import { GraphQLError, GraphQLScalarType, Kind } from 'graphql';
import { CalendarDate } from 'calendar-date';

export const GraphQLCalendarDate: GraphQLScalarType = new GraphQLScalarType({
    name: 'CalendarDate',

    description:
    'A field representing a date without time information according to ISO 8601. E.g. "2020-01-01".',
    
    serialize(value: unknown) {
        if (value instanceof CalendarDate) {
            return value.toString();
        }
        if (typeof value === 'string') {
            try {
                const calendarDate = new CalendarDate(value);
                return calendarDate.toString();
            } catch (e) {
                throw new TypeError(
                    `Value of type string does not represent a valid calendar date: ${value}`,
                );
            }
        }
        throw new TypeError(`Value is not an instance of CalendarDate and not a string: ${value}`);
    },
    
    parseValue(value: unknown) {
        if (value instanceof CalendarDate) {
           return value;
        }
        if (typeof value === 'string') {
            try {
                return new CalendarDate(value);
            } catch (e) {
                throw new TypeError(
                    `Value of type string does not represent a valid calendar date: ${value}`,
                );
            }
        }
        throw new TypeError(`Value is not an instance of CalendarDate and not a string: ${value}`);
    },
    
    parseLiteral(ast) {
        if (ast.kind !== Kind.STRING) {
            throw new GraphQLError(`Can only validate strings as CalendarDates but got a: ${ast.kind}`);
        }
        try {
            return new CalendarDate(ast.value);
        } catch (e) {
            throw new TypeError(
                `Value of type string does not represent a valid calendar date: ${ast.kind}`,
            );
        }
    },
});