# All files / platform_browser webchannel_connection.ts

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     /**
     * Copyright 2017 Google Inc.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    import {
      ErrorCode,
      EventType,
      WebChannel,
      XhrIoPool,
      createWebChannelTransport
    } from '@firebase/webchannel-wrapper';

    import { Token } from '../api/credentials';
    import { DatabaseId, DatabaseInfo } from '../core/database_info';
    import { SDK_VERSION } from '../core/version';
    import { Connection, Stream } from '../remote/connection';
    import {
      mapCodeFromHttpStatus,
      mapCodeFromRpcStatus
    } from '../remote/rpc_error';
    import { StreamBridge } from '../remote/stream_bridge';
    import { assert, fail } from '../util/assert';
    import { Code, FirestoreError } from '../util/error';
    import * as log from '../util/log';
    import { Rejecter, Resolver } from '../util/promise';
    import { StringMap } from '../util/types';

    const LOG_TAG = 'Connection';

    const RPC_STREAM_SERVICE = 'google.firestore.v1beta1.Firestore';
    const RPC_URL_VERSION = 'v1beta1';

    /** Maps RPC names to the corresponding REST endpoint name. */
    const RPC_NAME_REST_MAPPING = {
      BatchGetDocuments: 'batchGet',
      Commit: 'commit'
    };

    // TODO(b/38203344): The SDK_VERSION is set independently from Firebase because
    // we are doing out-of-band releases. Once we release as part of Firebase, we
    // should use the Firebase version instead.
    const X_GOOG_API_CLIENT_VALUE = 'gl-js/ fire/' + SDK_VERSION;

    const XHR_TIMEOUT_SECS = 15;

    export class WebChannelConnection implements Connection {
      private readonly databaseId: DatabaseId;
      private readonly baseUrl: string;
      private readonly pool: XhrIoPool;

      constructor(info: DatabaseInfo) {
        this.databaseId = info.databaseId;
        this.pool = new XhrIoPool();
        const proto = info.ssl ? 'https' : 'http';
        this.baseUrl = proto + '://' + info.host;
      }

      /**
       * Modifies the headers for a request, adding any authorization token if
       * present and any additional headers for the request.
       */
      private modifyHeadersForRequest(headers: StringMap, token: Token | null) {
        Iif (token) {
          for (const header in token.authHeaders) {
            if (token.authHeaders.hasOwnProperty(header)) {
              headers[header] = token.authHeaders[header];
            }
          }
        }
        headers['X-Goog-Api-Client'] = X_GOOG_API_CLIENT_VALUE;
      }

      invokeRPC<Req, Resp>(
        rpcName: string,
        request: Req,
        token: Token | null
      ): Promise<Resp> {
        const url = this.makeUrl(rpcName);

        return new Promise((resolve: Resolver<Resp>, reject: Rejecter) => {
          // tslint:disable-next-line:no-any XhrIoPool doesn't have TS typings.
          this.pool.getObject((xhr: any) => {
            xhr.listenOnce(EventType.COMPLETE, () => {
              try {
                switch (xhr.getLastErrorCode()) {
                  case ErrorCode.NO_ERROR:
                    const json = xhr.getResponseJson() as Resp;
                    log.debug(LOG_TAG, 'XHR received:', JSON.stringify(json));
                    resolve(json);
                    break;
                  case ErrorCode.TIMEOUT:
                    log.debug(LOG_TAG, 'RPC "' + rpcName + '" timed out');
                    reject(
                      new FirestoreError(Code.DEADLINE_EXCEEDED, 'Request time out')
                    );
                    break;
                  case ErrorCode.HTTP_ERROR:
                    const status = xhr.getStatus();
                    log.debug(
                      LOG_TAG,
                      'RPC "' + rpcName + '" failed with status:',
                      status,
                      'response text:',
                      xhr.getResponseText()
                    );
                    Eif (status > 0) {
                      reject(
                        new FirestoreError(
                          mapCodeFromHttpStatus(status),
                          'Server responded with status ' + xhr.getStatusText()
                        )
                      );
                    } else {
                      // If we received an HTTP_ERROR but there's no status code,
                      // it's most probably a connection issue
                      log.debug(LOG_TAG, 'RPC "' + rpcName + '" failed');
                      reject(
                        new FirestoreError(Code.UNAVAILABLE, 'Connection failed.')
                      );
                    }
                    break;
                  default:
                    fail(
                      'RPC "' +
                        rpcName +
                        '" failed with unanticipated ' +
                        'webchannel error ' +
                        xhr.getLastErrorCode() +
                        ': ' +
                        xhr.getLastError() +
                        ', giving up.'
                    );
                }
              } finally {
                log.debug(LOG_TAG, 'RPC "' + rpcName + '" completed.');
                this.pool.releaseObject(xhr);
              }
            });

