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Simplify

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This commit is contained in:
Manav Rathi 2024-05-04 16:59:10 +05:30
parent b6add9650a
commit 438b6430e0
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1 changed files with 15 additions and 32 deletions
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47
web/apps/cast/src/services/cast.ts
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@ -91,31 +91,20 @@ type RenderableImageURLPair = [url: string, nextURL: string];
export const renderableImageURLs = async function* (castData: CastData) {
const { collectionKey, castToken } = castData;
/** The URL that we gave out second most recently. */
let oldURL: string | undefined;
/**
* The URL that we gave out most recently. This is the URL that is currently
* being shown in the slideshow.
*/
let url: string | undefined;
/**
* The two URLs we will give out when we next yield, plus an extra one that
* we have pre-fetched.
*/
const nextURLs: string[] = [];
/**
* We can revoke an object URL when it no longer the one being displayed and
* it is not one of those that we're planning to give out next.
* We have a sliding window of four URLs, with the `urls[1]` being the one
* that is the one currently being shown in the slideshow.
*
* We have a sliding window of five URLs:
* At each step, we shift the window towards the right by shifting out the
* leftmost (oldest) `urls[0]`, and adding a new one at the end.
*
* [oldURL, url, nextURLs[0], nextURLs[1], nextURLs[2]]
* We can revoke url[0] when we shift it out because we know it is not being
* used anymore.
*
* Note that for small albums of only a few renderable items, these URLs
* might possibly be the same as each other.
* To start off, we put two dummy entries, empty strings, in the array to
* avoid needing to special case the first render too much.
*/
const canRevokeURL = (u: string) => ![url, ...nextURLs].includes(u);
const urls: string[] = ["", ""];
while (true) {
const collection = await getCastCollection(castToken, collectionKey);
@ -127,9 +116,9 @@ export const renderableImageURLs = async function* (castData: CastData) {
outer: for (const file of files) {
if (!isFileEligibleForCast(file)) continue;
while (nextURLs.length < 3) {
while (urls.length < 4) {
try {
nextURLs.push(await createRenderableURL(castToken, file));
urls.push(await createRenderableURL(castToken, file));
} catch (e) {
log.error("Skipping unrenderable file", e);
continue outer;
@ -138,16 +127,10 @@ export const renderableImageURLs = async function* (castData: CastData) {
haveEligibleFiles = true;
const urlPair: RenderableImageURLPair = [
ensure(nextURLs[0]),
ensure(nextURLs[1]),
];
// Revoke the oldest one.
if (oldURL && canRevokeURL(oldURL)) URL.revokeObjectURL(oldURL);
// Slide the window to the right.
oldURL = url;
url = nextURLs.shift();
yield urlPair;
const oldestURL = urls.shift();
if (oldestURL) URL.revokeObjectURL(oldestURL);
yield [ensure(urls[0]), ensure(urls[1])];
}
// This collection does not have any files that we can show.