path: root/ui.js

// The UI in MTUI! Interfaces with the backend to form the complete mtui app.

'use strict'

const { getAllCrawlersForArg } = require('./crawlers')
const processSmartPlaylist = require('./smart-playlist')
const UndoManager = require('./undo-manager')

const {
  shuffleArray,
  getTimeStringsFromSec
} = require('./general-util')

const {
  cloneGrouplike,
  countTotalTracks,
  flattenGrouplike,
  getCorrespondingFileForItem,
  getCorrespondingPlayableForFile,
  getItemPath,
  getNameWithoutTrackNumber,
  isGroup,
  isOpenable,
  isPlayable,
  isTrack,
  parentSymbol,
  reverseOrderOfGroups,
  searchForItem,
  shuffleOrderOfGroups
} = require('./playlist-utils')

const {
  ui: {
    Dialog,
    DisplayElement,
    Label,
    Pane,
    WrapLabel,
    form: {
      Button,
      FocusElement,
      Form,
      ListScrollForm,
      TextInput,
    }
  },
  util: {
    ansi,
    telchars: telc,
    unichars: unic,
  }
} = require('tui-lib')

const TuiTextEditor = require('tui-text-editor')

const { promisify } = require('util')
const fs = require('fs')
const open = require('open')
const path = require('path')
const url = require('url')
const readFile = promisify(fs.readFile)
const writeFile = promisify(fs.writeFile)

const input = {}

const keyBindings = [
  ['isUp', telc.isUp],
  ['isDown', telc.isDown],
  ['isLeft', telc.isLeft],
  ['isRight', telc.isRight],
  ['isSelect', telc.isSelect],
  ['isBackspace', telc.isBackspace],
  ['isMenu', 'm'],
  ['isMenu', 'f'],
  ['isScrollToStart', 'g', {caseless: false}],
  ['isScrollToEnd', 'G', {caseless: false}],
  ['isScrollToStart', telc.isHome],
  ['isScrollToEnd', telc.isEnd],
  ['isTogglePause', telc.isSpace],
  ['isToggleLoop', 'l', {caseless: false}],
  ['isStop', telc.isEscape],
  ['isVolumeUp', 'v', {caseless: false}],
  ['isVolumeDown', 'V', {caseless: false}],
  ['isSkipBack', telc.isControlUp],
  ['isSkipAhead', telc.isControlDown],
  ['isSkipBack', 'p'],
  ['isSkipAhead', 'n'],
  ['isFocusTabber', '['],
  ['isFocusQueue', ']'],
  ['isFocusPlaybackInfo', '|'],
  ['isNextTab', 't', {caseless: false}],
  ['isPreviousTab', 'T', {caseless: false}],
  ['isDownload', 'd'],
  ['isRemove', 'x'],
  ['isQueueAfterSelectedTrack', 'q'],
  ['isOpenThroughSystem', 'o'],
  ['isShuffleQueue', 's'],
  ['isClearQueue', 'c'],
  ['isFocusMenubar', ';'],
  ['isFocusLabels', 'L', {caseless: false}], // todo: better key? to let isToggleLoop be caseless again
  ['isSelectUp', telc.isShiftUp],
  ['isSelectDown', telc.isShiftDown],

  ['isPreviousPlayer', telc.isMetaUp],
  ['isPreviousPlayer', [0x1b, 'p']],
  ['isNextPlayer', telc.isMetaDown],
  ['isNextPlayer', [0x1b, 'n']],
  ['isNewPlayer', [0x1b, 'c']],
  ['isRemovePlayer', [0x1b, 'x']],
  ['isActOnPlayer', [0x1b, 'a']],
  ['isActOnPlayer', [0x1b, '!']],

  ['isFocusTextEditor', [0x05]], // ^E
  ['isSaveTextEditor', [0x13]], // ^S
  ['isDeselectTextEditor', [0x18]], // ^X
  ['isDeselectTextEditor', telc.isEscape],

  // Number pad
  ['isUp', '8'],
  ['isDown', '2'],
  ['isLeft', '4'],
  ['isRight', '6'],
  ['isSpace', '5'],
  ['isTogglePause', '5'],
  ['isBackspace', '.'],
  ['isMenu', '+'],
  ['isSkipBack', '1'],
  ['isSkipAhead', '3'],
  // Disabled because this is the jump key! Oops.
  // ['isVolumeDown', '/'],
  // ['isVolumeUp', '*'],
  ['isFocusTabber', '7'],
  ['isFocusQueue', '9'],
  ['isFocusMenubar', '*'],

  // HJKL
  ['isDown', 'j'],
  ['isUp', 'k'],
  // Don't use these for now... currently L is used for toggling loop.
  // May want to look into changing that (so we can re-enable these).
  // ['isLeft', 'h'],
  // ['isRight', 'l'],
]

const addKey = (prop, keyOrFunc, {caseless = true} = {}) => {
  const oldFunc = input[prop] || (() => false)
  let newFunc
  if (typeof keyOrFunc === 'function') {
    newFunc = keyOrFunc
  } else if (typeof keyOrFunc === 'string') {
    const key = keyOrFunc
    if (caseless) {
      newFunc = input => input.toString().toLowerCase() === key.toLowerCase()
    } else {
      newFunc = input => input.toString() === key
    }
  } else if (Array.isArray(keyOrFunc)) {
    const buf = Buffer.from(keyOrFunc.map(k => typeof k === 'string' ? k.charCodeAt(0) : k))
    newFunc = keyBuf => keyBuf.equals(buf)
  }
  input[prop] = keyBuf => newFunc(keyBuf) || oldFunc(keyBuf)
}

for (const entry of keyBindings) {
  addKey(...entry)
}

// Some things just need to be overridden in order for the rest of tui-lib to
// recognize our new keys.
telc.isUp = input.isUp
telc.isDown = input.isDown
telc.isLeft = input.isLeft
telc.isRight = input.isRight
telc.isSelect = input.isSelect
telc.isBackspace = input.isBackspace

class AppElement extends FocusElement {
  constructor(backend, config = {}) {
    super()

    this.backend = backend
    this.telnetServer = null
    this.isPartyHost = false

    this.config = Object.assign({
      canControlPlayback: true,
      canControlQueue: true,
      canControlQueuePlayers: true,
      canProcessMetadata: true,
      canSuspend: true,
      menubarColor: 4, // blue
      showTabberPane: true,
      stopPlayingUponQuit: true
    }, config)

    // TODO: Move edit mode stuff to the backend!
    this.undoManager = new UndoManager()
    this.markGrouplike = {name: 'Selected Items', items: []}
    this.editMode = false

    // We add this is a child later (so that it's on top of every element).
    this.menuLayer = new DisplayElement()
    this.menuLayer.clickThrough = true
    this.showContextMenu = this.showContextMenu.bind(this)

    this.menubar = new Menubar(this.showContextMenu)
    this.addChild(this.menubar)

    this.menubar.color = this.config.menubarColor

    this.tabberPane = new Pane()
    this.addChild(this.tabberPane)

    this.queuePane = new Pane()
    this.addChild(this.queuePane)

    this.textInfoPane = new Pane()
    this.addChild(this.textInfoPane)

    this.textEditor = new NotesTextEditor()
    this.textInfoPane.addChild(this.textEditor)
    this.textInfoPane.visible = false

    this.textEditor.on('deselect', () => {
      this.root.select(this.tabber)
      this.fixLayout()
    })

    if (!this.config.showTabberPane) {
      this.tabberPane.visible = false
    }

    this.tabber = new Tabber()
    this.tabberPane.addChild(this.tabber)

    this.metadataStatusLabel = new Label()
    this.metadataStatusLabel.visible = false
    this.tabberPane.addChild(this.metadataStatusLabel)

    this.newGrouplikeListing()

    this.queueListingElement = new QueueListingElement(this)
    this.setupCommonGrouplikeListingEvents(this.queueListingElement)
    this.queuePane.addChild(this.queueListingElement)

    this.queueLengthLabel = new Label('')
    this.queuePane.addChild(this.queueLengthLabel)

    this.queueTimeLabel = new Label('')
    this.queuePane.addChild(this.queueTimeLabel)

    this.queueListingElement.on('open', item => this.openSpecialOrThroughSystem(item))
    this.queueListingElement.on('queue', item => this.play(item))
    this.queueListingElement.on('remove', item => this.unqueue(item))
    this.queueListingElement.on('shuffle', () => this.shuffleQueue())
    this.queueListingElement.on('clear', () => this.clearQueue())
    this.queueListingElement.on('select main listing',
      () => this.selected())

    this.playbackPane = new Pane()
    this.addChild(this.playbackPane)

    this.playbackForm = new ListScrollForm()
    this.playbackPane.addChild(this.playbackForm)

    this.playbackInfoElements = []

    this.partyTop = new DisplayElement()
    this.partyBottom = new DisplayElement()
    this.addChild(this.partyTop)
    this.addChild(this.partyBottom)
    this.partyTop.visible = false
    this.partyBottom.visible = false

    this.partyTopBanner = new PartyBanner(1)
    this.partyBottomBanner = new PartyBanner(-1)
    this.partyTop.addChild(this.partyTopBanner)
    this.partyBottom.addChild(this.partyBottomBanner)

    this.partyLabel = new Label('')
    this.partyTop.addChild(this.partyLabel)

    // Dialogs

    this.openPlaylistDialog = new OpenPlaylistDialog()
    this.setupDialog(this.openPlaylistDialog)

    this.openPlaylistDialog.on('source selected', source => this.handlePlaylistSource(source))
    this.openPlaylistDialog.on('source selected (new tab)', source => this.handlePlaylistSource(source, true))

    this.alertDialog = new AlertDialog()
    this.setupDialog(this.alertDialog)

    // Should be placed on top of everything else!
    this.addChild(this.menuLayer)

    this.whereControl = new InlineListPickerElement('Where?', [
      {value: 'next-selected', label: 'After selected song'},
      {value: 'next', label: 'After current song'},
      {value: 'end', label: 'At end of queue'},
      {value: 'distribute-evenly', label: 'Distributed across queue evenly'},
      {value: 'distribute-randomly', label: 'Distributed across queue randomly'}
    ], this.showContextMenu)

    this.orderControl = new InlineListPickerElement('Order?', [
      {value: 'shuffle', label: 'Shuffle all'},
      {value: 'shuffle-groups', label: 'Shuffle order of groups'},
      {value: 'reverse', label: 'Reverse all'},
      {value: 'reverse-groups', label: 'Reverse order of groups'},
      {value: 'normal', label: 'In order'}
    ], this.showContextMenu)

    this.menubar.buildItems([
      {text: 'mtui', menuItems: [
        {label: 'mtui (perpetual development)'},
        {divider: true},
        {label: 'Quit', action: () => this.shutdown()},
        this.config.canSuspend && {label: 'Suspend', action: () => this.suspend()}
      ]},
      {text: 'Playback', menuFn: () => {
        const { playingTrack } = this.SQP
        const { items } = this.SQP.queueGrouplike
        const curIndex = items.indexOf(playingTrack)
        const next = (curIndex >= 0) && items[curIndex + 1]
        const previous = (curIndex >= 0) && items[curIndex - 1]

        return [
          {label: playingTrack ? `("${playingTrack.name}")` : '(No track playing.)'},
          {divider: true},
          playingTrack && {element: this.playingControl},
          {element: this.loopingControl},
          {element: this.pauseNextControl},
          {element: this.volumeSlider},
          {divider: true},
          previous && {label: `Previous (${previous.name})`, action: () => this.SQP.playPrevious(playingTrack)},
          next && {label: `Next (${next.name})`, action: () => this.SQP.playNext(playingTrack)},
          next && {label: '- Play later', action: () => this.playLater(next)}
        ]
      }},
      {text: 'Queue', menuFn: () => {
        const { items } = this.SQP.queueGrouplike
        const curIndex = items.indexOf(this.playingTrack)

        return [
          {label: `(Queue - ${curIndex >= 0 ? `${curIndex + 1}/` : ''}${items.length} items.)`},
          {divider: true},
          items.length && {label: 'Shuffle', action: () => this.shuffleQueue()},
          items.length && {label: 'Clear', action: () => this.clearQueue()}
        ]
      }},
      {text: 'Multi', menuFn: () => {
        const { queuePlayers } = this.backend
        return [
          {label: `(Multi-players - ${queuePlayers.length})`},
          {divider: true},
          ...queuePlayers.map((queuePlayer, index) => {
            const PIE = new PlaybackInfoElement(queuePlayer, this)
            PIE.displayMode = 'collapsed'
            PIE.updateTrack()
            return {element: PIE}
          })
        ]
      }}
    ])

    this.playingControl = new ToggleControl('Pause?', {
      setValue: val => this.SQP.setPause(val),
      getValue: () => this.SQP.player.isPaused,
      getEnabled: () => this.config.canControlPlayback
    })

    this.loopingControl = new ToggleControl('Loop current track?', {
      setValue: val => this.SQP.setLoop(val),
      getValue: () => this.SQP.player.isLooping,
      getEnabled: () => this.config.canControlPlayback
    })

    this.pauseNextControl = new ToggleControl('Pause when this track ends?', {
      setValue: val => this.SQP.setPauseNextTrack(val),
      getValue: () => this.SQP.pauseNextTrack,
      getEnabled: () => this.config.canControlPlayback
    })

    this.volumeSlider = new SliderElement('Volume', {
      setValue: val => this.SQP.setVolume(val),
      getValue: () => this.SQP.player.volume,
      getEnabled: () => this.config.canControlPlayback
    })

    this.bindListeners()
    this.initialAttachListeners()

    // Also handy to be bound to the app.
    this.showContextMenu = this.showContextMenu.bind(this)

    this.queuePlayersToActOn = []
    this.selectQueuePlayer(this.backend.queuePlayers[0])
  }

  bindListeners() {
    for (const key of [
      'handlePlaying',
      'handleReceivedTimeData',
      'handleProcessMetadataProgress',
      'handleQueueUpdated',
      'handleAddedQueuePlayer',
      'handleRemovedQueuePlayer'
    ]) {
      this[key] = this[key].bind(this)
    }
  }

  initialAttachListeners() {
    this.attachBackendListeners()
    for (const queuePlayer of this.backend.queuePlayers) {
      this.attachQueuePlayerListenersAndUI(queuePlayer)
    }
  }

  removeListeners() {
    this.removeBackendListeners()
    for (const queuePlayer of this.backend.queuePlayers) {
      // Don't update the UI - removeListeners is only called just before the
      // AppElement is done being used.
      this.removeQueuePlayerListenersAndUI(queuePlayer, false)
    }
  }

  attachQueuePlayerListenersAndUI(queuePlayer) {
    const PIE = new PlaybackInfoElement(queuePlayer, this)
    this.playbackInfoElements.push(PIE)
    this.playbackForm.addInput(PIE)
    this.fixLayout()

