team/packages/lib/providers/ChannelListProvider.tsx

import { FrappeError, useFrappeGetCall, SWRConfiguration, useFrappeEventListener } from 'frappe-react-sdk'
import { createContext, useContext, useEffect, useMemo, useState } from 'react'
import { KeyedMutator } from 'swr'
import { useSWRConfig } from 'frappe-react-sdk'
import { ChannelList } from '@raven/types/common/ChannelListItem'

export interface ChannelListContextType extends ChannelList {
    mutate: KeyedMutator<{ message: ChannelList }>,
    error?: FrappeError,
    isLoading: boolean,
    hasData: boolean
}
export const ChannelListContext = createContext<ChannelListContextType | null>(null)


/** Use this hook to get the channel list */
export const useChannelList = (): ChannelListContextType => {
    const context = useContext(ChannelListContext)
    if (!context) {
        throw new Error('useChannelList must be used within a ChannelListProvider')
    }
    return context
}

/**
 * Hook to fetch the channel list - all channels + DM's + other users if any. The channel list is sorted by the last message timestamp.
 * Also listens to the channel_list_updated event to update the channel list
 * 
 * This is supposed to be used in the ChannelListContext and only once in the app since it has realtime event listeners
 */
export const useChannelListProvider = (swrConfig?: SWRConfiguration): ChannelListContextType => {

    const { mutate: globalMutate } = useSWRConfig()
    const { data, mutate, ...rest } = useFrappeGetCall<{ message: ChannelList }>("raven.api.raven_channel.get_all_channels", {
        hide_archived: false
    }, `channel_list`, {
        revalidateOnFocus: true,
        ...(swrConfig || {})
    })

    const [newUpdatesAvailable, setNewUpdatesAvailable] = useState(0)

    useEffect(() => {
        let timeout: NodeJS.Timeout | undefined
        if (newUpdatesAvailable) {
            timeout = setTimeout(() => {
                mutate()
                // Also update the unread channel count
                globalMutate('unread_channel_count')
                setNewUpdatesAvailable(0)
            }, 1000) // 1 second
        }
        return () => clearTimeout(timeout)
    }, [newUpdatesAvailable])

    /** 
     * If a bulk import happens, this gets called multiple times potentially causing the server to go down.
     * Instead, throttle this - wait for all events to subside
     */
    useFrappeEventListener('channel_list_updated', () => {
        if (!rest.isValidating) {
            setNewUpdatesAvailable((n) => n + 1)
        }
    })

    const { sortedChannels, sortedDMChannels } = useMemo(() => {
        let sortedChannels = data?.message.channels ?? []
        let sortedDMChannels = data?.message.dm_channels ?? []

        sortedChannels = sortedChannels.sort((a, b) => {
            const bTimestamp = b.last_message_timestamp ? new Date(b.last_message_timestamp).getTime() : 0
            const aTimestamp = a.last_message_timestamp ? new Date(a.last_message_timestamp).getTime() : 0
            return new Date(bTimestamp).getTime() - new Date(aTimestamp).getTime()
        })

        sortedDMChannels = sortedDMChannels.sort((a, b) => {
            const bTimestamp = b.last_message_timestamp ? new Date(b.last_message_timestamp).getTime() : 0
            const aTimestamp = a.last_message_timestamp ? new Date(a.last_message_timestamp).getTime() : 0
            return new Date(bTimestamp).getTime() - new Date(aTimestamp).getTime()
        })

        return { sortedChannels, sortedDMChannels }
    }, [data])

    return {
        hasData: !!data,
        channels: sortedChannels,
        dm_channels: sortedDMChannels,
        mutate,
        ...rest
    }

}