Merge branch 'master' into active-infractions-validation

1 files changed, 260 insertions, 0 deletions

diff --git a/pydis_site/apps/home/signals.py b/pydis_site/apps/home/signals.py
new file mode 100644
index 00000000..9f286882
--- /dev/null
+++ b/pydis_site/apps/home/signals.py
@@ -0,0 +1,260 @@
+from typing import List, Optional, Type
+
+from allauth.account.signals import user_logged_in
+from allauth.socialaccount.models import SocialAccount, SocialLogin
+from allauth.socialaccount.providers.base import Provider
+from allauth.socialaccount.providers.discord.provider import DiscordProvider
+from allauth.socialaccount.signals import (
+    pre_social_login, social_account_added, social_account_removed,
+    social_account_updated)
+from django.contrib.auth.models import Group, User as DjangoUser
+from django.db.models.signals import post_save, pre_delete, pre_save
+
+from pydis_site.apps.api.models import User as DiscordUser
+from pydis_site.apps.staff.models import RoleMapping
+
+
+class AllauthSignalListener:
+    """
+    Listens to and processes events via the Django Signals system.
+
+    Django Signals is basically an event dispatcher. It consists of Signals (which are the events)
+    and Receivers, which listen for and handle those events. Signals are triggered by Senders,
+    which are essentially just any class at all, and Receivers can filter the Signals they listen
+    for by choosing a Sender, if required.
+
+    Signals themselves define a set of arguments that they will provide to Receivers when the
+    Signal is sent. They are always keyword arguments, and Django recommends that all Receiver
+    functions accept them as `**kwargs` (and will supposedly error if you don't do this),
+    supposedly because Signals can change in the future and your receivers should still work.
+
+    Signals do provide a list of their arguments when they're initially constructed, but this
+    is purely for documentation purposes only and Django does not enforce it.
+
+    The Django Signals docs are here: https://docs.djangoproject.com/en/2.2/topics/signals/
+    """
+
+    def __init__(self):
+        post_save.connect(self.user_model_updated, sender=DiscordUser)
+
+        pre_delete.connect(self.mapping_model_deleted, sender=RoleMapping)
+        pre_save.connect(self.mapping_model_updated, sender=RoleMapping)
+
+        pre_social_login.connect(self.social_account_updated)
+        social_account_added.connect(self.social_account_updated)
+        social_account_updated.connect(self.social_account_updated)
+        social_account_removed.connect(self.social_account_removed)
+
+        user_logged_in.connect(self.user_logged_in)
+
+    def user_logged_in(self, sender: Type[DjangoUser], **kwargs) -> None:
+        """
+        Processes Allauth login signals to ensure a user has the correct perms.
+
+        This method tries to find a Discord SocialAccount for a user - this should always
+        be the case, but the admin user likely won't have one, so we do check for it.
+
+        After that, we try to find the user's stored Discord account details, provided by the
+        bot on the server. Finally, we pass the relevant information over to the
+        `_apply_groups()` method for final processing.
+        """
+        user: DjangoUser = kwargs["user"]
+
+        try:
+            account: SocialAccount = SocialAccount.objects.get(
+                user=user, provider=DiscordProvider.id
+            )
+        except SocialAccount.DoesNotExist:
+            return  # User's never linked a Discord account
+
+        try:
+            discord_user: DiscordUser = DiscordUser.objects.get(id=int(account.uid))
+        except DiscordUser.DoesNotExist:
+            return
+
+        self._apply_groups(discord_user, account)
+
+    def social_account_updated(self, sender: Type[SocialLogin], **kwargs) -> None:
+        """
+        Processes Allauth social account update signals to ensure a user has the correct perms.
+
+        In this case, a SocialLogin is provided that we can check against. We check that this
+        is a Discord login in order to ensure that future OAuth logins using other providers
+        don't break things.
+
+        Like most of the other methods that handle signals, this method defers to the
+        `_apply_groups()` method for final processing.
+        """
+        social_login: SocialLogin = kwargs["sociallogin"]
+
+        account: SocialAccount = social_login.account
+        provider: Provider = account.get_provider()
+
+        if not isinstance(provider, DiscordProvider):
+            return
+
+        try:
+            user: DiscordUser = DiscordUser.objects.get(id=int(account.uid))
+        except DiscordUser.DoesNotExist:
+            return
+
+        self._apply_groups(user, account)
+
+    def social_account_removed(self, sender: Type[SocialLogin], **kwargs) -> None:
+        """
+        Processes Allauth social account reomval signals to ensure a user has the correct perms.
+
+        In this case, a SocialAccount is provided that we can check against. If this is a
+        Discord OAuth being removed from the account, we want to ensure that the user loses
+        their permissions groups as well.
+
+        While this isn't a realistic scenario to reach in our current setup, I've provided it
+        for the sake of covering any edge cases and ensuring that SocialAccounts can be removed
+        from Django users in the future if required.
+
+        Like most of the other methods that handle signals, this method defers to the
+        `_apply_groups()` method for final processing.