    PIE.on('seek back', () => PIE.queuePlayer.seekBack(5))
    PIE.on('seek ahead', () => PIE.queuePlayer.seekAhead(5))
    PIE.on('toggle pause', () => PIE.queuePlayer.togglePause())

    queuePlayer.on('received time data', this.handleReceivedTimeData)
    queuePlayer.on('playing', this.handlePlaying)
    queuePlayer.on('queue updated', this.handleQueueUpdated)
  }

  removeQueuePlayerListenersAndUI(queuePlayer, updateUI = true) {
    if (updateUI) {
      const PIE = this.getPlaybackInfoElementForQueuePlayer(queuePlayer)
      if (PIE) {
        const PIEs = this.playbackInfoElements
        const oldIndex = PIEs.indexOf(PIE)
        if (this.playbackForm.curIndex > oldIndex) {
          this.playbackForm.curIndex--
        }
        PIEs.splice(oldIndex, 1)
        this.playbackForm.removeInput(PIE)
        if (this.SQP === queuePlayer) {
          const { queuePlayer } = PIEs[Math.min(oldIndex, PIEs.length - 1)]
          this.selectQueuePlayer(queuePlayer)
        }
        this.fixLayout()
      }
    }

    const index = this.queuePlayersToActOn.indexOf(queuePlayer)
    if (index >= 0) {
      this.queuePlayersToActOn.splice(index, 1)
    }

    queuePlayer.removeListener('receivedTimeData', this.handleReceivedTimeData)
    queuePlayer.removeListener('playing', this.handlePlaying)
    queuePlayer.removeListener('queue updated', this.handleQueueUpdated)
    queuePlayer.stopPlaying()
  }

  attachBackendListeners() {
    this.backend.on('processMetadata progress', this.handleProcessMetadataProgress)
    this.backend.on('added queue player', this.handleAddedQueuePlayer)
    this.backend.on('removed queue player', this.handleRemovedQueuePlayer)
  }

  removeBackendListeners() {
    this.backend.removeListener('processMetadata progress', this.handleProcessMetadataProgress)
    this.backend.removeListener('added queue player', this.handleAddedQueuePlayer)
    this.backend.removeListener('removed queue player', this.handleRemovedQueuePlayer)
  }

  handleAddedQueuePlayer(queuePlayer) {
    this.attachQueuePlayerListenersAndUI(queuePlayer)
  }

  handleRemovedQueuePlayer(queuePlayer) {
    this.removeQueuePlayerListenersAndUI(queuePlayer)
  }

  handlePlaying(track, oldTrack, queuePlayer) {
    const PIE = this.getPlaybackInfoElementForQueuePlayer(queuePlayer)
    if (PIE) {
      PIE.updateTrack()
    }

    if (queuePlayer === this.SQP) {
      this.updateQueueLengthLabel()
      if (track && this.queueListingElement.currentItem === oldTrack) {
        this.queueListingElement.selectAndShow(track)
      }
    }
  }

  handleReceivedTimeData(data, queuePlayer) {
    const PIE = this.getPlaybackInfoElementForQueuePlayer(queuePlayer)
    if (PIE) {
      PIE.updateProgress()
    }

    if (queuePlayer === this.SQP) {
      this.updateQueueLengthLabel()
    }
  }

  handleProcessMetadataProgress(remaining) {
    this.metadataStatusLabel.text = `Processing metadata - ${remaining} to go.`
  }

  handleQueueUpdated() {
    this.queueListingElement.buildItems()
  }

  selectQueuePlayer(queuePlayer) {
    // You can use this.SQP as a shorthand to get this.
    this.selectedQueuePlayer = queuePlayer

    this.queueListingElement.loadGrouplike(queuePlayer.queueGrouplike)

    this.playbackForm.curIndex = this.playbackForm.inputs
      .findIndex(el => el.queuePlayer === queuePlayer)
    this.playbackForm.scrollSelectedElementIntoView()
  }

  selectNextQueuePlayer() {
    const { queuePlayers } = this.backend
    let index = queuePlayers.indexOf(this.SQP) + 1
    if (index >= queuePlayers.length) {
      index = 0
    }
    this.selectQueuePlayer(queuePlayers[index])
  }

  selectPreviousQueuePlayer() {
    const { queuePlayers } = this.backend
    let index = queuePlayers.indexOf(this.SQP) - 1
    if (index <= -1) {
      index = queuePlayers.length - 1
    }
    this.selectQueuePlayer(queuePlayers[index])
  }

  async addQueuePlayer() {
    if (!this.config.canControlQueuePlayers) {
      return false
    }

    const queuePlayer = await this.backend.addQueuePlayer()
    this.selectQueuePlayer(queuePlayer)
  }

  removeQueuePlayer(queuePlayer) {
    if (!this.config.canControlQueuePlayers) {
      return false
    }

    this.backend.removeQueuePlayer(queuePlayer)
  }

  toggleActOnQueuePlayer(queuePlayer) {
    const index = this.queuePlayersToActOn.indexOf(queuePlayer)
    if (index >= 0) {
      this.queuePlayersToActOn.splice(index, 1)
    } else {
      this.queuePlayersToActOn.push(queuePlayer)
    }

    for (const PIE of this.playbackInfoElements) {
      PIE.fixLayout()
    }
  }

  getPlaybackInfoElementForQueuePlayer(queuePlayer) {
    return this.playbackInfoElements
      .find(el => el.queuePlayer === queuePlayer)
  }

  selected() {
    if (this.tabberPane.visible) {
      this.root.select(this.tabber)
    } else {
      if (this.queueListingElement.selectable) {
        this.root.select(this.queueListingElement)
      } else {
        this.menubar.select()
      }
    }
  }

  newGrouplikeListing() {
    const grouplikeListing = new GrouplikeListingElement(this)
    this.tabber.addTab(grouplikeListing)
    this.tabber.selectTab(grouplikeListing)

    grouplikeListing.on('browse', item => grouplikeListing.loadGrouplike(item))
    grouplikeListing.on('download', item => this.SQP.download(item))
    grouplikeListing.on('open', item => this.openSpecialOrThroughSystem(item))
    grouplikeListing.on('queue', (item, opts) => this.handleQueueOptions(item, opts))

    const updateListingsFor = item => {
      for (const grouplikeListing of this.tabber.tabberElements) {
        if (grouplikeListing.grouplike === item) {
          grouplikeListing.loadGrouplike(item, false)
        }
      }
    }

    grouplikeListing.on('remove', item => {
      if (this.editMode) {
        const parent = item[parentSymbol]
        const index = parent.items.indexOf(item)

        this.undoManager.pushAction({
          activate: () => {
            parent.items.splice(index, 1)
            delete item[parentSymbol]
            updateListingsFor(item)
            updateListingsFor(parent)
          },
          undo: () => {
            parent.items.splice(index, 0, item)
            item[parentSymbol] = parent
            updateListingsFor(item)
            updateListingsFor(parent)
          }
        })
      }
    })

    grouplikeListing.on('mark', item => {
      if (this.editMode) {
        if (!this.markGrouplike.items.includes(item)) {
          this.undoManager.pushAction({
            activate: () => {
              this.markGrouplike.items.push(item)
            },
            undo: () => {
              this.markGrouplike.items.pop()
            }
          })
        } else {
          const index = this.markGrouplike.items.indexOf(item)
          this.undoManager.pushAction({
            activate: () => {
              this.markGrouplike.items.splice(index, 1)
            },
            undo: () => {
              this.markGrouplike.items.splice(index, 0, item)
            }
          })
        }
      }
    })

    grouplikeListing.on('paste', (item, {where = 'below'} = {}) => {
      if (this.editMode && this.markGrouplike.items.length) {
        let parent, index

        if (where === 'above') {
          parent = item[parentSymbol]
          index = parent.items.indexOf(item)
        } else if (where === 'below') {
          parent = item[parentSymbol]
          index = parent.items.indexOf(item) + 1
        }

        this.undoManager.pushAction({
          activate: () => {
            parent.items.splice(index, 0, ...cloneGrouplike(this.markGrouplike).items.map(
              item => Object.assign({}, item, {[parentSymbol]: parent})
            ))
            updateListingsFor(parent)
          },
          undo: () => {
            parent.items.splice(index, this.markGrouplike.items.length)
            updateListingsFor(parent)
          }
        })
      }
    })

    this.setupCommonGrouplikeListingEvents(grouplikeListing)

    return grouplikeListing
  }

  setupCommonGrouplikeListingEvents(grouplikeListing) {
    // Sets up event listeners that are common to ordinary grouplike listings
    // (made by newGrouplikeListing) as well as the queue grouplike listing.

    grouplikeListing.pathElement.on('select', item => this.reveal(item))
    grouplikeListing.on('menu', (item, el) => this.showMenuForItemElement(el, grouplikeListing))
    grouplikeListing.on('selected', item => this.editNotesFile(item, false))
    grouplikeListing.on('edit-notes', item => {
      this.reveal(item)
      this.editNotesFile(item, true)
    })
  }

  showContextMenu(opts) {
    const menu = new ContextMenu(this.showContextMenu)
    this.menuLayer.addChild(menu)
    if (opts.beforeShowing) {
      opts.beforeShowing(menu)
    }
    menu.show(opts)
    return menu
  }

  reveal(item) {
    if (!this.tabberPane.visible) {
      return
    }

    const tabberListing = this.tabber.currentElement
    this.root.select(tabberListing)

    const parent = item[parentSymbol]
    if (isGroup(item)) {
      tabberListing.loadGrouplike(item)
    } else if (parent) {
      if (tabberListing.grouplike !== parent) {
        tabberListing.loadGrouplike(parent)
      }
      tabberListing.selectAndShow(item)
    }
  }

  play(item) {
    if (!this.config.canControlQueue) {
      return
    }

    this.SQP.play(item)
  }

  unqueue(item) {
    if (!this.config.canControlQueue) {
      return
    }

    let focusItem = this.queueListingElement.currentItem
    focusItem = this.SQP.unqueue(item, focusItem)

    this.queueListingElement.buildItems()
    this.updateQueueLengthLabel()

    if (focusItem) {
      this.queueListingElement.selectAndShow(focusItem)
    }
  }

  playSooner(item) {
    if (!this.config.canControlQueue) {
      return
    }

    this.SQP.playSooner(item)
    // It may not have queued as soon as the user wants; in that case, they'll
    // want to queue it sooner again. Automatically reselect the track so that
    // this they don't have to navigate back to it by hand.
    this.queueListingElement.selectAndShow(item)
  }

  playLater(item) {
    if (!this.config.canControlQueue) {
      return
    }

    this.SQP.playLater(item)
    // Just for consistency with playSooner (you can press ^-L to quickly get
    // back to the current track).
    this.queueListingElement.selectAndShow(item)
  }

  clearQueuePast(item) {
    if (!this.config.canControlQueue) {
      return
    }

    this.SQP.clearQueuePast(item)
    this.queueListingElement.selectAndShow(item)
  }

  clearQueueUpTo(item) {
    if (!this.config.canControlQueue) {
      return
    }

    this.SQP.clearQueueUpTo(item)
    this.queueListingElement.selectAndShow(item)
  }

  deselectAll() {
    this.markGrouplike.items.splice(0)
  }

  pauseAll() {
    if (!this.config.canControlPlayback) {
      return
    }

    for (const queuePlayer of this.backend.queuePlayers) {
      queuePlayer.setPause(true)
    }
  }

  resumeAll() {
    if (!this.config.canControlPlayback) {
      return
    }

    for (const queuePlayer of this.backend.queuePlayers) {
      queuePlayer.setPause(false)
    }
  }

  async createNotesFile(item) {
    if (!item[parentSymbol]) {
      return
    }

    if (!item.url) {
      return
    }

    if (getCorrespondingFileForItem(item, '.txt')) {
      return
    }

    let itemPath
    try {
      itemPath = url.fileURLToPath(item.url)
    } catch (error) {
      return
    }

    const dirname = path.dirname(itemPath)
    const extname = path.extname(itemPath)
    const basename = path.basename(itemPath, extname)
    const name = basename + '.txt'
    const filePath = path.join(dirname, name)
    const fileURL = url.pathToFileURL(filePath).toString()
    const file = {name, url: fileURL}
    await writeFile(filePath, '\n')

    const { items } = item[parentSymbol]
    items.splice(items.indexOf(item), 0, file)
  }

  async editNotesFile(item, focus) {
    if (!item) {
      return
    }

    // Creates it, if it doesn't exist.
    // We only do this when we're manually selecting the file (and expect to
    // focus it). Otherwise we'd create a notes file for every track hovered
    // over!
    if (focus) {
      await this.createNotesFile(item)
    }

    const doubleCheckItem = () => {
      const listing = this.root.selectedElement.directAncestors.find(el => el instanceof GrouplikeListingElement)
      return listing && listing.currentItem === item
    }

    if (!doubleCheckItem()) {
      return
    }

    const status = await this.textEditor.openItem(item, {doubleCheckItem})

    let fixLayout
    if (status === true) {
      this.textInfoPane.visible = true
      fixLayout = true
    } else if (status === false) {
      this.textInfoPane.visible = false
      fixLayout = true
    }

    if (focus && (status === true || status === null) && doubleCheckItem()) {
      this.root.select(this.textEditor)
      fixLayout = true
    }

    if (fixLayout) {
      this.fixLayout()
    }
  }

  openSpecialOrThroughSystem(item) {
    if (item.url.endsWith('.json')) {
      return this.handlePlaylistSource(item.url, true)
    } else if (item.url.endsWith('.txt')) {
      if (this.textInfoPane.visible) {
        this.root.select(this.textEditor)
      }
    } else {
      return this.openThroughSystem(item)
    }
  }

  openThroughSystem(item) {
    if (!isOpenable(item)) {
      return
    }

    open(item.url)
  }

  set actOnAllPlayers(val) {
    if (val) {
      this.queuePlayersToActOn = this.backend.queuePlayers.slice()
    } else {
      this.queuePlayersToActOn = []
    }
  }

  get actOnAllPlayers() {
    return this.queuePlayersToActOn.length === this.backend.queuePlayers.length
  }

  willActOnQueuePlayer(queuePlayer) {
    if (this.queuePlayersToActOn.length) {
      if (this.queuePlayersToActOn.includes(queuePlayer)) {
        return 'marked'
      }
    } else if (queuePlayer === this.SQP) {
      return '=SQP'
    }
  }

  actOnQueuePlayers(fn) {
    const actOn = this.queuePlayersToActOn.length ? this.queuePlayersToActOn : [this.SQP]
    for (const queuePlayer of actOn) {
      fn(queuePlayer)
      const PIE = this.getPlaybackInfoElementForQueuePlayer(queuePlayer)
      if (PIE) {
        PIE.updateProgress()
      }
    }
  }

  showMenuForItemElement(el, listing) {
    const emitControls = play => () => {
      this.handleQueueOptions(item, {
        where: this.whereControl.curValue,
        order: this.orderControl.curValue,
        play: play
      })
    }

    let item
    if (this.markGrouplike.items.length) {
      item = this.markGrouplike
    } else {
      item = el.item
    }

