text: /**
   * --------------------------------------------------------------------------
   * Bootstrap (v5.1.0): util/focustrap.js
   * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
   * --------------------------------------------------------------------------
   */
  
  import EventHandler from '../dom/event-handler'
  import SelectorEngine from '../dom/selector-engine'
  import { typeCheckConfig } from './index'
  
  const Default = {
    trapElement: null, // The element to trap focus inside of
    autofocus: true
  }
  
  const DefaultType = {
    trapElement: 'element',
    autofocus: 'boolean'
  }
  
  const NAME = 'focustrap'
  const DATA_KEY = 'bs.focustrap'
  const EVENT_KEY = `.${DATA_KEY}`
  const EVENT_FOCUSIN = `focusin${EVENT_KEY}`
  const EVENT_KEYDOWN_TAB = `keydown.tab${EVENT_KEY}`
  
  const TAB_KEY = 'Tab'
  const TAB_NAV_FORWARD = 'forward'
  const TAB_NAV_BACKWARD = 'backward'
  
  class FocusTrap {
    constructor(config) {
      this._config = this._getConfig(config)
      this._isActive = false
      this._lastTabNavDirection = null
    }
  
    activate() {
      const { trapElement, autofocus } = this._config
  
      if (this._isActive) {
        return
      }
  
      if (autofocus) {
        trapElement.focus()
      }
  
      EventHandler.off(document, EVENT_KEY) // guard against infinite focus loop
      EventHandler.on(document, EVENT_FOCUSIN, event => this._handleFocusin(event))
      EventHandler.on(document, EVENT_KEYDOWN_TAB, event => this._handleKeydown(event))
  
      this._isActive = true
    }
  
    deactivate() {
      if (!this._isActive) {
        return
      }
  
      this._isActive = false
      EventHandler.off(document, EVENT_KEY)
    }
  
    // Private
  
    _handleFocusin(event) {
      const { target } = event
      const { trapElement } = this._config
  
      if (
        target === document ||
        target === trapElement ||
        trapElement.contains(target)
      ) {
        return
      }
  
      const elements = SelectorEngine.focusableChildren(trapElement)
  
      if (elements.length === 0) {
        trapElement.focus()
      } else if (this._lastTabNavDirection === TAB_NAV_BACKWARD) {
        elements[elements.length - 1].focus()
      } else {
        elements[0].focus()
      }
    }
  
    _handleKeydown(event) {
      if (event.key !== TAB_KEY) {
        return
      }
  
      this._lastTabNavDirection = event.shiftKey ? TAB_NAV_BACKWARD : TAB_NAV_FORWARD
    }
  
    _getConfig(config) {
      config = {
        ...Default,
        ...(typeof config === 'object' ? config : {})
      }
      typeCheckConfig(NAME, config, DefaultType)
      return config
    }
  }
  
  export default FocusTrap
  