"""
全局异常体系。

只统一*错误*响应格式 {error_code, message, request_id}。
成功响应直接返回 Pydantic model / FileResponse / 原始结构，不强制包装。
"""

from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
from loguru import logger


class AppError(Exception):
    """Base application exception."""

    def __init__(
        self,
        message: str = "内部服务器错误",
        *,
        status_code: int = 500,
        error_code: str = "INTERNAL_ERROR",
    ):
        self.message = message
        self.status_code = status_code
        self.error_code = error_code
        super().__init__(message)


class NotFoundError(AppError):
    def __init__(self, message: str = "资源不存在"):
        super().__init__(message, status_code=404, error_code="NOT_FOUND")


class AuthenticationError(AppError):
    def __init__(self, message: str = "认证失败"):
        super().__init__(message, status_code=401, error_code="AUTHENTICATION_FAILED")


class AuthorizationError(AppError):
    def __init__(self, message: str = "权限不足"):
        super().__init__(message, status_code=403, error_code="FORBIDDEN")


class ValidationError(AppError):
    def __init__(self, message: str = "请求参数无效"):
        super().__init__(message, status_code=422, error_code="VALIDATION_ERROR")


class ProviderError(AppError):
    def __init__(self, message: str = "外部服务异常", *, provider: str = ""):
        super().__init__(message, status_code=502, error_code="PROVIDER_ERROR")
        self.provider = provider


class QuotaExceededError(AppError):
    def __init__(self, message: str = "配额已用尽"):
        super().__init__(message, status_code=429, error_code="QUOTA_EXCEEDED")


# ── Exception handler registration ──────────────────────────


def _get_request_id(request: Request) -> str:
    return getattr(request.state, "request_id", "-")


def register_exception_handlers(app: FastAPI) -> None:
    """Register global exception handlers on the FastAPI app."""

    @app.exception_handler(AppError)
    async def app_error_handler(request: Request, exc: AppError):
        request_id = _get_request_id(request)
        logger.warning(
            "AppError: error_code={} message={} request_id={}",
            exc.error_code,
            exc.message,
            request_id,
        )
        return JSONResponse(
            status_code=exc.status_code,
            content={
                "error_code": exc.error_code,
                "message": exc.message,
                "request_id": request_id,
            },
        )

    @app.exception_handler(Exception)
    async def unhandled_error_handler(request: Request, exc: Exception):
        request_id = _get_request_id(request)
        logger.exception("Unhandled exception: request_id={}", request_id)
        return JSONResponse(
            status_code=500,
            content={
                "error_code": "INTERNAL_ERROR",
                "message": "服务器内部错误",
                "request_id": request_id,
            },
        )