overleaf/services/web/frontend/js/features/source-editor/extensions/math-preview.ts

import {
  EditorView,
  repositionTooltips,
  showTooltip,
  Tooltip,
  ViewPlugin,
} from '@codemirror/view'
import {
  Compartment,
  EditorState,
  Extension,
  StateEffect,
  StateField,
  TransactionSpec,
} from '@codemirror/state'
import { loadMathJax } from '../../mathjax/load-mathjax'
import { descendantsOfNodeWithType } from '../utils/tree-query'
import {
  MathContainer,
  mathAncestorNode,
  parseMathContainer,
} from '../utils/tree-operations/math'
import { documentCommands } from '../languages/latex/document-commands'
import { debugConsole } from '@/utils/debugging'
import { nodeHasError } from '../utils/tree-operations/common'
import { documentEnvironments } from '../languages/latex/document-environments'

const REPOSITION_EVENT = 'editor:repositionMathTooltips'
const HIDE_TOOLTIP_EVENT = 'editor:hideMathTooltip'

export const mathPreview = (enabled: boolean): Extension => {
  return mathPreviewConf.of(
    enabled ? [mathPreviewTheme, mathPreviewStateField] : [mathPreviewTheme]
  )
}

export const hideTooltipEffect = StateEffect.define<null>()

const mathPreviewConf = new Compartment()

export const setMathPreview = (enabled: boolean): TransactionSpec => ({
  effects: mathPreviewConf.reconfigure(enabled ? mathPreviewStateField : []),
})

export const mathPreviewStateField = StateField.define<{
  tooltip: Tooltip | null
  hide: boolean
}>({
  create: buildInitialState,

  update(state, tr) {
    for (const effect of tr.effects) {
      if (effect.is(hideTooltipEffect)) {
        return { tooltip: null, hide: true }
      }
    }

    if (tr.docChanged || tr.selection) {
      const mathContainer = getMathContainer(tr.state)

      if (mathContainer) {
        if (state.hide) {
          return { tooltip: null, hide: true }
        } else {
          const mathContent = buildTooltipContent(tr.state, mathContainer)

          return {
            tooltip: buildTooltip(mathContainer, mathContent),
            hide: false,
          }
        }
      }

      return { tooltip: null, hide: false }
    }

    return state
  },

  provide: field => [
    showTooltip.compute([field], state => state.field(field).tooltip),

    ViewPlugin.define(view => {
      const listener = () => repositionTooltips(view)
      const hideTooltip = () => {
        view.dispatch({
          effects: hideTooltipEffect.of(null),
        })
      }

      window.addEventListener(REPOSITION_EVENT, listener)
      window.addEventListener(HIDE_TOOLTIP_EVENT, hideTooltip)

      return {
        destroy() {
          window.removeEventListener(REPOSITION_EVENT, listener)
          window.removeEventListener(HIDE_TOOLTIP_EVENT, hideTooltip)
        },
      }
    }),
  ],
})

function buildInitialState(state: EditorState) {
  const mathContainer = getMathContainer(state)

  if (mathContainer) {
    const mathContent = buildTooltipContent(state, mathContainer)

    return {
      tooltip: buildTooltip(mathContainer, mathContent),
      mathContent,
      hide: false,
    }
  }

  return { tooltip: null, hide: false, mathContent: null }
}

const renderMath = async (
  content: string,
  displayMode: boolean,
  element: HTMLElement,
  definitions: string
) => {
  const MathJax = await loadMathJax()

  MathJax.texReset([0]) // equation numbering is disabled, but this is still needed

  try {
    await MathJax.tex2svgPromise(definitions)
  } catch {
    // ignore errors thrown during parsing command definitions
  }

  const math = await MathJax.tex2svgPromise(content, {
    ...MathJax.getMetricsFor(element),
    display: displayMode,
  })
  element.textContent = ''
  element.append(math)
}

function buildTooltip(
  mathContainer: MathContainer,
  mathContent: HTMLDivElement | null
): Tooltip | null {
  if (!mathContent || !mathContainer) {
    return null
  }

  return {
    pos: mathContainer.pos,
    above: true,
    strictSide: true,
    arrow: false,
    create() {
      const dom = document.createElement('div')
      dom.classList.add('ol-cm-math-tooltip-container')
      const innerElt = document.createElement('div')
      innerElt.classList.add('ol-cm-math-tooltip')
      innerElt.id = 'ol-cm-math-tooltip'
      innerElt.appendChild(mathContent)
      dom.appendChild(innerElt)

      return { dom, overlap: true, offset: { x: 0, y: 8 } }
    },
  }
}

const getMathContainer = (state: EditorState) => {
  const range = state.selection.main

  if (!range.empty) {
    return null
  }

  // if anywhere inside Math, find the whole Math node
  const ancestorNode = mathAncestorNode(state, range.from)
  if (!ancestorNode) return null

  const [node] = descendantsOfNodeWithType(ancestorNode, 'Math', 'Math')
  if (!node) return null

  if (nodeHasError(ancestorNode)) return null

  return parseMathContainer(state, node, ancestorNode)
}

const buildTooltipContent = (
  state: EditorState,
  math: MathContainer | null
): HTMLDivElement | null => {
  if (!math || !math.content.length) return null

  const element = document.createElement('div')
  element.style.opacity = '0'
  element.textContent = math.content

  let definitions = ''

  const environmentState = state.field(documentEnvironments, false)
  if (environmentState?.items) {
    for (const environment of environmentState.items) {
      if (environment.type === 'definition') {
        definitions += `${environment.raw}\n`
      }
    }
  }

  const commandState = state.field(documentCommands, false)
  if (commandState?.items) {
    for (const command of commandState.items) {
      if (command.type === 'definition' && command.raw) {
        definitions += `${command.raw}\n`
      }
    }
  }

  renderMath(math.content, math.displayMode, element, definitions)
    .then(() => {
      element.style.opacity = '1'
      window.dispatchEvent(new Event(REPOSITION_EVENT))
    })
    .catch(error => {
      debugConsole.error(error)
    })

  return element
}

/**
 * Styles for the preview tooltip
 */
const mathPreviewTheme = EditorView.baseTheme({
  '&light .ol-cm-math-tooltip': {
    boxShadow: '0px 2px 4px 0px #1e253029',
    border: '1px solid #e7e9ee !important',
    backgroundColor: 'white !important',
  },
  '&dark .ol-cm-math-tooltip': {
    boxShadow: '0px 2px 4px 0px #1e253029',
    border: '1px solid #2f3a4c !important',
    backgroundColor: '#1b222c !important',
  },
})