import { GraphQLError } from '../../error'; /**
                                             * 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.
                                             *
                                             *  strict
                                             */

export function duplicateArgMessage(argName) {
  return 'There can be only one argument named "' + argName + '".';
}

/**
 * Unique argument names
 *
 * A GraphQL field or directive is only valid if all supplied arguments are
 * uniquely named.
 */
export function UniqueArgumentNames(context) {
  var knownArgNames = Object.create(null);
  return {
    Field: function Field() {
      knownArgNames = Object.create(null);
    },
    Directive: function Directive() {
      knownArgNames = Object.create(null);
    },
    Argument: function Argument(node) {
      var argName = node.name.value;
      if (knownArgNames[argName]) {
        context.reportError(new GraphQLError(duplicateArgMessage(argName), [knownArgNames[argName], node.name]));
      } else {
        knownArgNames[argName] = node.name;
      }
      return false;
    }
  };
}