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import {useEffect, useState, useMemo, useCallback, useRef} from 'react'
import EventEmitter from 'eventemitter3'
import {AppBskyFeedDefs} from '@atproto/api'
import {Shadow} from './types'
export type {Shadow} from './types'
const emitter = new EventEmitter()
export interface PostShadow {
likeUri: string | undefined
likeCount: number | undefined
repostUri: string | undefined
repostCount: number | undefined
isDeleted: boolean
}
export const POST_TOMBSTONE = Symbol('PostTombstone')
interface CacheEntry {
ts: number
value: PostShadow
}
export function usePostShadow(
post: AppBskyFeedDefs.PostView,
ifAfterTS: number,
): Shadow<AppBskyFeedDefs.PostView> | typeof POST_TOMBSTONE {
const [state, setState] = useState<CacheEntry>({
ts: Date.now(),
value: fromPost(post),
})
const firstRun = useRef(true)
const onUpdate = useCallback(
(value: Partial<PostShadow>) => {
setState(s => ({ts: Date.now(), value: {...s.value, ...value}}))
},
[setState],
)
// react to shadow updates
useEffect(() => {
emitter.addListener(post.uri, onUpdate)
return () => {
emitter.removeListener(post.uri, onUpdate)
}
}, [post.uri, onUpdate])
// react to post updates
useEffect(() => {
// dont fire on first run to avoid needless re-renders
if (!firstRun.current) {
setState({ts: Date.now(), value: fromPost(post)})
}
firstRun.current = false
}, [post])
return useMemo(() => {
return state.ts > ifAfterTS
? mergeShadow(post, state.value)
: {...post, isShadowed: true}
}, [post, state, ifAfterTS])
}
export function updatePostShadow(uri: string, value: Partial<PostShadow>) {
emitter.emit(uri, value)
}
export function isPostShadowed(
v: AppBskyFeedDefs.PostView | Shadow<AppBskyFeedDefs.PostView>,
): v is Shadow<AppBskyFeedDefs.PostView> {
return 'isShadowed' in v && !!v.isShadowed
}
function fromPost(post: AppBskyFeedDefs.PostView): PostShadow {
return {
likeUri: post.viewer?.like,
likeCount: post.likeCount,
repostUri: post.viewer?.repost,
repostCount: post.repostCount,
isDeleted: false,
}
}
function mergeShadow(
post: AppBskyFeedDefs.PostView,
shadow: PostShadow,
): Shadow<AppBskyFeedDefs.PostView> | typeof POST_TOMBSTONE {
if (shadow.isDeleted) {
return POST_TOMBSTONE
}
return {
...post,
likeCount: shadow.likeCount,
repostCount: shadow.repostCount,
viewer: {
...(post.viewer || {}),
like: shadow.likeUri,
repost: shadow.repostUri,
},
isShadowed: true,
}
}
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