320 lines
11 KiB
JavaScript
320 lines
11 KiB
JavaScript
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class StartupError extends Error {}
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/*
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* We need to know the bundle path before we can fetch the sourcemap files. In a production environment, we can guess
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* it using this.
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*/
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async function getBundleName() {
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const res = await fetch("../index.html");
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if (!res.ok) {
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throw new StartupError(`Couldn't fetch index.html to prefill bundle; ${res.status} ${res.statusText}`);
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}
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const index = await res.text();
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return index.split("\n").map((line) =>
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line.match(/<script src="bundles\/([^/]+)\/bundle.js"/),
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)
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.filter((result) => result)
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.map((result) => result[1])[0];
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}
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function validateBundle(value) {
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return value.match(/^[0-9a-f]{20}$/) ? Some.of(value) : None;
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}
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/* A custom fetcher that abandons immediately upon getting a response.
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* The purpose of this is just to validate that the user entered a real bundle, and provide feedback.
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*/
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const bundleCache = new Map();
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function bundleSubject(bundle) {
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if (!bundle.match(/^[0-9a-f]{20}$/)) throw new Error("Bad input");
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if (bundleCache.has(bundle)) {
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return bundleCache.get(bundle);
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}
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const fetcher = new rxjs.BehaviorSubject(Pending.of());
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bundleCache.set(bundle, fetcher);
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fetch(`/bundles/${bundle}/bundle.js.map`).then((res) => {
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res.body.cancel(); /* Bail on the download immediately - it could be big! */
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const status = res.ok;
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if (status) {
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fetcher.next(Success.of());
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} else {
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fetcher.next(FetchError.of(`Failed to fetch: ${res.status} ${res.statusText}`));
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}
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});
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return fetcher;
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}
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/*
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* Convert a ReadableStream of bytes into an Observable of a string
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* The observable will emit a stream of Pending objects and will concatenate
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* the number of bytes received with whatever pendingContext has been supplied.
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* Finally, it will emit a Success containing the result.
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* You'd use this on a Response.body.
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*/
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function observeReadableStream(readableStream, pendingContext = {}) {
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let bytesReceived = 0;
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let buffer = "";
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const pendingSubject = new rxjs.BehaviorSubject(Pending.of({ ...pendingContext, bytesReceived }));
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const throttledPending = pendingSubject.pipe(rxjs.operators.throttleTime(100));
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const resultObservable = new rxjs.Subject();
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const reader = readableStream.getReader();
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const utf8Decoder = new TextDecoder("utf-8");
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function readNextChunk() {
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reader.read().then(({ done, value }) => {
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if (done) {
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pendingSubject.complete();
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resultObservable.next(Success.of(buffer));
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return;
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}
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bytesReceived += value.length;
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pendingSubject.next(Pending.of({...pendingContext, bytesReceived }));
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/* string concatenation is apparently the most performant way to do this */
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buffer += utf8Decoder.decode(value);
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readNextChunk();
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});
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}
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readNextChunk();
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return rxjs.concat(throttledPending, resultObservable);
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}
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/*
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* A wrapper which converts the browser's `fetch()` mechanism into an Observable. The Observable then provides us with
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* a stream of datatype values: first, a sequence of Pending objects that keep us up to date with the download progress,
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* finally followed by either a Success or Failure object. React then just has to render each of these appropriately.
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*/
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const fetchCache = new Map();
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function fetchAsSubject(endpoint) {
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if (fetchCache.has(endpoint)) {
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// TODO: expiry/retry logic here?
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return fetchCache.get(endpoint);
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}
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const fetcher = new rxjs.BehaviorSubject(Pending.of());
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fetchCache.set(endpoint, fetcher);
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fetch(endpoint).then((res) => {
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if (!res.ok) {
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fetcher.next(FetchError.of(`Failed to fetch endpoint ${endpoint}: ${res.status} ${res.statusText}`));
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return;
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}
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const contentLength = res.headers.get("content-length");
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const context = contentLength ? { length: parseInt(contentLength) } : {};
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const streamer = observeReadableStream(res.body, context, endpoint);
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streamer.subscribe((value) => {
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fetcher.next(value);
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});
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});
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return fetcher;
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}
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/* ===================== */
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/* ==== React stuff ==== */
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/* ===================== */
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/* Rather than importing an entire build infrastructure, for now we just use React without JSX */
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const e = React.createElement;
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/*
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* Provides user feedback given a FetchStatus object.
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*/
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function ProgressBar({ fetchStatus }) {
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return e('span', { className: "progress "},
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fetchStatus.fold({
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pending: ({ bytesReceived, length }) => {
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if (!bytesReceived) {
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return e('span', { className: "spinner" }, "\u29b5");
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}
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const kB = Math.floor(10 * bytesReceived / 1024) / 10;
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if (!length) {
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return e('span', null, `Fetching (${kB}kB)`);
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}
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const percent = Math.floor(100 * bytesReceived / length);
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return e('span', null, `Fetching (${kB}kB) ${percent}%`);
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},
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success: () => e('span', null, "\u2713"),
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error: (reason) => {
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return e('span', { className: 'error'}, `\u2717 ${reason}`);
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},
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},
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));
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}
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/*
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* The main component.
