"""AwoooP Phase 2.4: Project ID Context Variable
================================================
2026-05-04 ogt + Claude Sonnet 4.6（ADR-123 background loop tagging）

設計原則：
- Python asyncio.create_task() 自動繼承父任務的 ContextVar 值
- 起始流程不再在 lifespan 強制寫入固定 PROJECT_ID；呼叫端需明確提供 project_id
- get_db_context() 僅接受明確參數或已注入的 contextvar 作為 tenant 來源
- 多租戶未來：呼叫端傳入不同 project_id 即可隔離，無需改 loop 本體
"""
from __future__ import annotations

from contextvars import ContextVar, Token

# 追蹤當前非同步任務的 project_id
# Fail-Closed: 移除 default="awoooi"，進 DB 路徑需要明確租戶標籤
PROJECT_ID: ContextVar[str | None] = ContextVar("project_id")
PROJECT_ID_SOURCE: ContextVar[str | None] = ContextVar("project_id_source")
PROJECT_ID_REQUEST_ID: ContextVar[str | None] = ContextVar("project_id_request_id")


def set_project_context(
    project_id: str | None,
    source: str = "runtime",
    request_id: str | None = None,
) -> tuple[Token[str | None], Token[str | None], Token[str | None]]:
    """
    設定當前 request/context 的 project 上下文，並回傳 ContextVar token 供 restore。
    """
    return (
        PROJECT_ID.set(project_id),
        PROJECT_ID_SOURCE.set(source),
        PROJECT_ID_REQUEST_ID.set(request_id),
    )


def clear_project_context(tokens: tuple[Token[str | None], Token[str | None], Token[str | None]]) -> None:
    """清除 request 上下文，回復前一個 ContextVar 狀態。"""
    PROJECT_ID_REQUEST_ID.reset(tokens[2])
    PROJECT_ID_SOURCE.reset(tokens[1])
    PROJECT_ID.reset(tokens[0])


def get_project_context() -> dict[str, str | None]:
    """取得目前上下文快照（可直接寫入 audit log）。"""
    return {
        "project_id": PROJECT_ID.get(None),
        "source": PROJECT_ID_SOURCE.get(None),
        "request_id": PROJECT_ID_REQUEST_ID.get(None),
    }


def get_current_project_id() -> str | None:
    """取得當前任務的 project_id（給 service 層使用）"""
    return PROJECT_ID.get(None)


def get_current_project_context() -> dict[str, str | None]:
    """取得可追溯上下文（同 get_project_context，保留 API 命名）。"""
    return get_project_context()