Sith/eboutic/forms.py

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#
# Copyright 2022
# - Maréchal <thgirod@hotmail.com
#
# Ce fichier fait partie du site de l'Association des Étudiants de l'UTBM,
# http://ae.utbm.fr.
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License a published by the Free Software
# Foundation; either version 3 of the License, or (at your option) any later
# version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
# details.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Sofware Foundation, Inc., 59 Temple
# Place - Suite 330, Boston, MA 02111-1307, USA.
#
#
import json
import re
import typing
from urllib.parse import unquote
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from django.http import HttpRequest
from django.utils.translation import gettext as _
from sentry_sdk import capture_message
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from eboutic.models import get_eboutic_products
class BasketForm:
"""
Class intended to perform checks on the request sended to the server when
the user submits his basket from /eboutic/
Because it must check an unknown number of fields, coming from a cookie
and needing some databases checks to be performed, inheriting from forms.Form
or using formset would have been likely to end in a big ball of wibbly-wobbly hacky stuff.
Thus this class is a pure standalone and performs its operations by its own means.
However, it still tries to share some similarities with a standard django Form.
Example:
::
def my_view(request):
form = BasketForm(request)
form.clean()
if form.is_valid():
# perform operations
else:
errors = form.get_error_messages()
# return the cookie that was in the request, but with all
# incorrects elements removed
cookie = form.get_cleaned_cookie()
You can also use a little shortcut by directly calling `form.is_valid()`
without calling `form.clean()`. In this case, the latter method shall be
implicitly called.
"""
# check the json is an array containing non-nested objects.
# values must be strings or numbers
# this is matched :
# [{"id": 4, "name": "[PROMO 22] badges", "unit_price": 2.3, "quantity": 2}]
# but this is not :
# [{"id": {"nested_id": 10}, "name": "[PROMO 22] badges", "unit_price": 2.3, "quantity": 2}]
# and neither does this :
# [{"id": ["nested_id": 10], "name": "[PROMO 22] badges", "unit_price": 2.3, "quantity": 2}]
# and neither does that :
# [{"id": null, "name": "[PROMO 22] badges", "unit_price": 2.3, "quantity": 2}]
json_cookie_re = re.compile(
r"^\[\s*(\{\s*(\"[^\"]*\":\s*(\"[^\"]{0,64}\"|\d{0,5}\.?\d+),?\s*)*\},?\s*)*\s*\]$"
)
def __init__(self, request: HttpRequest):
self.user = request.user
self.cookies = request.COOKIES
self.error_messages = set()
self.correct_cookie = []
def clean(self) -> None:
"""
Perform all the checks, but return nothing.
To know if the form is valid, the `is_valid()` method must be used.
The form shall be considered as valid if it meets all the following conditions :
- it contains a "basket_items" key in the cookies of the request given in the constructor
- this cookie is a list of objects formatted this way : `[{'id': <int>, 'quantity': <int>,
'name': <str>, 'unit_price': <float>}, ...]`. The order of the fields in each object does not matter
- all the ids are positive integers
- all the ids refer to products available in the EBOUTIC
- all the ids refer to products the user is allowed to buy
- all the quantities are positive integers
"""
# replace escaped double quotes by single quotes, as the RegEx used to check the json
# does not support escaped double quotes
basket = unquote(self.cookies.get("basket_items", "")).replace('\\"', "'")
if basket in ("[]", ""):
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self.error_messages.add(_("You have no basket."))
return
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# check that the json is not nested before parsing it to make sure
# malicious user can't DDoS the server with deeply nested json
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if not BasketForm.json_cookie_re.match(basket):
# As the validation of the cookie goes through a rather boring regex,
# we can regularly have to deal with subtle errors that we hadn't forecasted,
# so we explicitly lay a Sentry message capture here.
capture_message(
"Eboutic basket regex checking failed to validate basket json",
level="error",
)
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self.error_messages.add(_("The request was badly formatted."))
return
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try:
basket = json.loads(basket)
except json.JSONDecodeError:
self.error_messages.add(_("The basket cookie was badly formatted."))
return
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if type(basket) is not list or len(basket) == 0:
self.error_messages.add(_("Your basket is empty."))
return
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for item in basket:
expected_keys = {"id", "quantity", "name", "unit_price"}
if type(item) is not dict or set(item.keys()) != expected_keys:
self.error_messages.add("One or more items are badly formatted.")
continue
# check the id field is a positive integer
if type(item["id"]) is not int or item["id"] < 0:
self.error_messages.add(
_("%(name)s : this product does not exist.")
% {"name": item["name"]}
)
continue
# check a product with this id does exist
ids = {product.id for product in get_eboutic_products(self.user)}
if not item["id"] in ids:
self.error_messages.add(
_(
"%(name)s : this product does not exist or may no longer be available."
)
% {"name": item["name"]}
)
continue
if type(item["quantity"]) is not int or item["quantity"] < 0:
self.error_messages.add(
_("You cannot buy %(nbr)d %(name)s.")
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% {"nbr": item["quantity"], "name": item["name"]}
)
continue
# if we arrive here, it means this item has passed all tests
self.correct_cookie.append(item)
# for loop for item checking ends here
# this function does not return anything.
# instead, it fills a set containing the collected error messages
# an empty set means that no error was seen thus everything is ok
# and the form is valid.
# a non-empty set means there was at least one error thus
# the form is invalid
def is_valid(self) -> bool:
"""
return True if the form is correct else False.
If the `clean()` method has not been called beforehand, call it
"""
if self.error_messages == set() and self.correct_cookie == []:
self.clean()
if self.error_messages:
return False
return True
def get_error_messages(self) -> typing.List[str]:
return list(self.error_messages)
def get_cleaned_cookie(self) -> str:
if not self.correct_cookie:
return ""
return json.dumps(self.correct_cookie)