diff --git a/example/content/categories/index.yml b/example/content/categories/index.yml
deleted file mode 100644
index 3882978..0000000
--- a/example/content/categories/index.yml
+++ /dev/null
@@ -1,15 +0,0 @@
-- name: Journal
-  slug: journal
-  cover: journal.jpg
-  description: serving as a platform for academic exchange and dissemination of knowledge
-  meta:
-    title: Journal
-    description: with a focus on timely updates and research results. It is a reference tool for scholars and professionals in various fields.
-
-- name: Travel
-  slug: travel
-  description: All travel logs
-
-- name: Photography
-  slug: photography
-  description: All photography logs
diff --git a/example/content/categories/journal.yml b/example/content/categories/journal.yml
new file mode 100644
index 0000000..e2c9d2e
--- /dev/null
+++ b/example/content/categories/journal.yml
@@ -0,0 +1,7 @@
+name: Journal
+slug: journal
+cover: journal.jpg
+description: serving as a platform for academic exchange and dissemination of knowledge
+meta:
+  title: Journal
+  description: with a focus on timely updates and research results. It is a reference tool for scholars and professionals in various fields.
diff --git a/example/content/categories/photography.yml b/example/content/categories/photography.yml
new file mode 100644
index 0000000..9b0b220
--- /dev/null
+++ b/example/content/categories/photography.yml
@@ -0,0 +1,3 @@
+name: Travel
+slug: travel
+description: All travel logs
diff --git a/example/content/categories/travel.yml b/example/content/categories/travel.yml
new file mode 100644
index 0000000..7d33e15
--- /dev/null
+++ b/example/content/categories/travel.yml
@@ -0,0 +1,3 @@
+name: Photography
+slug: photography
+description: All photography logs
diff --git a/example/velite.config.ts b/example/velite.config.ts
index c63f674..74ead57 100644
--- a/example/velite.config.ts
+++ b/example/velite.config.ts
@@ -35,7 +35,7 @@ export default defineConfig({
     },
     categories: {
       name: 'Category',
-      pattern: 'categories/index.yml',
+      pattern: 'categories/*.yml',
       fields: s
         .object({
           name: s.name(),
@@ -77,8 +77,8 @@ export default defineConfig({
         .object({
           title: s.title(),
           slug: s.slug('post'),
-          date: s.date(),
-          updated: s.date().optional(),
+          date: s.isodate(),
+          updated: s.isodate().optional(),
           cover: s.image().optional(),
           description: s.paragraph().optional(),
           draft: s.boolean().default(false),
diff --git a/readme.md b/readme.md
index 324c604..b55218e 100644
--- a/readme.md
+++ b/readme.md
@@ -8,6 +8,20 @@
 [![NPM Version][version-img]][version-url]
 [![Code Style][style-img]][style-url]
 
+## TODOs
+
+example
+copy-linked-files
+--watch
+mdx
+reference parent
+
+- [ ] excerpt
+- [ ] nextjs plugin
+- [ ] types generate
+- [ ] image command (compress, resize, etc.)
+- [ ] docs
+
 ## Backups
 
 ```typescript
@@ -84,14 +98,6 @@ export const mdx = ({ gfm = true, removeComments = true, flattenImage = true, fl
 }
 ```
 
-## TODOs
-
-- [ ] excerpt
-- [ ] nextjs plugin
-- [ ] types generate
-- [ ] image command (compress, resize, etc.)