    // TODO: Implement this! :P
    const isMarked = false

    const { editMode } = this
    const { canControlQueue, canProcessMetadata } = this.config
    const anyMarked = editMode && this.markGrouplike.items.length > 0
    const hasNotesFile = !!getCorrespondingFileForItem(item, '.txt')

    let items;
    if (listing.grouplike.isTheQueue && isTrack(item)) {
      items = [
        this.tabberPane.visible && {label: 'Reveal', action: () => this.reveal(item)},
        {divider: true},
        canControlQueue && {label: 'Play later', action: () => this.playLater(item)},
        canControlQueue && {label: 'Play sooner', action: () => this.playSooner(item)},
        {divider: true},
        canControlQueue && {label: 'Clear past this track', action: () => this.clearQueuePast(item)},
        canControlQueue && {label: 'Clear up to this track', action: () => this.clearQueueUpTo(item)},
        {divider: true},
        canControlQueue && {label: 'Remove from queue', action: () => this.unqueue(item)}
      ]
    } else {
      const numTracks = countTotalTracks(item)
      const { string: durationString } = this.backend.getDuration(item)
      items = [
        // A label that just shows some brief information about the item.
        {label:
          `(${item.name ? `"${item.name}"` : 'Unnamed'}` +
          (isGroup(item) ? (
            ' -' +
            ` ${numTracks} track${numTracks === 1 ? '' : 's'}` +
            `, ${durationString}`)
          : '') + ')',
          keyboardIdentifier: item.name
        },

        // The actual controls!
        {divider: true},

        // TODO: Don't emit these on the element (and hence receive them from
        // the listing) - instead, handle their behavior directly. We'll want
        // to move the "mark"/"paste" (etc) code into separate functions,
        // instead of just defining their behavior inside the listing event
        // handlers.
        /*
        editMode && {label: isMarked ? 'Unmark' : 'Mark', action: () => el.emit('mark')},
        anyMarked && {label: 'Paste (above)', action: () => el.emit('paste', {where: 'above'})},
        anyMarked && {label: 'Paste (below)', action: () => el.emit('paste', {where: 'below'})},
        // anyMarked && !this.isReal && {label: 'Paste', action: () => this.emit('paste')}, // No "above" or "elow" in the label because the "fake" item/row will be replaced (it'll disappear, since there'll be an item in the group)
        {divider: true},
        */

        canControlQueue && isPlayable(item) && {element: this.whereControl},
        canControlQueue && isGroup(item) && {element: this.orderControl},
        canControlQueue && isPlayable(item) && {label: 'Play!', action: emitControls(true)},
        canControlQueue && isPlayable(item) && {label: 'Queue!', action: emitControls(false)},
        {divider: true},

        canProcessMetadata && isGroup(item) && {label: 'Process metadata (new entries)', action: () => this.processMetadata(item, false)},
        canProcessMetadata && isGroup(item) && {label: 'Process metadata (reprocess)', action: () => this.processMetadata(item, true)},
        canProcessMetadata && isTrack(item) && {label: 'Process metadata', action: () => this.processMetadata(item, true)},
        isOpenable(item) && item.url.endsWith('.json') && {label: 'Open (JSON Playlist)', action: () => this.openSpecialOrThroughSystem(item)},
        isOpenable(item) && {label: 'Open (System)', action: () => this.openThroughSystem(item)},
        !hasNotesFile && isPlayable(item) && {label: 'Create notes file', action: () => this.editNotesFile(item, true)},
        hasNotesFile && isPlayable(item) && {label: 'Edit notes file', action: () => this.editNotesFile(item, true)},
        canControlQueue && isPlayable(item) && {label: 'Remove from queue', action: () => this.unqueue(item)},
        {divider: true},

        item === this.markGrouplike && {label: 'Deselect', action: () => this.deselectAll()}
      ]
    }

    this.showContextMenu({
      x: el.absLeft,
      y: el.absTop + 1,
      items
    })
  }

  async handlePlaylistSource(source, newTab = false) {
    if (this.openPlaylistDialog.visible) {
      this.openPlaylistDialog.close()
    }

    this.alertDialog.showMessage('Opening playlist...', false)

    let grouplike
    try {
      grouplike = await this.openPlaylist(source)
    } catch (error) {
      if (error === 'unknown argument') {
        this.alertDialog.showMessage('Could not figure out how to load a playlist from: ' + source)
      } else if (typeof error === 'string') {
        this.alertDialog.showMessage(error)
      } else {
        throw error
      }

      return
    }

    this.alertDialog.close()

    grouplike = await processSmartPlaylist(grouplike)

    if (newTab || !this.tabber.currentElement) {
      const grouplikeListing = this.newGrouplikeListing()
      grouplikeListing.loadGrouplike(grouplike)
    } else {
      this.tabber.currentElement.loadGrouplike(grouplike)
    }
  }

  openPlaylist(arg) {
    const crawlers = getAllCrawlersForArg(arg)

    if (crawlers.length === 0) {
      throw 'unknown argument'
    }

    const crawler = crawlers[0]

    return crawler(arg)
  }

  setupDialog(dialog) {
    dialog.visible = false
    this.addChild(dialog)

    dialog.on('cancelled', () => {
      dialog.close()
    })
  }

  async shutdown() {
    if (this.config.stopPlayingUponQuit) {
      await this.backend.stopPlayingAll()
    }

    await this.textEditor.save()
    this.emit('quitRequested')
  }

  suspend() {
    if (this.config.canSuspend) {
      this.emit('suspendRequested')
    }
  }

  fixLayout() {
    if (this.parent) {
      this.fillParent()
    }

    this.menubar.fixLayout()

    let topY = this.contentH

    if (this.partyBottom.visible) {
      this.partyBottom.w = this.contentW
      this.partyBottom.h = 1
      this.partyBottom.x = 0
      this.partyBottom.y = topY - this.partyBottom.h
      topY = this.partyBottom.top
      this.partyBottomBanner.w = this.partyBottom.w
    }

    this.playbackPane.w = this.contentW
    this.playbackPane.h = 5
    this.playbackPane.x = 0
    this.playbackPane.y = topY - this.playbackPane.h
    topY = this.playbackPane.top

    for (const PIE of this.playbackInfoElements) {
      if (this.playbackInfoElements.length === 1) {
        PIE.displayMode = 'expanded'
      } else {
        PIE.displayMode = 'collapsed'
      }
    }
    this.playbackForm.fillParent()
    this.playbackForm.fixLayout()

    let bottomY = 1

    if (this.partyTop.visible) {
      this.partyTop.w = this.contentW
      this.partyTop.h = 1
      this.partyTop.x = 0
      this.partyTop.y = 1
      bottomY = this.partyTop.bottom

      this.partyTopBanner.w = this.partyTop.w
      this.partyTopBanner.y = this.partyTop.contentH - 1

      this.alignPartyLabel()
    }

    const leftWidth = Math.max(Math.floor(0.8 * this.contentW), this.contentW - 80)

    if (this.textInfoPane.visible) {
      this.textInfoPane.w = leftWidth
      if (this.textEditor.isSelected) {
        this.textInfoPane.h = 8
      } else {
        this.textEditor.w = this.textInfoPane.contentW
        this.textEditor.rebuildUiLines()
        this.textInfoPane.h = Math.min(8, this.textEditor.getOptimalHeight() + 2)
      }

      this.textEditor.fillParent()
      this.textEditor.fixLayout()
    }

    if (this.tabberPane.visible) {
      this.tabberPane.w = leftWidth
      this.tabberPane.y = bottomY
      this.tabberPane.h = topY - this.tabberPane.y
      if (this.textInfoPane.visible) {
        this.tabberPane.h -= this.textInfoPane.h
        this.textInfoPane.y = this.tabberPane.bottom
      }
      this.queuePane.x = this.tabberPane.right
      this.queuePane.w = this.contentW - this.tabberPane.right
    } else {
      this.queuePane.x = 0
      this.queuePane.w = this.contentW
      if (this.textInfoPane.visible) {
        this.textInfoPane.y = bottomY
      }
    }

    this.queuePane.y = bottomY
    this.queuePane.h = topY - this.queuePane.y
    topY = this.queuePane.y

    this.tabber.fillParent()

    if (this.metadataStatusLabel.visible) {
      this.tabber.h--
      this.metadataStatusLabel.y = this.tabberPane.contentH - 1
    }

    this.tabber.fixLayout()

    this.queueListingElement.fillParent()
    this.queueListingElement.h -= 2

    this.updateQueueLengthLabel()

    this.menuLayer.fillParent()
  }

  alignPartyLabel() {
    this.partyLabel.centerInParent()
    this.partyLabel.y = 0
  }

  attachAsServerHost(telnetServer) {
    this.isPartyHost = true
    this.attachAsServer(telnetServer)
  }

  attachAsServerClient(telnetServer) {
    this.isPartyHost = false
    this.attachAsServer(telnetServer)
  }

  attachAsServer(telnetServer) {
    this.telnetServer = telnetServer
    this.updatePartyLabel()

    this.telnetServer.on('joined', () => this.updatePartyLabel())
    this.telnetServer.on('left', () => this.updatePartyLabel())

    this.partyTop.visible = true
    this.partyBottom.visible = true
    this.fixLayout()
  }

  updatePartyLabel() {
    const clients = this.telnetServer.sockets.length
    const clientsMsg = clients === 1 ? '1-ish connection' : `${clients}-ish connections`
    let msg = `${process.env.USER} playing for ${clientsMsg}`

    this.partyLabel.text = `  ${msg}  `
    this.alignPartyLabel()
  }

  keyPressed(keyBuf) {
    if (keyBuf[0] === 0x03) { // Ctrl-C
      this.shutdown()
      return
    } else if (keyBuf[0] === 0x1a) { // Ctrl-Z
      this.suspend()
      return
    }

    if ((telc.isEscape(keyBuf) || telc.isBackspace(keyBuf)) && this.menubar.isSelected) {
      this.menubar.restoreSelection()
      return
    }

    if (this.config.canControlPlayback) {
      if ((telc.isLeft(keyBuf) || telc.isRight(keyBuf)) && this.menubar.isSelected) {
        return // le sigh
      } else if (input.isRight(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.seekAhead(10))
      } else if (input.isLeft(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.seekBack(10))
      } else if (input.isTogglePause(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.togglePause())
      } else if (input.isToggleLoop(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.toggleLoop())
      } else if (input.isVolumeUp(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.volUp())
      } else if (input.isVolumeDown(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.volDown())
      } else if (input.isStop(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.stopPlaying())
      } else if (input.isSkipBack(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.playPrevious(qp.playingTrack, true))
      } else if (input.isSkipAhead(keyBuf)) {
        this.actOnQueuePlayers(qp => qp.playNext(qp.playingTrack, true))
      }
    }

    if (input.isFocusTabber(keyBuf) && this.tabberPane.visible && this.tabber.selectable) {
      this.root.select(this.tabber)
    } else if (input.isFocusQueue(keyBuf) && this.queueListingElement.selectable) {
      this.root.select(this.queueListingElement)
    } else if (input.isFocusPlaybackInfo(keyBuf) && this.backend.queuePlayers.length > 1) {
      this.root.select(this.playbackForm)
    } else if (input.isFocusMenubar(keyBuf)) {
      if (this.menubar.isSelected) {
        this.menubar.restoreSelection()
      } else {
        // If we've got a menu open, close it, restoring selection to the
        // element selected before the menu was opened, so the menubar will
        // see that as the previously selected element (instead of the context
        // menu - which will be closed irregardless and gone when the menubar
        // tries to restore the selection).
        if (this.menuLayer.children[0]) {
          this.menuLayer.children[0].close()
        }
        this.menubar.select()
      }
    } else if (this.editMode && keyBuf.equals(Buffer.from([14]))) { // ctrl-N
      this.newEmptyTab()
    } else if (keyBuf.equals(Buffer.from([15]))) { // ctrl-O
      this.openPlaylistDialog.open()
    } else if (this.tabber.isSelected && keyBuf.equals(Buffer.from([20]))) { // ctrl-T
      this.cloneCurrentTab()
    } else if (this.tabber.isSelected && keyBuf.equals(Buffer.from([23]))) { // ctrl-W
      if (this.tabber.tabberElements.length > 1) {
        this.closeCurrentTab()
      }
    } else if (telc.isCharacter(keyBuf, 'u')) {
      this.undoManager.undoLastAction()
    } else if (telc.isCharacter(keyBuf, 'U')) {
      this.undoManager.redoLastUndoneAction()
    } else if (this.tabber.isSelected && keyBuf.equals(Buffer.from(['t'.charCodeAt(0)]))) {
      this.tabber.nextTab()
    } else if (this.tabber.isSelected && keyBuf.equals(Buffer.from(['T'.charCodeAt(0)]))) {
      this.tabber.previousTab()
    } else if (input.isPreviousPlayer(keyBuf)) {
      this.selectPreviousQueuePlayer()
    } else if (input.isNextPlayer(keyBuf)) {
      this.selectNextQueuePlayer()
    } else if (input.isNewPlayer(keyBuf)) {
      this.addQueuePlayer()
    } else if (input.isRemovePlayer(keyBuf)) {
      this.removeQueuePlayer(this.SQP)
    } else if (input.isActOnPlayer(keyBuf)) {
      this.toggleActOnQueuePlayer(this.SQP)
    } else {
      super.keyPressed(keyBuf)
    }
  }

  newEmptyTab() {
    const listing = this.newGrouplikeListing()
    listing.loadGrouplike({
      name: 'New Playlist',
      items: []
    })
  }

  cloneCurrentTab() {
    const grouplike = this.tabber.currentElement.grouplike
    const listing = this.newGrouplikeListing()
    listing.loadGrouplike(grouplike)
  }

  closeCurrentTab() {
    const listing = this.tabber.currentElement
    let index
    this.undoManager.pushAction({
      activate: () => {
        index = this.tabber.currentElementIndex
        this.tabber.closeTab(this.tabber.currentElement)
      },
      undo: () => {
        this.tabber.addTab(listing, index)
        this.tabber.selectTab(listing)
      }
    })
  }

  shuffleQueue() {
    this.SQP.shuffleQueue()
  }

  clearQueue() {
    this.SQP.clearQueue()
    this.queueListingElement.selectNone()
    this.updateQueueLengthLabel()

    if (this.queueListingElement.isSelected && !this.queueListingElement.selectable) {
      this.root.select(this.tabber)
    }
  }

