app/deps/request_params.py

import json
from typing import Callable, Optional, Type

from fastapi import HTTPException, Query
from sqlalchemy import UnaryExpression, asc, desc

from app.db import Base
from app.schemas.request_params import RequestParams


def parse_react_admin_params(model: Type[Base]) -> Callable:
    """Parses sort and range parameters coming from a react-admin request"""

    def inner(
        sort_: Optional[str] = Query(
            None,
            alias="sort",
            description='Format: `["field_name", "direction"]`',
            example='["id", "ASC"]',
        ),
        range_: Optional[str] = Query(
            None,
            alias="range",
            description="Format: `[start, end]`",
            example="[0, 10]",
        ),
    ) -> RequestParams:
        skip, limit = 0, 10
        if range_:
            start, end = json.loads(range_)
            skip, limit = start, (end - start + 1)

        order_by: UnaryExpression = desc(model.id)
        if sort_:
            sort_column, sort_order = json.loads(sort_)
            if sort_order.lower() == "asc":
                direction = asc
            elif sort_order.lower() == "desc":
                direction = desc
            else:
                raise HTTPException(400, f"Invalid sort direction {sort_order}")
            order_by = direction(model.__table__.c[sort_column])

        return RequestParams(skip=skip, limit=limit, order_by=order_by)

    return inner