channel: add dm_checks module

- channel.messages: check block state before message send

litecord/blueprints/channel/dm_checks.py

@@ -0,0 +1,26 @@
+from quart import current_app as app
+
+from litecord.errors import Forbidden
+from litecord.enums import RelationshipType
+
+
+class ForbiddenDM(Forbidden):
+    error_code = 50007
+
+
+async def dm_pre_check(user_id: int, channel_id: int, peer_id: int):
+    """Check if the user can DM the peer."""
+    # first step is checking if there is a block in any direction
+    blockrow = await app.db.fetchrow("""
+    SELECT rel_type
+    FROM relationships
+    WHERE rel_type = $3
+      AND user_id IN ($1, $2)
+      AND peer_id IN ($1, $2)
+    """, user_id, peer_id, RelationshipType.BLOCK.value)
+
+    if blockrow is not None:
+        raise ForbiddenDM()
+
+    # TODO: check mutual guilds and guild settings for
+    # each user

litecord/blueprints/channel/messages.py

@@ -14,6 +14,7 @@ from litecord.schemas import validate, MESSAGE_CREATE
 from litecord.utils import pg_set_json
 
 from litecord.embed.sanitizer import fill_embed, proxify, fetch_metadata
+from litecord.blueprints.channel.dm_checks import dm_pre_check
 
 
 log = Logger(__name__)
@@ -307,6 +308,10 @@ async def _create_message(channel_id):
 
     # TODO: check connection to the gateway
 
+    if ctype == ChannelType.DM:
+        # guild_id is the dm's peer_id
+        await dm_pre_check(user_id, channel_id, guild_id)
+
     can_everyone = await channel_perm_check(
         user_id, channel_id, 'mention_everyone', False
     )