From d36885728f4daab4cc6dceae5cf2e41c55f4bf28 Mon Sep 17 00:00:00 2001
From: Ryan Barrett <git@ryanb.org>
Date: Thu, 18 Apr 2024 15:56:40 -0700
Subject: [PATCH] Protocol.receive: blocking protocol user disables that
 protocol

for #880
---
 common.py              | 11 +++++++++++
 protocol.py            | 28 +++++++++++++++++++++++++++-
 tests/test_protocol.py | 28 ++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/common.py b/common.py
index 2cf858e..35d397a 100644
--- a/common.py
+++ b/common.py
@@ -33,6 +33,8 @@ CONTENT_TYPE_HTML = 'text/html; charset=utf-8'
 
 # Protocol pairs that we currently support bridging between. Values must be
 # Protocol LABELs. Each pair must be lexicographically sorted!
+# TODO: remove in favor of Protocol.DEFAULT_ENABLED_PROTOCOLS and
+# User.enabled_protocols
 ENABLED_BRIDGES = frozenset((
     ('activitypub', 'web'),
     ('atproto', 'web'),
@@ -255,6 +257,15 @@ def add(seq, val):
         seq.append(val)
 
 
+def remove(seq, val):
+    """Removes ``val`` to ``seq`` if seq contains it.
+
+    Useful for treating repeated ndb properties like sets instead of lists.
+    """
+    if val in seq:
+        seq.remove(val)
+
+
 def create_task(queue, delay=None, **params):
     """Adds a Cloud Tasks task.
 
diff --git a/protocol.py b/protocol.py
index 9ffb96d..4e6b8a8 100644
--- a/protocol.py
+++ b/protocol.py
@@ -20,7 +20,16 @@ from oauth_dropins.webutil.util import json_dumps, json_loads
 import werkzeug.exceptions
 
 import common
-from common import add, DOMAIN_BLOCKLIST, DOMAIN_RE, DOMAINS, error, subdomain_wrap
+from common import (
+    add,
+    DOMAIN_BLOCKLIST,
+    DOMAIN_RE,
+    DOMAINS,
+    error,
+    PROTOCOL_DOMAINS,
+    remove,
+    subdomain_wrap,
+)
 from flask_app import app
 from ids import translate_object_id, translate_user_id
 from models import Follower, get_originals, Object, PROTOCOLS, Target, User
@@ -29,6 +38,7 @@ SUPPORTED_TYPES = (
     'accept',
     'article',
     'audio',
+    'block',
     'comment',
     'delete',
     'follow',
@@ -783,6 +793,22 @@ class Protocol:
 
             # fall through to deliver to followers
 
+        elif obj.type == 'block':
+            proto = Protocol.for_bridgy_subdomain(inner_obj_id)
+            if not proto:
+                logger.info("Ignoring block, target isn't one of our protocol domains")
+                return 'OK', 200
+
+            @ndb.transactional()
+            def block():
+                nonlocal from_user
+                from_user = from_user.key.get()
+                remove(from_user.enabled_protocols, proto.LABEL)
+                from_user.put()
+
+            block()
+            return 'OK', 200
+
         # fetch actor if necessary
         if actor and actor.keys() == set(['id']):
             logger.info('Fetching actor so we have name, profile photo, etc')
diff --git a/tests/test_protocol.py b/tests/test_protocol.py
index c1f4a73..0ab7812 100644
--- a/tests/test_protocol.py
+++ b/tests/test_protocol.py
@@ -1779,6 +1779,34 @@ class ProtocolReceiveTest(TestCase):
             }],
         }, obj.key.get().our_as1)
 
+    def test_block_protocol_user_removes_from_enabled_protocols(self):
+        block = {
+            'objectType': 'activity',
+            'verb': 'block',
+            'id': 'eefake:block',
+            'actor': 'eefake:user',
+            'object': 'fa.brid.gy',
+        }
+
+        user = self.make_user('eefake:user', cls=ExplicitEnableFake)
+        self.assertFalse(ExplicitEnableFake.is_enabled_to(Fake, user))
+
+        # protocol isn't enabled yet, block is a noop
+        self.assertEqual(('OK', 200), ExplicitEnableFake.receive_as1(block))
+        user = user.key.get()
+        self.assertEqual([], user.enabled_protocols)
+
+        # enable protocol, now block should remove it
+        user.enabled_protocols = ['fake']
+        user.put()
+        self.assertTrue(ExplicitEnableFake.is_enabled_to(Fake, user))
+
+        block['id'] += '2'
+        self.assertEqual(('OK', 200), ExplicitEnableFake.receive_as1(block))
+        user = user.key.get()
+        self.assertEqual([], user.enabled_protocols)
+        self.assertFalse(ExplicitEnableFake.is_enabled_to(Fake, user))
+
     def test_receive_task_handler(self):
         note = {
             'id': 'fake:post',