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;
  var _iteratorNormalCompletion = true;
  var _didIteratorError = false;
  var _iteratorError = undefined;

  try {
    for (var _iterator = documentAST.definitions[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
      var definition = _step.value;

      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;
        }
      }
    }
  } catch (err) {
    _didIteratorError = true;
    _iteratorError = err;
  } finally {
    try {
      if (!_iteratorNormalCompletion && _iterator.return != null) {
        _iterator.return();
      }
    } finally {
      if (_didIteratorError) {
        throw _iteratorError;
      }
    }
  }

  return operation;
}