Add feed loader
This commit is contained in:
Jon Staab
@@ -0,0 +1,257 @@
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import {inc, max, min, now, isNil} from '@coracle.social/lib'
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import type {Rumor, Filter} from '@coracle.social/util'
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import {Tags, EPOCH, getIdFilters, guessFilterDelta, mergeFilters} from '@coracle.social/util'
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import type {DVMRequest, Scope, Feed, DynamicFilter} from './core'
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import {FeedType} from './core'
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import type {FeedCompiler} from './compiler'
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export type LoaderOpts<E> = {
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onEvent: (event: E) => void
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onExhausted: () => void
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}
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export type Loader = (limit: number) => Promise<void>
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export class FeedLoader<E extends Rumor> {
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_loader: Promise<Loader>
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constructor(readonly compiler: FeedCompiler<E>, feed: Feed, opts: LoaderOpts<E>) {
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this._loader = this.getLoader(feed, opts)
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}
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loadMore(limit: number) {
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this._loader.then(loader => loader(limit))
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}
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async getLoader([type, ...feed]: Feed, opts: LoaderOpts<E>) {
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if (this.compiler.canCompile([type, ...feed] as Feed)) {
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const filters = await this.compiler.compile([type, ...feed] as Feed)
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return this._getFilterLoader(filters, opts)
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}
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switch(type) {
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case FeedType.Difference:
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return this._getDifferenceLoader(feed as Feed[], opts)
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case FeedType.Intersection:
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return this._getIntersectionLoader(feed as Feed[], opts)
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case FeedType.SymmetricDifference:
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return this._getSymmetricDifferenceLoader(feed as Feed[], opts)
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case FeedType.Union:
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return this._getUnionLoader(feed as Feed[], opts)
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default:
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throw new Error(`Unable to convert feed of type ${type} to loader`)
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}
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}
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async _getFilterLoader(filters: Filter[], {onEvent, onExhausted}: LoaderOpts<E>) {
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const untils = filters.flatMap((filter: Filter) => filter.until ? [filter.until] : [])
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const sinces = filters.flatMap((filter: Filter) => filter.since ? [filter.since] : [])
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const maxUntil = untils.length === filters.length ? max(untils) : now()
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const minSince = sinces.length === filters.length ? min(sinces) : EPOCH
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const initialDelta = guessFilterDelta(filters)
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let delta = initialDelta
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let since = maxUntil - delta
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let until = maxUntil
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return async (limit: number) => {
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const reqFilters = filters
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// Remove filters that don't fit our window
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.filter((filter: Filter) => {
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const filterSince = filter.since || EPOCH
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const filterUntil = filter.until || now()
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return filterSince < until && filterUntil > since
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})
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// Modify the filters to define our window
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.map((filter: Filter) => ({...filter, until, limit, since}))
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let count = 0
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await this.compiler.opts.reqFilters(filters, {
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onEvent: (event: E) => {
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count += 1
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since = Math.min(since, event.created_at)
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onEvent(event)
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},
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})
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// Relays can't be relied upon to return events in descending order, do exponential
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// windowing to ensure we get the most recent stuff on first load, but eventually find it all
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if (count === 0) {
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delta *= 10
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}
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since = Math.max(minSince, since - delta)
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if (since === minSince) {
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onExhausted()
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}
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}
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}
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async _getDifferenceLoader(feeds: Feed[], {onEvent, onExhausted}: LoaderOpts<E>) {
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const exhausted = new Set<number>()
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const skip = new Set<string>()
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const events: E[] = []
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const seen = new Set()
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const loaders = await Promise.all(
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feeds.map((feed: Feed, i: number) =>
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this.getLoader(feed, {
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onExhausted: () => exhausted.add(i),
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onEvent: (event: E) => {
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if (i === 0) {
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events.push(event)
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} else {
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skip.add(event.id)
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}
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},
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})
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)
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)
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return async (limit: number) => {
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await Promise.all(
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loaders.map(async (loader: Loader, i: number) => {
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if (exhausted.has(i)) {
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return
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}
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await loader(limit)
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})
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)
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for (const event of events.splice(0)) {
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if (!skip.has(event.id) && !seen.has(event.id)) {
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onEvent(event)
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seen.add(event.id)
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}
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}
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if (exhausted.size === loaders.length) {
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onExhausted()
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}
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}
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}
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async _getIntersectionLoader(feeds: Feed[], {onEvent, onExhausted}: LoaderOpts<E>) {
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const exhausted = new Set<number>()
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const counts = new Map<string, number>()
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const events: E[] = []
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const seen = new Set()
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const loaders = await Promise.all(
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feeds.map((feed: Feed, i: number) =>
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this.getLoader(feed, {
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onExhausted: () => exhausted.add(i),
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onEvent: (event: E) => {
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events.push(event)
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counts.set(event.id, inc(counts.get(event.id)))
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},
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})
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)
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)
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return async (limit: number) => {
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await Promise.all(
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loaders.map(async (loader: Loader, i: number) => {
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if (exhausted.has(i)) {
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return
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}
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await loader(limit)
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})
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)
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for (const event of events.splice(0)) {
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if (counts.get(event.id) === loaders.length && !seen.has(event.id)) {
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onEvent(event)
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seen.add(event.id)
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}
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}
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if (exhausted.size === loaders.length) {
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onExhausted()
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}
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}
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}
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async _getSymmetricDifferenceLoader(feeds: Feed[], {onEvent, onExhausted}: LoaderOpts<E>) {
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const exhausted = new Set<number>()
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const counts = new Map<string, number>()
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const events: E[] = []
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const seen = new Set()
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const loaders = await Promise.all(
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feeds.map((feed: Feed, i: number) =>
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this.getLoader(feed, {
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onExhausted: () => exhausted.add(i),
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onEvent: (event: E) => {
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events.push(event)
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counts.set(event.id, inc(counts.get(event.id)))
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},
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})
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)
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)
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return async (limit: number) => {
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await Promise.all(
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loaders.map(async (loader: Loader, i: number) => {
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if (exhausted.has(i)) {
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return
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}
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await loader(limit)
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})
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)
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for (const event of events.values()) {
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if (counts.get(event.id) === 1 && !seen.has(event.id)) {
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onEvent(event)
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seen.add(event.id)
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}
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}
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if (exhausted.size === loaders.length) {
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onExhausted()
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}
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}
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}
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async _getUnionLoader(feeds: Feed[], {onEvent, onExhausted}: LoaderOpts<E>) {
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const exhausted = new Set<number>()
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const seen = new Set()
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const loaders = await Promise.all(
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feeds.map((feed: Feed, i: number) =>
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this.getLoader(feed, {
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onExhausted: () => exhausted.add(i),
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onEvent: (event: E) => {
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if (!seen.has(event.id)) {
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onEvent(event)
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seen.add(event.id)
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}
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},
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})
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)
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)
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return async (limit: number) => {
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await Promise.all(
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loaders.map(async (loader: Loader, i: number) => {
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if (exhausted.has(i)) {
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return
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}
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await loader(limit)
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})
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)
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if (exhausted.size === loaders.length) {
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onExhausted()
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}
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}
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}
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}
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