const fs = require('node:fs')
const path = require('node:path')
const { withDangerousMod } = require('expo/config-plugins')

// Why: Expo SDK 58's template adopts the UIScene lifecycle the iOS 27 SDK requires (TN3187), and
// its ExpoAppSceneDelegate forwards URLs and user activities. It starts React Native on every
// scene connect, though, and iOS may disconnect the app's only scene in the background and
// reconnect it later. Reattach the running root then, so a reconnect keeps the app's state
// instead of starting a second React Native instance.
const MARKER = 'orca: UIScene reconnect'
const EXTENSION_POINT = '  // Extension point for config plugins.\n'
const TEMPLATE_CLASS = 'class SceneDelegate: ExpoAppSceneDelegate {\n'

const RECONNECT_OVERRIDE = `  // ${MARKER}, generated by plugins/ios-scene-lifecycle.js.
  override func scene(
    _ scene: UIScene,
    willConnectTo session: UISceneSession,
    options connectionOptions: UIScene.ConnectionOptions
  ) {
    guard let windowScene = scene as? UIWindowScene,
      let provider = UIApplication.shared.delegate as? ExpoReactNativeFactoryProvider,
      let runningRoot = provider.window?.rootViewController
    else {
      super.scene(scene, willConnectTo: session, options: connectionOptions)
      return
    }
    let window = UIWindow(windowScene: windowScene)
    self.window = window
    provider.window = window
    window.rootViewController = runningRoot
    window.makeKeyAndVisible()
    if !connectionOptions.urlContexts.isEmpty {
      self.scene(scene, openURLContexts: connectionOptions.urlContexts)
    }
    for activity in connectionOptions.userActivities {
      self.scene(scene, continue: activity)
    }
  }
`

function patchSceneDelegate(contents) {
  if (contents.includes(MARKER)) {
    return contents
  }
  // A changed template must fail prebuild rather than silently drop the reconnect behavior.
  if (!contents.includes(TEMPLATE_CLASS) || !contents.includes(EXTENSION_POINT)) {
    throw new Error(
      "ios-scene-lifecycle: Expo's SceneDelegate template changed; update the plugin before building."
    )
  }
  return contents.replace(EXTENSION_POINT, `${EXTENSION_POINT}\n${RECONNECT_OVERRIDE}`)
}

module.exports = function withIosSceneLifecycle(config) {
  return withDangerousMod(config, [
    'ios',
    (cfg) => {
      const { platformProjectRoot, projectName } = cfg.modRequest
      const file = path.join(platformProjectRoot, projectName, 'SceneDelegate.swift')
      fs.writeFileSync(file, patchSceneDelegate(fs.readFileSync(file, 'utf8')))
      return cfg
    }
  ])
}