selection.js

const {Point, Range} = require('text-buffer')
const {pick} = require('underscore-plus')
const {Emitter} = require('event-kit')

const NonWhitespaceRegExp = /\S/
let nextId = 0

// Extended: Represents a selection in the {TextEditor}.
module.exports =
class Selection {
  constructor ({cursor, marker, editor, id}) {
    this.id = (id != null) ? id : nextId++
    this.cursor = cursor
    this.marker = marker
    this.editor = editor
    this.emitter = new Emitter()
    this.initialScreenRange = null
    this.wordwise = false
    this.cursor.selection = this
    this.decoration = this.editor.decorateMarker(this.marker, {type: 'highlight', class: 'selection'})
    this.marker.onDidChange(e => this.markerDidChange(e))
    this.marker.onDidDestroy(() => this.markerDidDestroy())
  }

  destroy () {
    this.marker.destroy()
  }

  isLastSelection () {
    return this === this.editor.getLastSelection()
  }

  /*
  Section: Event Subscription
  */

  // Extended: Calls your `callback` when the selection was moved.
  //
  // * `callback` {Function}
  //   * `event` {Object}
  //     * `oldBufferRange` {Range}
  //     * `oldScreenRange` {Range}
  //     * `newBufferRange` {Range}
  //     * `newScreenRange` {Range}
  //     * `selection` {Selection} that triggered the event
  //
  // Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
  onDidChangeRange (callback) {
    return this.emitter.on('did-change-range', callback)
  }

  // Extended: Calls your `callback` when the selection was destroyed
  //
  // * `callback` {Function}
  //
  // Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
  onDidDestroy (callback) {
    return this.emitter.once('did-destroy', callback)
  }

  /*
  Section: Managing the selection range
  */

  // Public: Returns the screen {Range} for the selection.
  getScreenRange () {
    return this.marker.getScreenRange()
  }

  // Public: Modifies the screen range for the selection.
  //
  // * `screenRange` The new {Range} to use.
  // * `options` (optional) {Object} options matching those found in {::setBufferRange}.
  setScreenRange (screenRange, options) {
    return this.setBufferRange(this.editor.bufferRangeForScreenRange(screenRange), options)
  }

  // Public: Returns the buffer {Range} for the selection.
  getBufferRange () {
    return this.marker.getBufferRange()
  }

  // Public: Modifies the buffer {Range} for the selection.
  //
  // * `bufferRange` The new {Range} to select.
  // * `options` (optional) {Object} with the keys:
  //   * `preserveFolds` if `true`, the fold settings are preserved after the
  //     selection moves.
  //   * `autoscroll` {Boolean} indicating whether to autoscroll to the new
  //     range. Defaults to `true` if this is the most recently added selection,
  //     `false` otherwise.
  setBufferRange (bufferRange, options = {}) {
    bufferRange = Range.fromObject(bufferRange)
    if (options.reversed == null) options.reversed = this.isReversed()
    if (!options.preserveFolds) this.editor.destroyFoldsContainingBufferPositions([bufferRange.start, bufferRange.end], true)
    this.modifySelection(() => {
      const needsFlash = options.flash
      options.flash = null
      this.marker.setBufferRange(bufferRange, options)
      const autoscroll = options.autoscroll != null ? options.autoscroll : this.isLastSelection()
      if (autoscroll) this.autoscroll()
      if (needsFlash) this.decoration.flash('flash', this.editor.selectionFlashDuration)
    })
  }

