fix(docs): resolve repository links with a Markdown plugin

docs/.vitepress/config.mts

@@ -1,6 +1,37 @@
 import taskLists from 'markdown-it-task-lists'
+import { statSync } from 'node:fs'
+import { dirname, isAbsolute, relative, resolve, sep } from 'node:path'
+import { fileURLToPath } from 'node:url'
 import { defineConfig } from 'vitepress'
 
+const repoRoot = fileURLToPath(new URL('../../', import.meta.url))
+const sourceRepo = 'https://github.com/redai-studio/Relax'
+const sourceRef = 'main'
+
+function toSourceUrl(href: string, documentPath?: string): string {
+  if (!documentPath) return href
+  if (!href.startsWith('../') && !href.startsWith('./')) return href
+
+  const [, pathname, suffix] = href.match(/^([^?#]*)(.*)$/)!
+  let targetPath: string
+  try {
+    targetPath = resolve(dirname(documentPath), decodeURIComponent(pathname))
+  } catch {
+    return href
+  }
+
+  const repoPath = relative(repoRoot, targetPath)
+  const pathParts = repoPath.split(sep)
+  if (isAbsolute(repoPath) || pathParts[0] === '..' || pathParts[0] === 'docs') return href
+
+  const targetStats = statSync(targetPath, { throwIfNoEntry: false })
+  if (!targetStats) return href
+
+  const kind = targetStats.isDirectory() ? 'tree' : 'blob'
+  const urlPath = pathParts.map(encodeURIComponent).join('/')
+  return `${sourceRepo}/${kind}/${sourceRef}/${urlPath}${suffix}`
+}
+
 // https://vitepress.dev/reference/site-config
 export default defineConfig({
   vite: {
@@ -215,6 +246,14 @@ export default defineConfig({
     math: true,
     config(md) {
       md.use(taskLists)
+
+      const renderLink = md.renderer.rules.link_open!
+      md.renderer.rules.link_open = (tokens, index, options, env, self) => {
+        const token = tokens[index]
+        const href = token.attrGet('href')
+        if (href) token.attrSet('href', toSourceUrl(href, env.path))
+        return renderLink(tokens, index, options, env, self)
+      }
     }
   },