client/src/app/shared/renderer/markdown.service.ts

   1 import { Injectable } from '@angular/core'
   2 import { MarkdownIt } from 'markdown-it'
   3 import { HtmlRendererService } from '@app/shared/renderer/html-renderer.service'
   4 import { mark } from '@angular/compiler-cli/src/ngtsc/perf/src/clock'
   5
   6 type MarkdownParsers = {
   7   textMarkdownIt: MarkdownIt
   8   enhancedMarkdownIt: MarkdownIt
   9   enhancedMarkdownWithHTMLIt: MarkdownIt
  10   completeMarkdownIt: MarkdownIt
  11 }
  12
  13 type MarkdownConfig = {
  14   rules: string[]
  15   html: boolean
  16   escape?: boolean
  17 }
  18
  19 type MarkdownParserConfigs = {
  20   [id in keyof MarkdownParsers]: MarkdownConfig
  21 }
  22
  23 @Injectable()
  24 export class MarkdownService {
  25   static TEXT_RULES = [
  26     'linkify',
  27     'autolink',
  28     'emphasis',
  29     'link',
  30     'newline',
  31     'list'
  32   ]
  33   static ENHANCED_RULES = MarkdownService.TEXT_RULES.concat([ 'image' ])
  34   static ENHANCED_WITH_HTML_RULES = MarkdownService.ENHANCED_RULES.concat([ 'html_inline', 'html_block' ])
  35   static COMPLETE_RULES = MarkdownService.ENHANCED_WITH_HTML_RULES.concat([ 'block', 'inline', 'heading', 'paragraph' ])
  36
  37   private markdownParsers: MarkdownParsers = {
  38     textMarkdownIt: null,
  39     enhancedMarkdownIt: null,
  40     enhancedMarkdownWithHTMLIt: null,
  41     completeMarkdownIt: null
  42   }
  43   private parsersConfig: MarkdownParserConfigs = {
  44     textMarkdownIt: { rules: MarkdownService.TEXT_RULES, html: false },
  45     enhancedMarkdownIt: { rules: MarkdownService.ENHANCED_RULES, html: false },
  46     enhancedMarkdownWithHTMLIt: { rules: MarkdownService.ENHANCED_WITH_HTML_RULES, html: true, escape: true },
  47     completeMarkdownIt: { rules: MarkdownService.COMPLETE_RULES, html: true }
  48   }
  49
  50   constructor (private htmlRenderer: HtmlRendererService) {}
  51
  52   textMarkdownToHTML (markdown: string) {
  53     return this.render('textMarkdownIt', markdown)
  54   }
  55
  56   async enhancedMarkdownToHTML (markdown: string, withHtml = false) {
  57     if (withHtml) return this.render('enhancedMarkdownWithHTMLIt', markdown)
  58
  59     return this.render('enhancedMarkdownIt', markdown)
  60   }
  61
  62   async completeMarkdownToHTML (markdown: string) {
  63     return this.render('completeMarkdownIt', markdown)
  64   }
  65
  66   private async render (name: keyof MarkdownParsers, markdown: string) {
  67     if (!markdown) return ''
  68
  69     const config = this.parsersConfig[ name ]
  70     if (!this.markdownParsers[ name ]) {
  71       this.markdownParsers[ name ] = await this.createMarkdownIt(config)
  72     }
  73
  74     let html = this.markdownParsers[ name ].render(markdown)
  75     html = this.avoidTruncatedTags(html)
  76
  77     console.log(html)
  78
  79     if (config.escape) return this.htmlRenderer.toSafeHtml(html)
  80
  81     return html
  82   }
  83
  84   private async createMarkdownIt (config: MarkdownConfig) {
  85     // FIXME: import('...') returns a struct module, containing a "default" field corresponding to our sanitizeHtml function
  86     const MarkdownItClass: typeof import ('markdown-it') = (await import('markdown-it') as any).default
  87
  88     const markdownIt = new MarkdownItClass('zero', { linkify: true, breaks: true, html: config.html })
  89
  90     for (const rule of config.rules) {
  91       markdownIt.enable(rule)
  92     }
  93
  94     this.setTargetToLinks(markdownIt)
  95
  96     return markdownIt
  97   }
  98
  99   private setTargetToLinks (markdownIt: MarkdownIt) {
 100     // Snippet from markdown-it documentation: https://github.com/markdown-it/markdown-it/blob/master/docs/architecture.md#renderer
 101     const defaultRender = markdownIt.renderer.rules.link_open || function (tokens, idx, options, env, self) {
 102       return self.renderToken(tokens, idx, options)
 103     }
 104
 105     markdownIt.renderer.rules.link_open = function (tokens, index, options, env, self) {
 106       const token = tokens[index]
 107
 108       const targetIndex = token.attrIndex('target')
 109       if (targetIndex < 0) token.attrPush([ 'target', '_blank' ])
 110       else token.attrs[targetIndex][1] = '_blank'
 111
 112       const relIndex = token.attrIndex('rel')
 113       if (relIndex < 0) token.attrPush([ 'rel', 'noopener noreferrer' ])
 114       else token.attrs[relIndex][1] = 'noopener noreferrer'
 115
 116       // pass token to default renderer.
 117       return defaultRender(tokens, index, options, env, self)
 118     }
 119   }
 120
 121   private avoidTruncatedTags (html: string) {
 122     return html.replace(/\*\*?([^*]+)$/, '$1')
 123       .replace(/<a[^>]+>([^<]+)<\/a>\s*...((<\/p>)|(<\/li>)|(<\/strong>))?$/mi, '$1...')
 124       .replace(/\[[^\]]+\]\(([^\)]+)$/m, '$1')
 125       .replace(/\s?\[[^\]]+\]?[.]{3}<\/p>$/m, '...</p>')
 126   }
 127 }