  // TODO: I'd like to name/incorporate this function better.. for now it's
  // just directly moved from the old event listener on grouplikeListings for
  // 'queue'.
  handleQueueOptions(item, {where = 'end', order = 'normal', play = false, skip = false} = {}) {
    if (!this.config.canControlQueue) {
      return
    }

    const passedItem = item

    let { playingTrack } = this.SQP

    if (skip && playingTrack === item) {
      this.SQP.playNext(playingTrack)
    }

    if (isGroup(item)) {
      if (order === 'shuffle') {
        item = {items: shuffleArray(flattenGrouplike(item).items)}
      } else if (order === 'shuffle-groups') {
        item = shuffleOrderOfGroups(item)
      } else if (order === 'reverse') {
        item = {items: flattenGrouplike(item).items.reverse()}
      } else if (order === 'reverse-groups') {
        item = reverseOrderOfGroups(item)
      }
    } else {
      // Make it into a grouplike that just contains itself.
      item = {items: [item]}
    }

    if (where === 'next' || where === 'next-selected' || where === 'end') {
      let afterItem = null
      if (where === 'next') {
        afterItem = playingTrack
      } else if (where === 'next-selected') {
        afterItem = this.queueListingElement.currentItem
      }

      this.SQP.queue(item, afterItem, {
        movePlayingTrack: order === 'normal'
      })

      if (isTrack(passedItem)) {
        this.queueListingElement.selectAndShow(passedItem)
      }
    } else if (where.startsWith('distribute-')) {
      this.SQP.distributeQueue(item, {
        how: where.slice('distribute-'.length)
      })
    }

    this.updateQueueLengthLabel()

    if (play) {
      this.play(item)
    }
  }

  async processMetadata(item, reprocess = false) {
    if (!this.config.canProcessMetadata) {
      return
    }

    if (this.clearMetadataStatusTimeout) {
      clearTimeout(this.clearMetadataStatusTimeout)
    }

    this.metadataStatusLabel.text = 'Processing metadata...'
    this.metadataStatusLabel.visible = true
    this.fixLayout()

    const counter = await this.backend.processMetadata(item, reprocess)

    const tracksMsg = (counter === 1) ? '1 track' : `${counter} tracks`
    this.metadataStatusLabel.text = `Done processing metadata of ${tracksMsg}!`

    this.clearMetadataStatusTimeout = setTimeout(() => {
      this.clearMetadataStatusTimeout = null
      this.metadataStatusLabel.text = ''
      this.metadataStatusLabel.visible = false
      this.fixLayout()
    }, 3000)
  }

  updateQueueLengthLabel() {
    if (!this.SQP) {
      this.queueTimeLabel.text = ''
      return
    }

    const { playingTrack, timeData } = this.SQP
    const { items } = this.SQP.queueGrouplike

    let trackRemainSec = 0

    if (timeData) {
      const { curSecTotal = 0, lenSecTotal = 0 } = timeData
      trackRemainSec = lenSecTotal - curSecTotal
    }

    // Index of tracks "ahead" of the current track. All tracks before this
    // index are accounted for by either being behind the current track (and
    // thus ignorable) or being the current track (and thus having its
    // remaining duration be counted by the time data stored on the playback
    // info element).
    let index = 0

    if (playingTrack) {
      index = items.indexOf(playingTrack)
      // If it's NOT counted by the playback info element's time data yet,
      // we skip this - the current track is counted as "ahead" and its
      // duration will be tallied like the rest of the "ahead" tracks.
      if (timeData) {
        index++
      }
    }

    const { seconds: aheadRemainSec, approxSymbol } = this.backend.getDuration({items: items.slice(index)})
    const totalRemainSec = trackRemainSec + aheadRemainSec

    const { duration } = getTimeStringsFromSec(0, totalRemainSec)

    this.queueLengthLabel.text = (playingTrack && items.includes(playingTrack)
      ? `(${this.SQP.playSymbol} ${index} / ${items.length})`
      : `(${items.length})`)

    this.queueTimeLabel.text = `(${duration + approxSymbol})`

    this.queueLengthLabel.centerInParent()
    this.queueTimeLabel.centerInParent()
    this.queueLengthLabel.y = this.queuePane.contentH - 2
    this.queueTimeLabel.y = this.queuePane.contentH - 1
  }

  get SQP() {
    // Just a convenient shorthand.
    return this.selectedQueuePlayer
  }

  get selectedQueuePlayer() { return this.getDep('selectedQueuePlayer') }
  set selectedQueuePlayer(v) { return this.setDep('selectedQueuePlayer', v) }
}

class GrouplikeListingElement extends Form {
  // TODO: This is a Form, which means that it captures the tab key. The result
  // of this is that you cannot use Tab to navigate the top-level application.
  // Accordingly, I've made AppElement a FocusElement and not a Form and re-
  // factored calls of addInput to addChild. However, I'm not sure that this is
  // the "correct" or most intuitive behavior. Should the tab key be usable to
  // navigate the entire interface? I don't know. I've gone with the current
  // behavior (GrouplikeListingElement as a Form) because it feels right at the
  // moment, but we'll see, I suppose.
  //
  // In order to let tab navigate through all UI elements (or rather, the top-
  // level application as well as GrouplikeListingElements, which are a sort of
  // nested Form), the AppElement would have to be changed to be a Form again
  // (replacing addChild with addInput where appropriate). Furthermore, while
  // the GrouplikeListingElement should stay as a Form subclass, it should be
  // modified so that it does not capture tab if there is no next element to
  // select, and vice versa for shift-tab and the previous element. This should
  // probably be implemented in tui-lib as a flag on Form (captureTabOnEnds,
  // or something).
  //
  // (PS AppElement apparently used a "this.form" property, instead of directly
  // inheriting from Form, apparently. That's more or less adjacent to the
  // point. It's removed now. You'll have to add it back, if wanted.)
  //
  // August 15th, 2018

  constructor(app) {
    super()

    this.grouplike = null
    this.app = app

    this.form = this.getNewForm()
    this.addInput(this.form)

    this.form.on('selected', input => {
      if (input && this.pathElement) {
        this.pathElement.showItem(input.item)
        this.emit('selected', input.item)
      }
    })

    this.jumpElement = new ListingJumpElement()
    this.addChild(this.jumpElement)
    this.jumpElement.visible = false
    this.oldFocusedIndex = null // To restore to, if a jump is canceled.
    this.previousJumpValue = '' // To default to, if the user doesn't enter anything.

    this.jumpElement.on('cancel', () => this.hideJumpElement(true))
    this.jumpElement.on('change', value => this.handleJumpValue(value, false))
    this.jumpElement.on('confirm', value => this.handleJumpValue(value, true))

    this.pathElement = new PathElement()
    this.addInput(this.pathElement)

    this.commentLabel = new WrapLabel()
    this.addChild(this.commentLabel)
  }

  getNewForm() {
    return new GrouplikeListingForm(this.app)
  }

  fixLayout() {
    this.commentLabel.w = this.contentW

    this.form.w = this.contentW
    this.form.h = this.contentH
    this.form.y = this.commentLabel.bottom
    this.form.h -= this.commentLabel.h
    this.form.h -= 1 // For the path element
    if (this.jumpElement.visible) this.form.h -= 1

    this.form.fixLayout() // Respond to being resized
    this.form.scrollSelectedElementIntoView()

    this.pathElement.y = this.contentH - 1
    this.pathElement.w = this.contentW

    this.jumpElement.y = this.pathElement.y - 1
    this.jumpElement.w = this.contentW
  }

  selected() {
    this.curIndex = 0
    this.root.select(this.form)
    this.emit('selected', this.currentItem)
  }

  clicked(button) {
    if (button === 'left') {
      this.selected()
      return false
    }
  }

  get selectable() {
    return this.form.selectable
  }

  keyPressed(keyBuf) {
    // Just about everything here depends on the grouplike existing, so let's
    // not continue if it doesn't!
    if (!this.grouplike) {
      return
    }

    if (telc.isBackspace(keyBuf)) {
      this.loadParentGrouplike()
    } else if (telc.isCharacter(keyBuf, '/') || keyBuf[0] === 6) { // '/', ctrl-F
      this.showJumpElement()
    } else if (input.isScrollToStart(keyBuf)) {
      this.form.selectAndShow(this.grouplike.items[0])
      this.form.scrollToBeginning()
    } else if (input.isScrollToEnd(keyBuf)) {
      this.form.selectAndShow(this.grouplike.items[this.grouplike.items.length - 1])
    } else if (keyBuf[0] === 12) { // ctrl-L
      if (this.grouplike.isTheQueue) {
        this.form.selectAndShow(this.app.SQP.playingTrack)
      } else {
        this.toggleExpandLabels()
      }
    } else if (keyBuf[0] === 1) { // ctrl-A
      this.toggleSelectAll()
    } else {
      return super.keyPressed(keyBuf)
    }
  }

  loadGrouplike(grouplike, resetIndex = true) {
    this.grouplike = grouplike
    this.buildItems(resetIndex)
    if (this.root.select) this.hideJumpElement()
  }

  selectNone() {
    // nb: this is unrelated to the actual track selection system!
    // just clears the form selection
    this.pathElement.showItem(null)
    this.form.curIndex = 0
    this.form.scrollItems = 0
  }

  toggleSelectAll() {
    const { items } = this.grouplike
    if (items.every(item => this.app.markGrouplike.items.includes(item))) {
      this.app.markGrouplike.items = []
    } else {
      this.app.markGrouplike.items = items.slice(0) // Don't share the array! :)
    }
  }

  toggleExpandLabels() {
    this.expandLabels = !this.expandLabels
    for (const input of this.form.inputs) {
      if (!(input instanceof InteractiveGrouplikeItemElement)) {
        continue
      }
      if (!input.labelsSelected) {
        input.expandLabels = this.expandLabels
        input.computeText()
      }
    }
  }

  buildItems(resetIndex = false) {
    if (!this.grouplike) {
      throw new Error('Attempted to call buildItems before a grouplike was loaded')
    }

    this.commentLabel.text = this.grouplike.comment || ''

    const wasSelected = this.isSelected
    const form = this.form

    // Just outright scrap the old items - don't deal with any selection stuff
    // (as a result of removeInput) yet.
    form.children = form.children.filter(child => !form.inputs.includes(child));
    form.inputs = []

    const parent = this.grouplike[parentSymbol]
    if (parent) {
      const upButton = new BasicGrouplikeItemElement(`Up (to ${parent.name || 'unnamed group'})`)
      upButton.on('pressed', () => this.loadParentGrouplike())
      form.addInput(upButton)
    }

    if (this.grouplike.items.length) {
      // Add an element for controlling this whole group. Particularly handy
      // for operating on the top-level group, which itself is not contained
      // within any groups (so you can't bworse a parent and access its menu
      // from there).
      if (!this.grouplike.isTheQueue) {
        const ownElement = new BasicGrouplikeItemElement(`This group: ${this.grouplike.name || '(Unnamed group)'}`)
        ownElement.item = this.grouplike
        ownElement.app = this.app
        ownElement.isGroup = true
        ownElement.on('pressed', () => {
          ownElement.emit('menu', ownElement)
        })
        this.addEventListeners(ownElement)
        form.addInput(ownElement)
      }

      // Add the elements for all the actual items within this playlist.
      for (const item of this.grouplike.items) {
        if (!isPlayable(item) && getCorrespondingPlayableForFile(item)) {
          continue
        }

        const itemElement = new InteractiveGrouplikeItemElement(item, this.app)
        this.addEventListeners(itemElement)
        form.addInput(itemElement)

        if (this.grouplike.isTheQueue) {
          itemElement.hideMetadata = true
          itemElement.text = getNameWithoutTrackNumber(item)
        }
      }
    } else if (!this.grouplike.isTheQueue) {
      form.addInput(new BasicGrouplikeItemElement('(This group is empty)'))
    }

    if (wasSelected) {
      if (resetIndex) {
        form.scrollItems = 0
        form.selectInput(form.inputs[form.firstItemIndex])
      } else {
        this.root.select(form)
      }
    }

    // Just to make the selected-track-info bar fill right away (if it wasn't
    // already filled by a previous this.curIndex set).
    form.curIndex = form.curIndex

    this.fixAllLayout()
  }

  addEventListeners(itemElement) {
    for (const evtName of [
      'browse',
      'download',
      'edit-notes',
      'mark',
      'menu',
      'open',
      'paste',
      'queue',
      'remove',
      'unqueue'
    ]) {
      itemElement.on(evtName, (...data) => this.emit(evtName, itemElement.item, ...data))
    }

    itemElement.on('unselected labels', () => {
      if (!this.expandLabels) {
        itemElement.expandLabels = false
        itemElement.computeText()
      }
    })
  }

  loadParentGrouplike() {
    if (!this.grouplike) {
      return
    }

    const parent = this.grouplike[parentSymbol]
    if (parent) {
      const oldGrouplike = this.grouplike
      this.loadGrouplike(parent)

      const form = this.form
      const index = form.inputs.findIndex(inp => inp.item === oldGrouplike)
      if (typeof index === 'number') {
        form.curIndex = index
      } else {
        form.curIndex = form.firstItemIndex
      }
      form.updateSelectedElement()
      form.scrollSelectedElementIntoView()
    }
  }

  selectAndShow(item) {
    return this.form.selectAndShow(item)
  }

  handleJumpValue(value, isConfirm) {
    // If the user doesn't enter anything, we won't perform a search -- unless
    // the user just pressed enter. If that's the case, we'll search for
    // whatever was previously entered into the form. This is to strike a
    // balance between keeping the jump form simple and unsurprising but also
    // powerful, i.e. to support easy "repeated" searches (see the below
    // cmoment about search match prioritization).
    if (!value.length && isConfirm && this.previousJumpValue) {
      value = this.previousJumpValue
    }

    const grouplike = {items: this.form.inputs.map(inp => inp.item)}

    // We prioritize searching past the index that the user opened the jump
    // element from (oldFocusedIndex). This is so that it's more practical
    // to do a "repeated" search, wherein the user searches for the same
    // value over and over, each time jumping to the next match, until they
    // have found the one they're looking for.
    const preferredStartIndex = this.oldFocusedIndex

    const item = searchForItem(grouplike, value, preferredStartIndex)

