import base64
import ipaddress
import struct
from .abstract import Session
from .memory import MemorySession
from ..crypto import AuthKey
_STRUCT_PREFORMAT = '>B{}sH256s'
CURRENT_VERSION = '1'
class StringSession(MemorySession):
"""
This session file can be easily saved and loaded as a string. According
to the initial design, it contains only the data that is necessary for
successful connection and authentication, so takeout ID is not stored.
It is thought to be used where you don't want to create any on-disk
files but would still like to be able to save and load existing sessions
by other means.
You can use custom `encode` and `decode` functions, if present:
* `encode` definition must be ``def encode(value: bytes) -> str:``.
* `decode` definition must be ``def decode(value: str) -> bytes:``.
"""
def __init__(self, string: str = None):
super().__init__()
if string:
if string[0] != CURRENT_VERSION:
raise ValueError('Not a valid string')
string = string[1:]
ip_len = 4 if len(string) == 352 else 16
self._dc_id, ip, self._port, key = struct.unpack(
_STRUCT_PREFORMAT.format(ip_len), StringSession.decode(string))
self._server_address = ipaddress.ip_address(ip).compressed
if any(key):
self._auth_key = AuthKey(key)
@staticmethod
def encode(x: bytes) -> str:
return base64.urlsafe_b64encode(x).decode('ascii')
@staticmethod
def decode(x: str) -> bytes:
return base64.urlsafe_b64decode(x)
def save(self: Session):
if not self.auth_key:
return ''
ip = ipaddress.ip_address(self.server_address).packed
return CURRENT_VERSION + StringSession.encode(struct.pack(
_STRUCT_PREFORMAT.format(len(ip)),
self.dc_id,
ip,
self.port,
self.auth_key.key
))