            const requestString = JSON.stringify(request);
            log.debug(LOG_TAG, 'XHR sending: ', url + ' ' + requestString);
            // Content-Type: text/plain will avoid preflight requests which might
            // mess with CORS and redirects by proxies. If we add custom headers
            // we will need to change this code to potentially use the
            // $httpOverwrite parameter supported by ESF to avoid
            // triggering preflight requests.
            const headers: StringMap = { 'Content-Type': 'text/plain' };

            this.modifyHeadersForRequest(headers, token);

            xhr.send(url, 'POST', requestString, headers, XHR_TIMEOUT_SECS);
          });
        });
      }

      invokeStreamingRPC<Req, Resp>(
        rpcName: string,
        request: Req,
        token: Token | null
      ): Promise<Resp[]> {
        // The REST API automatically aggregates all of the streamed results, so we
        // can just use the normal invoke() method.
        return this.invokeRPC<Req, Resp[]>(rpcName, request, token);
      }

      openStream<Req, Resp>(
        rpcName: string,
        token: Token | null
      ): Stream<Req, Resp> {
        const urlParts = [
          this.baseUrl,
          '/',
          RPC_STREAM_SERVICE,
          '/',
          rpcName,
          '/channel'
        ];
        const webchannelTransport = createWebChannelTransport();
        const request = {
          // Background channel test avoids the initial two test calls and decreases
          // initial cold start time.
          // TODO(dimond): wenboz@ mentioned this might affect use with proxies and
          // we should monitor closely for any reports.
          backgroundChannelTest: true,
          // Required for backend stickiness, routing behavior is based on this
          // parameter.
          httpSessionIdParam: 'gsessionid',
          initMessageHeaders: {},
          // Send our custom headers as a '$httpHeaders=' url param to avoid CORS
          // preflight round-trip. This is formally defined here:
          // https://github.com/google/closure-library/blob/b0e1815b13fb92a46d7c9b3c30de5d6a396a3245/closure/goog/net/rpc/httpcors.js#L40
          httpHeadersOverwriteParam: '$httpHeaders',
          messageUrlParams: {
            // This param is used to improve routing and project isolation by the
            // backend and must be included in every request.
            database: `projects/${this.databaseId.projectId}/databases/${
              this.databaseId.database
            }`
          },
          sendRawJson: true,
          supportsCrossDomainXhr: true
        };
        this.modifyHeadersForRequest(request.initMessageHeaders, token);
        const url = urlParts.join('');
        log.debug(LOG_TAG, 'Creating WebChannel: ' + url + ' ' + request);
        // tslint:disable-next-line:no-any Because listen isn't defined on it.
        const channel = webchannelTransport.createWebChannel(url, request) as any;

        // WebChannel supports sending the first message with the handshake - saving
        // a network round trip. However, it will have to call send in the same
        // JS event loop as open. In order to enforce this, we delay actually
        // opening the WebChannel until send is called. Whether we have called
        // open is tracked with this variable.
        let opened = false;

        // A flag to determine whether the stream was closed (by us or through an
        // error/close event) to avoid delivering multiple close events or sending
        // on a closed stream
        let closed = false;

        const streamBridge = new StreamBridge<Req, Resp>({
          sendFn: (msg: Req) => {
            Eif (!closed) {
              if (!opened) {
                log.debug(LOG_TAG, 'Opening WebChannel transport.');
                channel.open();
                opened = true;
              }
              log.debug(LOG_TAG, 'WebChannel sending:', msg);
              channel.send(msg);
            } else {
              log.debug(LOG_TAG, 'Not sending because WebChannel is closed:', msg);
            }
          },
          closeFn: () => channel.close()
        });

