decorators.py

# Copyright The IETF Trust 2016-2020, All Rights Reserved
# -*- coding: utf-8 -*-


import datetime

from functools import wraps

from django.conf import settings
from django.contrib.auth import login
from django.http import HttpResponse
from django.shortcuts import render
from django.utils import timezone
from django.utils.encoding import force_bytes

import debug                            # pyflakes:ignore

from ietf.person.models import Person, PersonalApiKey, PersonApiKeyEvent
from ietf.utils import log


def person_required(f):
    @wraps(f)
    def _wrapper(request, *args, **kwargs):
        if not request.user.is_authenticated:
            raise ValueError("The @person_required decorator should be called after @login_required.")
        try:
            request.user.person
        except Person.DoesNotExist:
            return render(request, 'registration/missing_person.html')
        return  f(request, *args, **kwargs)
    return _wrapper


def require_api_key(f):
    @wraps(f)
    def _wrapper(request, *args, **kwargs):
        def err(code, text):
            return HttpResponse(text, status=code, content_type=f"text/plain; charset={settings.DEFAULT_CHARSET}")
        # Check method and get hash
        if request.method == 'POST':
            hash = request.POST.get('apikey')
        elif request.method == 'GET':
            hash = request.GET.get('apikey')
        else:
            return err(405, "Method not allowed")
        if not hash:
            return err(400, "Missing apikey parameter")
        # Check hash
        key = PersonalApiKey.validate_key(force_bytes(hash))
        if not key:
            return err(403, "Invalid apikey")
        # Check endpoint
        urlpath = request.META.get('PATH_INFO')
        if not (urlpath and urlpath == key.endpoint):
            return err(400, "Apikey endpoint mismatch") 
        # Check time since regular login
        person = key.person
        last_login = person.user.last_login
        if not person.user.is_staff:
            time_limit = (timezone.now() - datetime.timedelta(days=settings.UTILS_APIKEY_GUI_LOGIN_LIMIT_DAYS))
            if last_login == None or last_login < time_limit:
                return err(400, "Too long since last regular login")
        # Log in
        login(request, person.user)
        # restore the user.last_login field, so it reflects only gui logins
        person.user.last_login = last_login
        person.user.save()
        # Update stats
        key.count += 1
        key.latest = timezone.now()
        key.save()
        PersonApiKeyEvent.objects.create(person=person, type='apikey_login', key=key, desc="Logged in with key ID %s, endpoint %s" % (key.id, key.endpoint))
        # Execute decorated function
        try:
            ret = f(request, *args, **kwargs)
        except AttributeError as e:
            log.log("Bad API call: args: %s, kwargs: %s, exception: %s" % (args, kwargs, e))
            return err(400, "Bad or missing parameters")
        return ret
    return _wrapper


def memoize(func):
    @wraps(func)
    def _memoize(self, *args, **kwargs):
        '''Memoize wrapper for instance methods.  Use @lru_cache for functions.'''
        if kwargs:  # frozenset is used to ensure hashability
            key = args, frozenset(list(kwargs.items()))
        else:
            key = args
        # instance method, set up cache if needed
        if not hasattr(self, '_cache'):
            self._cache = {}
        if not func in self._cache:
            self._cache[func] = {}            
        #
        cache = self._cache[func]
        if key not in cache:
            cache[key] = func(self, *args, **kwargs)
        return cache[key]

    if not hasattr(func, '__class__'):
        raise NotImplementedError("Use @lru_cache instead of memoize() for functions.")
    # For methods, we want the cache on the object, not on the class, in order
    # to not having to think about cache bloat and content becoming stale, so
    # we cannot set up the cache here.
    return _memoize


def ignore_view_kwargs(*args):
    """Ignore the specified kwargs if they are present

    Usage: 
      @ignore_view_kwargs("ignore_arg1", "ignore_arg2")
      def my_view(request, good_arg):
        ...

      This will allow my_view() to be used in url() paths that have zero, one, or both of
      ignore_arg1 and ignore_arg2 captured. These will be ignored, while good_arg will still
      be captured as usual.
    """
    kwargs_to_ignore = args

    def decorate(view):
        @wraps(view)
        def wrapped(*args, **kwargs):
            for kwarg in kwargs_to_ignore:
                kwargs.pop(kwarg, None)
            return view(*args, **kwargs)

        return wrapped

    return decorate