/** @category Operations */

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

import type {
  OperationDefinitionNode,
  OperationTypeDefinitionNode,
} from '../language/ast';

import type { GraphQLObjectType } from '../type/definition';
import type { GraphQLSchema } from '../type/schema';

/**
 * Extracts the root type of the operation from the schema. This deprecated
 * helper is retained for backwards compatibility; call
 * `GraphQLSchema.getRootType` instead because getOperationRootType will be
 * removed in v17.
 * @param schema - GraphQL schema to use.
 * @param operation - The operation definition to inspect.
 * @returns The resolved operation root type.
 * @example
 * ```ts
 * import { buildSchema, getOperationRootType } from 'graphql/utilities';
 * import { parse } from 'graphql/language';
 *
 * const schema = buildSchema('type Query { name: String }');
 * const operation = parse('{ name }').definitions[0];
 * const rootType = getOperationRootType(schema, operation);
 *
 * rootType.name; // => 'Query'
 * ```
 * @deprecated Please use `GraphQLSchema.getRootType` instead. Will be removed in v17
 */
export function getOperationRootType(
  schema: GraphQLSchema,
  operation: OperationDefinitionNode | OperationTypeDefinitionNode,
): GraphQLObjectType {
  if (operation.operation === 'query') {
    const queryType = schema.getQueryType();
    if (!queryType) {
      throw new GraphQLError(
        'Schema does not define the required query root type.',
        { nodes: operation },
      );
    }
    return queryType;
  }

  if (operation.operation === 'mutation') {
    const mutationType = schema.getMutationType();
    if (!mutationType) {
      throw new GraphQLError('Schema is not configured for mutations.', {
        nodes: operation,
      });
    }
    return mutationType;
  }

  if (operation.operation === 'subscription') {
    const subscriptionType = schema.getSubscriptionType();
    if (!subscriptionType) {
      throw new GraphQLError('Schema is not configured for subscriptions.', {
        nodes: operation,
      });
    }
    return subscriptionType;
  }

  throw new GraphQLError(
    'Can only have query, mutation and subscription operations.',
    { nodes: operation },
  );
}