""" This module deals with correct handling of updates, including gaps, and knowing when the code should "get difference" (the set of updates that the client should know by now minus the set of updates that it actually knows). Each chat has its own [`Entry`] in the [`MessageBox`] (this `struct` is the "entry point"). At any given time, the message box may be either getting difference for them (entry is in [`MessageBox::getting_diff_for`]) or not. If not getting difference, a possible gap may be found for the updates (entry is in [`MessageBox::possible_gaps`]). Otherwise, the entry is on its happy path. Gaps are cleared when they are either resolved on their own (by waiting for a short time) or because we got the difference for the corresponding entry. While there are entries for which their difference must be fetched, [`MessageBox::check_deadlines`] will always return [`Instant::now`], since "now" is the time to get the difference. """ import asyncio from dataclasses import dataclass, field from .._sessions.types import SessionState, ChannelState # Telegram sends `seq` equal to `0` when "it doesn't matter", so we use that value too. NO_SEQ = 0 # See https://core.telegram.org/method/updates.getChannelDifference. BOT_CHANNEL_DIFF_LIMIT = 100000 USER_CHANNEL_DIFF_LIMIT = 100 # > It may be useful to wait up to 0.5 seconds POSSIBLE_GAP_TIMEOUT = 0.5 # After how long without updates the client will "timeout". # # When this timeout occurs, the client will attempt to fetch updates by itself, ignoring all the # updates that arrive in the meantime. After all updates are fetched when this happens, the # client will resume normal operation, and the timeout will reset. # # Documentation recommends 15 minutes without updates (https://core.telegram.org/api/updates). NO_UPDATES_TIMEOUT = 15 * 60 # Entry "enum". # Account-wide `pts` includes private conversations (one-to-one) and small group chats. ENTRY_ACCOUNT = object() # Account-wide `qts` includes only "secret" one-to-one chats. ENTRY_SECRET = object() # Integers will be Channel-specific `pts`, and includes "megagroup", "broadcast" and "supergroup" channels. def next_updates_deadline(): return asyncio.get_running_loop().time() + NO_UPDATES_TIMEOUT class GapError(ValueError): pass # Represents the information needed to correctly handle a specific `tl::enums::Update`. @dataclass class PtsInfo: pts: int pts_count: int entry: object @classmethod def from_update(cls, update): pts = getattr(update, 'pts', None) if pts: pts_count = getattr(update, 'pts_count', None) or 0 entry = getattr(update, 'channel_id', None) or ENTRY_ACCOUNT return cls(pts=pts, pts_count=pts_count, entry=entry) qts = getattr(update, 'qts', None) if qts: pts_count = 1 if isinstance(update, _tl.UpdateNewEncryptedMessage) else 0 return cls(pts=qts, pts_count=pts_count, entry=ENTRY_SECRET) return None # The state of a particular entry in the message box. @dataclass class State: # Current local persistent timestamp. pts: int # Next instant when we would get the update difference if no updates arrived before then. deadline: float # > ### Recovering gaps # > […] Manually obtaining updates is also required in the following situations: # > • Loss of sync: a gap was found in `seq` / `pts` / `qts` (as described above). # > It may be useful to wait up to 0.5 seconds in this situation and abort the sync in case a new update # > arrives, that fills the gap. # # This is really easy to trigger by spamming messages in a channel (with as little as 3 members works), because # the updates produced by the RPC request take a while to arrive (whereas the read update comes faster alone). @dataclass class PossibleGap: deadline: float # Pending updates (those with a larger PTS, producing the gap which may later be filled). updates: list # of updates # Represents a "message box" (event `pts` for a specific entry). # # See https://core.telegram.org/api/updates#message-related-event-sequences. @dataclass class MessageBox: # Map each entry to their current state. map: dict = field(default_factory=dict) # entry -> state # Additional fields beyond PTS needed by `ENTRY_ACCOUNT`. date: int = 1 seq: int = 0 # Holds the entry with the closest deadline (optimization to avoid recalculating the minimum deadline). next_deadline: object = None # entry # Which entries have a gap and may soon trigger a need to get difference. # # If a gap is found, stores the required information to resolve it (when should it timeout and what updates # should be held in case the gap is resolved on its own). # # Not stored directly in `map` as an optimization (else we would need another way of knowing which entries have # a gap in them). possible_gaps: dict = field(default_factory=dict) # entry -> possiblegap # For which entries are we currently getting difference. getting_diff_for: set = field(default_factory=set) # entry # Temporarily stores which entries should have their update deadline reset. # Stored in the message box in order to reuse the allocation. reset_deadlines_for: set = field(default_factory=set) # entry # region Creation, querying, and setting base state. @classmethod def load(cls, session_state, channel_states): """ Create a [`MessageBox`] from a previously known update state. """ deadline = next_updates_deadline() return cls( map={ ENTRY_ACCOUNT: State(pts=session_state.pts, deadline=deadline), ENTRY_SECRET: State(pts=session_state.qts, deadline=deadline), **{s.channel_id: s.pts for s in channel_states} }, date=session_state.date, seq=session_state.seq, next_deadline=ENTRY_ACCOUNT, ) @classmethod def session_state(self): """ Return the current state in a format that sessions understand. This should be used for persisting the state. """ return SessionState( user_id=0, dc_id=0, bot=False, pts=self.map.get(ENTRY_ACCOUNT, 0), qts=self.map.get(ENTRY_SECRET, 0), date=self.date, seq=self.seq, takeout_id=None, ), [ChannelState(channel_id=id, pts=pts) for id, pts in self.map.items() if isinstance(id, int)] def is_empty(self) -> bool: """ Return true if the message box is empty and has no state yet. """ return self.map.get(ENTRY_ACCOUNT, NO_SEQ) == NO_SEQ def check_deadlines(self): """ Return the next deadline when receiving updates should timeout. If a deadline expired, the corresponding entries will be marked as needing to get its difference. While there are entries pending of getting their difference, this method returns the current instant. """ now = asyncio.get_running_loop().time() if self.getting_diff_for: return now deadline = next_updates_deadline() # Most of the time there will be zero or one gap in flight so finding the minimum is cheap. if self.possible_gaps: deadline = min(deadline, *self.possible_gaps.values()) elif self.next_deadline in self.map: deadline = min(deadline, self.map[self.next_deadline]) if now > deadline: # Check all expired entries and add them to the list that needs getting difference. self.getting_diff_for.update(entry for entry, gap in self.possible_gaps.items() if now > gap.deadline) self.getting_diff_for.update(entry for entry, state in self.map.items() if now > state.deadline) # When extending `getting_diff_for`, it's important to have the moral equivalent of # `begin_get_diff` (that is, clear possible gaps if we're now getting difference). for entry in self.getting_diff_for: self.possible_gaps.pop(entry, None) return deadline # Reset the deadline for the periods without updates for a given entry. # # It also updates the next deadline time to reflect the new closest deadline. def reset_deadline(self, entry, deadline): if entry in self.map: self.map[entry].deadline = deadline # TODO figure out why not in map may happen if self.next_deadline == entry: # If the updated deadline was the closest one, recalculate the new minimum. self.next_deadline = min(self.map.items(), key=lambda entry_state: entry_state[1].deadline)[0] elif deadline < self.map.get(self.next_deadline, 0): # If the updated deadline is smaller than the next deadline, change the next deadline to be the new one. self.next_deadline = entry # else an unrelated deadline was updated, so the closest one remains unchanged. # Convenience to reset a channel's deadline, with optional timeout. def reset_channel_deadline(self, channel_id, timeout): self.reset_deadlines(channel_id, asyncio.get_running_loop().time() + (timeout or NO_UPDATES_TIMEOUT)) # Reset all the deadlines in `reset_deadlines_for` and then empty the set. def apply_deadlines_reset(self): next_deadline = next_updates_deadline() reset_deadlines_for = self.reset_deadlines_for self.reset_deadlines_for = set() # "move" the set to avoid self.reset_deadline() from touching it during iter for entry in reset_deadlines_for: self.reset_deadline(entry, next_deadline) reset_deadlines_for.clear() # reuse allocation, the other empty set was a temporary dummy value self.reset_deadlines_for = reset_deadlines_for # Sets the update state. # # Should be called right after login if [`MessageBox::new`] was used, otherwise undesirable # updates will be fetched. def set_state(self, state): deadline = next_updates_deadline() self.map[ENTRY_ACCOUNT] = State(pts=state.pts, deadline=deadline) self.map[ENTRY_SECRET] = State(pts=state.qts, deadline=deadline) self.date = state.date self.seq = state.seq # Like [`MessageBox::set_state`], but for channels. Useful when getting dialogs. # # The update state will only be updated if no entry was known