[Clipclops] External store, suspend/resume (#3829)

* Initial working external store

* Clean up WIP, explore suspend/resume

* Clean up state, bindings, snapshots, add some logs

* Reduce snapshots, add better logic check

* Bump interval a smidge

* Remove unused type

src/logger/debugContext.ts

···
   // e.g. composer: 'composer'
   session: 'session',
   notifications: 'notifications',
+  convo: 'convo',
 } as const

src/screens/Messages/Conversation/MessagesList.tsx

···
   }, [])
 
   const onEndReached = useCallback(() => {
-    chat.service.fetchMessageHistory()
+    if (chat.status === ConvoStatus.Ready) {
+      chat.fetchMessageHistory()
+    }
   }, [chat])
 
   const onInputFocus = useCallback(() => {
···
 
   const onSendMessage = useCallback(
     (text: string) => {
-      chat.service.sendMessage({
-        text,
-      })
+      if (chat.status === ConvoStatus.Ready) {
+        chat.sendMessage({
+          text,
+        })
+      }
     },
-    [chat.service],
+    [chat],
   )
 
   const onScroll = React.useCallback(
···
       contentContainerStyle={a.flex_1}>
       <FlatList
         ref={flatListRef}
-        data={
-          chat.state.status === ConvoStatus.Ready ? chat.state.items : undefined
-        }
+        data={chat.status === ConvoStatus.Ready ? chat.items : undefined}
         keyExtractor={keyExtractor}
         renderItem={renderItem}
         contentContainerStyle={{paddingHorizontal: 10}}
···
         ListFooterComponent={
           <MaybeLoader
             isLoading={
-              chat.state.status === ConvoStatus.Ready &&
-              chat.state.isFetchingHistory
+              chat.status === ConvoStatus.Ready && chat.isFetchingHistory
             }
           />
         }

src/screens/Messages/Conversation/index.tsx

···
 import React, {useCallback} from 'react'
 import {TouchableOpacity, View} from 'react-native'
 import {AppBskyActorDefs} from '@atproto/api'
-import {ChatBskyConvoDefs} from '@atproto-labs/api'
 import {FontAwesomeIcon} from '@fortawesome/react-native-fontawesome'
 import {msg} from '@lingui/macro'
 import {useLingui} from '@lingui/react'
···
   const myDid = currentAccount?.did
 
   const otherProfile = React.useMemo(() => {
-    if (chat.state.status !== ConvoStatus.Ready) return
-    return chat.state.convo.members.find(m => m.did !== myDid)
-  }, [chat.state, myDid])
+    if (chat.status !== ConvoStatus.Ready) return
+    return chat.convo.members.find(m => m.did !== myDid)
+  }, [chat, myDid])
 
   // TODO whenever we have error messages, we should use them in here -hailey
-  if (chat.state.status !== ConvoStatus.Ready || !otherProfile) {
+  if (chat.status !== ConvoStatus.Ready || !otherProfile) {
     return (
       <ListMaybePlaceholder
         isLoading={true}
-        isError={chat.state.status === ConvoStatus.Error}
+        isError={chat.status === ConvoStatus.Error}
       />
     )
   }
···
   const {_} = useLingui()
   const {gtTablet} = useBreakpoints()
   const navigation = useNavigation<NavigationProp>()
-  const {service} = useChat()
+  const chat = useChat()
 
   const onPressBack = useCallback(() => {
     if (isWeb) {
···
     }
   }, [navigation])
 
-  const onUpdateConvo = useCallback(
-    (convo: ChatBskyConvoDefs.ConvoView) => {
-      service.convo = convo
-    },
-    [service],
-  )
+  const onUpdateConvo = useCallback(() => {
+    // TODO eric update muted state
+  }, [])
 
   return (
     <View
···
         <PreviewableUserAvatar size={32} profile={profile} />
         <Text style={[a.text_lg, a.font_bold]}>{profile.displayName}</Text>
       </View>
-      {service.convo ? (
+      {chat.status === ConvoStatus.Ready ? (
         <ConvoMenu
-          convo={service.convo}
+          convo={chat.convo}
           profile={profile}
           onUpdateConvo={onUpdateConvo}
           currentScreen="conversation"

src/state/messages/__tests__/convo.test.ts

···
     })
   })
 
