forgeplus-react/src/components/render-html.jsx

import React, { useEffect, useRef, useMemo , useState } from 'react'
import "../modules/courses/katex.css";
import marked, { getTocContent, cleanToc, getMathExpressions, resetMathExpressions } from '../common/marked';
import 'code-prettify';
import dompurify from 'dompurify';
import { getEmoji } from '../forge/Main/emoji';
import { emojiList } from '../common/util/emoji';
import axios from 'axios';
import imgError from '../images/img-error.png'

import { renderToString } from 'katex'

const preRegex = /<pre[^>]*>/g;
const strRegexSub = /:([a-zA-Z_]+):/g;
const quoteRegex = /\[[#][0-9]{0,}\]\(\/[A-Za-z0-9]{0,}\/[A-Za-z0-9]{0,}\/issues\/[0-9]{0,}\)/g;
function _unescape(str) {
  let div = document.createElement('div')
  div.innerHTML = str
  return div.childNodes.length === 0 ? "" : div.childNodes[0].nodeValue
}



export default ({
  value = '',
  className,
  style = {},
  url,
  owner=undefined,
  projectsId=undefined
}) => {
  const [ issues , setIssues ] = useState([]);

  useEffect(()=>{
    if(owner&&projectsId){
      getIssueList();
    }
  },[owner,projectsId])

  function getIssueList(){
    let matchQuote = str.match(quoteRegex);
    let array = [];
    if(matchQuote && matchQuote.length>0){
      for(var x=0;x<matchQuote.length;x++){
        let getIndex = matchQuote[x].match(/#(\S*)\]/)[1];
        getIndex && array.push(getIndex);
      }
      axios.get(`/${owner}/${projectsId}/issues/index_to_name`,{params:{
        index:array
      }}).then(result=>{
        if(result){
          setIssues(result.data);
        }
      })
    }
  }

  let str = String(value);
  const html = useMemo(() => {
    let rs = marked(str);
    const math_expressions = getMathExpressions();
    if (str.match(/\[TOC\]/)) {
      rs = rs.replace("<p>[TOC]</p>", getTocContent())
      cleanToc()
    }
    // 循环匹配所有emoji
    let matchStr = str.match(strRegexSub);
    if(matchStr && matchStr.length>0){
      for(var i=0;i < matchStr.length;i++){
        rs = rs.replace(matchStr[i],getEmoji(matchStr[i]));
      }
    }
    if(rs){
      for(let i = 0;i<emojiList.length;i++){
        if(rs.indexOf(emojiList[i].code)>=0){
          let reg = '/\\'+emojiList[i].code+'/g'
          if (emojiList[i].code === ':+1:') {
            // 匹配+1
            reg = /:\+1:/g
          }
          switch(emojiList[i].index){
            case 1:
              rs = rs.replace(eval(reg), `<img style="width:24px;" src="https://testforum.trustie.net/editormd/emoji/${emojiList[i].name}.png"/>`)
            case 2:
                rs = rs.replace(eval(reg), `<img style="width:24px;" src="https://twemoji.maxcdn.com/36x36/${emojiList[i].name}.png"/>`)
            case 3:
              rs = rs.replace(eval(reg), `<i class="fa fa-emoji fa-${emojiList[i].name}"></i>`)
            case 4:
              rs = rs.replace(eval(reg), `<i class="${emojiList[i].name}"></i>`)
          }
        }
      }
    }

    if(owner && projectsId && issues && issues.length>0){
      for(var x=0;x<issues.length;x++){
        let item = issues[x];
        let content = item.id ? `<a href="`+`/${owner}/${projectsId}/issues/${item.project_issues_index}`+`">#${item.project_issues_index}:${item.subject}</a>` : `<span>#${item.project_issues_index}(已删除)</span>`;
        rs = rs.split(`<a href="`+`/${owner}/${projectsId}/issues/${item.project_issues_index}`+`">#${item.project_issues_index}</a>`).join(content);
      }
    }
    rs = rs.replace(/(__special_katext_id_\d+__)/g, (_match, capture) => {
      const { type, expression } = math_expressions[capture];      
      return renderToString(_unescape(expression) || '', { displayMode: true, throwOnError: false,macros: { 
        "\\mbox": "\\text{#1}",
        "\\textrm": "\\text{#1}",
        "\\textnormal": "\\text{#1}",
      },
      trust: false})
    })
    rs = dompurify.sanitize(rs.replace(/▁/g, "▁▁▁"))
    rs = rs.split('<img ').join(`<img onerror="javascript:this.src='${ imgError }';"`) // 替换replaceall
    resetMathExpressions()
    return rs
  }, [str,issues]);

  // 锚点跳转，链接地址里含#对应的id
  useEffect(()=>{
    if(url && url.hash && html){
      let u = url.hash;
      if(u){
        let id = decodeURIComponent(u.split("#")[1]);
        let ele = document.getElementById(id);
        if(ele){
          window.scrollTo(0, ele.offsetTop);
        }
      }
    }
  },[url,html])

  const el = useRef();
  function onAncherHandler(e) {
    let target = e.target;
    if (target.tagName.toUpperCase() === 'A') {
      let ancher = target.getAttribute('href');
      if (ancher && ancher.startsWith('#')) {
        e.preventDefault()
        let viewEl = document.getElementById(ancher.replace('#', ''))
        if (viewEl) {
          viewEl.scrollIntoView(true)
        }
      }
    }
  }

  useEffect(() => {
    if (el.current && html) {
      if (html.match(preRegex)) {
        window.PR.prettyPrint()
      }
    }
    if (el.current) {
      el.current.addEventListener('click', onAncherHandler)
      return () => {
        el.current.removeEventListener('click', onAncherHandler)
        resetMathExpressions()
        cleanToc()
      }
    }
  }, [html, el.current, onAncherHandler])
  return (
    <div
      ref={el}
      style={style}
      className={`${className ? className : ''} markdown-body`}
      dangerouslySetInnerHTML={{ __html: html }}
    ></div>
  )
}