Validate JSON request data

expects_json.py

def expects_json(obj: dict, schema: tuple):
    # or use library `flask-expects-json`
    _type = type(obj)
    if _type != dict:
        raise werkzeug.exceptions.BadRequest(f"wrong type of root object, except dict, got {str(_type.__name__)}")
    _keys = schema
    for _key in _keys:
        assert len(_key) >= 2
        if _key[0] not in obj:
            if len(_key) >= 3 and _key[2] is False:
                continue
            raise werkzeug.exceptions.BadRequest(f"missing required parameter: {_key[0]}")
        _type = type(obj[_key[0]])
        if _type != _key[1]:
            raise werkzeug.exceptions.BadRequest(
                f"wrong type of {'optional' if len(_key) >= 3 and _key[2] is False else 'required'} parameter: "
                f"{_key[0]}, excepted {str(_key[1].__name__)}, got {str(_type.__name__)}"
            )

# usage
challenge_dict = request.get_json()
if request.method != 'POST':
    raise BadRequest("POST only")

expects_json(challenge_dict, (
    # name, type, required (default is True), ...
    ("person", dict,),
    ("questionText", str,),
    ("answers", list,),
))