/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

import type { ValidationContext } from '../index';
import { GraphQLError } from '../../error';


export function unknownFragmentMessage(fragName: string): string {
  return `Unknown fragment "${fragName}".`;
}

/**
 * Known fragment names
 *
 * A GraphQL document is only valid if all `...Fragment` fragment spreads refer
 * to fragments defined in the same document.
 */
export function KnownFragmentNames(context: ValidationContext): any {
  return {
    FragmentSpread(node) {
      const fragmentName = node.name.value;
      const fragment = context.getFragment(fragmentName);
      if (!fragment) {
        context.reportError(new GraphQLError(
          unknownFragmentMessage(fragmentName),
          [ node.name ]
        ));
      }
    }
  };
}