  // Public: Returns the starting and ending buffer rows the selection is
  // highlighting.
  //
  // Returns an {Array} of two {Number}s: the starting row, and the ending row.
  getBufferRowRange () {
    const range = this.getBufferRange()
    const start = range.start.row
    let end = range.end.row
    if (range.end.column === 0) end = Math.max(start, end - 1)
    return [start, end]
  }

  getTailScreenPosition () {
    return this.marker.getTailScreenPosition()
  }

  getTailBufferPosition () {
    return this.marker.getTailBufferPosition()
  }

  getHeadScreenPosition () {
    return this.marker.getHeadScreenPosition()
  }

  getHeadBufferPosition () {
    return this.marker.getHeadBufferPosition()
  }

  /*
  Section: Info about the selection
  */

  // Public: Determines if the selection contains anything.
  isEmpty () {
    return this.getBufferRange().isEmpty()
  }

  // Public: Determines if the ending position of a marker is greater than the
  // starting position.
  //
  // This can happen when, for example, you highlight text "up" in a {TextBuffer}.
  isReversed () {
    return this.marker.isReversed()
  }

  // Public: Returns whether the selection is a single line or not.
  isSingleScreenLine () {
    return this.getScreenRange().isSingleLine()
  }

  // Public: Returns the text in the selection.
  getText () {
    return this.editor.buffer.getTextInRange(this.getBufferRange())
  }

  // Public: Identifies if a selection intersects with a given buffer range.
  //
  // * `bufferRange` A {Range} to check against.
  //
  // Returns a {Boolean}
  intersectsBufferRange (bufferRange) {
    return this.getBufferRange().intersectsWith(bufferRange)
  }

  intersectsScreenRowRange (startRow, endRow) {
    return this.getScreenRange().intersectsRowRange(startRow, endRow)
  }

  intersectsScreenRow (screenRow) {
    return this.getScreenRange().intersectsRow(screenRow)
  }

  // Public: Identifies if a selection intersects with another selection.
  //
  // * `otherSelection` A {Selection} to check against.
  //
  // Returns a {Boolean}
  intersectsWith (otherSelection, exclusive) {
    return this.getBufferRange().intersectsWith(otherSelection.getBufferRange(), exclusive)
  }

  /*
  Section: Modifying the selected range
  */

  // Public: Clears the selection, moving the marker to the head.
  //
  // * `options` (optional) {Object} with the following keys:
  //   * `autoscroll` {Boolean} indicating whether to autoscroll to the new
  //     range. Defaults to `true` if this is the most recently added selection,
  //     `false` otherwise.
  clear (options) {
    this.goalScreenRange = null
    if (!this.retainSelection) this.marker.clearTail()
    const autoscroll = options && options.autoscroll != null
      ? options.autoscroll
      : this.isLastSelection()
    if (autoscroll) this.autoscroll()
    this.finalize()
  }

  // Public: Selects the text from the current cursor position to a given screen
  // position.
  //
  // * `position` An instance of {Point}, with a given `row` and `column`.
  selectToScreenPosition (position, options) {
    position = Point.fromObject(position)

    this.modifySelection(() => {
      if (this.initialScreenRange) {
        if (position.isLessThan(this.initialScreenRange.start)) {
          this.marker.setScreenRange([position, this.initialScreenRange.end], {reversed: true})
        } else {
          this.marker.setScreenRange([this.initialScreenRange.start, position], {reversed: false})
        }
      } else {
        this.cursor.setScreenPosition(position, options)
      }

      if (this.linewise) {
        this.expandOverLine(options)
      } else if (this.wordwise) {
        this.expandOverWord(options)
      }
    })
  }

  // Public: Selects the text from the current cursor position to a given buffer
  // position.
  //
  // * `position` An instance of {Point}, with a given `row` and `column`.
  selectToBufferPosition (position) {
    this.modifySelection(() => this.cursor.setBufferPosition(position))
  }

  // Public: Selects the text one position right of the cursor.
  //
  // * `columnCount` (optional) {Number} number of columns to select (default: 1)
  selectRight (columnCount) {
    this.modifySelection(() => this.cursor.moveRight(columnCount))
  }

  // Public: Selects the text one position left of the cursor.
  //
  // * `columnCount` (optional) {Number} number of columns to select (default: 1)
  selectLeft (columnCount) {
    this.modifySelection(() => this.cursor.moveLeft(columnCount))
  }

