const path = require('path')
const {CompositeDisposable} = require('event-kit')

class PaneElement extends HTMLElement {
  createdCallback () {
    this.attached = false
    this.subscriptions = new CompositeDisposable()
    this.inlineDisplayStyles = new WeakMap()
    this.initializeContent()
    this.subscribeToDOMEvents()
  }

  attachedCallback () {
    this.attached = true
    if (this.model.isFocused()) {
      this.focus()
    }
  }

  detachedCallback () {
    this.attached = false
  }

  initializeContent () {
    this.setAttribute('class', 'pane')
    this.setAttribute('tabindex', -1)
    this.itemViews = document.createElement('div')
    this.appendChild(this.itemViews)
    this.itemViews.setAttribute('class', 'item-views')
  }

  subscribeToDOMEvents () {
    const handleFocus = event => {
      if (
        !(
          this.isActivating ||
          this.model.isDestroyed() ||
          this.contains(event.relatedTarget)
        )
      ) {
        this.model.focus()
      }
      if (event.target !== this) return
      const view = this.getActiveView()
      if (view) {
        view.focus()
        event.stopPropagation()
      }
    }
    const handleBlur = event => {
      if (!this.contains(event.relatedTarget)) {
        this.model.blur()
      }
    }
    const handleDragOver = event => {
      event.preventDefault()
      event.stopPropagation()
    }
    const handleDrop = event => {
      event.preventDefault()
      event.stopPropagation()
      this.getModel().activate()
      const pathsToOpen = [...event.dataTransfer.files].map(file => file.path)
      if (pathsToOpen.length > 0) {
        this.applicationDelegate.open({pathsToOpen})
      }
    }
    this.addEventListener('focus', handleFocus, true)
    this.addEventListener('blur', handleBlur, true)
    this.addEventListener('dragover', handleDragOver)
    this.addEventListener('drop', handleDrop)
  }

  initialize (model, {views, applicationDelegate}) {
    this.model = model
    this.views = views
    this.applicationDelegate = applicationDelegate
    if (this.views == null) {
      throw new Error(
        'Must pass a views parameter when initializing PaneElements'
      )
    }
    if (this.applicationDelegate == null) {
      throw new Error(
        'Must pass an applicationDelegate parameter when initializing PaneElements'
      )
    }
    this.subscriptions.add(this.model.onDidActivate(this.activated.bind(this)))
    this.subscriptions.add(
      this.model.observeActive(this.activeStatusChanged.bind(this))
    )
    this.subscriptions.add(
      this.model.observeActiveItem(this.activeItemChanged.bind(this))
    )
    this.subscriptions.add(
      this.model.onDidRemoveItem(this.itemRemoved.bind(this))
    )
    this.subscriptions.add(
      this.model.onDidDestroy(this.paneDestroyed.bind(this))
    )
    this.subscriptions.add(
      this.model.observeFlexScale(this.flexScaleChanged.bind(this))
    )
    return this
  }

  getModel () {
    return this.model
  }

  activated () {
    this.isActivating = true
    if (!this.hasFocus()) {
      // Don't steal focus from children.
      this.focus()
    }
    this.isActivating = false
  }

  activeStatusChanged (active) {
    if (active) {
      this.classList.add('active')
    } else {
      this.classList.remove('active')
    }
  }

  activeItemChanged (item) {
    delete this.dataset.activeItemName
    delete this.dataset.activeItemPath
    if (this.changePathDisposable != null) {
      this.changePathDisposable.dispose()
    }
    if (item == null) {
      return
    }
    const hasFocus = this.hasFocus()
    const itemView = this.views.getView(item)
    const itemPath = typeof item.getPath === 'function' ? item.getPath() : null
    if (itemPath) {
      this.dataset.activeItemName = path.basename(itemPath)
      this.dataset.activeItemPath = itemPath
      if (item.onDidChangePath != null) {
        this.changePathDisposable = item.onDidChangePath(() => {
          const itemPath = item.getPath()
          this.dataset.activeItemName = path.basename(itemPath)
          this.dataset.activeItemPath = itemPath
        })
      }
    }
    if (!this.itemViews.contains(itemView)) {
      this.itemViews.appendChild(itemView)
    }
    for (const child of this.itemViews.children) {
      if (child === itemView) {
        if (this.attached) {
          this.showItemView(child)
        }
      } else {
        this.hideItemView(child)
      }
    }
    if (hasFocus) {
      itemView.focus()
    }
  }

  showItemView (itemView) {
    const inlineDisplayStyle = this.inlineDisplayStyles.get(itemView)
    if (inlineDisplayStyle != null) {
      itemView.style.display = inlineDisplayStyle
    } else {
      itemView.style.display = ''
    }
  }

  hideItemView (itemView) {
    const inlineDisplayStyle = itemView.style.display
    if (inlineDisplayStyle !== 'none') {
      if (inlineDisplayStyle != null) {
        this.inlineDisplayStyles.set(itemView, inlineDisplayStyle)
      }
      itemView.style.display = 'none'
    }
  }

  itemRemoved ({item, index, destroyed}) {
    const viewToRemove = this.views.getView(item)
    if (viewToRemove) {
      viewToRemove.remove()
    }
  }

  paneDestroyed () {
    this.subscriptions.dispose()
    if (this.changePathDisposable != null) {
      this.changePathDisposable.dispose()
    }
  }

  flexScaleChanged (flexScale) {
    this.style.flexGrow = flexScale
  }

  getActiveView () {
    return this.views.getView(this.model.getActiveItem())
  }

  hasFocus () {
    return (
      this === document.activeElement || this.contains(document.activeElement)
    )
  }
}

module.exports = document.registerElement('atom-pane', {
  prototype: PaneElement.prototype
})