/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * 
 */
import { Kind } from '../language/kinds';

/**
 * Returns an operation AST given a document AST and optionally an operation
 * name. If a name is not provided, an operation is only returned if only one is
 * provided in the document.
 */
export function getOperationAST(documentAST, operationName) {
  var operation = null;

  for (var i = 0; i < documentAST.definitions.length; i++) {
    var definition = documentAST.definitions[i];

    if (definition.kind === Kind.OPERATION_DEFINITION) {
      if (!operationName) {
        // If no operation name was provided, only return an Operation if there
        // is one defined in the document. Upon encountering the second, return
        // null.
        if (operation) {
          return null;
        }

        operation = definition;
      } else if (definition.name && definition.name.value === operationName) {
        return definition;
      }
    }
  }

  return operation;
}