+  describe(`read states`, () => {
+    it.todo(`should mark messages as read as they come in`)
+  })
+
   describe(`history fetching`, () => {
     it.todo(`fetches initial chat history`)
     it.todo(`fetches additional chat history`)

src/state/messages/convo.ts

···
   ChatBskyConvoDefs,
   ChatBskyConvoSendMessage,
 } from '@atproto-labs/api'
-import {EventEmitter} from 'eventemitter3'
 import {nanoid} from 'nanoid/non-secure'
 
+import {logger} from '#/logger'
 import {isNative} from '#/platform/detection'
 
 export type ConvoParams = {
···
 export enum ConvoStatus {
   Uninitialized = 'uninitialized',
   Initializing = 'initializing',
+  Resuming = 'resuming',
   Ready = 'ready',
   Error = 'error',
-  Destroyed = 'destroyed',
+  Backgrounded = 'backgrounded',
+  Suspended = 'suspended',
 }
 
 export type ConvoItem =
···
 export type ConvoState =
   | {
       status: ConvoStatus.Uninitialized
+      items: []
+      convo: undefined
+      error: undefined
+      isFetchingHistory: false
+      deleteMessage: undefined
+      sendMessage: undefined
+      fetchMessageHistory: undefined
     }
   | {
       status: ConvoStatus.Initializing
+      items: []
+      convo: undefined
+      error: undefined
+      isFetchingHistory: boolean
+      deleteMessage: undefined
+      sendMessage: undefined
+      fetchMessageHistory: undefined
     }
   | {
       status: ConvoStatus.Ready
       items: ConvoItem[]
       convo: ChatBskyConvoDefs.ConvoView
+      error: undefined
       isFetchingHistory: boolean
+      deleteMessage: (messageId: string) => void
+      sendMessage: (
+        message: ChatBskyConvoSendMessage.InputSchema['message'],
+      ) => void
+      fetchMessageHistory: () => void
+    }
+  | {
+      status: ConvoStatus.Suspended
+      items: ConvoItem[]
+      convo: ChatBskyConvoDefs.ConvoView
+      error: undefined
+      isFetchingHistory: boolean
+      deleteMessage: (messageId: string) => void
+      sendMessage: (
+        message: ChatBskyConvoSendMessage.InputSchema['message'],
+      ) => void
+      fetchMessageHistory: () => void
+    }
+  | {
+      status: ConvoStatus.Backgrounded
+      items: ConvoItem[]
+      convo: ChatBskyConvoDefs.ConvoView
+      error: undefined
+      isFetchingHistory: boolean
+      deleteMessage: (messageId: string) => void
+      sendMessage: (
+        message: ChatBskyConvoSendMessage.InputSchema['message'],
+      ) => void
+      fetchMessageHistory: () => void
+    }
+  | {
+      status: ConvoStatus.Resuming
+      items: ConvoItem[]
+      convo: ChatBskyConvoDefs.ConvoView
+      error: undefined
+      isFetchingHistory: boolean
+      deleteMessage: (messageId: string) => void
+      sendMessage: (
+        message: ChatBskyConvoSendMessage.InputSchema['message'],
+      ) => void
+      fetchMessageHistory: () => void
     }
   | {
       status: ConvoStatus.Error
+      items: []
+      convo: undefined
       error: any
+      isFetchingHistory: false
+      deleteMessage: undefined
+      sendMessage: undefined
+      fetchMessageHistory: undefined
     }
-  | {
-      status: ConvoStatus.Destroyed
-    }
+
+const ACTIVE_POLL_INTERVAL = 2e3
+const BACKGROUND_POLL_INTERVAL = 10e3
 
 export function isConvoItemMessage(
   item: ConvoItem,
···
   private agent: BskyAgent
   private __tempFromUserDid: string
 
