Introduce Markdown extensions (#1614)

* Introduce markdown extensions

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/components/markdown-renderer/markdown-extension/vimeo/replace-vimeo-link.ts

@@ -0,0 +1,27 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import type { RegexOptions } from '../../../../external-types/markdown-it-regex/interface'
+import { VimeoMarkdownExtension } from './vimeo-markdown-extension'
+
+const protocolRegex = /(?:http(?:s)?:\/\/)?/
+const domainRegex = /(?:player\.)?(?:vimeo\.com\/)(?:(?:channels|album|ondemand|groups)\/\w+\/)?(?:video\/)?/
+const idRegex = /([\d]{6,11})/
+const tailRegex = /(?:[?#].*)?/
+const vimeoVideoUrlRegex = new RegExp(
+  `(?:${protocolRegex.source}${domainRegex.source}${idRegex.source}${tailRegex.source})`
+)
+const linkRegex = new RegExp(`^${vimeoVideoUrlRegex.source}$`, 'i')
+
+export const replaceVimeoLink: RegexOptions = {
+  name: 'vimeo-link',
+  regex: linkRegex,
+  replace: (match) => {
+    // ESLint wants to collapse this tag, but then the tag won't be valid html anymore.
+    // noinspection CheckTagEmptyBody
+    return `<${VimeoMarkdownExtension.tagName} id='${match}'></${VimeoMarkdownExtension.tagName}>`
+  }
+}