from __future__ import absolute_import

import json

from graphql import Undefined
from graphql.language.ast import StringValueNode

from .scalars import Scalar


class JSONString(Scalar):
    """
    Allows use of a JSON String for input / output from the GraphQL schema.

    Use of this type is *not recommended* as you lose the benefits of having a defined, static
    schema (one of the key benefits of GraphQL).
    """

    @staticmethod
    def serialize(dt):
        return json.dumps(dt)

    @staticmethod
    def parse_literal(node, _variables=None):
        if isinstance(node, StringValueNode):
            try:
                return json.loads(node.value)
            except Exception as error:
                raise ValueError(f"Badly formed JSONString: {str(error)}")
        return Undefined

    @staticmethod
    def parse_value(value):
        return json.loads(value)