Add new get_permissions method (#1575)

Closes #1574.

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