utils.py

import datetime
import hashlib
import hmac
import logging
import random
import re
import string
import sys

from google.appengine.ext import db
from google.appengine.api import images
from google.appengine.api import memcache
from pytz.gae import pytz
from secret import *


def is_img_square(img):
	img = images.Image(img)
	if img.width == img.height:
		return True
	else:
		return False


def img_square_ratios(img):
	"""Output is in form of width ratio, height ratio."""
	img = images.Image(img)
	if img.width > img.height:
		cropped_width = float(img.height)/float(img.width)
		left_x = (1.0 - cropped_width)/2.0
		right_x = 1.0 - left_x
		top_y = 0.0
		bottom_y = 1.0
	elif img.height > img.width:
		cropped_height = float(img.width)/float(img.height)
		top_y = (1.0 - cropped_height)/2.0
		bottom_y = 1.0 - top_y
		left_x = 0.0
		right_x = 1.0
	return left_x, top_y, right_x, bottom_y



def date_to_date_key(date_object):
	return date_object.strftime('%d-%m-%Y')

def date_key_to_date(date_key):
	return datetime.datetime.strptime(date_key, '%d-%m-%Y').date()

def done_list_key(username, date_object):
	return username + '/' + date_object.strftime('%d-%m-%Y')


def done_list_cache_key(user_id, date_object):
	return str(user_id) + '_' + date_string(date_object)


def date_string(date_object):
	return date_object.strftime('%a %d %b %Y')


def timezone_now(timezone = 'Asia/Kolkata'):
	pytz_timezone = pytz.timezone(timezone)
	return pytz_timezone.normalize(aware_utcnow().astimezone(pytz_timezone))


def aware_utcnow():
	"""Get aware utcnow to store it in the date_createrd property."""
	return datetime.datetime.utcnow().replace(tzinfo = pytz.UTC)


def what_attribute(uid_or_username_or_email):
	"""
	Helper function for master Query function User.get_user().
	It tells the function the attribute the user wants to query.
	"""
	if uid_or_username_or_email.isdigit():
		return 'uid'
	elif valid_email(uid_or_username_or_email):
		return 'email'
	else:
		return 'username'


def set_cache(cache_key, value):
	"""
	Sets memcache using Check & Set.
	It uses only 'set' if the key is uninitialized.
	"""
	client = memcache.Client()
	try:
		while True:
			old_value = client.gets(cache_key)
			assert old_value, 'Uninitialized Key'
			if client.cas(cache_key, value):
				break
	except AssertionError:
		client.add(cache_key, value)
		logging.error('Initializing Key')


def make_salt():
	"""	
	Returns a random 5 letter salt used for hashing the password.
	Helper function for: make_pw_hash()

	Input: NA
	Returns: String
	"""
	return ''.join(random.choice(string.letters) for x in xrange(5))


def make_pw_hash(name, pw, salt = make_salt()):
	"""
	Returns the valid password hash: 'string of password hash','salt'
	The hashed password has a comma , as the separator.

	name: String
	pw: String
	Salt: String

	Returns: String
	"""
	h = hashlib.sha256(name + pw + salt).hexdigest()
	return '%s,%s' % (h, salt)


def valid_pw(name, pw, h):
	"""
	Returns a boolean for whether the given password is valid.

	name: String
	pw: String
	h: String
	Returns: Boolean
	"""
	return h == make_pw_hash(name, pw, h.split(',')[-1])


def hash_str(val):
	"""
	Helper function for make_secure_val(). Hashes the val with the SECRET in
	the global environment.

	val: String
	Returns: String
	"""
	return hmac.new(SECRET, val).hexdigest()


def make_secure_val(val):
	"""
	Makes the hashed cookie for a given val.
	The hashed cookie uses a pipe | as the separator between the value and it's
	hash.

	val: String
	Returns: String
	"""
	return '%(value)s|%(hashed)s' % {'value': val, 'hashed': hash_str(val)}


def check_secure_val(h):
	"""
	Used to validate the hashed cookie when received from the browser in a
	request.
	if valid -> Returns the val of the cookie

	h: String
	Returns: String
	"""
	val = h.split('|')[0]
	if h == make_secure_val(val):
		return val


USER_RE = re.compile(r"^[a-zA-Z][a-zA-Z0-9_-]{3,20}$")
PASS_RE = re.compile(r"^.{6,20}$")
EMAIL_RE = re.compile(r"^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$")


def valid_username(username):
    return USER_RE.match(username)


def valid_password(password):
    return PASS_RE.match(password)


def valid_email(email):
    return EMAIL_RE.match(email)


def valid_image(image):
	if sys.getsizeof(image) < 950000:
		return True
	else:
		return False



def validate_signup(username, email, fullname, password, profile_picture):
	all_errors  = {"username_error": "",
				   "password_error": "",
				   "signup_error": "",
				   "email_error": "",
				   "fullname_error": "",
				   "profile_picture_error": ""}
	valid_entries = True
	if not valid_username(username):
		all_errors["username_error"] = "That's not a valid username."
		valid_entries = False
	if not valid_password(password):
		all_errors["password_error"] = "That wasn't a valid password."
		valid_entries = False
	if not valid_email(email):
		all_errors["email_error"] = "That's not a valid email."
		valid_entries = False
	if not fullname:
		all_errors["fullname_error"] = "Please enter your full name."
	if not profile_picture:
		all_errors[
		"profile_picture_error"
		] = "Please upload a Profile Picture."
	elif not valid_image(profile_picture):
		all_errors[
		"profile_picture_error"
		] = "Image should be less 1MB. Sorry!"
		valid_entries = False
	if valid_entries:
		if not "@spacecom.in" in email:
			all_errors[
				"signup_error"
				] = "You are not authorized to sign up."
			valid_entries = False
	return valid_entries, all_errors