from fastapi import Request, HTTPException
from starlette.middleware.base import BaseHTTPMiddleware
from app.core.config import get_settings

settings = get_settings()


class SecurityMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        if request.method in ("POST", "PUT", "PATCH"):
            content_length = request.headers.get("content-length")
            if content_length and int(content_length) > settings.MAX_UPLOAD_SIZE:
                raise HTTPException(
                    status_code=413,
                    detail=f"文件大小不能超过 {settings.MAX_UPLOAD_SIZE // 1024 // 1024}MB",
                )
        response = await call_next(request)
        return response


ALLOWED_EXTENSIONS = {".docx", ".txt", ".pdf"}


def validate_file_extension(filename: str) -> str:
    import os
    ext = os.path.splitext(filename)[1].lower()
    if ext not in ALLOWED_EXTENSIONS:
        raise HTTPException(
            status_code=400,
            detail=f"不支持的文件类型: {ext}，允许的类型: {', '.join(ALLOWED_EXTENSIONS)}",
        )
    return ext