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1 | import { Injectable } from '@angular/core' | |
2 | ||
3 | import * as MarkdownIt from 'markdown-it' | |
4 | ||
5 | @Injectable() | |
6 | export class MarkdownService { | |
7 | static TEXT_RULES = [ | |
8 | 'linkify', | |
9 | 'autolink', | |
10 | 'emphasis', | |
11 | 'link', | |
12 | 'newline', | |
13 | 'list' | |
14 | ] | |
15 | static ENHANCED_RULES = MarkdownService.TEXT_RULES.concat([ 'image' ]) | |
16 | ||
17 | private textMarkdownIt: MarkdownIt.MarkdownIt | |
18 | private enhancedMarkdownIt: MarkdownIt.MarkdownIt | |
19 | ||
20 | constructor () { | |
21 | this.textMarkdownIt = this.createMarkdownIt(MarkdownService.TEXT_RULES) | |
22 | this.enhancedMarkdownIt = this.createMarkdownIt(MarkdownService.ENHANCED_RULES) | |
23 | } | |
24 | ||
25 | textMarkdownToHTML (markdown: string) { | |
26 | if (!markdown) return '' | |
27 | ||
28 | const html = this.textMarkdownIt.render(markdown) | |
29 | return this.avoidTruncatedTags(html) | |
30 | } | |
31 | ||
32 | enhancedMarkdownToHTML (markdown: string) { | |
33 | if (!markdown) return '' | |
34 | ||
35 | const html = this.enhancedMarkdownIt.render(markdown) | |
36 | return this.avoidTruncatedTags(html) | |
37 | } | |
38 | ||
39 | private createMarkdownIt (rules: string[]) { | |
40 | const markdownIt = new MarkdownIt('zero', { linkify: true, breaks: true }) | |
41 | ||
42 | for (let rule of rules) { | |
43 | markdownIt.enable(rule) | |
44 | } | |
45 | ||
46 | this.setTargetToLinks(markdownIt) | |
47 | ||
48 | return markdownIt | |
49 | } | |
50 | ||
51 | private setTargetToLinks (markdownIt: MarkdownIt.MarkdownIt) { | |
52 | // Snippet from markdown-it documentation: https://github.com/markdown-it/markdown-it/blob/master/docs/architecture.md#renderer | |
53 | const defaultRender = markdownIt.renderer.rules.link_open || function (tokens, idx, options, env, self) { | |
54 | return self.renderToken(tokens, idx, options) | |
55 | } | |
56 | ||
57 | markdownIt.renderer.rules.link_open = function (tokens, index, options, env, self) { | |
58 | const token = tokens[index] | |
59 | ||
60 | const targetIndex = token.attrIndex('target') | |
61 | if (targetIndex < 0) token.attrPush([ 'target', '_blank' ]) | |
62 | else token.attrs[targetIndex][1] = '_blank' | |
63 | ||
64 | const relIndex = token.attrIndex('rel') | |
65 | if (relIndex < 0) token.attrPush([ 'rel', 'noopener noreferrer' ]) | |
66 | else token.attrs[relIndex][1] = 'noopener noreferrer' | |
67 | ||
68 | // pass token to default renderer. | |
69 | return defaultRender(tokens, index, options, env, self) | |
70 | } | |
71 | } | |
72 | ||
73 | private avoidTruncatedTags (html: string) { | |
74 | return html.replace(/\*\*?([^*]+)$/, '$1') | |
75 | .replace(/<a[^>]+>([^<]+)<\/a>\s*...((<\/p>)|(<\/li>)|(<\/strong>))?$/mi, '$1...') | |
76 | .replace(/\[[^\]]+\]?\(?([^\)]+)$/, '$1') | |
77 | ||
78 | } | |
79 | } |