Jon Staab
60 lines
1.5 KiB
TypeScript
60 lines
1.5 KiB
TypeScript
import {readable, derived, type Readable} from 'svelte/store'
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import {indexBy, type Maybe, now} from '@welshman/lib'
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import {withGetter} from '@welshman/store'
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import {getFreshness, setFreshness} from './freshness'
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export const collection = <T, LoadArgs extends any[]>({
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name,
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store,
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getKey,
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load,
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}: {
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name: string
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store: Readable<T[]>
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getKey: (item: T) => string
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load: (key: string, ...args: LoadArgs) => Promise<any>
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}) => {
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const indexStore = withGetter(derived(store, $items => indexBy(getKey, $items)))
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const getItem = (key: string) => indexStore.get().get(key)
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const pending = new Map<string, Promise<Maybe<T>>>()
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const loadItem = async (key: string, ...args: LoadArgs) => {
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const item = indexStore.get().get(key)
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const delta = item ? 3600 : 300
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if (getFreshness(name, key) > now() - delta) {
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return item
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}
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if (pending.has(key)) {
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await pending.get(key)
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} else {
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setFreshness(name, key, now())
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const promise = load(key, ...args)
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pending.set(key, promise)
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await promise
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pending.delete(key)
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}
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return indexStore.get().get(key)
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}
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const deriveItem = (key: Maybe<string>, ...args: LoadArgs) => {
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if (!key) {
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return readable(undefined)
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}
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// If we don't yet have the item, or it's stale, trigger a request for it. The derived
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// store will update when it arrives
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loadItem(key, ...args)
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return derived(indexStore, $index => $index.get(key))
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}
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return {indexStore, deriveItem, loadItem, getItem}
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}
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