  // Public: Selects all the text one position above the cursor.
  //
  // * `rowCount` (optional) {Number} number of rows to select (default: 1)
  selectUp (rowCount) {
    this.modifySelection(() => this.cursor.moveUp(rowCount))
  }

  // Public: Selects all the text one position below the cursor.
  //
  // * `rowCount` (optional) {Number} number of rows to select (default: 1)
  selectDown (rowCount) {
    this.modifySelection(() => this.cursor.moveDown(rowCount))
  }

  // Public: Selects all the text from the current cursor position to the top of
  // the buffer.
  selectToTop () {
    this.modifySelection(() => this.cursor.moveToTop())
  }

  // Public: Selects all the text from the current cursor position to the bottom
  // of the buffer.
  selectToBottom () {
    this.modifySelection(() => this.cursor.moveToBottom())
  }

  // Public: Selects all the text in the buffer.
  selectAll () {
    this.setBufferRange(this.editor.buffer.getRange(), {autoscroll: false})
  }

  // Public: Selects all the text from the current cursor position to the
  // beginning of the line.
  selectToBeginningOfLine () {
    this.modifySelection(() => this.cursor.moveToBeginningOfLine())
  }

  // Public: Selects all the text from the current cursor position to the first
  // character of the line.
  selectToFirstCharacterOfLine () {
    this.modifySelection(() => this.cursor.moveToFirstCharacterOfLine())
  }

  // Public: Selects all the text from the current cursor position to the end of
  // the screen line.
  selectToEndOfLine () {
    this.modifySelection(() => this.cursor.moveToEndOfScreenLine())
  }

  // Public: Selects all the text from the current cursor position to the end of
  // the buffer line.
  selectToEndOfBufferLine () {
    this.modifySelection(() => this.cursor.moveToEndOfLine())
  }

  // Public: Selects all the text from the current cursor position to the
  // beginning of the word.
  selectToBeginningOfWord () {
    this.modifySelection(() => this.cursor.moveToBeginningOfWord())
  }

  // Public: Selects all the text from the current cursor position to the end of
  // the word.
  selectToEndOfWord () {
    this.modifySelection(() => this.cursor.moveToEndOfWord())
  }

  // Public: Selects all the text from the current cursor position to the
  // beginning of the next word.
  selectToBeginningOfNextWord () {
    this.modifySelection(() => this.cursor.moveToBeginningOfNextWord())
  }

  // Public: Selects text to the previous word boundary.
  selectToPreviousWordBoundary () {
    this.modifySelection(() => this.cursor.moveToPreviousWordBoundary())
  }

  // Public: Selects text to the next word boundary.
  selectToNextWordBoundary () {
    this.modifySelection(() => this.cursor.moveToNextWordBoundary())
  }

  // Public: Selects text to the previous subword boundary.
  selectToPreviousSubwordBoundary () {
    this.modifySelection(() => this.cursor.moveToPreviousSubwordBoundary())
  }

  // Public: Selects text to the next subword boundary.
  selectToNextSubwordBoundary () {
    this.modifySelection(() => this.cursor.moveToNextSubwordBoundary())
  }

  // Public: Selects all the text from the current cursor position to the
  // beginning of the next paragraph.
  selectToBeginningOfNextParagraph () {
    this.modifySelection(() => this.cursor.moveToBeginningOfNextParagraph())
  }

  // Public: Selects all the text from the current cursor position to the
  // beginning of the previous paragraph.
  selectToBeginningOfPreviousParagraph () {
    this.modifySelection(() => this.cursor.moveToBeginningOfPreviousParagraph())
  }