previously. def try_set_channel_state(self, id, pts): if id not in self.map: self.map[id] = State(pts=pts, deadline=next_updates_deadline()) # Begin getting difference for the given entry. # # Clears any previous gaps. def begin_get_diff(self, entry): self.getting_diff_for.add(entry) self.possible_gaps.pop(entry, None) # Finish getting difference for the given entry. # # It also resets the deadline. def end_get_diff(self, entry): self.getting_diff_for.pop(entry, None) self.reset_deadline(entry, next_updates_deadline()) assert entry not in self.possible_gaps, "gaps shouldn't be created while getting difference" # endregion Creation, querying, and setting base state. # region "Normal" updates flow (processing and detection of gaps). # Process an update and return what should be done with it. # # Updates corresponding to entries for which their difference is currently being fetched # will be ignored. While according to the [updates' documentation]: # # > Implementations [have] to postpone updates received via the socket while # > filling gaps in the event and `Update` sequences, as well as avoid filling # > gaps in the same sequence. # # In practice, these updates should have also been retrieved through getting difference. # # [updates documentation] https://core.telegram.org/api/updates def process_updates( self, updates, chat_hashes, result, # out list of updates; returns list of user, chat, or raise if gap ): # XXX adapt updates and chat hashes into updatescombined, raise gap on too long date = updates.date seq_start = updates.seq_start seq = updates.seq updates = updates.updates users = updates.users chats = updates.chats # > For all the other [not `updates` or `updatesCombined`] `Updates` type constructors # > there is no need to check `seq` or change a local state. if updates.seq_start != NO_SEQ: if self.seq + 1 > updates.seq_start: # Skipping updates that were already handled return (updates.users, updates.chats) elif self.seq + 1 < updates.seq_start: # Gap detected self.begin_get_diff(ENTRY_ACCOUNT) raise GapError # else apply self.date = updates.date if updates.seq != NO_SEQ: self.seq = updates.seq result.extend(filter(None, (self.apply_pts_info(u, reset_deadline=True) for u in updates.updates))) self.apply_deadlines_reset() def _sort_gaps(update): pts = PtsInfo.from_update(u) return pts.pts - pts.pts_count if pts else 0 if self.possible_gaps: # For each update in possible gaps, see if the gap has been resolved already. for key in list(self.possible_gaps.keys()): self.possible_gaps[key].updates.sort(key=_sort_gaps) for _ in range(len(self.possible_gaps[key].updates)): update = self.possible_gaps[key].updates.pop(0) # If this fails to apply, it will get re-inserted at the end. # All should fail, so the order will be preserved (it would've cycled once). update = self.apply_pts_info(update, reset_deadline=False) if update: result.append(update) # Clear now-empty gaps. self.possible_gaps = {entry: gap for entry, gap in self.possible_gaps if gap.updates} return (updates.users, updates.chats) # Tries to apply the input update if its `PtsInfo` follows the correct order. # # If the update can be applied, it is returned; otherwise, the update is stored in a # possible gap (unless it was already handled or would be handled through getting # difference) and `None` is returned. def apply_pts_info( self, update, *, reset_deadline, ): pts = PtsInfo.from_update(update) if not pts: # No pts means that the update can be applied in any order. return update # As soon as we receive an update of any form related to messages (has `PtsInfo`), # the "no updates" period for that entry is reset. # # Build the `HashSet` to avoid calling `reset_deadline` more than once for the same entry. if reset_deadline: self.reset_deadlines_for.insert(pts.entry) if pts.entry in self.getting_diff_for: # Note: early returning here also prevents gap from being inserted (which they should # not be while getting difference). return None if pts.entry in self.map: local_pts = self.map[pts.entry].pts if local_pts + pts.pts_count > pts.pts: # Ignore return None elif local_pts + pts.pts_count < pts.pts: # Possible gap # TODO store chats too? if pts.entry not in self.possible_gaps: self.possible_gaps[pts.entry] = PossibleGap( deadline=asyncio.get_running_loop().time() + POSSIBLE_GAP_TIMEOUT, updates=[] ) self.possible_gaps[pts.entry].updates.append(update) return None else: # Apply pass else: # No previous `pts` known, and because this update has to be "right" (it's the first one) our # `local_pts` must be one less. local_pts = pts.pts - 1 # For example, when we're in a channel, we immediately receive: # * ReadChannelInbox (pts = X) # * NewChannelMessage (pts = X, pts_count = 1) # # Notice how both `pts` are the same. If we stored the one from the first, then the second one would # be considered "already handled" and ignored, which is not desirable. Instead, advance local `pts` # by `pts_count` (which is 0 for updates not directly related to messages, like reading inbox). if pts.entry in self.map: self.map[pts.entry].pts = local_pts + pts.pts_count else: self.map[pts.entry] = State(pts=local_pts + pts.pts_count, deadline=next_updates_deadline()) return update # endregion "Normal" updates flow (processing and detection of gaps). # region Getting and applying account difference. # Return the request that needs to be made to get the difference, if any. def get_difference(self): entry = ENTRY_ACCOUNT if entry in self.getting_diff_for: if entry in self.map: return _tl.fn.updates.GetDifference( pts=state.pts, pts_total_limit=None, date=self.date, qts=self.map[ENTRY_SECRET].pts, ) else: # TODO investigate when/why/if this can happen self.end_get_diff(entry) return None # Similar to [`MessageBox::process_updates`], but using the result from getting difference. def apply_difference( self, diff, chat_hashes, ): if isinstance(diff, _tl.updates.DifferenceEmpty): self.date = diff.date self.seq = diff.seq self.end_get_diff(ENTRY_ACCOUNT) return [], [], [] elif isinstance(diff, _tl.updates.Difference): self.end_get_diff(ENTRY_ACCOUNT) chat_hashes.extend(diff.users, diff.chats) return self.apply_difference_type(diff) elif isinstance(diff, _tl.updates.DifferenceSlice): chat_hashes.extend(diff.users, diff.chats) return self.apply_difference_type(diff) elif isinstance(diff, _tl.updates.DifferenceTooLong): # TODO when are deadlines reset if we update the map?? self.map[ENTRY_ACCOUNT].pts = diff.pts self.end_get_diff(ENTRY_ACCOUNT) return [], [], [] def apply_difference_type( self, diff, ): state = getattr(diff, 'intermediate_state', None) or diff.state self.map[ENTRY_ACCOUNT].pts = state.pts self.map[ENTRY_SECRET].pts = state.qts self.date = state.date self.seq = state.seq for u in diff.updates: if isinstance(u, _tl.UpdateChannelTooLong): self.begin_get_diff(u.channel_id) updates.extend(_tl.UpdateNewMessage( message=m, pts=NO_SEQ, pts_count=NO_SEQ, ) for m in diff.new_messages) updates.extend(_tl.UpdateNewEncryptedMessage( message=m, qts=NO_SEQ, ) for m in diff.new_encrypted_messages) return diff.updates, diff.users, diff.chats # endregion Getting and applying account difference. # region Getting and applying channel difference. # Return the request that needs to be made to get a channel's difference, if any. def get_channel_difference( self, chat_hashes, ): entry = next((id for id in self.getting_diff_for if isinstance(id, int)), None) if not entry: return None packed = chat_hashes.get(entry) if not packed: # Cannot get channel difference as we're missing its hash self.end_get_diff(entry) # Remove the outdated `pts` entry from the map so that the next update can correct # it. Otherwise, it will spam that the access hash is missing. self.map.pop(entry, None) return None state = self.map.get(entry) if not state: # TODO investigate when/why/if this can happen # Cannot get channel difference as we're missing its pts self.end_get_diff(entry) return None return _tl.fn.updates.GetChannelDifference( force=False, channel=channel, filter=_tl.ChannelMessagesFilterEmpty(), pts=state.pts, limit=BOT_CHANNEL_DIFF_LIMIT if chat_hashes.is_self_bot() else USER_CHANNEL_DIFF_LIMIT ) # Similar to [`MessageBox::process_updates`], but using the result from getting difference. def apply_channel_difference( self, request, diff, chat_hashes, ): entry = request.channel.channel_id self.possible_gaps.remove(entry) if isinstance(diff, _tl.updates.ChannelDifferenceEmpty): assert diff.final self.end_get_diff(entry) self.map[entry].pts = diff.pts return [], [], [] elif isinstance(diff, _tl.updates.ChannelDifferenceTooLong): assert diff.final self.map[entry].pts = diff.dialog.pts chat_hashes.extend(diff.users, diff.chats) self.reset_channel_deadline(channel_id, diff.timeout) # This `diff` has the "latest messages and corresponding chats", but it would # be strange to give the user only partial changes of these when they would # expect all updates to be fetched. Instead, nothing is returned. return [], [], [] elif isinstance(diff, _tl.updates.ChannelDifference): if diff.final: self.end_get_diff(entry) self.map[entry].pts = pts updates.extend(_tl.UpdateNewMessage( message=m, pts=NO_SEQ, pts_count=NO_SEQ, ) for m in diff.new_messages) chat_hashes.extend(diff.users, diff.chats); self.reset_channel_deadline(channel_id, timeout) (diff.updates, diff.users, diff.chats) # endregion Getting and applying channel difference.