+  private pollInterval = ACTIVE_POLL_INTERVAL
   private status: ConvoStatus = ConvoStatus.Uninitialized
   private error: any
   private historyCursor: string | undefined | null = undefined
   private isFetchingHistory = false
   private eventsCursor: string | undefined = undefined
 
-  convoId: string
-  convo: ChatBskyConvoDefs.ConvoView | undefined
-  sender: AppBskyActorDefs.ProfileViewBasic | undefined
-
   private pastMessages: Map<
     string,
     ChatBskyConvoDefs.MessageView | ChatBskyConvoDefs.DeletedMessageView
···
   private pendingEventIngestion: Promise<void> | undefined
   private isProcessingPendingMessages = false
 
+  convoId: string
+  convo: ChatBskyConvoDefs.ConvoView | undefined
+  sender: AppBskyActorDefs.ProfileViewBasic | undefined
+  snapshot: ConvoState | undefined
+
   constructor(params: ConvoParams) {
     this.convoId = params.convoId
     this.agent = params.agent
     this.__tempFromUserDid = params.__tempFromUserDid
+
+    this.subscribe = this.subscribe.bind(this)
+    this.getSnapshot = this.getSnapshot.bind(this)
+    this.sendMessage = this.sendMessage.bind(this)
+    this.deleteMessage = this.deleteMessage.bind(this)
+    this.fetchMessageHistory = this.fetchMessageHistory.bind(this)
   }
 
-  async initialize() {
-    if (this.status !== 'uninitialized') return
-    this.status = ConvoStatus.Initializing
+  private commit() {
+    this.snapshot = undefined
+    this.subscribers.forEach(subscriber => subscriber())
+  }
 
-    try {
-      const response = await this.agent.api.chat.bsky.convo.getConvo(
-        {
-          convoId: this.convoId,
-        },
-        {
-          headers: {
-            Authorization: this.__tempFromUserDid,
-          },
-        },
-      )
-      const {convo} = response.data
+  private subscribers: (() => void)[] = []
+
+  subscribe(subscriber: () => void) {
+    if (this.subscribers.length === 0) this.init()
 
-      this.convo = convo
-      this.sender = this.convo.members.find(
-        m => m.did === this.__tempFromUserDid,
-      )
-      this.status = ConvoStatus.Ready
+    this.subscribers.push(subscriber)
 
-      this.commit()
+    return () => {
+      this.subscribers = this.subscribers.filter(s => s !== subscriber)
+      if (this.subscribers.length === 0) this.suspend()
+    }
+  }
 
-      await this.fetchMessageHistory()
+  getSnapshot(): ConvoState {
+    if (!this.snapshot) this.snapshot = this.generateSnapshot()
+    logger.debug('Convo: snapshotted', {}, logger.DebugContext.convo)
+    return this.snapshot
+  }
 