-- [ ] docs
-
 ## Installation
 
 ```shell
diff --git a/src/builder.ts b/src/build.ts
similarity index 77%
rename from src/builder.ts
rename to src/build.ts
index 846e26a..2265626 100644
--- a/src/builder.ts
+++ b/src/build.ts
@@ -1,7 +1,3 @@
-/**
- * @file Builder
- */
-
 import { mkdir, rm, watch, writeFile } from 'node:fs/promises'
 import { join } from 'node:path'
 import glob from 'fast-glob'
@@ -31,6 +27,51 @@ class Builder {
     this.result = {}
   }
 
+  /**
+   * create builder instance
+   */
+  static async create(options: Options) {
+    // resolve config
+    const config = await resolveConfig({ filename: options.config, clean: options.clean, verbose: options.verbose })
+
+    // register user loaders
+    config.loaders.forEach(addLoader)
+
+    // init static output config
+    initOutputConfig(config.output)
+
+    // prerequisite
+    if (config.clean) {
+      // clean output directories if `--clean` requested
+      await rm(config.output.data, { recursive: true, force: true })
+      await rm(config.output.static, { recursive: true, force: true })
+      config.verbose && console.log('cleaned output directories')
+    }
+
+    return new Builder(config)
+  }
+
+  /**
+   * output result to dist
+   */
+  async output() {
+    const { output } = this.config
+
+    await mkdir(output.data, { recursive: true })
+
+    await Promise.all(
+      Object.entries(this.result).map(async ([name, data]) => {
+        if (data == null) return
+        const json = JSON.stringify(data, null, 2)
+        await writeFile(join(output.data, name + '.json'), json)
+        console.log(`wrote ${data.length ?? 1} ${name} to '${join(output.data, name + '.json')}'`)
+      })
+    )
+  }
+
+  /**
+   * build content with config
+   */
   async build() {
     if (this.config == null) throw new Error('config not initialized')
     const { root, verbose, schemas, onSuccess } = this.config
@@ -39,26 +80,22 @@ class Builder {
 
     cache.clear() // clear cache in case of rebuild
 
+    const files: File[] = []
+
     const tasks = Object.entries(schemas).map(async ([name, schema]) => {
       const filenames = await glob(schema.pattern, { cwd: root, onlyFiles: true, ignore: ['**/_*'] })
       verbose && console.log(`found ${filenames.length} files matching '${schema.pattern}'`)
 
-      const files = await Promise.all(
-        filenames.map(async file => {
-          const doc = await File.create(join(root, file))
-          await doc.load()
-          await doc.parse(schema.fields)
-          return doc
+      const result = await Promise.all(
+        filenames.map(async filename => {
+          const file = await File.create(join(root, filename))
+          const result = await file.parse(schema.fields)
+          files.push(file)
+          return result
         })
       )
 
-      const report = reporter(files, { quiet: true, verbose })
-      report.length > 0 && console.log(report)
-
-      const data = files
-        .map(f => f.data.result ?? [])
-        .flat()
-        .filter(Boolean)
+      const data = result.flat().filter(Boolean)
 
       if (schema.single) {
         if (data.length > 1) {
@@ -70,37 +107,25 @@ class Builder {
       return [name, data] as const
     })
 
-    const collections = await Promise.all(tasks)
-
-    const result = Object.fromEntries<any>(collections)
+    const entities = await Promise.all(tasks)
 
-    // user callback
-    onSuccess != null && (await onSuccess(result))
+    // report if any error in parsing
+    const report = reporter(files, { quiet: true, verbose })
+    report.length > 0 && console.log(report)
 
-    Object.assign(this.result, result)
-  }
+    const collections = Object.fromEntries<any>(entities)
 
-  /**
-   * output result to dist
-   */
-  async output() {
-    const { output } = this.config
+    // user callback
+    if (typeof onSuccess === 'function') {
+      await onSuccess(collections)
+    }
 
-    await mkdir(output.data, { recursive: true })
+    Object.assign(this.result, collections)
 
-    await Promise.all(
-      Object.entries(this.result).map(async ([name, data]) => {
-        if (data == null) return
-        const json = JSON.stringify(data, null, 2)
-        await writeFile(join(output.data, name + '.json'), json)
-        console.log(`wrote ${data.length ?? 1} ${name} to '${join(output.data, name + '.json')}'`)
-      })
-    )
+    await this.output()
   }
 
   async watch() {
-    if (!this.config.watch) return
-
     console.log('watching for changes')
 
     const { schemas } = this.config
@@ -112,38 +137,15 @@ class Builder {
       const { filename } = event
       if (filename == null) continue
       if (!allPatterns.some(pattern => micromatch.isMatch(filename, pattern))) continue
-      // TODO: rebuild only changed file
       // rebuild all
