ApolloServer.ts

import { ApolloServerBase } from 'apollo-server-core';
import { GraphQLOptions, Config } from 'apollo-server-core';
import {
  renderPlaygroundPage,
  RenderPageOptions as PlaygroundRenderPageOptions,
} from '@apollographql/graphql-playground-html';

import { graphqlCloudFunction } from './googleCloudApollo';

export interface CreateHandlerOptions {
  cors?: {
    origin?: boolean | string | string[];
    methods?: string | string[];
    allowedHeaders?: string | string[];
    exposedHeaders?: string | string[];
    credentials?: boolean;
    maxAge?: number;
  };
}

export class ApolloServer extends ApolloServerBase {
  // If you feel tempted to add an option to this constructor. Please consider
  // another place, since the documentation becomes much more complicated when
  // the constructor is not longer shared between all integration
  constructor(options: Config) {
    if (process.env.ENGINE_API_KEY || options.engine) {
      options.engine = {
        sendReportsImmediately: true,
        ...(typeof options.engine !== 'boolean' ? options.engine : {}),
      };
    }
    super(options);
  }

  // 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
  createGraphQLServerOptions(req, res): Promise<GraphQLOptions> {
    return super.graphQLServerOptions({ req, res });
  }

  public createHandler({ cors }: CreateHandlerOptions = { cors: undefined }) {
    const corsHeaders = {};

    if (cors) {
      if (cors.methods) {
        if (typeof cors.methods === 'string') {
          corsHeaders['Access-Control-Allow-Methods'] = cors.methods;
        } else if (Array.isArray(cors.methods)) {
          corsHeaders['Access-Control-Allow-Methods'] = cors.methods.join(',');
        }
      }

      if (cors.allowedHeaders) {
        if (typeof cors.allowedHeaders === 'string') {
          corsHeaders['Access-Control-Allow-Headers'] = cors.allowedHeaders;
        } else if (Array.isArray(cors.allowedHeaders)) {
          corsHeaders[
            'Access-Control-Allow-Headers'
          ] = cors.allowedHeaders.join(',');
        }
      }

      if (cors.exposedHeaders) {
        if (typeof cors.exposedHeaders === 'string') {
          corsHeaders['Access-Control-Expose-Headers'] = cors.exposedHeaders;
        } else if (Array.isArray(cors.exposedHeaders)) {
          corsHeaders[
            'Access-Control-Expose-Headers'
          ] = cors.exposedHeaders.join(',');
        }
      }

      if (cors.credentials) {
        corsHeaders['Access-Control-Allow-Credentials'] = 'true';
      }
      if (cors.maxAge) {
        corsHeaders['Access-Control-Max-Age'] = cors.maxAge;
      }
    }

    return (req: any, res: any) => {
      if (cors) {
        if (typeof cors.origin === 'string') {
          res.set('Access-Control-Allow-Origin', cors.origin);
        } else if (
          typeof cors.origin === 'boolean' ||
          (Array.isArray(cors.origin) &&
            cors.origin.includes(req.get('origin')))
        ) {
          res.set('Access-Control-Allow-Origin', req.get('origin'));
        }

        if (!cors.allowedHeaders) {
          res.set(
            'Access-Control-Allow-Headers',
            req.get('Access-Control-Request-Headers'),
          );
        }
      }

      if (req.method === 'OPTIONS') {
        res.status(204).send('');
        return;
      }

      if (this.playgroundOptions && req.method === 'GET') {
        if (req.accepts('text/html')) {
          const playgroundRenderPageOptions: PlaygroundRenderPageOptions = {
            endpoint: req.get('referer'),
            ...this.playgroundOptions,
          };

          res
            .status(200)
            .send(renderPlaygroundPage(playgroundRenderPageOptions));
          return;
        }
      }

      res.set(corsHeaders);

      graphqlCloudFunction(this.createGraphQLServerOptions.bind(this))(
        req,
        res,
      );
    };
  }
}