from __future__ import annotations

from dataclasses import dataclass
from typing import Tuple

from fastapi import HTTPException, Request
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.db.models.dataset_management import Dataset

HEADER_USER_ID = "X-User-Id"
HEADER_USER_NAME = "X-User-Name"
HEADER_USER_ROLES = "X-User-Roles"
ADMIN_ROLE_CODE = "ROLE_ADMIN"


@dataclass(frozen=True)
class RequestUserContext:
    user_id: str
    username: str | None
    roles: Tuple[str, ...]

    @property
    def is_admin(self) -> bool:
        return any(role.upper() == ADMIN_ROLE_CODE for role in self.roles)


def get_request_user_context(request: Request) -> RequestUserContext:
    user_id = (request.headers.get(HEADER_USER_ID) or "").strip()
    username = (request.headers.get(HEADER_USER_NAME) or "").strip() or None
    role_header = request.headers.get(HEADER_USER_ROLES) or ""
    roles = tuple(
        role.strip()
        for role in role_header.split(",")
        if role and role.strip()
    )
    if not user_id:
        raise HTTPException(status_code=403, detail="权限不足：缺少用户身份")
    return RequestUserContext(user_id=user_id, username=username, roles=roles)


def ensure_dataset_owner_access(
    user_context: RequestUserContext,
    dataset_owner_user_id: str | None,
    dataset_id: str,
) -> None:
    if user_context.is_admin:
        return
    if not dataset_owner_user_id or dataset_owner_user_id != user_context.user_id:
        raise HTTPException(
            status_code=403,
            detail=f"无权访问数据集: {dataset_id}",
        )


async def assert_dataset_access(
    db: AsyncSession,
    dataset_id: str,
    user_context: RequestUserContext,
) -> None:
    owner_result = await db.execute(
        select(Dataset.created_by).where(Dataset.id == dataset_id)
    )
    dataset_owner = owner_result.scalar_one_or_none()
    if dataset_owner is None:
        raise HTTPException(status_code=404, detail=f"数据集不存在: {dataset_id}")
    ensure_dataset_owner_access(user_context, str(dataset_owner), dataset_id)