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
   5 type MarkdownParsers = {
   6   textMarkdownIt: MarkdownIt
   7   textWithHTMLMarkdownIt: MarkdownIt
   8
   9   enhancedMarkdownIt: MarkdownIt
  10   enhancedWithHTMLMarkdownIt: MarkdownIt
  11
  12   completeMarkdownIt: MarkdownIt
  13 }
  14
  15 type MarkdownConfig = {
  16   rules: string[]
  17   html: boolean
  18   escape?: boolean
  19 }
  20
  21 type MarkdownParserConfigs = {
  22   [id in keyof MarkdownParsers]: MarkdownConfig
  23 }
  24
  25 @Injectable()
  26 export class MarkdownService {
  27   static TEXT_RULES = [
  28     'linkify',
  29     'autolink',
  30     'emphasis',
  31     'link',
  32     'newline',
  33     'list'
  34   ]
  35   static TEXT_WITH_HTML_RULES = MarkdownService.TEXT_RULES.concat([ 'html_inline', 'html_block' ])
  36
  37   static ENHANCED_RULES = MarkdownService.TEXT_RULES.concat([ 'image' ])
  38   static ENHANCED_WITH_HTML_RULES = MarkdownService.TEXT_WITH_HTML_RULES.concat([ 'image' ])
  39
  40   static COMPLETE_RULES = MarkdownService.ENHANCED_WITH_HTML_RULES.concat([ 'block', 'inline', 'heading', 'paragraph' ])
  41
  42   private markdownParsers: MarkdownParsers = {
  43     textMarkdownIt: null,
  44     textWithHTMLMarkdownIt: null,
  45     enhancedMarkdownIt: null,
  46     enhancedWithHTMLMarkdownIt: null,
  47     completeMarkdownIt: null
  48   }
  49   private parsersConfig: MarkdownParserConfigs = {
  50     textMarkdownIt: { rules: MarkdownService.TEXT_RULES, html: false },
  51     textWithHTMLMarkdownIt: { rules: MarkdownService.TEXT_WITH_HTML_RULES, html: true, escape: true },
  52
  53     enhancedMarkdownIt: { rules: MarkdownService.ENHANCED_RULES, html: false },
  54     enhancedWithHTMLMarkdownIt: { rules: MarkdownService.ENHANCED_WITH_HTML_RULES, html: true, escape: true },
  55
  56     completeMarkdownIt: { rules: MarkdownService.COMPLETE_RULES, html: true }
  57   }
  58
  59   constructor (private htmlRenderer: HtmlRendererService) {}
  60
  61   textMarkdownToHTML (markdown: string, withHtml = false) {
  62     if (withHtml) return this.render('textWithHTMLMarkdownIt', markdown)
  63
  64     return this.render('textMarkdownIt', markdown)
  65   }
  66
  67   enhancedMarkdownToHTML (markdown: string, withHtml = false) {
  68     if (withHtml) return this.render('enhancedWithHTMLMarkdownIt', markdown)
  69
  70     return this.render('enhancedMarkdownIt', markdown)
  71   }
  72
  73   completeMarkdownToHTML (markdown: string) {
  74     return this.render('completeMarkdownIt', markdown)
  75   }
  76
  77   private async render (name: keyof MarkdownParsers, markdown: string) {
  78     if (!markdown) return ''
  79
  80     const config = this.parsersConfig[ name ]
  81     if (!this.markdownParsers[ name ]) {
  82       this.markdownParsers[ name ] = await this.createMarkdownIt(config)
  83     }
  84
  85     let html = this.markdownParsers[ name ].render(markdown)
  86     html = this.avoidTruncatedTags(html)
  87
  88     console.log(html)
  89
  90     if (config.escape) return this.htmlRenderer.toSafeHtml(html)
  91
  92     return html
  93   }
  94
  95   private async createMarkdownIt (config: MarkdownConfig) {
  96     // FIXME: import('...') returns a struct module, containing a "default" field corresponding to our sanitizeHtml function
  97     const MarkdownItClass: typeof import ('markdown-it') = (await import('markdown-it') as any).default
  98
  99     const markdownIt = new MarkdownItClass('zero', { linkify: true, breaks: true, html: config.html })
 100
 101     for (const rule of config.rules) {
 102       markdownIt.enable(rule)
 103     }
 104
 105     this.setTargetToLinks(markdownIt)
 106
 107     return markdownIt
 108   }
 109
 110   private setTargetToLinks (markdownIt: MarkdownIt) {
 111     // Snippet from markdown-it documentation: https://github.com/markdown-it/markdown-it/blob/master/docs/architecture.md#renderer
 112     const defaultRender = markdownIt.renderer.rules.link_open || function (tokens, idx, options, env, self) {
 113       return self.renderToken(tokens, idx, options)
 114     }
 115
 116     markdownIt.renderer.rules.link_open = function (tokens, index, options, env, self) {
 117       const token = tokens[index]
 118
 119       const targetIndex = token.attrIndex('target')
 120       if (targetIndex < 0) token.attrPush([ 'target', '_blank' ])
 121       else token.attrs[targetIndex][1] = '_blank'
 122
 123       const relIndex = token.attrIndex('rel')
 124       if (relIndex < 0) token.attrPush([ 'rel', 'noopener noreferrer' ])
 125       else token.attrs[relIndex][1] = 'noopener noreferrer'
 126
 127       // pass token to default renderer.
 128       return defaultRender(tokens, index, options, env, self)
 129     }
 130   }
 131
 132   private avoidTruncatedTags (html: string) {
 133     return html.replace(/\*\*?([^*]+)$/, '$1')
 134       .replace(/<a[^>]+>([^<]+)<\/a>\s*...((<\/p>)|(<\/li>)|(<\/strong>))?$/mi, '$1...')
 135       .replace(/\[[^\]]+\]\(([^\)]+)$/m, '$1')
 136       .replace(/\s?\[[^\]]+\]?[.]{3}<\/p>$/m, '...</p>')
 137   }
 138 }