from typing import Optional, List
from fastapi.exceptions import RequestValidationError
from backend.models.permission.models import RoleDoc, UserRoleDoc
from beanie import PydanticObjectId


class UserRoleHandler:
    def __init__(self):
        pass

    async def assign_roles_to_user(self, user_id: str, role_ids: List[str]) -> Optional[UserRoleDoc]:
        """Assign roles to a user by updating or creating the UserRoleDoc"""
        if not user_id or not role_ids:
            raise RequestValidationError("user_id and role_ids are required.")

        # Validate that all role_ids exist in the role collection
        for role_id in role_ids:
            role_doc = await RoleDoc.get(PydanticObjectId(role_id))
            if not role_doc:
                raise RequestValidationError(f"Role with id {role_id} not found.")

        # Remove duplicates from role_ids
        unique_role_ids = list(dict.fromkeys(role_ids))

        # Check if UserRoleDoc already exists for this user
        existing_user_role = await UserRoleDoc.find_one(UserRoleDoc.user_id == user_id)

        if existing_user_role:
            # Update existing UserRoleDoc
            existing_user_role.role_ids = unique_role_ids
            await existing_user_role.save()
            return existing_user_role
        else:
            # Create new UserRoleDoc
            user_role_doc = UserRoleDoc(
                user_id=user_id,
                role_ids=unique_role_ids
            )
            await user_role_doc.insert()
            return user_role_doc