  // Public: Modifies the selection to encompass the current word.
  //
  // Returns a {Range}.
  selectWord (options = {}) {
    if (this.cursor.isSurroundedByWhitespace()) options.wordRegex = /[\t ]*/
    if (this.cursor.isBetweenWordAndNonWord()) {
      options.includeNonWordCharacters = false
    }

    this.setBufferRange(this.cursor.getCurrentWordBufferRange(options), options)
    this.wordwise = true
    this.initialScreenRange = this.getScreenRange()
  }

  // Public: Expands the newest selection to include the entire word on which
  // the cursors rests.
  expandOverWord (options) {
    this.setBufferRange(this.getBufferRange().union(this.cursor.getCurrentWordBufferRange()), {autoscroll: false})
    const autoscroll = options && options.autoscroll != null ? options.autoscroll : this.isLastSelection()
    if (autoscroll) this.cursor.autoscroll()
  }

  // Public: Selects an entire line in the buffer.
  //
  // * `row` The line {Number} to select (default: the row of the cursor).
  selectLine (row, options) {
    if (row != null) {
      this.setBufferRange(this.editor.bufferRangeForBufferRow(row, {includeNewline: true}), options)
    } else {
      const startRange = this.editor.bufferRangeForBufferRow(this.marker.getStartBufferPosition().row)
      const endRange = this.editor.bufferRangeForBufferRow(this.marker.getEndBufferPosition().row, {includeNewline: true})
      this.setBufferRange(startRange.union(endRange), options)
    }

    this.linewise = true
    this.wordwise = false
    this.initialScreenRange = this.getScreenRange()
  }

  // Public: Expands the newest selection to include the entire line on which
  // the cursor currently rests.
  //
  // It also includes the newline character.
  expandOverLine (options) {
    const range = this.getBufferRange().union(this.cursor.getCurrentLineBufferRange({includeNewline: true}))
    this.setBufferRange(range, {autoscroll: false})
    const autoscroll = options && options.autoscroll != null ? options.autoscroll : this.isLastSelection()
    if (autoscroll) this.cursor.autoscroll()
  }

  /*
  Section: Modifying the selected text
  */

  // Public: Replaces text at the current selection.
  //
  // * `text` A {String} representing the text to add
  // * `options` (optional) {Object} with keys:
  //   * `select` If `true`, selects the newly added text.
  //   * `autoIndent` If `true`, indents all inserted text appropriately.
  //   * `autoIndentNewline` If `true`, indent newline appropriately.
  //   * `autoDecreaseIndent` If `true`, decreases indent level appropriately
  //     (for example, when a closing bracket is inserted).
  //   * `preserveTrailingLineIndentation` By default, when pasting multiple
  //   lines, Atom attempts to preserve the relative indent level between the
  //   first line and trailing lines, even if the indent level of the first
  //   line has changed from the copied text. If this option is `true`, this
  //   behavior is suppressed.
  //     level between the first lines and the trailing lines.
  //   * `normalizeLineEndings` (optional) {Boolean} (default: true)
  //   * `undo` If `skip`, skips the undo stack for this operation.
  insertText (text, options = {}) {
    let desiredIndentLevel, indentAdjustment
    const oldBufferRange = this.getBufferRange()
    const wasReversed = this.isReversed()
    this.clear(options)

    let autoIndentFirstLine = false
    const precedingText = this.editor.getTextInRange([[oldBufferRange.start.row, 0], oldBufferRange.start])
    const remainingLines = text.split('\n')
    const firstInsertedLine = remainingLines.shift()

    if (options.indentBasis != null && !options.preserveTrailingLineIndentation) {
      indentAdjustment = this.editor.indentLevelForLine(precedingText) - options.indentBasis
      this.adjustIndent(remainingLines, indentAdjustment)
    }

