Added a Session class

tl/session.py

@@ -0,0 +1,47 @@
+# This file is based on TLSharp
+# https://github.com/sochix/TLSharp/blob/master/TLSharp.Core/Session.cs
+from os.path import isfile as file_exists
+import time
+import pickle
+import utils.helpers as utils
+
+
+class Session:
+    def __init__(self, session_user_id):
+        self.session_user_id = session_user_id
+        self.server_address = '91.108.56.165'
+        self.port = 443
+        self.auth_key = None
+        self.id = utils.generate_random_long(signed=False)
+        self.sequence = 0
+        self.salt = 0  # Unsigned long
+        self.time_offset = 0
+        self.last_message_id = 0  # Long
+        self.session_expires = 0
+        self.user = None
+
+    def save(self):
+        """Saves the current session object as session_user_id.session"""
+        with open('{}.session'.format(self.session_user_id), 'wb') as file:
+            pickle.dump(self, file)
+
+    @staticmethod
+    def try_load_or_create_new(self, session_user_id):
+        """Loads a saved session_user_id session, or creates a new one if none existed before"""
+        filepath = '{}.session'.format(self.session_user_id)
+
+        if file_exists(filepath):
+            with open(filepath, 'rb') as file:
+                return pickle.load(self)
+        else:
+            return Session(session_user_id)
+
+    def get_new_msg_id(self):
+        """Generates a new message ID based on the current time (in ms) since epoch"""
+        # Refer to mtproto_plain_sender.py for the original method, this is a simple copy
+        new_msg_id = int(self.time_offset + time.time() * 1000)
+        if self._last_msg_id >= new_msg_id:
+            new_msg_id = self._last_msg_id + 4
+
+        self._last_msg_id = new_msg_id
+        return new_msg_id