-      this.pollEvents()
-    } catch (e) {
-      this.status = ConvoStatus.Error
-      this.error = e
+  private generateSnapshot(): ConvoState {
+    switch (this.status) {
+      case ConvoStatus.Initializing: {
+        return {
+          status: ConvoStatus.Initializing,
+          items: [],
+          convo: undefined,
+          error: undefined,
+          isFetchingHistory: this.isFetchingHistory,
+          deleteMessage: undefined,
+          sendMessage: undefined,
+          fetchMessageHistory: undefined,
+        }
+      }
+      case ConvoStatus.Suspended:
+      case ConvoStatus.Backgrounded:
+      case ConvoStatus.Resuming:
+      case ConvoStatus.Ready: {
+        return {
+          status: this.status,
+          items: this.getItems(),
+          convo: this.convo!,
+          error: undefined,
+          isFetchingHistory: this.isFetchingHistory,
+          deleteMessage: this.deleteMessage,
+          sendMessage: this.sendMessage,
+          fetchMessageHistory: this.fetchMessageHistory,
+        }
+      }
+      case ConvoStatus.Error: {
+        return {
+          status: ConvoStatus.Error,
+          items: [],
+          convo: undefined,
+          error: this.error,
+          isFetchingHistory: false,
+          deleteMessage: undefined,
+          sendMessage: undefined,
+          fetchMessageHistory: undefined,
+        }
+      }
+      default: {
+        return {
+          status: ConvoStatus.Uninitialized,
+          items: [],
+          convo: undefined,
+          error: undefined,
+          isFetchingHistory: false,
+          deleteMessage: undefined,
+          sendMessage: undefined,
+          fetchMessageHistory: undefined,
+        }
+      }
     }
   }
 
-  private async pollEvents() {
-    if (this.status === ConvoStatus.Destroyed) return
-    if (this.pendingEventIngestion) return
-    setTimeout(async () => {
-      this.pendingEventIngestion = this.ingestLatestEvents()
-      await this.pendingEventIngestion
-      this.pendingEventIngestion = undefined
-      this.pollEvents()
-    }, 5e3)
+  async init() {
+    logger.debug('Convo: init', {}, logger.DebugContext.convo)
+
+    if (this.status === ConvoStatus.Uninitialized) {
+      try {
+        this.status = ConvoStatus.Initializing
+        this.commit()
+
+        await this.refreshConvo()
+        this.status = ConvoStatus.Ready
+        this.commit()
+
+        await this.fetchMessageHistory()
+
+        this.pollEvents()
+      } catch (e) {
+        this.error = e
+        this.status = ConvoStatus.Error
+        this.commit()
+      }
+    } else {
+      logger.warn(`Convo: cannot init from ${this.status}`)
+    }
+  }
+
+  async resume() {
+    logger.debug('Convo: resume', {}, logger.DebugContext.convo)
+
+    if (
+      this.status === ConvoStatus.Suspended ||
+      this.status === ConvoStatus.Backgrounded
+    ) {
+      try {
+        this.status = ConvoStatus.Resuming
+        this.commit()
+
+        await this.refreshConvo()
+        this.status = ConvoStatus.Ready
+        this.commit()
+
+        await this.fetchMessageHistory()
+
+        this.pollInterval = ACTIVE_POLL_INTERVAL
+        this.pollEvents()
+      } catch (e) {
+        // TODO handle errors in one place
+        this.error = e
+        this.status = ConvoStatus.Error
+        this.commit()
+      }
+    } else {
+      logger.warn(`Convo: cannot resume from ${this.status}`)
+    }
+  }
+
+  async background() {
+    logger.debug('Convo: backgrounded', {}, logger.DebugContext.convo)
+    this.status = ConvoStatus.Backgrounded
+    this.pollInterval = BACKGROUND_POLL_INTERVAL
+    this.commit()
+  }
+
+  async suspend() {
+    logger.debug('Convo: suspended', {}, logger.DebugContext.convo)
+    this.status = ConvoStatus.Suspended
+    this.commit()
+  }
+
+  async refreshConvo() {
+    const response = await this.agent.api.chat.bsky.convo.getConvo(
+      {
+        convoId: this.convoId,
+      },
+      {
+        headers: {
+          Authorization: this.__tempFromUserDid,
+        },
+      },
+    )
+    this.convo = response.data.convo
+    this.sender = this.convo.members.find(m => m.did === this.__tempFromUserDid)
   }
 
   async fetchMessageHistory() {
-    if (this.status === ConvoStatus.Destroyed) return
-    // reached end
+    logger.debug('Convo: fetch message history', {}, logger.DebugContext.convo)
+
+    /*
+     * If historyCursor is null, we've fetched all history.
+     */
     if (this.historyCursor === null) return
+
+    /*
+     * Don't fetch again if a fetch is already in progress
+     */
     if (this.isFetchingHistory) return
 
     this.isFetchingHistory = true
     this.commit()
 
