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elk/composables/paginator.ts
2023-01-10 20:08:36 +01:00

133 lines
3.5 KiB
TypeScript

import type { Paginator, WsEvents, mastodon } from 'masto'
import type { PaginatorState } from '~/types'
export function usePaginator<T, P, U = T>(
_paginator: Paginator<T[], P>,
stream?: Promise<WsEvents>,
eventType: 'notification' | 'update' = 'update',
preprocess: (items: (T | U)[], context?: mastodon.v2.FilterContext) => U[] = items => items as unknown as U[],
context?: mastodon.v2.FilterContext,
buffer = 10,
) {
// called `next` method will mutate the internal state of the variable,
// and we need its initial state after HMR
// so clone it
const paginator = _paginator.clone()
const state = ref<PaginatorState>(isMastoInitialised.value ? 'idle' : 'loading')
const items = ref<U[]>([])
const nextItems = ref<U[]>([])
const prevItems = ref<T[]>([])
const endAnchor = ref<HTMLDivElement>()
const bound = reactive(useElementBounding(endAnchor))
const isInScreen = $computed(() => bound.top < window.innerHeight * 2)
const error = ref<unknown | undefined>()
const deactivated = useDeactivated()
async function update() {
(items.value as U[]).unshift(...preprocess(prevItems.value as T[], context))
prevItems.value = []
}
stream?.then((s) => {
s.on(eventType, (status) => {
if ('uri' in status)
cacheStatus(status, undefined, true)
const index = prevItems.value.findIndex((i: any) => i.id === status.id)
if (index >= 0)
prevItems.value.splice(index, 1)
prevItems.value.unshift(status as any)
})
// TODO: update statuses
s.on('status.update', (status) => {
cacheStatus(status, undefined, true)
const data = items.value as mastodon.v1.Status[]
const index = data.findIndex(s => s.id === status.id)
if (index >= 0)
data[index] = status
})
s.on('delete', (id) => {
removeCachedStatus(id)
const data = items.value as mastodon.v1.Status[]
const index = data.findIndex(s => s.id === id)
if (index >= 0)
data.splice(index, 1)
})
})
async function loadNext() {
if (state.value !== 'idle')
return
state.value = 'loading'
try {
const result = await paginator.next()
if (!result.done && result.value.length) {
const preprocessedItems = preprocess([...nextItems.value, ...result.value] as (U | T)[], context)
const itemsToShowCount
= preprocessedItems.length <= buffer
? preprocessedItems.length
: preprocessedItems.length - buffer
;(nextItems.value as U[]) = preprocessedItems.slice(itemsToShowCount)
;(items.value as U[]).push(...preprocessedItems.slice(0, itemsToShowCount))
state.value = 'idle'
}
else {
items.value.push(...nextItems.value)
nextItems.value = []
state.value = 'done'
}
}
catch (e) {
error.value = e
state.value = 'error'
}
await nextTick()
bound.update()
}
if (process.client) {
useIntervalFn(() => {
bound.update()
}, 1000)
if (!isMastoInitialised.value) {
onMastoInit(() => {
state.value = 'idle'
loadNext()
})
}
watch(
() => [isInScreen, state],
() => {
if (
isInScreen
&& state.value === 'idle'
// No new content is loaded when the keepAlive page enters the background
&& deactivated.value === false
)
loadNext()
},
)
}
return {
items,
prevItems,
update,
state,
error,
endAnchor,
}
}