    const textIsAutoIndentable = (text === '\n') || (text === '\r\n') || NonWhitespaceRegExp.test(text)
    if (options.autoIndent && textIsAutoIndentable && !NonWhitespaceRegExp.test(precedingText) && (remainingLines.length > 0)) {
      autoIndentFirstLine = true
      const firstLine = precedingText + firstInsertedLine
      const languageMode = this.editor.buffer.getLanguageMode()
      desiredIndentLevel = (
        languageMode.suggestedIndentForLineAtBufferRow &&
        languageMode.suggestedIndentForLineAtBufferRow(
          oldBufferRange.start.row,
          firstLine,
          this.editor.getTabLength()
        )
      )
      if (desiredIndentLevel != null) {
        indentAdjustment = desiredIndentLevel - this.editor.indentLevelForLine(firstLine)
        this.adjustIndent(remainingLines, indentAdjustment)
      }
    }

    text = firstInsertedLine
    if (remainingLines.length > 0) text += `\n${remainingLines.join('\n')}`

    const newBufferRange = this.editor.buffer.setTextInRange(oldBufferRange, text, pick(options, 'undo', 'normalizeLineEndings'))

    if (options.select) {
      this.setBufferRange(newBufferRange, {reversed: wasReversed})
    } else {
      if (wasReversed) this.cursor.setBufferPosition(newBufferRange.end)
    }

    if (autoIndentFirstLine) {
      this.editor.setIndentationForBufferRow(oldBufferRange.start.row, desiredIndentLevel)
    }

    if (options.autoIndentNewline && (text === '\n')) {
      this.editor.autoIndentBufferRow(newBufferRange.end.row, {preserveLeadingWhitespace: true, skipBlankLines: false})
    } else if (options.autoDecreaseIndent && NonWhitespaceRegExp.test(text)) {
      this.editor.autoDecreaseIndentForBufferRow(newBufferRange.start.row)
    }

    const autoscroll = options.autoscroll != null ? options.autoscroll : this.isLastSelection()
    if (autoscroll) this.autoscroll()

    return newBufferRange
  }

  // Public: Removes the first character before the selection if the selection
  // is empty otherwise it deletes the selection.
  backspace () {
    if (this.isEmpty()) this.selectLeft()
    this.deleteSelectedText()
  }

  // Public: Removes the selection or, if nothing is selected, then all
  // characters from the start of the selection back to the previous word
  // boundary.
  deleteToPreviousWordBoundary () {
    if (this.isEmpty()) this.selectToPreviousWordBoundary()
    this.deleteSelectedText()
  }

  // Public: Removes the selection or, if nothing is selected, then all
  // characters from the start of the selection up to the next word
  // boundary.
  deleteToNextWordBoundary () {
    if (this.isEmpty()) this.selectToNextWordBoundary()
    this.deleteSelectedText()
  }

  // Public: Removes from the start of the selection to the beginning of the
  // current word if the selection is empty otherwise it deletes the selection.
  deleteToBeginningOfWord () {
    if (this.isEmpty()) this.selectToBeginningOfWord()
    this.deleteSelectedText()
  }

  // Public: Removes from the beginning of the line which the selection begins on
  // all the way through to the end of the selection.
  deleteToBeginningOfLine () {
    if (this.isEmpty() && this.cursor.isAtBeginningOfLine()) {
      this.selectLeft()
    } else {
      this.selectToBeginningOfLine()
    }
    this.deleteSelectedText()
  }

  // Public: Removes the selection or the next character after the start of the
  // selection if the selection is empty.
  delete () {
    if (this.isEmpty()) this.selectRight()
    this.deleteSelectedText()
  }

  // Public: If the selection is empty, removes all text from the cursor to the
  // end of the line. If the cursor is already at the end of the line, it
  // removes the following newline. If the selection isn't empty, only deletes
  // the contents of the selection.
  deleteToEndOfLine () {
    if (this.isEmpty()) {
      if (this.cursor.isAtEndOfLine()) {
        this.delete()
        return
      }
      this.selectToEndOfLine()
    }
    this.deleteSelectedText()
  }