     /*
-     * Delay if paginating while scrolled.
-     *
-     * TODO why does the FlatList jump without this delay?
-     *
-     * Tbh it feels a little more natural with a slight delay.
+     * Delay if paginating while scrolled to prevent momentum scrolling from
+     * jerking the list around, plus makes it feel a little more human.
      */
     if (this.pastMessages.size > 0) {
       await new Promise(y => setTimeout(y, 500))
···
     this.commit()
   }
 
-  async ingestLatestEvents() {
-    if (this.status === ConvoStatus.Destroyed) return
+  private async pollEvents() {
+    if (
+      this.status === ConvoStatus.Ready ||
+      this.status === ConvoStatus.Backgrounded
+    ) {
+      if (this.pendingEventIngestion) return
 
+      setTimeout(async () => {
+        this.pendingEventIngestion = this.ingestLatestEvents()
+        await this.pendingEventIngestion
+        this.pendingEventIngestion = undefined
+        this.pollEvents()
+      }, this.pollInterval)
+    }
+  }
+
+  async ingestLatestEvents() {
     const response = await this.agent.api.chat.bsky.convo.getLog(
       {
         cursor: this.eventsCursor,
···
     )
     const {logs} = response.data
 
+    let needsCommit = false
+
     for (const log of logs) {
       /*
        * If there's a rev, we should handle it. If there's not a rev, we don't
···
               this.newMessages.delete(log.message.id)
             }
             this.newMessages.set(log.message.id, log.message)
+            needsCommit = true
           } else if (
             ChatBskyConvoDefs.isLogDeleteMessage(log) &&
             ChatBskyConvoDefs.isDeletedMessageView(log.message)
···
               this.pastMessages.delete(log.message.id)
               this.newMessages.delete(log.message.id)
               this.deletedMessages.delete(log.message.id)
+              needsCommit = true
             }
           }
         }
       }
     }
 
+    if (needsCommit) {
+      this.commit()
+    }
+  }
+
+  async sendMessage(message: ChatBskyConvoSendMessage.InputSchema['message']) {
+    // Ignore empty messages for now since they have no other purpose atm
+    if (!message.text.trim()) return
+
+    logger.debug('Convo: send message', {}, logger.DebugContext.convo)
+
+    const tempId = nanoid()
+
+    this.pendingMessages.set(tempId, {
+      id: tempId,
+      message,
+    })
     this.commit()
+
+    if (!this.isProcessingPendingMessages) {
+      this.processPendingMessages()
+    }
   }
 
   async processPendingMessages() {
+    logger.debug(
+      `Convo: processing messages (${this.pendingMessages.size} remaining)`,
+      {},
+      logger.DebugContext.convo,
+    )
+
     const pendingMessage = Array.from(this.pendingMessages.values()).shift()
 
     /*
···
   }
 
   async batchRetryPendingMessages() {
+    logger.debug(
+      `Convo: retrying ${this.pendingMessages.size} pending messages`,
+      {},
+      logger.DebugContext.convo,
+    )
+
     this.footerItems.delete('pending-retry')
     this.commit()
 
···
     }
   }
 
-  async sendMessage(message: ChatBskyConvoSendMessage.InputSchema['message']) {
-    if (this.status === ConvoStatus.Destroyed) return
-    // Ignore empty messages for now since they have no other purpose atm
-    if (!message.text.trim()) return
-
-    const tempId = nanoid()
-
-    this.pendingMessages.set(tempId, {
-      id: tempId,
-      message,
-    })
-    this.commit()
-
-    if (!this.isProcessingPendingMessages) {
-      this.processPendingMessages()
-    }
-  }
+  async deleteMessage(messageId: string) {
+    logger.debug('Convo: delete message', {}, logger.DebugContext.convo)
 