-      await this.build()
-      await this.output()
+      await this.build() // TODO: rebuild only changed file
     }
   }
-
-  static async create(options: Options) {
-    // resolve config
-    const config = await resolveConfig({ filename: options.config, clean: options.clean, verbose: options.verbose, watch: options.watch })
-
-    // register user loaders
-    config.loaders.forEach(addLoader)
-
-    // init static output config
-    initOutputConfig(config.output)
-
-    // prerequisite
-    if (config.clean) {
-      // clean output directories if `--clean` requested
-      await rm(config.output.data, { recursive: true, force: true })
-      await rm(config.output.static, { recursive: true, force: true })
-      config.verbose && console.log('cleaned output directories')
-    }
-
-    return new Builder(config)
-  }
 }
 
 export const build = async (options: Options) => {
   const builder = await Builder.create(options)
   await builder.build()
-  await builder.output()
+  if (!options.watch) return
   await builder.watch()
 }
diff --git a/src/cli.ts b/src/cli.ts
index bbfaa79..264a0e1 100755
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -1,12 +1,8 @@
 #!/usr/bin/env node
-
-/**
- * @file CLI entry point
- */
 import cac from 'cac'
 
 import { name, version } from '../package.json'
-import { build } from './builder'
+import { build } from './build'
 
 const cli = cac(name).version(version).help()
 
diff --git a/src/config.ts b/src/config.ts
index 6f6f256..b97b136 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -1,7 +1,3 @@
-/**
- * @file Load config from user's project
- */
-
 import { access, rm } from 'node:fs/promises'
 import { dirname, join, resolve } from 'node:path'
 import { pathToFileURL } from 'node:url'
@@ -75,7 +71,6 @@ const loadConfig = async (filename: string): Promise<UserConfig> => {
 interface Options {
   filename?: string
   clean?: boolean
-  watch?: boolean
   verbose?: boolean
 }
 
@@ -117,7 +112,6 @@ export const resolveConfig = async (options: Options = {}): Promise<Config> => {
       ignoreFileExtensions: userConfig.output?.ignoreFileExtensions ?? []
     },
     clean: options.clean ?? userConfig.clean ?? false,
-    watch: options.watch ?? false,
     verbose,
     schemas: userConfig.schemas,
     loaders: userConfig.loaders ?? [],
diff --git a/src/file.ts b/src/file.ts
index 71f3cd4..87a6118 100644
--- a/src/file.ts
+++ b/src/file.ts
@@ -1,46 +1,45 @@
-/**
- * @file Document
- */
-
 import { readFile } from 'node:fs/promises'
 import { VFile } from 'vfile'
-import { ZodType } from 'zod'
 
 import { resolveLoader } from './loaders'
 
-declare module 'vfile' {
-  interface DataMap {
-    original: Record<string, any> | Record<string, any>[]
-    result: Record<string, any> | Record<string, any>[]
-  }
-}
+import type { Collection } from './types'
+import type { ZodType } from 'zod'
 
 export class File extends VFile {
+  /**
+   * create file instance
+   * @param path file path
+   * @returns file instance
+   */
+  static async create(path: string) {
+    const value = await readFile(path, 'utf8')
+    return new File({ path, value })
+  }
+
   /**
    * load file content into `this.data.original`
+   * @returns original data from file
    */
-  async load(): Promise<void> {
-    try {
-      if (this.extname == null) {
-        throw new Error('can not parse file without extension')
-      }
-      const loader = resolveLoader(this.path)
-      if (loader == null) {
-        throw new Error(`no loader found for '${this.path}'`)
-      }
-      await loader.load(this)
-    } catch (err: any) {
-      this.message(err.message)
+  private async load(): Promise<Collection> {
+    if (this.extname == null) {
+      throw new Error('can not parse file without extension')
+    }
+    const loader = resolveLoader(this.path)
+    if (loader == null) {
+      throw new Error(`no loader found for '${this.path}'`)
     }
+    return loader.load(this)
   }
 
   /**
-   * parse `this.data.original` into `this.data.result` with given fields schema
+   * parse file content with given fields schema
    * @param fields fields schema
+   * @returns collection data from file, or undefined if parsing failed
    */
-  async parse(fields: ZodType): Promise<void> {
+  async parse(fields: ZodType): Promise<Collection | undefined> {
     try {
-      const { original } = this.data
+      const original = await this.load()
 
       if (original == null || Object.keys(original).length === 0) {
         throw new Error('no data parsed from this file')
@@ -64,14 +63,9 @@ export class File extends VFile {
         })
       )
 
-      this.data.result = processed.length === 1 ? processed[0] : processed
+      return processed.length === 1 ? processed[0] : processed
     } catch (err: any) {
