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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
"use strict";
class WorkerDispatcher {
#msgId = 1;
#worker = null;
// Map of message ids -> promise resolution functions, for dispatching worker responses
#pendingCalls = new Map();
#url = "";
constructor(url) {
this.#url = url;
}
start() {
// When running in debugger jest test, we don't have access to ChromeWorker
if (typeof ChromeWorker == "function") {
this.#worker = new ChromeWorker(this.#url);
} else {
this.#worker = new Worker(this.#url);
}
this.#worker.onerror = err => {
console.error(`Error in worker ${this.#url}`, err.message);
};
this.#worker.addEventListener("message", this.#onMessage);
}
stop() {
if (!this.#worker) {
return;
}
this.#worker.removeEventListener("message", this.#onMessage);
this.#worker.terminate();
this.#worker = null;
this.#pendingCalls.clear();
}
task(method, { queue = false } = {}) {
const calls = [];
const push = args => {
return new Promise((resolve, reject) => {
if (queue && calls.length === 0) {
Promise.resolve().then(flush);
}
calls.push({ args, resolve, reject });
if (!queue) {
flush();
}
});
};
const flush = () => {
const items = calls.slice();
calls.length = 0;
if (!this.#worker) {
this.start();
}
const id = this.#msgId++;
this.#worker.postMessage({
id,
method,
calls: items.map(item => item.args),
});
this.#pendingCalls.set(id, items);
};
return (...args) => push(args);
}
invoke(method, ...args) {
return this.task(method)(...args);
}
#onMessage = ({ data: result }) => {
const items = this.#pendingCalls.get(result.id);
this.#pendingCalls.delete(result.id);
if (!items) {
return;
}
if (!this.#worker) {
return;
}
result.results.forEach((resultData, i) => {
const { resolve, reject } = items[i];
if (resultData.error) {
const err = new Error(resultData.message);
err.metadata = resultData.metadata;
reject(err);
} else {
resolve(resultData.response);
}
});
};
}
function workerHandler(publicInterface) {
return function (msg) {
const { id, method, calls } = msg.data;
Promise.all(
calls.map(args => {
try {
const response = publicInterface[method].apply(undefined, args);
if (response instanceof Promise) {
return response.then(
val => ({ response: val }),
err => asErrorMessage(err)
);
}
return { response };
} catch (error) {
return asErrorMessage(error);
}
})
).then(results => {
globalThis.postMessage({ id, results });
});
};
}
function asErrorMessage(error) {
if (typeof error === "object" && error && "message" in error) {
// Error can't be sent via postMessage, so be sure to convert to
// string.
return {
error: true,
message: error.message,
metadata: error.metadata,
};
}
return {
error: true,
message: error == null ? error : error.toString(),
metadata: undefined,
};
}
// Might be loaded within a worker thread where `module` isn't available.
if (typeof module !== "undefined") {
module.exports = {
WorkerDispatcher,
workerHandler,
};
}
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