    if (item) {
      this.form.curIndex = this.form.inputs.findIndex(inp => inp.item === item)
      this.form.scrollSelectedElementIntoView()
    } else {
      // TODO: Feedback that the search failed.. right now we just close the
      // jump-to menu, which might not be right.
    }

    if (isConfirm) {
      this.previousJumpValue = value
      this.hideJumpElement()
    }
  }

  showJumpElement() {
    this.oldFocusedIndex = this.form.curIndex
    this.jumpElement.visible = true
    this.root.select(this.jumpElement)
    this.fixLayout()
  }

  hideJumpElement(isCancel) {
    if (isCancel) {
      this.form.curIndex = this.oldFocusedIndex
      this.form.scrollSelectedElementIntoView()
    }
    this.jumpElement.visible = false
    if (this.jumpElement.isSelected) {
      this.root.select(this)
    }
    this.fixLayout()
  }

  get tabberLabel() {
    if (this.grouplike) {
      return this.grouplike.name || 'Unnamed group'
    } else {
      return 'No group open'
    }
  }

  get currentItem() {
    const element = this.form.inputs[this.form.curIndex] || null
    return element && element.item
  }
}

class GrouplikeListingForm extends ListScrollForm {
  constructor(app) {
    super('vertical')

    this.app = app
    this.dragInputs = []
    this.selectMode = null
    this.keyboardDragDirection = null
    this.captureTab = false
  }

  keyPressed(keyBuf) {
    if (input.isSelectUp(keyBuf)) {
      this.selectUp()
    } else if (input.isSelectDown(keyBuf)) {
      this.selectDown()
    } else {
      if (telc.isUp(keyBuf) || telc.isDown(keyBuf)) {
        this.keyboardDragDirection = null
      }
      return super.keyPressed(keyBuf)
    }
  }

  set curIndex(newIndex) {
    this.setDep('curIndex', newIndex)
    this.emit('selected', this.inputs[this.curIndex])
    return newIndex
  }

  get curIndex() {
    return this.getDep('curIndex')
  }

  get firstItemIndex() {
    return Math.max(0, this.inputs.findIndex(el => el instanceof InteractiveGrouplikeItemElement))
  }

  selectAndShow(item) {
    const index = this.inputs.findIndex(inp => inp.item === item)
    if (index >= 0) {
      this.curIndex = index
      if (this.isSelected) {
        this.updateSelectedElement()
      }
      this.scrollSelectedElementIntoView()
      return true
    }
    return false
  }

  clicked(button, allData) {
    const { line, ctrl } = allData
    if (button === 'left') {
      this.dragStartLine = line - this.absTop + this.scrollItems
      this.dragStartIndex = this.inputs.findIndex(inp => inp.absTop === line - 1)
      if (this.dragStartIndex >= 0) {
        const input = this.inputs[this.dragStartIndex]
        if (!(input instanceof InteractiveGrouplikeItemElement)) {
          this.dragStartIndex = -1
          return
        }
        const { item } = input
        if (this.app.markGrouplike.items.includes(item)) {
          this.selectMode = 'deselect'
        } else {
          if (!ctrl) {
            this.app.markGrouplike.items = []
          }
          this.selectMode = 'select'
        }
        if (ctrl) {
          this.dragInputs = [item]
          this.dragEnteredRange(item)
        } else {
          this.dragInputs = []
        }
        this.oldMarkedItems = this.app.markGrouplike.items.slice()
      }
    } else if (button === 'drag-left' && this.dragStartIndex >= 0) {
      const offset = (line - this.absTop + this.scrollItems) - this.dragStartLine
      const rangeA = this.dragStartIndex
      const rangeB = this.dragStartIndex + offset
      const inputs = ((rangeA < rangeB)
        ? this.inputs.slice(rangeA, rangeB + 1)
        : this.inputs.slice(rangeB, rangeA + 1))
      let enteredRange = inputs.filter(inp => !this.dragInputs.includes(inp))
      let leftRange = this.dragInputs.filter(inp => !inputs.includes(inp))
      for (const { item } of enteredRange) {
        this.dragEnteredRange(item)
      }
      for (const { item } of leftRange) {
        this.dragLeftRange(item)
      }
      if (this.inputs[rangeB]) {
        this.root.select(this.inputs[rangeB])
      }
      this.dragInputs = inputs
    } else if (button === 'release') {
      this.dragStartIndex = -1
    } else {
      return super.clicked(button, allData)
    }
  }

  dragEnteredRange(item) {
    const { items } = this.app.markGrouplike
    if (this.selectMode === 'select') {
      if (!items.includes(item)) {
        items.push(item)
      }
    } else if (this.selectMode === 'deselect') {
      if (items.includes(item)) {
        items.splice(items.indexOf(item), 1)
      }
    }
  }

  dragLeftRange(item) {
    const { items } = this.app.markGrouplike
    if (this.selectMode === 'select') {
      if (items.includes(item) && !this.oldMarkedItems.includes(item)) {
        items.splice(items.indexOf(item), 1)
      }
    } else if (this.selectMode === 'deselect') {
      if (!items.includes(item) && this.oldMarkedItems.includes(item)) {
        items.push(item)
      }
    }
  }

  selectUp() {
    this.handleKeyboardSelect(-1)
  }

  selectDown() {
    this.handleKeyboardSelect(+1)
  }

  handleKeyboardSelect(direction) {
    const move = () => {
      if (direction === +1) {
        this.nextInput()
      } else {
        this.previousInput()
      }
      this.scrollSelectedElementIntoView()
    }

    const getItem = () => {
      const input = this.inputs[this.curIndex]
      if (input instanceof InteractiveGrouplikeItemElement) {
        return input.item
      } else {
        return null
      }
    }

    if (!this.keyboardDragDirection) {
      const item = getItem()
      if (!item) {
        move()
        return
      }
      this.keyboardDragDirection = direction
      this.oldMarkedItems = this.app.markGrouplike.items.slice()
      if (this.app.markGrouplike.items.includes(item)) {
        this.selectMode = 'deselect'
      } else {
        this.selectMode = 'select'
      }
      this.dragEnteredRange(item)
    }

    if (direction === this.keyboardDragDirection) {
      move()
      const item = getItem()
      if (!item) {
        return
      }
      this.dragEnteredRange(item)
    } else {
      const item = getItem()
      if (!item) {
        move()
        return
      }
      this.dragLeftRange(item)
      move()
    }
  }
}

class BasicGrouplikeItemElement extends Button {
  constructor(text) {
    super()

    this._text = this._rightText = ''

    this.text = text
    this.rightText = ''
    this.drawText = ''
  }

  fixLayout() {
    this.w = this.parent.contentW
    this.h = 1

    this.computeText()
  }

  set text(val) {
    if (this._text !== val) {
      this._text = val
      this.computeText()
    }
  }

  get text() {
    return this._text
  }

  set rightText(val) {
    if (this._rightText !== val) {
      this._rightText = val
      this.computeText()
    }
  }

  get rightText() {
    return this._rightText
  }

  getFormattedRightText() {
    return this.rightText
  }

  getRightTextColumns() {
    return ansi.measureColumns(this.rightText)
  }

  getMinLeftTextColumns() {
    return 12
  }

  getLeftPadding() {
    return 2
  }

  getSelfSelected() {
    return this.isSelected
  }

  computeText() {
    let w = this.w - this.x - this.getLeftPadding()

    // Also make space for the right text - if we choose to show it.
    const rightTextCols = this.getRightTextColumns()
    const showRightText = (w - rightTextCols > this.getMinLeftTextColumns())
    if (showRightText) {
      w -= rightTextCols
    }

    let text = ansi.trimToColumns(this.text, w)

    const width = ansi.measureColumns(this.text)
    if (width < w) {
      text += ' '.repeat(w - width)
    }

    if (showRightText) {
      text += this.getFormattedRightText()
    }

    text += ansi.resetAttributes()

    this.drawText = text
  }

  drawTo(writable) {
    const isCurrentInput = this.parent.inputs[this.parent.curIndex] === this
    // This line's commented out for now, so it'll show as selected (but
    // dimmed) even if you don't have the listing selected. To change that,
    // uncomment this and add it to the isCurrentInput line.
    // const isListingSelected = this.parent.parent.isSelected
    const isSelfSelected = this.getSelfSelected()

    if (isSelfSelected) {
      writable.write(ansi.invert())
    } else if (isCurrentInput) {
      // technically cheating - isPlayable is defined on InteractiveGrouplikeElement
      if (this.isPlayable === false) {
        writable.write(ansi.setAttributes([ansi.A_INVERT, ansi.C_BLACK, ansi.A_BRIGHT]))
      } else {
        writable.write(ansi.setAttributes([ansi.A_INVERT, ansi.A_DIM]))
      }
    }

    writable.write(ansi.moveCursor(this.absTop, this.absLeft))
    this.writeStatus(writable)
    writable.write(this.drawText)
  }

  writeStatus(writable) {
    // Add a couple spaces. This is less than the padding of the status text
    // of elements which represent real playlist items; that's to distinguish
    // "fake" rows from actual playlist items.
    writable.write('  ')
    this.drawX += 2
  }

  keyPressed(keyBuf) {
    // This function is overridden by InteractiveGrouplikeItemElement, but
    // it's still specified here that only enter counts as an action key.
    // By default for buttons, the space key also works, but since in this app
    // space is generally bound to mean "pause" instead of "select", we don't
    // check if space is pressed here.
    if (telc.isEnter(keyBuf) || input.isMenu(keyBuf)) {
      this.emit('pressed')
    }
  }

  clicked(button) {
    super.clicked(button)
  }
}

class InlineListPickerElement extends FocusElement {
  // And you thought my class names couldn't get any worse...
  // This is an element that looks something like the following:
  //    Fruit?  [Apple]
  // (Imagine that "[Apple]" just looks like "Apple" written in blue text.)
  // If you press the element (like a button), it'll pick the next item in its
  // list of options, like "Banana" or "Canteloupe" in this example. The arrow
  // keys also work to move through the list. You typically don't want to put
  // too many items in the list, since there's no visual way of telling what's
  // next or previous. (That's the point, it's inline.) This element is mainly
  // useful in forms or ContextMenus.

  constructor(labelText, options, showContextMenu = null) {
    super()
    this.labelText = labelText
    this.options = options
    this.showContextMenu = showContextMenu
    this.curIndex = 0
    this.keyboardIdentifier = this.labelText
  }

  fixLayout() {
    // We want to fill the parent's width, but also fit ourselves, so we need
    // to determine the ideal width which would fit us but not leave extra
    // space.
    const longestOptionLength = this.options.reduce(
      (soFar, { label }) => Math.max(soFar, ansi.measureColumns(label)), 0)
    const idealWidth = (
      ansi.measureColumns(this.labelText) + longestOptionLength + 4)

    // Then we use whichever is greater - our ideal width or the width of the
    // parent - as our own width. The parent should respect our needs by
    // growing if necessary. :)  (ContextMenu does this, which is where you'd
    // typically embed this element.)
    // I shall fill you, parent, even beyond your own bounds!!!
    this.w = Math.max(this.parent.contentW, idealWidth)

    // Height is always just 1.
    this.h = 1
  }

  drawTo(writable) {
    if (this.isSelected) {
      writable.write(ansi.invert())
    }

    const curOption = this.options[this.curIndex].label.toString()
    let drawX = 0
    writable.write(ansi.moveCursor(this.absTop, this.absLeft))

    writable.write(this.labelText + ' ')
    drawX += ansi.measureColumns(this.labelText) + 1

    writable.write(ansi.setAttributes([ansi.A_BRIGHT, ansi.C_BLUE]))
    writable.write(' ' + curOption + ' ')
    drawX += ansi.measureColumns(curOption) + 2

    writable.write(ansi.setForeground(ansi.C_RESET))
    writable.write(' '.repeat(Math.max(0, this.w - drawX)))

    writable.write(ansi.resetAttributes())
  }

  keyPressed(keyBuf) {
    if (telc.isSelect(keyBuf) || telc.isRight(keyBuf)) {
      this.nextOption()
    } else if (telc.isLeft(keyBuf)) {
      this.previousOption()
    } else if (input.isMenu(keyBuf) && this.showContextMenu) {
      this.showContextMenu({
        x: this.absLeft + ansi.measureColumns(this.labelText) + 1,
        y: this.absTop + 1,
        items: this.options.map(({ value, label }, index) => ({
          label: label,
          action: () => {
            this.curIndex = index
          },
          isDefault: index === this.curIndex
        }))
      })
    } else {
      return true
    }
    return false
  }

  clicked(button) {
    if (button === 'left') {
      if (this.isSelected) {
        this.nextOption()
      } else {
        this.root.select(this)
      }
    } else if (button === 'scroll-up') {
      this.previousOption()
    } else if (button === 'scroll-down') {
      this.nextOption()
    } else {
      return true
    }
    return false
  }

  nextOption() {
    this.curIndex++
    if (this.curIndex === this.options.length) {
      this.curIndex = 0
    }
  }

  previousOption() {
    this.curIndex--
    if (this.curIndex < 0) {
      this.curIndex = this.options.length - 1
    }
  }

  get curValue() {
    return this.options[this.curIndex].value
  }

  get curIndex() { return this.getDep('curIndex') }
  set curIndex(v) { return this.setDep('curIndex', v) }
}

// Quite hacky, but ATM I can't think of any way to neatly tie getDep/setDep
// into the slider and toggle elements.
const drawAfter = (fn, thisObj) => (...args) => {
  const ret = fn(...args)
  thisObj.scheduleDrawWithoutPropertyChange()
  return ret
}

class SliderElement extends FocusElement {
  // Same general principle and usage as InlineListPickerElement, but for
  // changing a numeric value.