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*/
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function BundlePicker() {
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const [bundle, setBundle] = React.useState("");
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const [file, setFile] = React.useState("");
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const [line, setLine] = React.useState("1");
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const [column, setColumn] = React.useState("");
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const [result, setResult] = React.useState(None);
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const [bundleFetchStatus, setBundleFetchStatus] = React.useState(None);
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const [fileFetchStatus, setFileFetchStatus] = React.useState(None);
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/* At startup, try to fill in the bundle name for the user */
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React.useEffect(() => {
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getBundleName().then((name) => {
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if (bundle === "" && validateBundle(name) !== None) {
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setBundle(name);
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}
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}, console.log.bind(console));
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}, []);
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/* ------------------------- */
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/* Follow user state changes */
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/* ------------------------- */
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const onBundleChange = React.useCallback((event) => {
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const value = event.target.value;
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setBundle(value);
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}, []);
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const onFileChange = React.useCallback((event) => {
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const value = event.target.value;
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setFile(value);
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}, []);
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const onLineChange = React.useCallback((event) => {
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const value = event.target.value;
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setLine(value);
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}, []);
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const onColumnChange = React.useCallback((event) => {
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const value = event.target.value;
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setColumn(value);
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}, []);
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/* ------------------------------------------------ */
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/* Plumb data-fetching observables through to React */
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/* ------------------------------------------------ */
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/* Whenever a valid bundle name is input, go see if it's a real bundle on the server */
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React.useEffect(() =>
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validateBundle(bundle).fold({
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some: (value) => {
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const subscription = bundleSubject(value)
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.pipe(rxjs.operators.map(Some.of))
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.subscribe(setBundleFetchStatus);
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return () => subscription.unsubscribe();
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},
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none: () => setBundleFetchStatus(None),
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}),
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[bundle]);
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/* Whenever a valid javascript file is input, see if it corresponds to a sourcemap file and initiate a fetch
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* if so. */
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React.useEffect(() => {
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if (!file.match(/.\.js$/) || validateBundle(bundle) === None) {
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setFileFetchStatus(None);
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return;
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}
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const observable = fetchAsSubject(`/bundles/${bundle}/${file}.map`)
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.pipe(
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rxjs.operators.map((fetchStatus) => fetchStatus.flatMap(value => {
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try {
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return Success.of(JSON.parse(value));
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} catch (e) {
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return FetchError.of(e);
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}
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})),
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rxjs.operators.map(Some.of),
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);
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const subscription = observable.subscribe(setFileFetchStatus);
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return () => subscription.unsubscribe();
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}, [bundle, file]);
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/*
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* Whenever we have a valid fetched sourcemap, and a valid line, attempt to find the original position from the
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* sourcemap.
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*/
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React.useEffect(() => {
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// `fold` dispatches on the datatype, like a switch statement
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fileFetchStatus.fold({
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some: (fetchStatus) =>
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// `fold` just returns null for all of the cases that aren't `Success` objects here
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fetchStatus.fold({
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success: (value) => {
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if (!line) return setResult(None);
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const pLine = parseInt(line);
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const pCol = parseInt(column);
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sourceMap.SourceMapConsumer.with(value, undefined, (consumer) =>
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consumer.originalPositionFor({ line: pLine, column: pCol }),
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).then((result) => setResult(Some.of(JSON.stringify(result))));
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},
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}),
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none: () => setResult(None),
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});
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}, [fileFetchStatus, line, column]);
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/* ------ */
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/* Render */
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/* ------ */
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return e('div', {},
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e('div', { className: 'inputs' },
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e('div', { className: 'bundle' },
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e('label', { htmlFor: 'bundle'}, 'Bundle'),
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e('input', {
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name: 'bundle',
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required: true,
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pattern: "[0-9a-f]{20}",
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onChange: onBundleChange,
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value: bundle,
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}),
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bundleFetchStatus.fold({
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some: (fetchStatus) => e(ProgressBar, { fetchStatus }),
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none: () => null,
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}),
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),
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e('div', { className: 'file' },
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e('label', { htmlFor: 'file' }, 'File'),
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e('input', {
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name: 'file',
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required: true,
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pattern: ".+\\.js",
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onChange: onFileChange,
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value: file,
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}),
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fileFetchStatus.fold({
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some: (fetchStatus) => e(ProgressBar, { fetchStatus }),
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none: () => null,
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}),
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),
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e('div', { className: 'line' },
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e('label', { htmlFor: 'line' }, 'Line'),
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e('input', {
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name: 'line',
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required: true,
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pattern: "[0-9]+",
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onChange: onLineChange,
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value: line,
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}),
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),
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e('div', { className: 'column' },
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e('label', { htmlFor: 'column' }, 'Column'),
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e('input', {
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name: 'column',
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required: true,
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pattern: "[0-9]+",
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onChange: onColumnChange,
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value: column,
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}),
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),
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),
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e('div', null,
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result.fold({
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none: () => "Select a bundle, file and line",
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some: (value) => e('pre', null, value),
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}),
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),
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);
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}
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/* Global stuff */
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window.Decoder = {
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BundlePicker,
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};
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