text: import re
  
  from django.conf import settings
  
  
  def set_cookie_without_samesite(request, response, key, *args, **kwargs):
      assert 'samesite' not in kwargs
      response.set_cookie(key, *args, **kwargs)
      is_secure = (
          kwargs.get('secure', False) or request.scheme == 'https' or
          settings.SITE_URL.startswith('https://')
      )
      if not is_secure:
          # https://www.chromestatus.com/feature/5633521622188032
          return
      if should_send_same_site_none(request.headers.get('User-Agent', '')):
          # Chromium is rolling out SameSite=Lax as a default
          # https://www.chromestatus.com/feature/5088147346030592
          # This however breaks all pretix-in-an-iframe things, such as the pretix Widget.
          # Sadly, this means we need to forcefully set SameSite=None and rely on our other
          # CSRF protections to be working.
          response.cookies[key]['samesite'] = 'None'
          # This will only work on secure cookies as well
          # https://www.chromestatus.com/feature/5633521622188032
          response.cookies[key]['secure'] = is_secure
  
  
  # Based on https://www.chromium.org/updates/same-site/incompatible-clients
  # Copyright 2019 Google LLC.
  # SPDX-License-Identifier: Apache-2.0
  
  
  def should_send_same_site_none(useragent):
      # Don’t send `SameSite=None` to known incompatible clients.
      return not has_web_kit_same_site_bug(useragent) and not drops_unrecognized_same_site_cookies(useragent)
  
  
  def has_web_kit_same_site_bug(useragent):
      return is_ios_version(12, useragent) or (
          is_macosx_version(10, 14, useragent) and (is_safari(useragent) or is_mac_embedded_browser(useragent))
      )
  
  
  def drops_unrecognized_same_site_cookies(useragent):
      if is_uc_browser(useragent):
          return not is_uc_browser_version_at_least(12, 13, 2, useragent)
      return (
          is_chromium_based(useragent) and is_chromium_version_at_least(51, useragent) and
          not is_chromium_version_at_least(67, useragent)
      )
  
  
  # Regex parsing of User-Agent string. (See note above!)
  RE_CHROMIUM = re.compile(r"Chrom(e|ium)")
  RE_CHROMIUM_VERSION = re.compile(r"Chrom[^ /]+[ /]([0-9]+)[.0-9]*")
  RE_UC_VERSION = re.compile(r"UC[ ]?Browser/([0-9]+)\.([0-9]+)\.([0-9]+)[.0-9]*")
  RE_IOS_VERSION = re.compile(r"\(iP.+; CPU .*OS ([0-9]+)[_0-9]*.*\) AppleWebKit/")
  RE_MAC_VERSION = re.compile(r"\(Macintosh;.*Mac OS X ([0-9]+)_([0-9]+)[_0-9]*.*\) AppleWebKit/")
  RE_SAFARI = re.compile(r"Version/.* Safari/")
  RE_MAC_EMBEDDED = re.compile(r"^Mozilla/[.0-9]+ \(Macintosh;.*Mac OS X [_0-9]+\) AppleWebKit/[.0-9]+ \(KHTML, "
                               r"like Gecko\)$")
  
  
  def is_ios_version(major, useragent):
      m = RE_IOS_VERSION.search(useragent)
      if not m:
          return False
      return m.group(1) == str(major)
  
  
  def is_macosx_version(major, minor, useragent):
      m = RE_MAC_VERSION.search(useragent)
      if not m:
          return False
  
      return m.group(1) == str(major) and m.group(2) == str(minor)
  
  
  def is_safari(useragent):
      return RE_SAFARI.search(useragent) and not is_chromium_based(useragent)
  
  
  def is_mac_embedded_browser(useragent):
      return RE_MAC_EMBEDDED.search(useragent)
  
  
  def is_chromium_based(useragent):
      return RE_CHROMIUM.search(useragent)
  
  
  def is_chromium_version_at_least(major, useragent):
      # Extract digits from first capturing group.
      match = RE_CHROMIUM_VERSION.search(useragent)
      if not match:
          return False
      version = int(match.group(1))
      return version >= major
  
  
  def is_uc_browser(useragent):
      return 'UCBrowser/' in useragent
  
  
  def is_uc_browser_version_at_least(major, minor, build, useragent):
      major_version = int(RE_UC_VERSION.search(useragent).group(1))
      minor_version = int(RE_UC_VERSION.search(useragent).group(2))
      build_version = int(RE_UC_VERSION.search(useragent).group(3))
      if major_version != major:
          return major_version > major
      if minor_version != minor:
          return minor_version > minor
      return build_version >= build
  