+        """
+        account: SocialAccount = kwargs["socialaccount"]
+        provider: Provider = account.get_provider()
+
+        if not isinstance(provider, DiscordProvider):
+            return
+
+        try:
+            user: DiscordUser = DiscordUser.objects.get(id=int(account.uid))
+        except DiscordUser.DoesNotExist:
+            return
+
+        self._apply_groups(user, account, deletion=True)
+
+    def mapping_model_deleted(self, sender: Type[RoleMapping], **kwargs) -> None:
+        """
+        Processes deletion signals from the RoleMapping model, removing perms from users.
+
+        We need to do this to ensure that users aren't left with permissions groups that
+        they shouldn't have assigned to them when a RoleMapping is deleted from the database.
+        """
+        instance: RoleMapping = kwargs["instance"]
+
+        for user in instance.group.user_set.all():
+            user.groups.remove(instance.group)
+
+    def mapping_model_updated(self, sender: Type[RoleMapping], **kwargs) -> None:
+        """
+        Processes update signals from the RoleMapping model.
+
+        This method is in charge of figuring out what changed when a RoleMapping is updated
+        (via the Django admin or otherwise). It operates based on what was changed, and can
+        handle changes to both the role and permissions group assigned to it.
+        """
+        instance: RoleMapping = kwargs["instance"]
+        raw: bool = kwargs["raw"]
+
+        if raw:
+            # Fixtures are being loaded, so don't touch anything
+            return
+
+        old_instance: Optional[RoleMapping] = None
+
+        if instance.id is not None:
+            # We don't try to catch DoesNotExist here because we can't test for it,
+            # it should never happen (unless we have a bad DB failure) but I'm still
+            # kind of antsy about not having the extra security here.
+
+            old_instance = RoleMapping.objects.get(id=instance.id)
+
+        if old_instance:
+            self.mapping_model_deleted(RoleMapping, instance=old_instance)
+
+        accounts = SocialAccount.objects.filter(
+            uid__in=(u.id for u in instance.role.user_set.all())
+        )
+
+        for account in accounts:
+            account.user.groups.add(instance.group)
+
+    def user_model_updated(self, sender: Type[DiscordUser], **kwargs) -> None:
+        """
+        Processes update signals from the Discord User model, assigning perms as required.
+
+        When a user's roles are changed on the Discord server, this method will ensure that
+        the user has only the permissions groups that they should have based on the RoleMappings
+        that have been set up in the Django admin.
+
+        Like some of the other signal handlers, this method ensures that a SocialAccount exists
+        for this Discord User, and defers to `_apply_groups()` to do the heavy lifting of
+        ensuring the permissions groups are correct.
+        """
+        instance: DiscordUser = kwargs["instance"]
+        raw: bool = kwargs["raw"]
+
+        # `update_fields` could be used for checking changes, but it's None here due to how the
+        # model is saved without using that argument - so we can't use it.
+
+        if raw:
+            # Fixtures are being loaded, so don't touch anything
+            return
+
+        try:
+            account: SocialAccount = SocialAccount.objects.get(
+                uid=str(instance.id), provider=DiscordProvider.id
+            )
+        except SocialAccount.DoesNotExist:
+            return  # User has never logged in with Discord on the site
+
+        self._apply_groups(instance, account)
+
+    def _apply_groups(
+            self, user: DiscordUser, account: SocialAccount, deletion: bool = False
+    ) -> None:
+        """
+        Ensures that the correct permissions are set for a Django user based on the RoleMappings.
+
+        This (private) method is designed to check a Discord User against a given SocialAccount,
+        and makes sure that the Django user associated with the SocialAccount has the correct
+        permissions groups.
+
+        While it would be possible to get the Discord User object with just the SocialAccount
+        object, the current approach results in less queries.
+
+        The `deletion` parameter is used to signify that the user's SocialAccount is about
+        to be removed, and so we should always remove all of their permissions groups. The
+        same thing will happen if the user is no longer actually on the Discord server, as
+        leaving the server does not currently remove their SocialAccount from the database.
+        """
+        mappings = RoleMapping.objects.all()
+
+        try:
+            current_groups: List[Group] = list(account.user.groups.all())
+        except SocialAccount.user.RelatedObjectDoesNotExist:
+            return  # There's no user account yet, this will be handled by another receiver
+
+        if not user.in_guild:
+            deletion = True
+
+        if deletion:
+            # They've unlinked Discord or left the server, so we have to remove their groups
+
+            if not current_groups:
+                return  # They have no groups anyway, no point in processing
+
+            account.user.groups.remove(
+                *(mapping.group for mapping in mappings)
+            )
+        else:
+            new_groups = []
+
+            for role in user.roles.all():
+                try:
+                    new_groups.append(mappings.get(role=role).group)
+                except RoleMapping.DoesNotExist:
+                    continue  # No mapping exists
+
+                account.user.groups.add(
+                    *[group for group in new_groups if group not in current_groups]
+                )
+
+                account.user.groups.remove(
+                    *[mapping.group for mapping in mappings if mapping.group not in new_groups]
+                )