Add new get_permissions method (#1575)

Closes #1574.

telethon/client/chats.py

@@ -1145,6 +1145,49 @@ class ChatMethods:
         else:
             raise ValueError('You must pass either a channel or a chat')
 
+    async def get_permissions(
+            self: 'TelegramClient',
+            entity: 'hints.EntityLike',
+            user: 'hints.EntityLike'
+    ) -> 'typing.Optional[custom.ParticipantPermissions]':
+        """
+        Fetches the permissions of a user in a specific chat or channel.
+
+        Arguments
+            entity (`entity`):
+                The channel or chat the user is participant of.
+
+            user (`entity`):
+                Target user.
+
+        Example
+            .. code-block:: python
+
+                permissions = await client.get_permissions(chat, user)
+                if permissions.is_admin:
+                    # do something
+        """
+        entity = await self.get_input_entity(entity)
+        user = await self.get_input_entity(user)
+        if helpers._entity_type(user) != helpers._EntityType.USER:
+            raise ValueError('You must pass a user entity')
+        if helpers._entity_type(entity) == helpers._EntityType.CHANNEL:
+            participant = await self(functions.channels.GetParticipantRequest(
+                entity,
+                user
+            ))
+            return custom.ParticipantPermissions(participant.participant, False)
+        elif helpers._entity_type(entity) == helpers._EntityType.CHAT:
+            chat = await self(functions.messages.GetFullChatRequest(
+                entity
+            ))
+            for participant in chat.participants.participants:
+                if participant.user_id == user.id:
+                    return custom.ParticipantPermissions(participant.participant, True)
+            raise errors.UserNotParticipantError(None)
+
+        raise ValueError('You must pass either a channel or a chat')
+
     async def get_stats(
             self: 'TelegramClient',
             entity: 'hints.EntityLike',

telethon/tl/custom/__init__.py

@@ -11,3 +11,4 @@ from .inlineresult import InlineResult
 from .inlineresults import InlineResults
 from .conversation import Conversation
 from .qrlogin import QRLogin
+from .participantpermissions import ParticipantPermissions

telethon/tl/custom/participantpermissions.py

@@ -0,0 +1,97 @@
+from .. import types
+
+
+class ParticipantPermissions:
+    """
+    Participant permissions information
+    """
+    def __init__(self, participant, chat):
+        self.participant = participant
+        self.is_chat: bool = chat
+
+    @property
+    def is_admin(self):
+        return self.is_creator or isinstance(self.participant, (
+            types.ChannelParticipantAdmin,
+            types.ChatParticipantAdmin
+        ))
+
+    @property
+    def is_creator(self):
+        return isinstance(self.participant, types.ChannelParticipantCreator)
+
+    @property
+    def has_default_permissions(self):
+        return isinstance(self.participant, (
+            types.ChannelParticipant,
+            types.ChatParticipant,
+            types.ChannelParticipantSelf
+        ))
+
+    @property
+    def is_banned(self):
+        return isinstance(self.participant, types.ChannelParticipantBanned)
+
+    @property
+    def ban_users(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.ban_users
+
+    @property
+    def pin_messages(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.pin_messages
+
+    @property
+    def add_admins(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat and not self.is_creator:
+            return False
+        return self.participant.admin_rights.add_admins
+
+    @property
+    def invite_users(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.invite_users
+
+    @property
+    def delete_messages(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.delete_messages
+
+    @property
+    def edit_messages(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.edit_messages
+
+    @property
+    def post_messages(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.post_messages
+
+    @property
+    def change_info(self):
+        if not self.is_admin:
+            return False
+        if self.is_chat:
+            return True
+        return self.participant.admin_rights.change_info