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


class DocumentNotFoundError(Exception):
    def __init__(self, document_id: str):
        self.document_id = document_id
        super().__init__(f"Document '{document_id}' not found")


class ContentTooLargeError(Exception):
    def __init__(self, size: int, limit: int = 200_000):
        super().__init__(f"Content size {size} bytes exceeds limit of {limit} bytes")


class ExportError(Exception):
    def __init__(self, reason: str):
        super().__init__(f"Export failed: {reason}")


class RecordNotFoundError(Exception):
    def __init__(self, record_id: str):
        self.record_id = record_id
        super().__init__(f"Export record '{record_id}' not found")


# (异常类, HTTP 状态码, 响应 code 字段)
_HANDLERS: list[tuple[type[Exception], int, int]] = [
    (DocumentNotFoundError, 404,  404),
    (ContentTooLargeError,  413,  413),
    (ExportError,           500,  500),
    (RecordNotFoundError,   404, 4041),
]


def register_exception_handlers(app: FastAPI) -> None:
    def _make_handler(http_status: int, code: int):
        async def handler(request: Request, exc: Exception) -> JSONResponse:
            return JSONResponse(
                status_code=http_status,
                content={"code": code, "message": str(exc), "data": None},
            )
        return handler

    for exc_class, http_status, code in _HANDLERS:
        app.add_exception_handler(exc_class, _make_handler(http_status, code))