overleaf/services/web/frontend/js/shared/context/layout-context.tsx

import {
  createContext,
  useContext,
  useCallback,
  useMemo,
  useEffect,
  Dispatch,
  SetStateAction,
  FC,
} from 'react'
import useScopeValue from '../hooks/use-scope-value'
import useDetachLayout from '../hooks/use-detach-layout'
import localStorage from '../../infrastructure/local-storage'
import getMeta from '../../utils/meta'
import { debugConsole } from '@/utils/debugging'
import { BinaryFile } from '@/features/file-view/types/binary-file'
import useScopeEventEmitter from '@/shared/hooks/use-scope-event-emitter'

export type IdeLayout = 'sideBySide' | 'flat'
export type IdeView = 'editor' | 'file' | 'pdf' | 'history'

type LayoutContextValue = {
  reattach: () => void
  detach: () => void
  detachIsLinked: boolean
  detachRole: 'detacher' | 'detached' | null
  changeLayout: (newLayout: IdeLayout, newView?: IdeView) => void
  view: IdeView
  setView: (view: IdeView) => void
  chatIsOpen: boolean
  setChatIsOpen: Dispatch<SetStateAction<LayoutContextValue['chatIsOpen']>>
  reviewPanelOpen: boolean
  setReviewPanelOpen: Dispatch<
    SetStateAction<LayoutContextValue['reviewPanelOpen']>
  >
  leftMenuShown: boolean
  setLeftMenuShown: Dispatch<
    SetStateAction<LayoutContextValue['leftMenuShown']>
  >
  loadingStyleSheet: boolean
  setLoadingStyleSheet: Dispatch<
    SetStateAction<LayoutContextValue['loadingStyleSheet']>
  >
  pdfLayout: IdeLayout
  pdfPreviewOpen: boolean
}

const debugPdfDetach = getMeta('ol-debugPdfDetach')

export const LayoutContext = createContext<LayoutContextValue | undefined>(
  undefined
)

function setLayoutInLocalStorage(pdfLayout: IdeLayout) {
  localStorage.setItem(
    'pdf.layout',
    pdfLayout === 'sideBySide' ? 'split' : 'flat'
  )
}

export const LayoutProvider: FC = ({ children }) => {
  // what to show in the "flat" view (editor or pdf)
  const [view, _setView] = useScopeValue<IdeView>('ui.view')
  const [openFile] = useScopeValue<BinaryFile | null>('openFile')
  const historyToggleEmitter = useScopeEventEmitter('history:toggle', true)

  const setView = useCallback(
    (value: IdeView) => {
      _setView(oldValue => {
        // ensure that the "history:toggle" event is broadcast when switching in or out of history view
        if (value === 'history' || oldValue === 'history') {
          historyToggleEmitter()
        }

        if (value === 'editor' && openFile) {
          // if a file is currently opened, ensure the view is 'file' instead of
          // 'editor' when the 'editor' view is requested. This is to ensure
          // that the entity selected in the file tree is the one visible and
          // that docs don't take precedence over files.
          return 'file'
        }

        return value
      })
    },
    [_setView, openFile, historyToggleEmitter]
  )

  // whether the chat pane is open
  const [chatIsOpen, setChatIsOpen] = useScopeValue<boolean>('ui.chatOpen')

  // whether the review pane is open
  const [reviewPanelOpen, setReviewPanelOpen] =
    useScopeValue('ui.reviewPanelOpen')

  // whether the menu pane is open
  const [leftMenuShown, setLeftMenuShown] =
    useScopeValue<boolean>('ui.leftMenuShown')

  // whether to display the editor and preview side-by-side or full-width ("flat")
  const [pdfLayout, setPdfLayout] = useScopeValue<IdeLayout>('ui.pdfLayout')

  // whether stylesheet on theme is loading
  const [loadingStyleSheet, setLoadingStyleSheet] = useScopeValue<boolean>(
    'ui.loadingStyleSheet'
  )

  const changeLayout = useCallback(
    (newLayout: IdeLayout, newView: IdeView = 'editor') => {
      setPdfLayout(newLayout)
      setView(newLayout === 'sideBySide' ? 'editor' : newView)
      setLayoutInLocalStorage(newLayout)
    },
    [setPdfLayout, setView]
  )

  const {
    reattach,
    detach,
    isLinking: detachIsLinking,
    isLinked: detachIsLinked,
    role: detachRole,
    isRedundant: detachIsRedundant,
  } = useDetachLayout()

  const pdfPreviewOpen =
    pdfLayout === 'sideBySide' || view === 'pdf' || detachRole === 'detacher'

  useEffect(() => {
    if (debugPdfDetach) {
      debugConsole.warn('Layout Effect', {
        detachIsRedundant,
        detachRole,
        detachIsLinking,
        detachIsLinked,
      })
    }

    if (detachRole !== 'detacher') return // not in a PDF detacher layout

    if (detachIsRedundant) {
      changeLayout('sideBySide')
      return
    }

    if (detachIsLinking || detachIsLinked) {
      // the tab is linked to a detached tab (or about to be linked); show
      // editor only
      changeLayout('flat', 'editor')
    }
  }, [
    detachIsRedundant,
    detachRole,
    detachIsLinking,
    detachIsLinked,
    changeLayout,
  ])

  const value = useMemo<LayoutContextValue>(
    () => ({
      reattach,
      detach,
      detachIsLinked,
      detachRole,
      changeLayout,
      chatIsOpen,
      leftMenuShown,
      pdfLayout,
      pdfPreviewOpen,
      reviewPanelOpen,
      loadingStyleSheet,
      setChatIsOpen,
      setLeftMenuShown,
      setPdfLayout,
      setReviewPanelOpen,
      setLoadingStyleSheet,
      setView,
      view,
    }),
    [
      reattach,
      detach,
      detachIsLinked,
      detachRole,
      changeLayout,
      chatIsOpen,
      leftMenuShown,
      pdfLayout,
      pdfPreviewOpen,
      reviewPanelOpen,
      loadingStyleSheet,
      setChatIsOpen,
      setLeftMenuShown,
      setPdfLayout,
      setReviewPanelOpen,
      setLoadingStyleSheet,
      setView,
      view,
    ]
  )

  return (
    <LayoutContext.Provider value={value}>{children}</LayoutContext.Provider>
  )
}

export function useLayoutContext() {
  const context = useContext(LayoutContext)
  if (!context) {
    throw new Error('useLayoutContext is only available inside LayoutProvider')
  }
  return context
}