import logging
import sys
from typing import Optional

from app.core.config import settings

try:
    from fluent import handler as fluent_handler
except Exception:  # pragma: no cover - 运行时兜底
    fluent_handler = None

def _build_fluent_handler() -> Optional[logging.Handler]:
    """
    创建 Fluentd Handler。
    若 fluent-logger 未安装或初始化失败，返回 None。
    """
    if not settings.FLUENTD_ENABLED:
        return None
    if fluent_handler is None:
        logging.getLogger(__name__).warning("fluent-logger 未安装，已跳过 Fluentd 日志输出。")
        return None

    try:
        fh = fluent_handler.FluentHandler(
            tag=settings.FLUENTD_EFFECTIVE_TAG,
            host=settings.FLUENTD_HOST,
            port=settings.FLUENTD_PORT,
            timeout=settings.FLUENTD_TIMEOUT_SEC
        )
        # 输出结构化字段，避免 record 退化为 string。
        if hasattr(fluent_handler, "FluentRecordFormatter"):
            fh.setFormatter(fluent_handler.FluentRecordFormatter({
                "level": "%(levelname)s",
                "logger": "%(name)s",
                "message": "%(message)s",
                "time": "%(asctime)s",
                "app": settings.APP_NAME,
                "env": settings.APP_ENV,
            }))
        return fh
    except Exception as e:
        logging.getLogger(__name__).exception("初始化 Fluentd Handler 失败: %s", str(e))
        return None


def setup_logging():
    """
    配置日志系统，使其同时输出到文件和控制台。
    这个函数应该在应用程序启动时只调用一次。
    """
    root_logger = logging.getLogger()

    # 避免重复初始化
    if root_logger.handlers:
        return

    root_logger.setLevel(getattr(logging, settings.LOG_LEVEL.upper(), logging.INFO))

    stream_formatter = logging.Formatter("%(asctime)s %(levelname)s [%(name)s] %(message)s")
    file_formatter = logging.Formatter("%(asctime)s %(levelname)s [%(name)s] %(message)s")

    console_handler = logging.StreamHandler(sys.stdout)
    console_handler.setFormatter(stream_formatter)
    root_logger.addHandler(console_handler)

    file_handler = logging.FileHandler('app.log', mode='w', encoding='utf-8')
    file_handler.setFormatter(file_formatter)
    root_logger.addHandler(file_handler)

    if not settings.FLUENTD_ENABLED:
        root_logger.info("日志系统已成功配置，将输出到控制台和 app.log 文件。")
        return

    fluentd_handler = _build_fluent_handler()
    if fluentd_handler:
        root_logger.addHandler(fluentd_handler)
        root_logger.info(
            "Fluentd日志输出已启用: host=%s port=%s tag=%s",
            settings.FLUENTD_HOST, settings.FLUENTD_PORT, settings.FLUENTD_EFFECTIVE_TAG
        )

    root_logger.info("日志系统已成功配置，将输出到控制台和 app.log 文件。")


def get_logger(name: str) -> logging.Logger:
    """
    获取一个指定名称的日志记录器实例。
    假设 setup_logging() 已经在此之前被调用。
    """
    return logging.getLogger(name)