-  async deleteMessage(messageId: string) {
     this.deletedMessages.add(messageId)
     this.commit()
 
···
   /*
    * Items in reverse order, since FlatList inverts
    */
-  get items(): ConvoItem[] {
+  getItems(): ConvoItem[] {
     const items: ConvoItem[] = []
 
     // `newMessages` is in insertion order, unshift to reverse
···
 
         return item
       })
-  }
-
-  destroy() {
-    this.status = ConvoStatus.Destroyed
-    this.commit()
-  }
-
-  get state(): ConvoState {
-    switch (this.status) {
-      case ConvoStatus.Initializing: {
-        return {
-          status: ConvoStatus.Initializing,
-        }
-      }
-      case ConvoStatus.Ready: {
-        return {
-          status: ConvoStatus.Ready,
-          items: this.items,
-          convo: this.convo!,
-          isFetchingHistory: this.isFetchingHistory,
-        }
-      }
-      case ConvoStatus.Error: {
-        return {
-          status: ConvoStatus.Error,
-          error: this.error,
-        }
-      }
-      case ConvoStatus.Destroyed: {
-        return {
-          status: ConvoStatus.Destroyed,
-        }
-      }
-      default: {
-        return {
-          status: ConvoStatus.Uninitialized,
-        }
-      }
-    }
-  }
-
-  private _emitter = new EventEmitter()
-
-  private commit() {
-    this._emitter.emit('update')
-  }
-
-  on(event: 'update', cb: () => void) {
-    this._emitter.on(event, cb)
-  }
-
-  off(event: 'update', cb: () => void) {
-    this._emitter.off(event, cb)
   }
 }

src/state/messages/index.tsx

···
-import React, {useContext, useEffect, useMemo, useState} from 'react'
+import React, {useContext, useState, useSyncExternalStore} from 'react'
 import {BskyAgent} from '@atproto-labs/api'
+import {useFocusEffect} from '@react-navigation/native'
 
-import {Convo, ConvoParams} from '#/state/messages/convo'
+import {Convo, ConvoParams, ConvoState} from '#/state/messages/convo'
 import {useAgent} from '#/state/session'
 import {useDmServiceUrlStorage} from '#/screens/Messages/Temp/useDmServiceUrlStorage'
 
-const ChatContext = React.createContext<{
-  service: Convo
-  state: Convo['state']
-} | null>(null)
+const ChatContext = React.createContext<ConvoState | null>(null)
 
 export function useChat() {
   const ctx = useContext(ChatContext)
···
 }: Pick<ConvoParams, 'convoId'> & {children: React.ReactNode}) {
   const {serviceUrl} = useDmServiceUrlStorage()
   const {getAgent} = useAgent()
-  const [service] = useState(
+  const [convo] = useState(
     () =>
       new Convo({
         convoId,
···
         __tempFromUserDid: getAgent().session?.did!,
       }),
   )
-  const [state, setState] = useState(service.state)
-
-  useEffect(() => {
-    service.initialize()
-  }, [service])
+  const service = useSyncExternalStore(convo.subscribe, convo.getSnapshot)
 
-  useEffect(() => {
-    const update = () => setState(service.state)
-    service.on('update', update)
-    return () => {
-      service.destroy()
-    }
-  }, [service])
+  useFocusEffect(
+    React.useCallback(() => {
+      convo.resume()
 
-  const value = useMemo(() => ({service, state}), [service, state])
+      return () => {
+        convo.background()
+      }
+    }, [convo]),
+  )
 
-  return <ChatContext.Provider value={value}>{children}</ChatContext.Provider>
+  return <ChatContext.Provider value={service}>{children}</ChatContext.Provider>
 }