feat: allow embedding youtube videos with the obsidian markdown syntax (#665)

* Add option to allow embedding YouTube videos with Obsidian Markdown syntax

* Update Obsidian compatability doc page

* Switch to converting YT links as an html plugin

docs/features/Obsidian compatibility.md

@@ -26,6 +26,7 @@ Finally, Quartz also provides `Plugin.CrawlLinks` which allows you to customize
     - `mermaid`: whether to enable [[Mermaid diagrams]]. Defaults to `true`
     - `parseTags`: whether to try and parse tags in the content body. Defaults to `true`
     - `enableInHtmlEmbed`: whether to try and parse Obsidian flavoured markdown in raw HTML. Defaults to `false`
+    - `enableYouTubeEmbed`: whether to enable embedded YouTube videos using external image Markdown syntax. Defaults to `false`
 - Link resolution behaviour:
   - Disabling: remove all instances of `Plugin.CrawlLinks()` from `quartz.config.ts`
   - Changing link resolution preference: set `markdownLinkResolution` to one of `absolute`, `relative` or `shortest`

quartz/plugins/transformers/ofm.ts

@@ -25,6 +25,7 @@ export interface Options {
   parseTags: boolean
   parseBlockReferences: boolean
   enableInHtmlEmbed: boolean
+  enableYouTubeEmbed: boolean
 }
 
 const defaultOptions: Options = {
@@ -36,6 +37,7 @@ const defaultOptions: Options = {
   parseTags: true,
   parseBlockReferences: true,
   enableInHtmlEmbed: false,
+  enableYouTubeEmbed: false,
 }
 
 const icons = {
@@ -127,6 +129,7 @@ const calloutLineRegex = new RegExp(/^> *\[\!\w+\][+-]?.*$/, "gm")
 // (?:\/[-_\p{L}\d\p{Z}]+)*)   -> non-capturing group, matches an arbitrary number of tag strings separated by "/"
 const tagRegex = new RegExp(/(?:^| )#((?:[-_\p{L}\p{Emoji}\d])+(?:\/[-_\p{L}\p{Emoji}\d]+)*)/, "gu")
 const blockReferenceRegex = new RegExp(/\^([A-Za-z0-9]+)$/, "g")
+const ytLinkRegex = /^.*(youtu.be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/
 
 export const ObsidianFlavoredMarkdown: QuartzTransformerPlugin<Partial<Options> | undefined> = (
   userOpts,
@@ -505,6 +508,30 @@ export const ObsidianFlavoredMarkdown: QuartzTransformerPlugin<Partial<Options>
         })
       }
 
+      if (opts.enableYouTubeEmbed) {
+        plugins.push(() => {
+          return (tree: HtmlRoot) => {
+            visit(tree, "element", (node) => {
+              if (node.tagName === "img" && typeof node.properties.src === "string") {
+                const match = node.properties.src.match(ytLinkRegex)
+                const videoId = match && match[2].length == 11 ? match[2] : null
+                if (videoId) {
+                  node.tagName = "iframe"
+                  node.properties = {
+                    class: "external-embed",
+                    allow: "fullscreen",
+                    frameborder: 0,
+                    width: "600px",
+                    height: "350px",
+                    src: `https://www.youtube.com/embed/${videoId}`,
+                  }
+                }
+              }
+            })
+          }
+        })
+      }
+
       return plugins
     },
     externalResources() {