# -*- coding: utf-8 -*-
from __future__ import annotations
from copy import deepcopy
from typing import Any

VALID_SESSION_STATUSES = {"planned", "in_progress", "stopped", "completed"}
VALID_ITEM_STATUSES = {"planned", "completed", "partial", "skipped"}


def merge_session_patch(existing: dict[str, Any], payload: dict[str, Any], now: str) -> dict[str, Any]:
    current_revision = int(existing.get("revision") or 1)
    expected = payload.get("expected_revision")
    if expected is not None and int(expected) != current_revision:
        raise RuntimeError(f"revision_conflict:{current_revision}")
    result = deepcopy(existing)
    profile = payload.get("profile")
    if isinstance(profile, dict):
        result["profile"] = deepcopy(profile)
    week_statuses = payload.get("week_statuses")
    if isinstance(week_statuses, dict):
        result["week_statuses"] = deepcopy(week_statuses)
    key = str(payload.get("session_key") or "")
    session = payload.get("session")
    if key and isinstance(session, dict):
        result.setdefault("sessions", {})[key] = deepcopy(session)
    result["revision"] = current_revision + 1
    result["updated_at"] = now
    return result