text: export default class HeaderConfigurer {
  
    constructor(crowi) {
      this.crowi = crowi;
  
      this.injectRevisionHeadClass = this.injectRevisionHeadClass.bind(this);
    }
  
    configure(md) {
      const rules = md.renderer.rules;
      const original = rules.heading_open;
      // combine rule and set
      // rules.heading_open = this.combineRules(this.injectRevisionHeadClass, headingOpenOrg);
      rules.heading_open = (tokens, idx, options, env, self) => {
        // Inject 'revision-head' class
        this.injectRevisionHeadClass(tokens, idx, options, env, self);
  
        if (original) {
          return original(tokens, idx, options, env, self);
        }
  
        return self.renderToken(tokens, idx, options, env, self);
      };
    }
  
    /**
     * Inject 'revision-head' class
     */
    injectRevisionHeadClass(tokens, idx, options, env, slf) {
      if (tokens[idx].map && tokens[idx].level === 0) {
        tokens[idx].attrJoin('class', 'revision-head');
      }
    }
  
  }
  