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nanobot/nanobot/webui/forking.py
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Python

"""WebUI chat fork orchestration."""
from __future__ import annotations
import re
import uuid
from collections.abc import Mapping
from typing import Any
from nanobot.session.manager import SessionManager
from nanobot.session.webui_turns import WEBUI_TITLE_METADATA_KEY, clean_generated_title
from nanobot.webui.transcript import (
append_fork_marker,
delete_webui_transcript,
fork_transcript_before_user_index,
write_session_messages_as_transcript,
)
_WEBUI_CHAT_ID_RE = re.compile(r"^[A-Za-z0-9_:-]{1,64}$")
def _valid_webui_chat_id(value: Any) -> bool:
return isinstance(value, str) and _WEBUI_CHAT_ID_RE.match(value) is not None
def create_webui_chat_fork(
session_manager: SessionManager,
*,
source_chat_id: str,
before_user_index: int,
title: str | None = None,
) -> tuple[str, str] | None:
"""Return ``(chat_id, session_key)`` for a new fork, or ``None`` for bad input."""
new_id = str(uuid.uuid4())
source_key = f"websocket:{source_chat_id}"
target_key = f"websocket:{new_id}"
try:
forked = session_manager.fork_session_before_user_index(
source_key,
target_key,
before_user_index,
)
if forked is None:
return None
transcript_ok = fork_transcript_before_user_index(
source_key,
target_key,
before_user_index,
)
if not transcript_ok:
write_session_messages_as_transcript(target_key, forked.messages)
append_fork_marker(target_key)
fork_title = clean_generated_title(title)
if fork_title:
forked.metadata[WEBUI_TITLE_METADATA_KEY] = fork_title
session_manager.save(forked, fsync=True)
except Exception:
delete_webui_transcript(target_key)
session_manager.delete_session(target_key)
raise
return new_id, target_key
async def handle_webui_fork_chat(channel: Any, connection: Any, envelope: Mapping[str, Any]) -> None:
"""Handle the WebUI/desktop ``fork_chat`` websocket command.
``websocket.py`` owns the transport. This module owns WebUI fork semantics:
validate the request, clone session/transcript state, attach the new chat,
and hydrate the client.
"""
source_chat_id = envelope.get("source_chat_id")
raw_index = envelope.get("before_user_index")
if not _valid_webui_chat_id(source_chat_id):
await channel._send_event(connection, "error", detail="invalid source_chat_id")
return
if isinstance(raw_index, bool) or not isinstance(raw_index, int) or raw_index < 0:
await channel._send_event(connection, "error", detail="invalid before_user_index")
return
session_manager = channel.gateway.session_manager
if session_manager is None:
await channel._send_event(connection, "error", detail="session_manager_unavailable")
return
try:
forked = create_webui_chat_fork(
session_manager,
source_chat_id=source_chat_id,
before_user_index=raw_index,
title=envelope.get("title") if isinstance(envelope.get("title"), str) else None,
)
if forked is None:
await channel._send_event(connection, "error", detail="invalid fork source or index")
return
fork_id, fork_key = forked
except Exception as exc:
channel.logger.warning("fork_chat failed: {}", exc)
await channel._send_event(connection, "error", detail="fork_chat_failed")
return
scope = channel._workspaces.scope_for_session_key(fork_key)
channel._attach(connection, fork_id)
await channel._send_event(connection, "attached", chat_id=fork_id)
await channel._send_event(
connection,
"session_updated",
chat_id=fork_id,
scope="metadata",
workspace_scope=scope.payload(),
)
await channel._hydrate_after_subscribe(fork_id)