@dillonkearns/elm-graphql/examples/src/subscription/node_modules/graphql/validation/rules/KnownDirectives.js.flow

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/**
 * 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';
import find from '../../jsutils/find';
import * as Kind from '../../language/kinds';
import { DirectiveLocation } from '../../type/directives';


export function unknownDirectiveMessage(directiveName: string): string {
  return `Unknown directive "${directiveName}".`;
}

export function misplacedDirectiveMessage(
  directiveName: string,
  location: string
): string {
  return `Directive "${directiveName}" may not be used on ${location}.`;
}

/**
 * Known directives
 *
 * A GraphQL document is only valid if all `@directives` are known by the
 * schema and legally positioned.
 */
export function KnownDirectives(context: ValidationContext): any {
  return {
    Directive(node, key, parent, path, ancestors) {
      const directiveDef = find(
        context.getSchema().getDirectives(),
        def => def.name === node.name.value
      );
      if (!directiveDef) {
        context.reportError(new GraphQLError(
          unknownDirectiveMessage(node.name.value),
          [ node ]
        ));
        return;
      }
      const candidateLocation = getDirectiveLocationForASTPath(ancestors);
      if (!candidateLocation) {
        context.reportError(new GraphQLError(
          misplacedDirectiveMessage(node.name.value, node.type),
          [ node ]
        ));
      } else if (directiveDef.locations.indexOf(candidateLocation) === -1) {
        context.reportError(new GraphQLError(
          misplacedDirectiveMessage(node.name.value, candidateLocation),
          [ node ]
        ));
      }
    }
  };
}

function getDirectiveLocationForASTPath(ancestors) {
  const appliedTo = ancestors[ancestors.length - 1];
  switch (appliedTo.kind) {
    case Kind.OPERATION_DEFINITION:
      switch (appliedTo.operation) {
        case 'query': return DirectiveLocation.QUERY;
        case 'mutation': return DirectiveLocation.MUTATION;
        case 'subscription': return DirectiveLocation.SUBSCRIPTION;
      }
      break;
    case Kind.FIELD: return DirectiveLocation.FIELD;
    case Kind.FRAGMENT_SPREAD: return DirectiveLocation.FRAGMENT_SPREAD;
    case Kind.INLINE_FRAGMENT: return DirectiveLocation.INLINE_FRAGMENT;
    case Kind.FRAGMENT_DEFINITION: return DirectiveLocation.FRAGMENT_DEFINITION;
    case Kind.SCHEMA_DEFINITION: return DirectiveLocation.SCHEMA;
    case Kind.SCALAR_TYPE_DEFINITION: return DirectiveLocation.SCALAR;
    case Kind.OBJECT_TYPE_DEFINITION: return DirectiveLocation.OBJECT;
    case Kind.FIELD_DEFINITION: return DirectiveLocation.FIELD_DEFINITION;
    case Kind.INTERFACE_TYPE_DEFINITION: return DirectiveLocation.INTERFACE;
    case Kind.UNION_TYPE_DEFINITION: return DirectiveLocation.UNION;
    case Kind.ENUM_TYPE_DEFINITION: return DirectiveLocation.ENUM;
    case Kind.ENUM_VALUE_DEFINITION: return DirectiveLocation.ENUM_VALUE;
    case Kind.INPUT_OBJECT_TYPE_DEFINITION:
      return DirectiveLocation.INPUT_OBJECT;
    case Kind.INPUT_VALUE_DEFINITION:
      const parentNode = ancestors[ancestors.length - 3];
      return parentNode.kind === Kind.INPUT_OBJECT_TYPE_DEFINITION ?
        DirectiveLocation.INPUT_FIELD_DEFINITION :
        DirectiveLocation.ARGUMENT_DEFINITION;
  }
}