/**
 * Copyright 2019 Google Inc. All Rights Reserved.
 * 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 { Observable , Transform } from "../types.js" ; import { externalPromise } from "../utils.js" ; typeparam returns export function switchAll < T > ( ) { const lastInnerDone = externalPromise ( ) ; let innerStreamCounter = 0 ; let outerDone = false ; let currentReader ; return new TransformStream ( { transform ( o , controller ) { innerStreamCounter ++ ; if ( currentReader ) { currentReader . cancel ( ) ; } currentReader = o . getReader ( ) ; ( async ( ) => { const readerCopy = currentReader ; while ( true ) { try { const { value , done } = await readerCopy . read ( ) ; if ( done ) { break ; } controller . enqueue ( value ! ) ; } catch ( e ) { break ; } } innerStreamCounter -- ; if ( innerStreamCounter === 0 ) { currentReader = null ; } if ( outerDone ) { lastInnerDone . resolve ( ) ; } } ) ( ) ; } , async flush ( ) { outerDone = true ; if ( currentReader ) { await lastInnerDone . promise ; } } } , { highWaterMark : 1 } , { highWaterMark : 0 } ) ; }