Refactor api.data.ts: Add comments and improve code clarity (vuejs#3098)

- Added comments to explain the purpose and functionality of key functions.
- Clarified the logic behind header parsing, slug generation, and file caching.
- Documented the use of regular expressions for header cleaning and anchor extraction.
- Improved readability and maintainability of the codebase.

Author: anjiri1684

src/api/api.data.ts

@@ -1,15 +1,16 @@
 // api.data.ts
-// a file ending with data.(j|t)s will be evaluated in Node.js
 import fs from 'fs'
 import path from 'path'
 import type { MultiSidebarConfig } from '@vue/theme/src/vitepress/config.ts'
 import { sidebar } from '../../.vitepress/config'
 
+// Interface defining the structure of a single header in the API
 interface APIHeader {
   anchor: string
   text: string
 }
 
+// Interface defining the structure of an API group with text, anchor, and items
 export interface APIGroup {
   text: string
   anchor: string
@@ -20,79 +21,108 @@ export interface APIGroup {
   }[]
 }
 
-// declare resolved data type
+// Declare the resolved data type for API groups
 export declare const data: APIGroup[]
 
-export default {
-  // declare files that should trigger HMR
-  watch: './*.md',
-  // read from fs and generate the data
-  load(): APIGroup[] {
-    return (sidebar as MultiSidebarConfig)['/api/'].map((group) => ({
-      text: group.text,
-      anchor: slugify(group.text),
-      items: group.items.map((item) => ({
-        ...item,
-        headers: parsePageHeaders(item.link)
-      }))
-    }))
-  }
+// Utility function to generate a slug from a string (used for anchor links)
+function slugify(text: string): string {
+  return (
+    text
+      // Replace special characters and spaces with hyphens
+      .replace(/[\s~`!@#$%^&*()\-_+=[\]{}|\\;:"'<>,.?/]+/g, '-')
+      // Remove continuous separators
+      .replace(/-{2,}/g, '-')
+      // Remove leading/trailing hyphens
+      .replace(/^-+|-+$/g, '')
+      // Ensure it doesn't start with a number (e.g. #121)
+      .replace(/^(\d)/, '_$1')
+      // Convert to lowercase
+      .toLowerCase()
+  )
 }
 
-const headersCache = new Map<
-  string,
-  {
-    headers: APIHeader[]
-    timestamp: number
-  }
->()
-
-function parsePageHeaders(link: string) {
-  const fullPath = path.join(__dirname, '../', link) + '.md'
-  const timestamp = fs.statSync(fullPath).mtimeMs
+// Utility function to parse headers from a markdown file at a given link
+function parsePageHeaders(link: string): APIHeader[] {
+  const fullPath = path.join(__dirname, '../', link) + '.md' // Resolve the full file path
+  const timestamp = fs.statSync(fullPath).mtimeMs // Get the last modified timestamp of the file
 
+  // Check if the file is cached and if its timestamp matches
   const cached = headersCache.get(fullPath)
   if (cached && timestamp === cached.timestamp) {
-    return cached.headers
+    return cached.headers // Return cached headers if they're up-to-date
   }
 
-  const src = fs.readFileSync(fullPath, 'utf-8')
-  const h2s = src.match(/^## [^\n]+/gm)
+  const src = fs.readFileSync(fullPath, 'utf-8') // Read the markdown file
+  const headers = extractHeadersFromMarkdown(src) // Extract headers from the file content
+
+  // Store the extracted headers along with the file's timestamp in the cache
+  headersCache.set(fullPath, {
+    timestamp,
+    headers
+  })
+
+  return headers
+}
+
+// Helper function to extract all headers (h2) from markdown content
+function extractHeadersFromMarkdown(src: string): APIHeader[] {
+  const h2s = src.match(/^## [^\n]+/gm) // Match all h2 headers (## header)
+  const anchorRE = /\{#([^}]+)\}/ // Regular expression to match the anchor link in header (e.g. {#some-anchor})
   let headers: APIHeader[] = []
+
   if (h2s) {
-    const anchorRE = /\{#([^}]+)\}/
+    // Process each h2 header and extract text and anchor
     headers = h2s.map((h) => {
-      const text = h
-        .slice(2)
-        .replace(/<sup class=.*/, '')
-        .replace(/\\</g, '<')
-        .replace(/`([^`]+)`/g, '$1')
-        .replace(anchorRE, '') // hidden anchor tag
-        .trim()
-      const anchor = h.match(anchorRE)?.[1] ?? slugify(text)
+      const text = cleanHeaderText(h, anchorRE) // Clean up header text
+      const anchor = extractAnchor(h, anchorRE, text) // Extract or generate anchor
       return { text, anchor }
     })
   }
-  headersCache.set(fullPath, {
-    timestamp,
-    headers
-  })
+
   return headers
 }
 
-// same as vitepress' slugify logic
-function slugify(text: string): string {
-  return (
-    text
-      // Replace special characters
-      .replace(/[\s~`!@#$%^&*()\-_+=[\]{}|\\;:"'<>,.?/]+/g, '-')
-      // Remove continuous separators
-      .replace(/-{2,}/g, '-')
-      // Remove prefixing and trailing separators
-      .replace(/^-+|-+$/g, '')
-      // ensure it doesn't start with a number (#121)
-      .replace(/^(\d)/, '_$1')
-      // lowercase
-      .toLowerCase()
-  )
+// Helper function to clean up header text (e.g., remove superscript, code formatting)
+function cleanHeaderText(h: string, anchorRE: RegExp): string {
+  return h
+    .slice(2) // Remove the "##" part of the header
+    .replace(/<sup class=.*/, '') // Remove superscript (e.g., <sup> tags)
+    .replace(/\\</g, '<') // Decode escaped characters like \<
+    .replace(/`([^`]+)`/g, '$1') // Remove inline code formatting (e.g., `code`)
+    .replace(anchorRE, '') // Remove anchor tags (e.g., {#anchor})
+    .trim() // Trim leading/trailing whitespace
+}
+
+// Helper function to extract the anchor link from a header (or generate one if missing)
+function extractAnchor(h: string, anchorRE: RegExp, text: string): string {
+  const anchorMatch = h.match(anchorRE) // Match anchor if it exists
+  return anchorMatch?.[1] ?? slugify(text) // If no anchor, generate one using slugify
+}
+
+// Cache for storing headers and their associated timestamps to avoid re-reading files
+const headersCache = new Map<
+  string,
+  {
+    headers: APIHeader[]
+    timestamp: number
+  }
+>()
+
+// Main export function for loading the API data
+export default {
+  // Declare files that should trigger Hot Module Replacement (HMR)
+  watch: './*.md',
+  
+  // Load API data and process sidebar items
+  load(): APIGroup[] {
+    // Generate the API group data by processing the sidebar configuration
+    return (sidebar as MultiSidebarConfig)['/api/'].map((group) => ({
+      text: group.text, // Text of the group (e.g., 'API')
+      anchor: slugify(group.text), // Generate anchor for the group title
+      items: group.items.map((item) => ({
+        ...item, // Spread the original item properties
+        headers: parsePageHeaders(item.link), // Parse the headers from the item's markdown link
+      }))
+    }))
+  }
 }