"""结构化日志 — 单行 JSON 输出 + 请求上下文注入

设计要点：
1. 零第三方依赖，只用 stdlib（logging + json + contextvars）。
2. 业务代码通过 `extra={"extra_fields": {...}}` 附加结构化字段，
   不要把可检索的字段拼进 msg 字符串 —— 拼进去就只能靠正则捞了。
3. request_id / user 走 contextvar。contextvar 在 asyncio 下按任务隔离，
   并发请求之间不会串号；由 RequestContextMiddleware 与 get_current_user 写入。
"""
from __future__ import annotations

import json
import logging
import sys
from contextvars import ContextVar
from datetime import datetime, timezone

# 请求级上下文
request_id_var: ContextVar[str | None] = ContextVar("request_id", default=None)
user_var: ContextVar[str | None] = ContextVar("user", default=None)


class _ContextFilter(logging.Filter):
    """把 contextvar 注入每条 record，使 JSON 自带 request_id / user"""

    def filter(self, record: logging.LogRecord) -> bool:
        record.request_id = request_id_var.get()
        record.user = user_var.get()
        return True


class JsonFormatter(logging.Formatter):
    """单行 JSON — 便于 Loki / ELK / CloudWatch 直接解析，无需正则"""

    def format(self, record: logging.LogRecord) -> str:
        payload: dict = {
            "ts": datetime.fromtimestamp(record.created, timezone.utc).isoformat(),
            "level": record.levelname,
            "logger": record.name,
            "msg": record.getMessage(),
        }
        if getattr(record, "request_id", None):
            payload["request_id"] = record.request_id
        if getattr(record, "user", None):
            payload["user"] = record.user
        payload.update(getattr(record, "extra_fields", None) or {})
        if record.exc_info:
            payload["exc"] = self.formatException(record.exc_info)
        return json.dumps(payload, ensure_ascii=False, default=str)


class TextFormatter(logging.Formatter):
    """本地开发可读格式（LOG_JSON=false 时启用）"""

    def format(self, record: logging.LogRecord) -> str:
        line = (
            f"{self.formatTime(record, '%H:%M:%S')} "
            f"{record.levelname:<5} {record.name} - {record.getMessage()}"
        )
        extras = getattr(record, "extra_fields", None)
        if extras:
            line += " | " + " ".join(f"{k}={v}" for k, v in extras.items())
        if record.exc_info:
            line += "\n" + self.formatException(record.exc_info)
        return line


def setup_logging(level: str = "INFO", json_output: bool = True) -> None:
    """配置根 logger。必须在应用启动前调用一次。"""
    handler = logging.StreamHandler(sys.stdout)
    handler.setFormatter(JsonFormatter() if json_output else TextFormatter())
    handler.addFilter(_ContextFilter())

    root = logging.getLogger()
    # 清空既有 handler：uvicorn --reload / 多 worker 下模块可能被重复导入，
    # 不清会看到每条日志打印 N 遍
    root.handlers.clear()
    root.addHandler(handler)
    root.setLevel(level.upper())

    # uvicorn 自带 handler 会绕过上面的 formatter，必须清掉并让它向根传播
    for name in ("uvicorn", "uvicorn.error", "uvicorn.access"):
        lg = logging.getLogger(name)
        lg.handlers.clear()
        lg.propagate = True

    # 访问日志统一由 RequestContextMiddleware 输出（含耗时 / 用户 / request_id），
    # 故关闭 uvicorn 自带的访问日志，避免重复
    logging.getLogger("uvicorn.access").disabled = True