concatenate.js
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/*
Copyright 2018 Google LLC
Use of this source code is governed by an MIT-style
license that can be found in the LICENSE file or at
https://opensource.org/licenses/MIT.
*/
import { logger } from 'workbox-core/_private/logger.js';
import { assert } from 'workbox-core/_private/assert.js';
import { Deferred } from 'workbox-core/_private/Deferred.js';
import './_version.js';
/**
* Takes either a Response, a ReadableStream, or a
* [BodyInit](https://fetch.spec.whatwg.org/#bodyinit) and returns the
* ReadableStreamReader object associated with it.
*
* @param {module:workbox-streams.StreamSource} source
* @return {ReadableStreamReader}
* @private
*/
function _getReaderFromSource(source) {
if (source instanceof Response) {
return source.body.getReader();
}
if (source instanceof ReadableStream) {
return source.getReader();
}
return new Response(source).body.getReader();
}
/**
* Takes multiple source Promises, each of which could resolve to a Response, a
* ReadableStream, or a [BodyInit](https://fetch.spec.whatwg.org/#bodyinit).
*
* Returns an object exposing a ReadableStream with each individual stream's
* data returned in sequence, along with a Promise which signals when the
* stream is finished (useful for passing to a FetchEvent's waitUntil()).
*
* @param {Array<Promise<module:workbox-streams.StreamSource>>} sourcePromises
* @return {Object<{done: Promise, stream: ReadableStream}>}
*
* @memberof module:workbox-streams
*/
function concatenate(sourcePromises) {
if (process.env.NODE_ENV !== 'production') {
assert.isArray(sourcePromises, {
moduleName: 'workbox-streams',
funcName: 'concatenate',
paramName: 'sourcePromises',
});
}
const readerPromises = sourcePromises.map((sourcePromise) => {
return Promise.resolve(sourcePromise).then((source) => {
return _getReaderFromSource(source);
});
});
const streamDeferred = new Deferred();
let i = 0;
const logMessages = [];
const stream = new ReadableStream({
pull(controller) {
return readerPromises[i]
.then((reader) => reader.read())
.then((result) => {
if (result.done) {
if (process.env.NODE_ENV !== 'production') {
logMessages.push(['Reached the end of source:',
sourcePromises[i]]);
}
i++;
if (i >= readerPromises.length) {
// Log all the messages in the group at once in a single group.
if (process.env.NODE_ENV !== 'production') {
logger.groupCollapsed(`Concatenating ${readerPromises.length} sources.`);
for (const message of logMessages) {
if (Array.isArray(message)) {
logger.log(...message);
}
else {
logger.log(message);
}
}
logger.log('Finished reading all sources.');
logger.groupEnd();
}
controller.close();
streamDeferred.resolve();
return;
}
// The `pull` method is defined because we're inside it.
return this.pull(controller);
}
else {
controller.enqueue(result.value);
}
}).catch((error) => {
if (process.env.NODE_ENV !== 'production') {
logger.error('An error occurred:', error);
}
streamDeferred.reject(error);
throw error;
});
},
cancel() {
if (process.env.NODE_ENV !== 'production') {
logger.warn('The ReadableStream was cancelled.');
}
streamDeferred.resolve();
},
});
return { done: streamDeferred.promise, stream };
}
export { concatenate };