apollo-server/packages/apollo-server-express/src/ApolloServer.ts

import express from 'express';
import corsMiddleware from 'cors';
import { json, OptionsJson } from 'body-parser';
import playgroundMiddleware from 'graphql-playground-middleware-express';
import { MiddlewareOptions as PlaygroundMiddlewareOptions } from 'graphql-playground-html';
import { ApolloServerBase, formatApolloErrors } from 'apollo-server-core';
import accepts from 'accepts';
import typeis from 'type-is';

import { graphqlExpress } from './expressApollo';

import {
  processRequest as processFileUploads,
  GraphQLUpload,
} from 'apollo-upload-server';

export { GraphQLOptions, GraphQLExtension } from 'apollo-server-core';
import { GraphQLOptions, gql, makeExecutableSchema } from 'apollo-server-core';

export interface ServerRegistration {
  // Note: You can also pass a connect.Server here. If we changed this field to
  // `express.Application | connect.Server`, it would be very hard to get the
  // app.use calls to typecheck even though they do work properly. Our
  // assumption is that very few people use connect with TypeScript (and in fact
  // we suspect the only connect users left writing GraphQL apps are Meteor
  // users).
  app: express.Application;
  path?: string;
  cors?: corsMiddleware.CorsOptions | boolean;
  bodyParserConfig?: OptionsJson | boolean;
  onHealthCheck?: (req: express.Request) => Promise<any>;
  disableHealthCheck?: boolean;
  gui?: boolean | PlaygroundMiddlewareOptions;
  //https://github.com/jaydenseric/apollo-upload-server#options
  uploads?: boolean | Record<string, any>;
}

const fileUploadMiddleware = (
  uploadsConfig: Record<string, any>,
  server: ApolloServerBase,
) => (
  req: express.Request,
  res: express.Response,
  next: express.NextFunction,
) => {
  // Note: we use typeis directly instead of via req.is for connect support.
  if (typeis(req, ['multipart/form-data'])) {
    processFileUploads(req, uploadsConfig)
      .then(body => {
        req.body = body;
        next();
      })
      .catch(error => {
        if (error.status && error.expose) res.status(error.status);

        next(
          formatApolloErrors([error], {
            formatter: server.requestOptions.formatError,
            debug: server.requestOptions.debug,
            logFunction: server.requestOptions.logFunction,
          }),
        );
      });
  } else {
    next();
  }
};

export class ApolloServer extends ApolloServerBase {
  //This translates the arguments from the middleware into graphQL options It
  //provides typings for the integration specific behavior, ideally this would
  //be propagated with a generic to the super class
  async createGraphQLServerOptions(
    req: express.Request,
    res: express.Response,
  ): Promise<GraphQLOptions> {
    return super.graphQLServerOptions({ req, res });
  }

  protected supportsSubscriptions(): boolean {
    return true;
  }

  public applyMiddleware({
    app,
    path,
    cors,
    bodyParserConfig,
    disableHealthCheck,
    gui,
    onHealthCheck,
    uploads,
  }: ServerRegistration) {
    if (!path) path = '/graphql';

    if (!disableHealthCheck) {
      //uses same path as engine proxy, but is generally useful.
      app.use('/.well-known/apollo/server-health', (req, res) => {
        //Response follows https://tools.ietf.org/html/draft-inadarei-api-health-check-01
        res.type('application/health+json');

        if (onHealthCheck) {
          onHealthCheck(req)
            .then(() => {
              res.json({ status: 'pass' });
            })
            .catch(() => {
              res.status(503).json({ status: 'fail' });
            });
        } else {
          res.json({ status: 'pass' });
        }
      });
    }

    let uploadsMiddleware;
    if (uploads !== false) {
      this.enhanceSchema(
        makeExecutableSchema({
          typeDefs: gql`
            scalar Upload
          `,
          resolvers: { Upload: GraphQLUpload },
        }),
      );

      uploadsMiddleware = fileUploadMiddleware(
        typeof uploads !== 'boolean' ? uploads : {},
        this,
      );
    }

    // XXX multiple paths?
    this.graphqlPath = path;

    // Note that we don't just pass all of these handlers to a single app.use call
    // for 'connect' compatibility.
    if (cors === true) {
      app.use(path, corsMiddleware());
    } else if (cors !== false) {
      app.use(path, corsMiddleware(cors));
    }

    if (bodyParserConfig === true) {
      app.use(path, json());
    } else if (bodyParserConfig !== false) {
      app.use(path, json(bodyParserConfig));
    }

    if (uploadsMiddleware) {
      app.use(path, uploadsMiddleware);
    }

    // Note: if you enable a gui in production and expect to be able to see your
    // schema, you'll need to manually specify `introspection: true` in the
    // ApolloServer constructor; by default, the introspection query is only
    // enabled in dev.
    const guiEnabled =
      !!gui || (gui === undefined && process.env.NODE_ENV !== 'production');

    app.use(path, (req, res, next) => {
      if (guiEnabled && req.method === 'GET') {
        //perform more expensive content-type check only if necessary
        const accept = accepts(req);
        const types = accept.types() as string[];
        const prefersHTML =
          types.find(
            (x: string) => x === 'text/html' || x === 'application/json',
          ) === 'text/html';

        if (prefersHTML) {
          const middlewareOptions = {
            endpoint: path,
            subscriptionEndpoint: this.subscriptionsPath,
            ...(typeof gui === 'boolean' ? {} : gui),
          };
          return playgroundMiddleware(middlewareOptions)(req, res, next);
        }
      }
      return graphqlExpress(this.createGraphQLServerOptions.bind(this))(
        req,
        res,
        next,
      );
    });
  }
}

export const registerServer = () => {
  throw new Error(
    'Please use server.applyMiddleware instead of registerServer. This warning will be removed in the next release',
  );
};