  constructor(labelText, {setValue, getValue, maxValue = 100, percent = true, getEnabled = () => true}) {
    super()
    this.labelText = labelText
    this.setValue = drawAfter(setValue, this)
    this.getValue = getValue
    this.getEnabled = getEnabled
    this.maxValue = maxValue
    this.percent = percent
    this.keyboardIdentifier = this.labelText
  }

  fixLayout() {
    const idealWidth = ansi.measureColumns(
      this.labelText +
      '  ' + this.getValueString(this.maxValue) +
      ' ' + this.getNumString(this.maxValue) +
      '  '
    )

    this.w = Math.max(this.parent.contentW, idealWidth)
    this.h = 1
  }

  drawTo(writable) {
    const enabled = this.getEnabled()

    if (this.isSelected) {
      writable.write(ansi.invert())
    }

    let drawX = 0
    writable.write(ansi.moveCursor(this.absTop, this.absLeft))

    if (!enabled) {
      writable.write(ansi.setAttributes([ansi.A_DIM, ansi.C_WHITE]))
    }

    writable.write(this.labelText + ' ')
    drawX += ansi.measureColumns(this.labelText) + 1

    if (enabled) {
      writable.write(ansi.setAttributes([ansi.A_BRIGHT, ansi.C_BLUE]))
    }
    writable.write(' ')
    drawX += 1

    const valueString = this.getValueString(this.getValue())
    writable.write(valueString)
    drawX += valueString.length

    const numString = this.getNumString(this.getValue())
    writable.write(' ' + numString + ' ')
    drawX += numString.length + 2

    if (enabled) {
      writable.write(ansi.setForeground(ansi.C_RESET))
    }

    writable.write(' '.repeat(Math.max(0, this.w - drawX)))

    writable.write(ansi.resetAttributes())
  }

  getValueString(value) {
    const maxLength = 10

    let length = Math.round(value / this.maxValue * maxLength)

    if (value < this.maxValue && length === maxLength) {
      length--
    }

    if (value > 0 && length === 0) {
      length++
    }

    return (
      '[' +
      '-'.repeat(length) +
      ' '.repeat(maxLength - length) +
      ']'
    )
  }

  getNumString(value) {
    const maxValueString = Math.round(this.maxValue).toString()
    const valueString = Math.round(value).toString()
    const paddedString = valueString.padStart(maxValueString.length)

    return paddedString + (this.percent ? '%' : '')
  }

  keyPressed(keyBuf) {
    const enabled = this.getEnabled()
    if (enabled && telc.isRight(keyBuf)) {
      this.increment()
    } else if (enabled && telc.isLeft(keyBuf)) {
      this.decrement()
    } else {
      return true
    }
    return false
  }

  clicked(button) {
    if (!this.getEnabled()) {
      return
    }

    if (button === 'left') {
      if (this.isSelected) {
        if (this.getValue() === this.maxValue) {
          this.setValue(0)
        } else {
          this.increment()
        }
      } else {
        this.root.select(this)
      }
    } else if (button === 'scroll-up') {
      this.increment()
    } else if (button === 'scroll-down') {
      this.decrement()
    }
  }

  increment() {
    this.setValue(this.getValue() + this.step)
  }

  decrement() {
    this.setValue(this.getValue() - this.step)
  }

  get step() {
    return this.maxValue / 10
  }
}

class ToggleControl extends FocusElement {
  constructor(labelText, {setValue, getValue, getEnabled = () => true}) {
    super()
    this.labelText = labelText
    this.setValue = drawAfter(setValue, this)
    this.getValue = getValue
    this.getEnabled = getEnabled
    this.keyboardIdentifier = this.labelText
  }

  keyPressed(keyBuf) {
    if (input.isSelect(keyBuf) && this.getEnabled()) {
      this.toggle()
    }
  }

  clicked(button) {
    if (!this.getEnabled()) {
      return
    }

    if (button === 'left') {
      if (this.isSelected) {
        this.toggle()
      } else {
        this.root.select(this)
      }
    } else if (button === 'scroll-up' || button === 'scroll-down') {
      this.toggle()
    } else {
      return true
    }
    return false
  }


  toggle() {
    this.setValue(!this.getValue())
  }

  fixLayout() {
    // Same general principle as ToggleControl - fill the parent, but always
    // fit ourselves!
    this.w = Math.max(this.parent.contentW, this.labelText.length + 5)
    this.h = 1
  }

  drawTo(writable) {
    if (this.isSelected) {
      writable.write(ansi.invert())
    }

    if (!this.getEnabled()) {
      writable.write(ansi.setAttributes([ansi.C_WHITE, ansi.A_DIM]))
    }

    writable.write(ansi.moveCursor(this.absTop, this.absLeft))

    writable.write(this.getValue() ? '[X] ' : '[.] ')
    writable.write(this.labelText)
    writable.write(' '.repeat(this.w - (this.labelText.length + 4)))

    writable.write(ansi.resetAttributes())
  }
}

class InteractiveGrouplikeItemElement extends BasicGrouplikeItemElement {
  constructor(item, app) {
    super(item.name)
    this.item = item
    this.app = app
    this.hideMetadata = false
    this.expandLabels = false
    this.labelsSelected = false
    this.selectedLabelIndex = 0
  }

  drawTo(writable) {
    this.rightText = ''
    if (!this.hideMetadata) {
      const metadata = this.app.backend.getMetadataFor(this.item)
      if (metadata) {
        const durationString = getTimeStringsFromSec(0, metadata.duration).duration
        this.rightText = `(${durationString}) `
      }
    }

    super.drawTo(writable)
  }

  selected() {
    this.computeText()
  }

  unselected() {
    this.unselectLabels()
  }

  getLabelTexts() {
    const separator = this.isSelected ? '' : ''
    let labels = []
    // let labels = ['Voice', 'Woof']
    if (this.expandLabels && this.labelsSelected) {
      labels = ['+', ...labels]
    }
    return labels.map((label, i) => {
      return [
        label,
        separator + (this.expandLabels
          ? (this.labelsSelected && i === this.selectedLabelIndex
            ? `<${label}>`
            : ` ${label} `)
          : label[0])
      ]
    })
  }

  getLabelColor(label) {
    if (label === '+') {
      return ansi.C_BLACK
    } else {
      return 30 + (label.charCodeAt(0) % 7)
    }
  }

  getFormattedRightText() {
    const labelTexts = this.getLabelTexts()

    if (labelTexts.length) {
      const lastColor = this.getLabelColor(labelTexts[labelTexts.length - 1][0])
      return (this.isSelected ? ' ' : '') +
        ansi.resetAttributes() +
        (this.isSelected ? '' : ' ') +
        ansi.setAttributes(this.isSelected ? [ansi.A_BRIGHT, 7] : []) +
        labelTexts.map(([ label, labelText ], i, arr) => {
          let text = ''

          if (this.isSelected) {
            text += ansi.setBackground(this.getLabelColor(label))
          } else {
            text += ansi.setForeground(this.getLabelColor(label))
          }

          text += labelText[0]

          // text += ansi.resetAttributes()
          text += ansi.setForeground(ansi.C_RESET)
          text += ansi.setBackground(this.getLabelColor(label))

          text += labelText.slice(1)

          return text
        }).join('') +
        ansi.setAttributes([ansi.A_RESET, this.isSelected ? 0 : lastColor]) +
        '▎' +
        ansi.resetAttributes() +
        super.getFormattedRightText()
    } else {
      return super.getFormattedRightText()
    }
  }

  getRightTextColumns() {
    const labelTexts = this.getLabelTexts()

    return labelTexts
      .reduce((acc, [l, lt]) => acc + lt.length, 0) +
      (labelTexts.length ? 2 : 0) +
      super.getRightTextColumns()
  }

  getMinLeftTextColumns() {
    return this.expandLabels ? 0 : super.getMinLeftTextColumns()
  }

  getLeftPadding() {
    return 3
  }

  getSelfSelected() {
    return !this.labelsSelected && super.getSelfSelected()
  }

  keyPressed(keyBuf) {
    if (this.labelsSelected) {
      if (input.isRight(keyBuf)) {
        this.selectNextLabel()
      } else if (input.isLeft(keyBuf)) {
        this.selectPreviousLabel()
      } else if (telc.isEscape(keyBuf) || input.isFocusLabels(keyBuf)) {
        this.unselectLabels()
        return false
      }
    } else if (input.isDownload(keyBuf)) {
      this.emit('download')
    } else if (input.isQueueAfterSelectedTrack(keyBuf)) {
      this.emit('queue', {where: 'next-selected'})
    } else if (input.isOpenThroughSystem(keyBuf)) {
      this.emit('open')
    } else if (telc.isEnter(keyBuf)) {
      if (isGroup(this.item)) {
        this.emit('browse')
      } else if (isTrack(this.item)) {
        this.emit('queue', {where: 'next', play: true})
      } else if (!this.isPlayable) {
        this.emit('open')
      }
    } else if (input.isRemove(keyBuf)) {
      this.emit('remove')
    } else if (input.isMenu(keyBuf)) {
      this.emit('menu', this)
    } else if (input.isFocusTextEditor(keyBuf)) {
      this.emit('edit-notes')
    } else if (input.isFocusLabels(keyBuf)) {
      this.labelsSelected = true
      this.expandLabels = true
      this.selectedLabelIndex = 0
    }
  }

  unselectLabels() {
    this.labelsSelected = false
    this.emit('unselected labels')
    this.computeText()
  }

  selectNextLabel() {
    this.selectedLabelIndex++
    if (this.selectedLabelIndex >= this.getLabelTexts().length) {
      this.selectedLabelIndex = 0
    }
    this.computeText()
  }

  selectPreviousLabel() {
    this.selectedLabelIndex--
    if (this.selectedLabelIndex < 0) {
      this.selectedLabelIndex = this.getLabelTexts().length - 1
    }
    this.computeText()
  }

  clicked(button, {ctrl}) {
    if (button === 'left') {
      if (this.isSelected) {
        if (ctrl) {
          return
        }
        if (this.isGroup) {
          this.emit('browse')
        } else if (this.isTrack) {
          this.emit('queue', {where: 'next', play: true})
        } else if (!this.isPlayable) {
          this.emit('open')
        }
        return false
      } else {
        this.parent.selectInput(this)
      }
    } else if (button === 'right') {
      this.parent.selectInput(this)
      this.emit('menu', this)
      return false
    }
  }

  writeStatus(writable) {
    if (this.isGroup) {
      // The ANSI attributes here will apply to the rest of the line, too.
      // (We don't reset the active attributes until after drawing the rest of
      // the line.)
      if (this.isMarked) {
        writable.write(ansi.setAttributes([ansi.C_BLUE + 10]))
      } else {
        writable.write(ansi.setAttributes([ansi.C_BLUE, ansi.A_BRIGHT]))
      }
    } else if (this.isTrack) {
      if (this.isMarked) {
        writable.write(ansi.setAttributes([ansi.C_WHITE + 10, ansi.C_BLACK, ansi.A_BRIGHT]))
      }
    } else if (!this.isPlayable) {
      if (this.isMarked) {
        writable.write(ansi.setAttributes([ansi.C_WHITE + 10, ansi.C_BLACK, ansi.A_BRIGHT]))
      } else {
        writable.write(ansi.setAttributes([ansi.A_DIM]))
      }
    }

    this.drawX += 3

    const braille = '⠈⠐⠠⠄⠂⠁'
    const brailleChar = braille[Math.floor(Date.now() / 250) % 6]

    const record = this.app.backend.getRecordFor(this.item)

    if (this.isMarked) {
      writable.write('>')
    } else {
      writable.write(' ')
    }

    if (this.isGroup) {
      writable.write('G')
    } else if (!this.isPlayable) {
      writable.write('F')
    } else if (record.downloading) {
      writable.write(braille[Math.floor(Date.now() / 250) % 6])
    } else if (this.app.SQP.playingTrack === this.item) {
      writable.write('\u25B6')
    } else {
      writable.write(' ')
    }

    writable.write(' ')
  }

  get isMarked() {
    return this.app.markGrouplike.items.includes(this.item)
  }

  get isGroup() {
    return isGroup(this.item)
  }

  get isTrack() {
    return isTrack(this.item)
  }

  get isPlayable() {
    return isPlayable(this.item)
  }
}

class ListingJumpElement extends Form {
  constructor() {
    super()

    this.label = new Label('Jump to: ')
    this.addChild(this.label)

    this.input = new TextInput()
    this.addInput(this.input)

    this.input.on('confirm', value => this.emit('confirm', value))
    this.input.on('change', value => this.emit('change', value))
    this.input.on('cancel', () => this.emit('cancel'))
  }

  selected() {
    this.input.value = ''
    this.input.keepCursorInRange()
    this.root.select(this.input)
  }

  fixLayout() {
    this.input.x = this.label.right
    this.input.w = this.contentW - this.input.x
  }

  keyPressed(keyBuf) {
    const val = super.keyPressed(keyBuf)
    if (typeof val !== 'undefined') {
      return val
    }

    // Don't bubble escape.
    if (telc.isEscape(keyBuf)) {
      return false
    }
  }
}

class PathElement extends ListScrollForm {
  constructor() {
    // TODO: Once we've got the horizontal scrollbar draw working, perhaps
    // enable this? Well probably not. This is more a TODO to just, well,
    // implement that horizontal scrollbar drawing anyway.
    super('horizontal', false)
    this.captureTab = false
  }

  showItem(item) {
    while (this.inputs.length) {
      this.removeInput(this.inputs[0])
    }

    if (!item) {
      return
    }

    const itemPath = getItemPath(item)
    const parentPath = itemPath.slice(0, -1)

    for (const pathItem of parentPath) {
      const isFirst = pathItem === parentPath[0]
      const element = new PathItemElement(pathItem, isFirst)
      element.on('select', () => this.emit('select', pathItem))
      element.fixLayout()
      this.addInput(element)
    }

    this.curIndex = this.inputs.length - 1

    this.scrollToEnd()
    this.fixLayout()
  }
}

class PathItemElement extends FocusElement {
  constructor(item, isFirst) {
    super()

    this.item = item
    this.isFirst = isFirst

    this.arrowLabel = new Label(isFirst ? 'In: ' : ' > ')
    this.addChild(this.arrowLabel)

    this.button = new Button(item.name || '(Unnamed)')
    this.addChild(this.button)

    this.button.on('pressed', () => {
      this.emit('select')
    })
  }

  selected() {
    this.root.select(this.button)
  }

  clicked(button) {
    if (button === 'left') {
      this.emit('select')
    }
  }

  fixLayout() {
    const text = this.item.name || '(Unnamed)'

    const maxWidth = this.parent ? this.parent.contentW : Infinity
    this.arrowLabel.fixLayout()

    const maxButtonWidth = maxWidth - this.arrowLabel.w

    if (text.length > maxButtonWidth) {
      this.button.text = unic.ELLIPSIS + text.slice(-(maxButtonWidth - 1))
    } else {
      this.button.text = text
    }

    this.button.fixLayout()

    this.w = this.button.w + this.arrowLabel.w
    this.button.x = this.arrowLabel.right
    this.h = 1
  }
}

class QueueListingElement extends GrouplikeListingElement {
  getNewForm() {
    return new QueueListingForm(this.app)
  }

  keyPressed(keyBuf) {
    if (input.isShuffleQueue(keyBuf)) {
      this.emit('shuffle')
    } else if (input.isClearQueue(keyBuf)) {
      this.emit('clear')
    } else {
      return super.keyPressed(keyBuf)
    }
  }
}

class QueueListingForm extends GrouplikeListingForm {
  updateSelectedElement() {
    if (this.inputs.length) {
      super.updateSelectedElement()
    } else {
      this.emit('select main listing')
    }
  }
}

