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import { Injectable } from '@angular/core'
import * as MarkdownIt from 'markdown-it'
@Injectable()
export class MarkdownService {
static TEXT_RULES = [
'linkify',
'autolink',
'emphasis',
'link',
'newline',
'list'
]
static ENHANCED_RULES = MarkdownService.TEXT_RULES.concat([ 'image' ])
private textMarkdownIt: MarkdownIt.MarkdownIt
private enhancedMarkdownIt: MarkdownIt.MarkdownIt
constructor () {
this.textMarkdownIt = this.createMarkdownIt(MarkdownService.TEXT_RULES)
this.enhancedMarkdownIt = this.createMarkdownIt(MarkdownService.ENHANCED_RULES)
}
textMarkdownToHTML (markdown: string) {
if (!markdown) return ''
const html = this.textMarkdownIt.render(markdown)
return this.avoidTruncatedLinks(html)
}
enhancedMarkdownToHTML (markdown: string) {
if (!markdown) return ''
const html = this.enhancedMarkdownIt.render(markdown)
return this.avoidTruncatedLinks(html)
}
private createMarkdownIt (rules: string[]) {
const markdownIt = new MarkdownIt('zero', { linkify: true, breaks: true })
for (let rule of rules) {
markdownIt.enable(rule)
}
this.setTargetToLinks(markdownIt)
return markdownIt
}
private setTargetToLinks (markdownIt: MarkdownIt.MarkdownIt) {
// Snippet from markdown-it documentation: https://github.com/markdown-it/markdown-it/blob/master/docs/architecture.md#renderer
const defaultRender = markdownIt.renderer.rules.link_open || function (tokens, idx, options, env, self) {
return self.renderToken(tokens, idx, options)
}
markdownIt.renderer.rules.link_open = function (tokens, index, options, env, self) {
const token = tokens[index]
const targetIndex = token.attrIndex('target')
if (targetIndex < 0) token.attrPush([ 'target', '_blank' ])
else token.attrs[targetIndex][1] = '_blank'
const relIndex = token.attrIndex('rel')
if (relIndex < 0) token.attrPush([ 'rel', 'noopener noreferrer' ])
else token.attrs[relIndex][1] = 'noopener noreferrer'
// pass token to default renderer.
return defaultRender(tokens, index, options, env, self)
}
}
private avoidTruncatedLinks (html: string) {
return html.replace(/<a[^>]+>([^<]+)<\/a>\s*...((<\/p>)|(<\/li>)|(<\/strong>))?$/mi, '$1...')
.replace(/\[[^\]]+\]?\(?([^\)]+)$/, '$1')
}
}
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