fix: prevent preset to be included more than once

src/config.ts

@@ -1,7 +1,7 @@
 import type { Config } from 'tailwindcss'
-import shurikenUIPreset from './preset'
+import { preset } from './preset'
 
 export default {
   content: [],
-  presets: [shurikenUIPreset],
+  presets: [preset],
 } satisfies Config

src/index.ts

@@ -1,7 +1,15 @@
 import type { Config } from 'tailwindcss'
-import { defu } from 'defu'
-import config from './config'
+import { preset, hasPreset } from './preset'
 
-export function withShurikenUI(userConfig: Config) {
-  return defu(userConfig, config)
+export * from './preset'
+
+export function withShurikenUI(config: Config) {
+  if (hasPreset(config)) {
+    return config
+  }
+
+  config.presets ??= []
+  config.presets.push(preset)
+
+  return config
 }

src/preset.ts

@@ -10,8 +10,18 @@ import shurikenUIBase from './plugins/base'
 import shurikenUIComponents from './plugins/components'
 import shurikenUIUtilities from './plugins/utilities'
 
+const ShurikenUISymbol = '__is_shuriken_ui'
+
+export function hasPreset(config: Config) {
+  if (config.presets && Array.isArray(config.presets)) {
+    return config.presets.some((preset) => preset && ShurikenUISymbol in preset)
+  }
+
+  return false
+}
+
 export function createPreset(options: PluginOption = {}) {
-  return {
+  const config = {
     darkMode: 'class',
     content: [],
     plugins: [
@@ -143,6 +153,14 @@ export function createPreset(options: PluginOption = {}) {
       },
     },
   } satisfies Config
+
+  Object.defineProperty(config, ShurikenUISymbol, {
+    value: true,
+    enumerable: false,
+    writable: false,
+  })
+
+  return config
 }
 
-export default createPreset()
+export const preset = createPreset()