Overleaf/services/web/frontend/js/features/chat/context/chat-context.js

import React, {
  createContext,
  useCallback,
  useContext,
  useState,
  useEffect
} from 'react'
import PropTypes from 'prop-types'
import { useApplicationContext } from '../../../shared/context/application-context'
import { useEditorContext } from '../../../shared/context/editor-context'
import { ChatStore } from '../store/chat-store'
import useBrowserWindow from '../../../infrastructure/browser-window-hook'

export const ChatContext = createContext()

export function ChatProvider({ children }) {
  const {
    hasFocus: windowHasFocus,
    flashTitle,
    stopFlashingTitle
  } = useBrowserWindow()
  const { user } = useApplicationContext()
  const {
    projectId,
    ui: { chatIsOpen }
  } = useEditorContext()

  const [unreadMessageCount, setUnreadMessageCount] = useState(0)
  function resetUnreadMessageCount() {
    setUnreadMessageCount(0)
  }

  const [atEnd, setAtEnd] = useState(false)
  const [loading, setLoading] = useState(false)
  const [messages, setMessages] = useState([])

  const [store] = useState(() => new ChatStore(user, projectId))

  useEffect(() => {
    if (windowHasFocus) {
      stopFlashingTitle()
      if (chatIsOpen) {
        setUnreadMessageCount(0)
      }
    }
    if (!windowHasFocus && unreadMessageCount > 0) {
      flashTitle('New Message')
    }
  }, [
    windowHasFocus,
    chatIsOpen,
    unreadMessageCount,
    flashTitle,
    stopFlashingTitle
  ])

  useEffect(() => {
    function updateState() {
      setAtEnd(store.atEnd)
      setLoading(store.loading)
      setMessages(store.messages)
    }

    function handleNewMessage() {
      setUnreadMessageCount(prevCount => prevCount + 1)
    }

    store.on('updated', updateState)
    store.on('message-received', handleNewMessage)

    updateState()

    return () => store.destroy()
  }, [store])

  const loadMoreMessages = useCallback(() => store.loadMoreMessages(), [store])
  const sendMessage = useCallback(message => store.sendMessage(message), [
    store
  ])

  const value = {
    userId: user.id,
    atEnd,
    loading,
    messages,
    unreadMessageCount,
    resetUnreadMessageCount,
    loadMoreMessages,
    sendMessage
  }

  return <ChatContext.Provider value={value}>{children}</ChatContext.Provider>
}

ChatProvider.propTypes = {
  children: PropTypes.any
}

export function useChatContext() {
  return useContext(ChatContext)
}