class PlaybackInfoElement extends FocusElement {
  constructor(queuePlayer, app) {
    super()

    this.queuePlayer = queuePlayer
    this.app = app

    this.displayMode = 'expanded'
    this.timeData = {}

    this.queuePlayerIndex = 0
    this.queuePlayerSelected = false

    this.progressBarLabel = new Label('')
    this.addChild(this.progressBarLabel)

    this.progressTextLabel = new Label('')
    this.addChild(this.progressTextLabel)

    this.trackNameLabel = new Label('')
    this.addChild(this.trackNameLabel)

    this.downloadLabel = new Label('')
    this.addChild(this.downloadLabel)

    this.queuePlayerIndexLabel = new Label('')
    this.addChild(this.queuePlayerIndexLabel)

    this.updateTrack()
    this.updateProgress()
  }

  fixLayout() {
    this.refreshProgressText()
    if (this.displayMode === 'expanded') {
      this.fixLayoutExpanded()
    } else if (this.displayMode === 'collapsed') {
      this.fixLayoutCollapsed()
    }
  }

  fixLayoutExpanded() {
    if (this.parent) {
      this.fillParent()
    }

    this.queuePlayerIndexLabel.visible = false
    this.downloadLabel.visible = true

    this.trackNameLabel.y = 0
    this.progressBarLabel.y = 1
    this.progressTextLabel.y = this.progressBarLabel.y
    this.downloadLabel.y = 2

    if (this.currentTrack) {
      const dl = this.currentTrack.downloaderArg
      let dlText = dl.slice(Math.max(dl.length - this.w + 20, 0))
      if (dlText !== dl) {
        dlText = unic.ELLIPSIS + dlText
      }
      this.downloadLabel.text = `(From: ${dlText})`
    }

    for (const el of [
      this.progressTextLabel,
      this.trackNameLabel,
      this.downloadLabel
    ]) {
      el.x = Math.round((this.w - el.w) / 2)
    }
  }

  fixLayoutCollapsed() {
    if (this.parent) {
      this.w = Math.max(30, this.parent.contentW)
    }
    this.h = 1

    this.queuePlayerIndexLabel.visible = true
    this.downloadLabel.visible = false

    const why = this.app.willActOnQueuePlayer(this.queuePlayer)
    const index = this.app.backend.queuePlayers.indexOf(this.queuePlayer)
    const msg = (why ? '!' : ' ') + index

    this.queuePlayerIndexLabel.text = (this.app.SQP === this.queuePlayer
      ? `<${msg}>`
      : ` ${msg} `)

    if (why === 'marked') {
      this.queuePlayerIndexLabel.textAttributes = [ansi.A_BRIGHT]
    } else {
      this.queuePlayerIndexLabel.textAttributes = []
    }

    this.queuePlayerIndexLabel.x = 1
    this.queuePlayerIndexLabel.y = 0

    this.trackNameLabel.x = this.queuePlayerIndexLabel.right + 1
    this.trackNameLabel.y = 0

    this.progressBarLabel.y = 0
    this.progressBarLabel.x = 0

    this.progressTextLabel.x = this.contentW - this.progressTextLabel.w - 1
    this.progressTextLabel.y = 0

    this.refreshTrackText(this.progressTextLabel.x - 2 - this.trackNameLabel.x)
    this.refreshProgressText()
  }

  clicked(button) {
    if (button === 'scroll-up') {
      this.emit('seek back')
    } else if (button === 'scroll-down') {
      this.emit('seek ahead')
    } else if (button === 'left') {
      if (this.displayMode === 'expanded') {
        this.emit('toggle pause')
      } else if (this.isSelected) {
        this.showMenu()
      } else {
        this.root.select(this)
      }
    }
  }

  keyPressed(keyBuf) {
    if (input.isSelect(keyBuf)) {
      this.showMenu()
      return false
    }
  }

  showMenu() {
    const fn = this.showContextMenu || this.app.showContextMenu
    fn({
      x: this.absLeft,
      y: this.absTop + 1,
      items: [
        {
          label: 'Select',
          action: () => {
            this.app.selectQueuePlayer(this.queuePlayer)
            this.parent.fixLayout()
          }
        },
        {
          label: (this.app.willActOnQueuePlayer(this.queuePlayer) === 'marked'
            ? 'Remove from multiple-player selection'
            : 'Add to multiple-player selection'),
          action: () => {
            this.app.toggleActOnQueuePlayer(this.queuePlayer)
            this.parent.fixLayout()
          }
        },
        this.app.backend.queuePlayers.length > 1 && {
          label: 'Delete',
          action: () => {
            const { parent } = this
            this.app.removeQueuePlayer(this.queuePlayer)
            if (parent) {
              parent.removeInput(this)
              parent.fixLayout()
              // uhhh for some reason this selects the app instead of the form
              // for all the PIEs? not sure why but it probably has to do with
              // context menu shenanigans. it's currently 29:50 and i am really
              // definitely not going to try to figure that out right now!
              parent.root.select(parent)
            }
          }
        }
      ]
    })
  }

  refreshProgressText() {
    const { player, timeData } = this.queuePlayer
    if (!timeData) {
      return
    }

    const { timeDone, duration, lenSecTotal, curSecTotal } = timeData
    this.timeData = timeData
    this.curSecTotal = curSecTotal
    this.lenSecTotal = lenSecTotal
    this.volume = player.volume
    this.isLooping = player.isLooping
    this.isPaused = player.isPaused

    this.progressBarLabel.text = '-'.repeat(Math.floor(this.w / lenSecTotal * curSecTotal))
    this.progressTextLabel.text = timeDone + ' / ' + duration
    if (player.isLooping) {
      this.progressTextLabel.text += ' [Looping]'
    }
    if (player.volume !== 100) {
      this.progressTextLabel.text += ` [Volume: ${Math.round(player.volume)}%]`
    }
  }

  refreshTrackText(maxNameWidth = Infinity) {
    const { playingTrack } = this.queuePlayer
    if (playingTrack) {
      this.currentTrack = playingTrack
      const { name } = playingTrack
      if (ansi.measureColumns(name) > maxNameWidth) {
        this.trackNameLabel.text = ansi.trimToColumns(name, maxNameWidth) + unic.ELLIPSIS
      } else {
        this.trackNameLabel.text = playingTrack.name
      }
      this.progressBarLabel.text = ''
      this.progressTextLabel.text = '(Starting..)'
      this.timeData = {}
    } else {
      this.clearInfoText()
    }
  }

  clearInfoText() {
    this.currentTrack = null
    this.progressBarLabel.text = ''
    this.progressTextLabel.text = ''
    this.trackNameLabel.text = ''
    this.downloadLabel.text = ''
    this.timeData = {}
  }

  updateProgress() {
    this.refreshProgressText()
    this.fixLayout()
  }

  updateTrack() {
    this.refreshTrackText()
    this.fixLayout()
  }

  clearInfo() {
    this.clearInfoText()
    this.fixLayout()
  }

  drawTo(writable) {
    if (this.isSelected) {
      this.progressBarLabel.textAttributes = [ansi.A_INVERT]
    } else {
      this.progressBarLabel.textAttributes = []
    }

    if (this.isSelected) {
      writable.write(ansi.invert())
      writable.write(ansi.moveCursor(this.absTop, this.absLeft))
      writable.write(' '.repeat(this.w))
    }
  }

  get curSecTotal() { return this.getDep('curSecTotal') }
  set curSecTotal(v) { return this.setDep('curSecTotal', v) }
  get lenSecTotal() { return this.getDep('lenSecTotal') }
  set lenSecTotal(v) { return this.setDep('lenSecTotal', v) }
  get volume() { return this.getDep('volume') }
  set volume(v) { return this.setDep('volume', v) }
  get isLooping() { return this.getDep('isLooping') }
  set isLooping(v) { return this.setDep('isLooping', v) }
  get isPaused() { return this.getDep('isPaused') }
  set isPaused(v) { return this.setDep('isPaused', v) }
  get currentTrack() { return this.getDep('currentTrack') }
  set currentTrack(v) { return this.setDep('currentTrack', v) }
}

class OpenPlaylistDialog extends Dialog {
  constructor() {
    super()

    this.label = new Label('Enter a playlist source:')
    this.pane.addChild(this.label)

    this.form = new Form()
    this.pane.addChild(this.form)

    this.input = new TextInput()
    this.form.addInput(this.input)

    this.button = new Button('Open')
    this.form.addInput(this.button)

    this.buttonNewTab = new Button('..in New Tab')
    this.form.addInput(this.buttonNewTab)

    this.button.on('pressed', () => {
      if (this.input.value) {
        this.emit('source selected', this.input.value)
      }
    })

    this.buttonNewTab.on('pressed', () => {
      if (this.input.value) {
        this.emit('source selected (new tab)', this.input.value)
      }
    })
  }

  opened() {
    this.input.setValue('')
    this.form.curIndex = 0
    this.form.updateSelectedElement()
  }

  fixLayout() {
    super.fixLayout()

    this.pane.w = Math.min(60, this.contentW)
    this.pane.h = 6
    this.pane.centerInParent()

    this.label.centerInParent()
    this.label.y = 0

    this.form.w = this.pane.contentW
    this.form.h = 2
    this.form.y = 1

    this.input.w = this.form.contentW

    this.button.centerInParent()
    this.button.y = 1

    this.buttonNewTab.centerInParent()
    this.buttonNewTab.y = 2
  }

  selected() {
    this.root.select(this.form)
  }
}

class AlertDialog extends Dialog {
  constructor() {
    super()

    this.label = new Label()
    this.pane.addChild(this.label)

    this.button = new Button('Close')
    this.button.on('pressed', () => {
      if (this.canClose) {
        this.emit('cancelled')
      }
    })
    this.pane.addChild(this.button)
  }

  selected() {
    this.root.select(this.button)
  }

  showMessage(message, canClose = true) {
    this.canClose = canClose
    this.label.text = message
    this.button.text = canClose ? 'Close' : '(Hold on...)'
    this.open()
  }

  fixLayout() {
    super.fixLayout()

    this.pane.w = Math.min(this.label.w + 4, this.contentW)
    this.pane.h = 4
    this.pane.centerInParent()

    this.label.centerInParent()
    this.label.y = 0

    this.button.fixLayout()
    this.button.centerInParent()
    this.button.y = 1
  }

  keyPressed() {
    // Don't handle the escape key.
  }
}

class Tabber extends FocusElement {
  constructor() {
    super()

    this.tabberElements = []
    this.currentElementIndex = 0

    this.listElement = new TabberList(this)
    this.addChild(this.listElement)

    this.listElement.on('selected', item => this.selectTab(item))
    this.listElement.on('next tab', () => this.nextTab())
    this.listElement.on('previous tab', () => this.previousTab())
  }

  fixLayout() {
    const el = this.currentElement
    if (el) {
      // Only make space for the tab list if there's more than one tab visible.
      // (The tab list isn't shown if there's only one.)
      if (this.tabberElements.length > 1) {
        el.w = this.contentW
        el.h = this.contentH - 1
        el.x = 0
        el.y = 1
      } else {
        el.fillParent()
        el.x = 0
        el.y = 0
      }
      el.fixLayout()
    }

    if (this.tabberElements.length > 1) {
      this.listElement.visible = true
      this.listElement.w = this.contentW
      this.listElement.h = 1
      this.listElement.fixLayout()
    } else {
      this.listElement.visible = false
    }
  }

  addTab(element, index = this.currentElementIndex) {
    element.visible = false
    this.tabberElements.splice(index + 1, 0, element)
    this.addChild(element, index + 1)
    this.listElement.buildItems()
  }

  nextTab() {
    this.currentElementIndex++
    if (this.currentElementIndex >= this.tabberElements.length) {
      this.currentElementIndex = 0
    }
    this.updateVisibleElement()
  }

  previousTab() {
    this.currentElementIndex--
    if (this.currentElementIndex < 0) {
      this.currentElementIndex = this.tabberElements.length - 1
    }
    this.updateVisibleElement()
  }

  selectTab(element) {
    if (!this.tabberElements.includes(element)) {
      throw new Error('That tab does not exist! (Perhaps it was removed, somehow, or was never added?)')
    }

    this.currentElementIndex = this.tabberElements.indexOf(element)
    this.updateVisibleElement()
  }

  closeTab(element) {
    if (!this.tabberElements.includes(element)) {
      return
    }

    const index = this.tabberElements.indexOf(element)
    this.tabberElements.splice(index, 1)
    if (index <= this.currentElementIndex) {
      this.currentElementIndex--
    }

    // Deliberately update the visible element before removing the child. If we
    // remove the child first, the isSelected in updateVisibleElement will be
    // false, so the new currentElement won't actually be root.select()'ed.
    this.updateVisibleElement()
    this.removeChild(element)
    this.listElement.buildItems()
  }

  updateVisibleElement() {
    const len = this.tabberElements.length - 1
    this.currentElementIndex = Math.min(len, Math.max(0, this.currentElementIndex))

    this.tabberElements.forEach((el, i) => {
      el.visible = (i === this.currentElementIndex)
    })

    if (this.isSelected) {
      if (this.currentElement) {
        this.root.select(this.currentElement)
      } else {
        this.root.select(this)
      }
    }

    this.fixLayout()
  }

  selected() {
    if (this.currentElement) {
      this.root.select(this.currentElement)
    }
  }

  get selectable() {
    return this.currentElement && this.currentElement.selectable
  }

  get currentElement() {
    return this.tabberElements[this.currentElementIndex] || null
  }
}

class TabberList extends ListScrollForm {
  constructor(tabber) {
    super('horizontal')
    this.tabber = tabber
    this.captureTab = false
  }

  buildItems() {
    while (this.inputs.length) {
      this.removeInput(this.inputs[0])
    }

    for (const item of this.tabber.tabberElements) {
      const element = new TabberListItem(item, this.tabber)
      this.addInput(element)
      element.fixLayout()
      element.on('selected', () => this.emit('selected', item))
    }

    this.scrollToEnd()
    this.fixLayout()
  }

  fixLayout() {
    this.w = this.parent.contentW
    this.h = 1
    this.x = 0
    this.y = 0
    this.scrollElementIntoEndOfView(this.inputs[this.curIndex])
    super.fixLayout()
  }

  drawTo() {
    let changed = false
    for (const input of this.inputs) {
      input.fixLayout()
      if (input._oldW !== input.w) {
        input._oldW = input.w
        changed = true
      }
    }
    if (changed) {
      this.fixLayout()
    }
  }

  clicked(button) {
    if (button === 'scroll-up') {
      this.emit('previous tab')
      return false
    } else if (button === 'scroll-down') {
      this.emit('next tab')
      return false
    }
  }