       this.message(err.message)
     }
   }
-
-  static async create(path: string) {
-    const value = await readFile(path, 'utf8')
-    return new File({ path, value })
-  }
 }
diff --git a/src/index.ts b/src/index.ts
index 6fb24fc..d5ee1a4 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,8 +1,4 @@
-/**
- * @file module entry point
- */
-
 export { z, s } from './shared'
 export { defineConfig, defineLoader } from './types'
 export { addLoader, removeLoader } from './loaders'
-export { build } from './builder'
+export { build } from './build'
diff --git a/src/loaders/json.ts b/src/loaders/json.ts
index a6e070b..e373e26 100644
--- a/src/loaders/json.ts
+++ b/src/loaders/json.ts
@@ -8,6 +8,6 @@ export default defineLoader({
   name: 'json',
   test: /\.json$/,
   load: async vfile => {
-    vfile.data.original = JSON.parse(vfile.toString())
+    return JSON.parse(vfile.toString())
   }
 })
diff --git a/src/loaders/markdown.ts b/src/loaders/markdown.ts
index 73dee99..4fce752 100644
--- a/src/loaders/markdown.ts
+++ b/src/loaders/markdown.ts
@@ -14,9 +14,7 @@ export default defineLoader({
     // https://github.com/vfile/vfile-matter/blob/main/lib/index.js
     const match = content.match(/^---(?:\r?\n|\r)(?:([\s\S]*?)(?:\r?\n|\r))?---(?:\r?\n|\r|$)/)
     if (match == null) {
-      // throw new Error('frontmatter is required')
-      vfile.data.original = { body: content }
-      return
+      return { body: content }
     }
 
     // TODO: output file meta data for later use
@@ -24,6 +22,6 @@ export default defineLoader({
     const data = yaml.parse(match[1])
     const raw = content.slice(match[0].length).trim()
     // keep original content with multiple keys in vfile.data for later use
-    vfile.data.original = Object.assign(data, { raw, excerpt: raw, plain: raw, html: raw, body: raw, code: raw })
+    return Object.assign(data, { raw, excerpt: raw, plain: raw, html: raw, body: raw, code: raw })
   }
 })
diff --git a/src/loaders/yaml.ts b/src/loaders/yaml.ts
index b1fe344..99302de 100644
--- a/src/loaders/yaml.ts
+++ b/src/loaders/yaml.ts
@@ -10,6 +10,6 @@ export default defineLoader({
   name: 'yaml',
   test: /\.(yaml|yml)$/,
   load: async vfile => {
-    vfile.data.original = yaml.parse(vfile.toString())
+    return yaml.parse(vfile.toString())
   }
 })
diff --git a/src/shared/shared.ts b/src/shared/shared.ts
index dc015ab..40d8775 100644
--- a/src/shared/shared.ts
+++ b/src/shared/shared.ts
@@ -52,7 +52,7 @@ export const name = () => z.string().max(20)
 
 export const title = () => z.string().max(99)
 
-export const date = () =>
+export const isodate = () =>
   z
     .string()
     .refine(value => !isNaN(Date.parse(value)), 'Invalid date')
diff --git a/src/static.ts b/src/static.ts
index 824e4d8..e1b2017 100644
--- a/src/static.ts
+++ b/src/static.ts
@@ -95,21 +95,23 @@ const outputStatic = async (ref: string, fromPath: string, isImage?: true): Prom
   })
 
   if (isImage == null) {
-    const files = cache.get('files') || new Set<string>()
+    const key = 'static:files'
+    const files = cache.get(key) || new Set<string>()
     if (files.has(filename)) return filename
     files.add(filename) // TODO: not await works, but await not works, becareful if copy failed
     await copy(from, filename)
-    cache.set('files', files)
+    cache.set(key, files)
     return filename
   }
 
-  const images = cache.get('images') || new Map<string, Image>()
+  const key = 'static:images'
+  const images = cache.get(key) || new Map<string, Image>()
   if (images.has(filename)) return images.get(filename) as Image
   const img = await getImageMetadata(source)
   if (img == null) return ref
   const image = { src: filename, ...img }
   images.set(filename, image)
-  cache.set('images', images)
+  cache.set(key, images)
   await copy(from, filename)
   return image
 }
diff --git a/src/types.ts b/src/types.ts
index b935c9a..eb3c4bf 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,10 +1,11 @@
-/**
- * @file shared types
- */
-
 import type { VFile } from 'vfile'
 import type { ZodType } from 'zod'
 
+/**
+ * Collection data from file
+ */
+export type Collection = Record<string, any> | Record<string, any>[]
+
 /**
  * File loader
  */
@@ -23,10 +24,10 @@ export interface Loader {
    */
   test: RegExp
   /**
-   * Load file content into `vfile.data.result`
+   * Load file content
    * @param vfile vfile
    */
-  load: (vfile: VFile) => void | Promise<void>
+  load: (vfile: VFile) => Collection | Promise<Collection>
 }
 
 export interface Output {
@@ -108,11 +109,6 @@ export interface Config<Schemas extends Record<string, Schema> = Record<string,
    * @default false
    */
   clean: boolean
-  /**
-   * Watch for changes and rebuild
-   * @default false
-   */
-  watch: boolean
   /**
    * Whether to print verbose log
    * @default false