor(self).get()
    log.delete()

class Transaction(db.Model):
  t_from = db.ReferenceProperty(User,collection_name="from_set")
  t_to = db.ReferenceProperty(User,collection_name="to_set")
  amount = db.IntegerProperty(required=True)
  state = db.IntegerProperty(required=True,default=STATE_START)

  def do_job(self):
    if self.state == STATE_START:
      logging.debug('start_trans called.')
      self.t_from.start_trans(self)
      return self.do_job()
    elif self.state == STATE_HALF:
      logging.debug('accept_trans called.')
      self.t_to.accept_trans(self)
      return self.do_job()
    elif self.state == STATE_FINISHED:
      log = TransactionLog.all().filter(
        'transaction =', self).ancestor(self.t_from).get()
      if log is not None:
        self.t_from.delete_log(self)
        return self.do_job()
      log = TransactionLog.all().filter(
        'transaction =', self).ancestor(self.t_to).get()
      if log is not None:
        self.t_to.delete_log(self)
        return self.do_job()
      self.delete()
      return True
    else:
      raise RuntimeError('It should never occur.')

class TransactionLog(db.Model):
  transaction = db.ReferenceProperty(Transaction)
  amount = db.IntegerProperty(required=True)


def init_data():
  users = User.all().fetch(100)
  db.delete(users)
  trans = Transaction.all().fetch(100)
  db.delete(trans)
  logs = TransactionLog.all().fetch(100)
  db.delete(logs)
  usera = User(name="A", sum=2000)
  userb = User(name="B", sum=3000)
  usera.put()
  userb.put()

class MainHandler(webapp.RequestHandler):

  def get(self):
    if self.request.get("init"):
      init_data()

    self.response.headers['Content-Type'] = 'text/html; charset=utf-8'
    self.response.out.write("<html><body>")
    self.response.out.write("<a href='/?init=1'>Initialize data</a><br/>")
    self.response.out.write("<table border='1'><tr>\n")
    self.response.out.write("<th>Name</th><th>Sum</th>")
    self.response.out.write("</tr>\n")

    query = User.all()
    users = query.fetch(4)
    for user in users:
      self.response.out.write("<tr><td>%s</td>" % user.name)
      self.response.out.write("<td>%s</td>" % user.sum)
      self.response.out.write("</tr>")
    self.response.out.write("</table>")

    self.response.out.write("<form method='POST'>")
    self.response.out.write("<input type='submit' value='send 100 from A to B.'></form>")
    self.response.out.write("</body></html>")

  def post(self):
    user_a = User.all().filter('name =', 'A').get()
    user_b = User.all().filter('name =', 'B').get()
    txn = Transaction(t_from=user_a, t_to=user_b, amount=100)
    txn.put()
    txn.do_job()
    self.redirect("/")

application = webapp.WSGIApplication([('/', MainHandler)],
                                       debug=True)

def main():
  logging.getLogger().setLevel(logging.DEBUG)
  run_wsgi_app(application)

if __name__ == "__main__":
  main()