  // TODO: Be less hacky about these! Right now the tabber list is totally not
  // interactive.
  get curIndex() { return this.tabber.currentElementIndex }
  set curIndex(newVal) {}
}

class TabberListItem extends FocusElement {
  constructor(tab, tabber) {
    super()

    this.tab = tab
    this.tabber = tabber
  }

  fixLayout() {
    this.w = ansi.measureColumns(this.text) + 3
    this.h = 1
  }

  drawTo(writable) {
    if (this.tabber.currentElement === this.tab) {
      writable.write(ansi.setAttributes([ansi.A_BRIGHT]))
      writable.write(ansi.moveCursor(this.absTop, this.absLeft))
      writable.write('<' + this.text + '>')
      writable.write(ansi.resetAttributes())
    } else {
      writable.write(ansi.moveCursor(this.absTop, this.absLeft + 1))
      writable.write(this.text)
    }
  }

  clicked(button) {
    if (button === 'left') {
      this.emit('selected')
      return false
    }
  }

  get text() {
    return this.tab.tabberLabel || 'a(n) ' + this.tab.constructor.name
  }
}

class ContextMenu extends FocusElement {
  constructor(showContextMenu) {
    super()

    this.pane = new Pane()
    this.addChild(this.pane)

    this.form = new ListScrollForm()
    this.pane.addChild(this.form)

    this.keyboardSelector = new KeyboardSelector(this.form)

    this.visible = false

    this.showContextMenu = showContextMenu
    this.showSubmenu = this.showSubmenu.bind(this)
    this.submenu = null
  }

  show({x = 0, y = 0, items}) {
    items = items.filter(Boolean)
    if (!items.length) {
      return
    }

    if (!this.root.selectedElement.directAncestors.includes(this)) {
      this.selectedBefore = this.root.selectedElement
    }

    this.clearItems()

    this.x = x
    this.y = y
    this.visible = true

    // This code is so that we don't show two dividers beside each other, or
    // end a menu with a divider!
    let wantDivider = false
    const addDividerIfWanted = () => {
      if (wantDivider) {
        const element = new HorizontalRule()
        this.form.addInput(element)
        wantDivider = false
      }
    }

    for (const item of items.filter(Boolean)) {
      if (item.element) {
        addDividerIfWanted()
        this.form.addInput(item.element)
        item.element.showContextMenu = this.showSubmenu
        if (item.isDefault) {
          this.root.select(item.element)
        }
      } else if (item.divider) {
        wantDivider = true
      } else {
        addDividerIfWanted()
        const button = new Button(item.label)
        button.keyboardIdentifier = item.keyboardIdentifier || item.label
        if (item.action) {
          button.on('pressed', () => {
            this.close()
            item.action()
          })
        }
        this.form.addInput(button)
        if (item.isDefault) {
          this.root.select(button)
        }
      }
    }

    this.fixLayout()

    if (!items.some(item => item.isDefault)) {
      this.form.firstInput()
    }

    this.keyboardSelector.reset()
  }

  showSubmenu(opts) {
    this.showContextMenu(Object.assign({}, opts, {
      // We need to get a reference to the submenu before it is shown, or else
      // the parent menu will be closed (from being unselected and not knowing
      // that a submenu was just opened).
      beforeShowing: menu => {
        this.submenu = menu
      }
    }))

    this.submenu.on('close', () => {
      this.submenu = null
    })
  }

  keyPressed(keyBuf) {
    if (telc.isEscape(keyBuf) || telc.isBackspace(keyBuf)) {
      this.close()
      return false
    } else if (this.keyboardSelector.keyPressed(keyBuf)) {
      return false
    } else if (input.isScrollToStart(keyBuf)) {
      this.form.firstInput()
      this.form.scrollToBeginning()
    } else if (input.isScrollToEnd(keyBuf)) {
      this.form.lastInput()
    } else {
      return super.keyPressed(keyBuf)
    }
  }

  unselected() {
    // Don't close if we just opened a submenu!
    const newEl = this.root.selectedElement
    if (this.submenu && newEl.directAncestors.includes(this.submenu)) {
      return
    }

    if (this.visible) {
      const newlySelected = this.root.selectedElement
      this.close()
      this.selectedBefore.root.select(newlySelected)
    }
  }

  close() {
    this.clearItems()
    this.visible = false
    this.selectedBefore.root.select(this.selectedBefore)
    this.parent.removeChild(this)
    this.emit('closed')
  }

  clearItems() {
    // Abhorrent hack - just erases children from memory. Leaves children
    // thinking they've still got a parent, though. (Necessary to avoid crazy
    // select() loops that probably explode the world... speaking of things
    // to forget, that one time when I was figuring out menus in the queue.
    // This makes them work.)
    this.form.children = this.form.children.filter(
      child => !this.form.inputs.includes(child))
    this.form.inputs = []
  }

  fixLayout() {
    // Do an initial pass to determine the width of this menu (or in particular
    // the form), which is the greatest width of all the inputs.
    let width = 10

    // Some elements resize to fill their parent (the menu)'s width. Since we
    // want to know what their *minimum* width is, we'll immediately change the
    // parent width that they see.
    this.form.w = width

    for (const input of this.form.inputs) {
      input.fixLayout()
      width = Math.max(width, input.w)
    }

    let height = Math.min(14, this.form.inputs.length)

    width += 2 // Space for the pane border
    height += 2 // Space for the pane border
    if (this.form.scrollBarShown) width++
    this.w = width
    this.h = height

    this.fitToParent()

    this.pane.fillParent()
    this.form.fillParent()
    this.form.fixLayout()

    // After everything else, do a second pass to apply the decided width
    // to every element, so that they expand to all be the same width.
    // In order to change the width of a button (which is what these elements
    // are), we need to append space characters.
    for (const input of this.form.inputs) {
      input.fixLayout()
      if (input.text) {
        const inputWidth = ansi.measureColumns(input.text)
        if (inputWidth < this.form.contentW) {
          input.text += ' '.repeat(this.form.contentW - inputWidth)
        }
      }
    }
  }

  selected() {
    this.root.select(this.form)
  }
}

class HorizontalRule extends FocusElement {
  // It's just a horizontal rule. Y'know..
  // --------------------------------------------------------------------------
  // You get the idea. :)

  get selectable() {
    // Just return false. A HorizontalRule is technically a FocusElement,
    // but that's just so that it can be used in place of other inputs
    // (e.g. in a ContextMenu).
    return false
  }

  fixLayout() {
    this.w = this.parent.contentW
    this.h = 1
  }

  drawTo(writable) {
    // For the character we draw with, we use an ordinary dash instead of
    // an actual box-drawing horizontal line. That's so that the rule is
    // distinguishable from the edge of a Pane.
    writable.write(ansi.moveCursor(this.absTop, this.absLeft))
    writable.write('-'.repeat(this.w))
  }
}

class KeyboardSelector {
  // Class used to select things when you type out their name. Specify strings
  // used to access each element of a form in the keyboardIdentifier property.
  // (Elements without a keyboardIdentifier, or which are !selectable, will be
  // skipped.)

  constructor(form) {
    this.value = ''
    this.form = form
  }

  reset() {
    this.value = ''
  }

  keyPressed(keyBuf) {
    // Don't do anything if the input isn't a single keyboard character.
    if (keyBuf.length !== 1 || keyBuf[0] <= 31 || keyBuf[0] >= 127) {
      return
    }

    // First see if a result is found when we append the typed character to our
    // recorded input.
    const char = keyBuf.toString()
    this.value += char
    if (!KeyboardSelector.find(this.value, this.form)) {
      // If we don't find a result, replace our recorded input with the single
      // character entered, then do a search. Start from the input after the
      // current-selected one, so that we don't just end up re-selecting the
      // element that was selected before, if there's another option that would
      // match this key ahead. (This is so that you can easily type a string or
      // character over and over to navigate through options that all start
      // with the same string/character.)
      this.value = char
      return KeyboardSelector.find(this.value, this.form, this.form.curIndex + 1)
    }
    return true
  }

  static find(text, form, fromIndex = form.curIndex) {
    // Most of this code is just stolen from AppElement's code for handling
    // input from JumpElement!

    const lower = text.toLowerCase()
    const getName = inp => inp.keyboardIdentifier ? inp.keyboardIdentifier.toLowerCase().trim() : ''

    const testStartsWith = inp => getName(inp).startsWith(lower)

    const searchPastCurrentIndex = test => {
      const start = fromIndex
      const match = form.inputs.slice(start).findIndex(test)
      if (match === -1) {
        return -1
      } else {
        return start + match
      }
    }

    const allIndexes = [
      searchPastCurrentIndex(testStartsWith),
      form.inputs.findIndex(testStartsWith),
    ]

    const matchedIndex = allIndexes.find(value => value >= 0)

    if (typeof matchedIndex !== 'undefined') {
      form.selectInput(form.inputs[matchedIndex])
      return true
    } else {
      return false
    }
  }
}

class Menubar extends ListScrollForm {
  constructor(showContextMenu) {
    super('horizontal')

    this.showContextMenu = showContextMenu
    this.contextMenu = null
    this.color = 4 // blue
    this.attribute = 2 // dim

    this.keyboardSelector = new KeyboardSelector(this)
  }

  select() {
    // When the menubar is selected from the menubar's context menu, the UI
    // looks like it's "popping" a state, so don't reset the selected index to
    // the start - something we only do when we "newly" select the menubar.
    if (this.contextMenu && this.contextMenu.isSelected) {
      this.root.select(this)
    } else {
      this.selectedBefore = this.root.selectedElement
      this.firstInput()
    }

    this.keyboardSelector.reset()
  }

  keyPressed(keyBuf) {
    super.keyPressed(keyBuf)

    // Don't pause the music from the menubar!
    if (telc.isSpace(keyBuf)) {
      return false
    }

    if (this.keyboardSelector.keyPressed(keyBuf)) {
      return false
    } else if (telc.isCaselessLetter(keyBuf, 'c')) {
      // For fun :)
      this.color = (this.color % 8) + 1
      return false
    } else if (telc.isCaselessLetter(keyBuf, 'a')) {
      this.attribute = (this.attribute % 3) + 1
      return false
    }
  }

  restoreSelection() {
    if (this.selectedBefore) {
      this.root.select(this.selectedBefore)
      this.selectedBefore = null
    }
  }

  buildItems(array) {
    for (const {text, menuItems, menuFn} of array) {
      const button = new Button(` ${text} `)

      const container = new FocusElement()
      container.addChild(button)
      button.x = 1
      container.w = button.w + 2
      container.h = 1
      container.selected = () => this.root.select(button)
      container.keyboardIdentifier = text

      button.on('pressed', () => {
        this.contextMenu = this.showContextMenu({
          x: container.absLeft, y: container.absY + 1,
          items: menuFn ? menuFn() : menuItems
        })
        this.contextMenu.on('closed', () => {
          this.contextMenu = null
        })
      })

      this.addInput(container)
    }
  }

  fixLayout() {
    this.x = 0
    this.y = 0
    this.w = this.parent.contentW
    this.h = 1
    super.fixLayout()
  }

  drawTo(writable) {
    writable.write(ansi.moveCursor(this.absTop, this.absLeft))
    writable.write(ansi.setAttributes([this.attribute, 30 + this.color, ansi.A_INVERT, ansi.C_WHITE + 10]))
    writable.write(' '.repeat(this.w))
    writable.write(ansi.resetAttributes())
  }

  get color() { return this.getDep('color') }
  set color(v) { return this.setDep('color', v) }
  get attribute() { return this.getDep('attribute') }
  set attribute(v) { return this.setDep('attribute', v) }
}

class PartyBanner extends DisplayElement {
  constructor(direction) {
    super()

    this.direction = direction
  }

  drawTo(writable) {
    writable.write(ansi.moveCursor(this.absTop, this.absLeft))

    // TODO: Figure out how to connect this to the draw dependency system.
    // Currently the party banner doesn't schedule any renders itself (meaning
    // if you have nothing playing or otherwise rendering, it'll just stay
    // still).
    const timerNum = Date.now() / 2000 * this.direction
    let lastAttribute = ''
    const updateAttribute = offsetNum => {
      const attr = (Math.cos(offsetNum - timerNum) < 0 ? '\x1b[0;1m' : '\x1b[0;2m')
      if (attr === lastAttribute) {
        return ''
      } else {
        lastAttribute = attr
        return attr
      }
    }
    let str = new Array(this.w).fill('0').map((_, i) => {
      const offsetNum = i / this.w * 2 * Math.PI
      return (
        updateAttribute(offsetNum) +
        (Math.sin(offsetNum + timerNum) < 0 ? '-' : '*')
      )
    }).join('')

    writable.write(str)
    writable.write(ansi.resetAttributes())
  }
}

class NotesTextEditor extends TuiTextEditor {
  constructor() {
    super()

    this.openedItem = null
  }

  keyPressed(keyBuf) {
    if (input.isDeselectTextEditor(keyBuf)) {
      this.emit('deselect')
      return false
    } else if (input.isSaveTextEditor(keyBuf)) {
      this.saveManually()
      return false
    } else {
      return super.keyPressed(keyBuf)
    }
  }

  async openItem(item, {doubleCheckItem}) {
    if (this.hasBeenEdited) {
      // Save in the background.
      this.save()
    }

    const textFile = getCorrespondingFileForItem(item, '.txt')
    if (!textFile) {
      this.openedItem = null
      return false
    }

    if (textFile === this.openedItem) {
      // This file is already open - don't do anything.
      return null
    }

    let filePath
    try {
      filePath = url.fileURLToPath(new URL(textFile.url))
    } catch (error) {
      this.openedItem = null
      return false
    }

    let buffer
    try {
      buffer = await readFile(filePath)
    } catch (error) {
      this.openedItem = null
      return false
    }

    if (!doubleCheckItem(item)) {
      return null
    }

    this.openedItem = textFile
    this.openedPath = filePath
    this.clearSourceAndLoadText(buffer.toString())
    return true
  }

  async saveManually() {
    if (!this.openedItem || !this.openedPath) {
      return
    }

    const item = this.openedItem

    if (await this.save()) {
      if (item === this.openedItem) {
        this.showStatusMessage('Saved manually.')
      }
    }
  }

  async save() {
    if (!this.openedItem || !this.openedPath) {
      return
    }

    const text = this.getSourceText()
    try {
      await writeFile(this.openedPath, text)
      this.clearEditStatus()
      return true
    } catch (error) {
      this.showStatusMessage(`Failed to save (${path.basename(this.openedPath)}: ${error.code}).`)
      return false
    }
  }
}

module.exports = AppElement