        // Closure events are guarded and exceptions are swallowed, so catch any
        // exception and rethrow using a setTimeout so they become visible again.
        // Note that eventually this function could go away if we are confident
        // enough the code is exception free.
        const unguardedEventListen = <T>(
          type: WebChannel.EventType,
          fn: (param?: T) => void
        ) => {
          // TODO(dimond): closure typing seems broken because WebChannel does
          // not implement goog.events.Listenable
          channel.listen(type, (param?: T) => {
            try {
              fn(param);
            } catch (e) {
              setTimeout(() => {
                throw e;
              }, 0);
            }
          });
        };

        unguardedEventListen(WebChannel.EventType.OPEN, () => {
          Eif (!closed) {
            log.debug(LOG_TAG, 'WebChannel transport opened.');
          }
        });

        unguardedEventListen(WebChannel.EventType.CLOSE, () => {
          if (!closed) {
            closed = true;
            log.debug(LOG_TAG, 'WebChannel transport closed');
            streamBridge.callOnClose();
          }
        });

        unguardedEventListen<Error>(WebChannel.EventType.ERROR, err => {
          if (!closed) {
            closed = true;
            log.debug(LOG_TAG, 'WebChannel transport errored:', err);
            streamBridge.callOnClose(
              new FirestoreError(
                Code.UNAVAILABLE,
                'The operation could not be completed'
              )
            );
          }
        });

        // WebChannel delivers message events as array. If batching is not enabled
        // (it's off by default) each message will be delivered alone, resulting in
        // a single element array.
        type WebChannelResponse = { data: Resp[] };

        unguardedEventListen<WebChannelResponse>(
          WebChannel.EventType.MESSAGE,
          msg => {
            Eif (!closed) {
              const msgData = msg.data[0];
              assert(!!msgData, 'Got a webchannel message without data.');
              // TODO(b/35143891): There is a bug in One Platform that caused errors
              // (and only errors) to be wrapped in an extra array. To be forward
              // compatible with the bug we need to check either condition. The latter
              // can be removed once the fix has been rolled out.
              const error =
                // tslint:disable-next-line:no-any msgData.error is not typed.
                (msgData as any).error || (msgData[0] && msgData[0].error);
              if (error) {
                log.debug(LOG_TAG, 'WebChannel received error:', error);
                // error.status will be a string like 'OK' or 'NOT_FOUND'.
                const status: string = error.status;
                let code = mapCodeFromRpcStatus(status);
                let message = error.message;
                Iif (code === undefined) {
                  code = Code.INTERNAL;
                  message =
                    'Unknown error status: ' +
                    status +
                    ' with message ' +
                    error.message;
                }
                // Mark closed so no further events are propagated
                closed = true;
                streamBridge.callOnClose(new FirestoreError(code, message));
                channel.close();
              } else {
                log.debug(LOG_TAG, 'WebChannel received:', msgData);
                streamBridge.callOnMessage(msgData);
              }
            }
          }
        );

        setTimeout(() => {
          // Technically we could/should wait for the WebChannel opened event,
          // but because we want to send the first message with the WebChannel
          // handshake we pretend the channel opened here (asynchronously), and
          // then delay the actual open until the first message is sent.
          streamBridge.callOnOpen();
        }, 0);
        return streamBridge;
      }

      // visible for testing
      makeUrl(rpcName: string): string {
        const urlRpcName = RPC_NAME_REST_MAPPING[rpcName];
        assert(urlRpcName !== undefined, 'Unknown REST mapping for: ' + rpcName);
        const url = [this.baseUrl, '/', RPC_URL_VERSION];
        url.push('/projects/');
        url.push(this.databaseId.projectId);

        url.push('/databases/');
        url.push(this.databaseId.database);
        url.push('/documents');

        url.push(':');
        url.push(urlRpcName);
        return url.join('');
      }
    }