  // Public: Removes the selection or all characters from the start of the
  // selection to the end of the current word if nothing is selected.
  deleteToEndOfWord () {
    if (this.isEmpty()) this.selectToEndOfWord()
    this.deleteSelectedText()
  }

  // Public: Removes the selection or all characters from the start of the
  // selection to the end of the current word if nothing is selected.
  deleteToBeginningOfSubword () {
    if (this.isEmpty()) this.selectToPreviousSubwordBoundary()
    this.deleteSelectedText()
  }

  // Public: Removes the selection or all characters from the start of the
  // selection to the end of the current word if nothing is selected.
  deleteToEndOfSubword () {
    if (this.isEmpty()) this.selectToNextSubwordBoundary()
    this.deleteSelectedText()
  }

  // Public: Removes only the selected text.
  deleteSelectedText () {
    const bufferRange = this.getBufferRange()
    if (!bufferRange.isEmpty()) this.editor.buffer.delete(bufferRange)
    if (this.cursor) this.cursor.setBufferPosition(bufferRange.start)
  }

  // Public: Removes the line at the beginning of the selection if the selection
  // is empty unless the selection spans multiple lines in which case all lines
  // are removed.
  deleteLine () {
    if (this.isEmpty()) {
      const start = this.cursor.getScreenRow()
      const range = this.editor.bufferRowsForScreenRows(start, start + 1)
      if (range[1] > range[0]) {
        this.editor.buffer.deleteRows(range[0], range[1] - 1)
      } else {
        this.editor.buffer.deleteRow(range[0])
      }
    } else {
      const range = this.getBufferRange()
      const start = range.start.row
      let end = range.end.row
      if (end !== this.editor.buffer.getLastRow() && range.end.column === 0) end--
      this.editor.buffer.deleteRows(start, end)
    }
  }

  // Public: Joins the current line with the one below it. Lines will
  // be separated by a single space.
  //
  // If there selection spans more than one line, all the lines are joined together.
  joinLines () {
    let joinMarker
    const selectedRange = this.getBufferRange()
    if (selectedRange.isEmpty()) {
      if (selectedRange.start.row === this.editor.buffer.getLastRow()) return
    } else {
      joinMarker = this.editor.markBufferRange(selectedRange, {invalidate: 'never'})
    }

    const rowCount = Math.max(1, selectedRange.getRowCount() - 1)
    for (let i = 0; i < rowCount; i++) {
      this.cursor.setBufferPosition([selectedRange.start.row])
      this.cursor.moveToEndOfLine()

      // Remove trailing whitespace from the current line
      const scanRange = this.cursor.getCurrentLineBufferRange()
      let trailingWhitespaceRange = null
      this.editor.scanInBufferRange(/[ \t]+$/, scanRange, ({range}) => {
        trailingWhitespaceRange = range
      })
      if (trailingWhitespaceRange) {
        this.setBufferRange(trailingWhitespaceRange)
        this.deleteSelectedText()
      }

      const currentRow = selectedRange.start.row
      const nextRow = currentRow + 1
      const insertSpace =
        (nextRow <= this.editor.buffer.getLastRow()) &&
        (this.editor.buffer.lineLengthForRow(nextRow) > 0) &&
        (this.editor.buffer.lineLengthForRow(currentRow) > 0)
      if (insertSpace) this.insertText(' ')

      this.cursor.moveToEndOfLine()

      // Remove leading whitespace from the line below
      this.modifySelection(() => {
        this.cursor.moveRight()
        this.cursor.moveToFirstCharacterOfLine()
      })
      this.deleteSelectedText()

      if (insertSpace) this.cursor.moveLeft()
    }

    if (joinMarker) {
      const newSelectedRange = joinMarker.getBufferRange()
      this.setBufferRange(newSelectedRange)
      joinMarker.destroy()
    }
  }

  // Public: Removes one level of indent from the currently selected rows.
  outdentSelectedRows () {
    const [start, end] = this.getBufferRowRange()
    const {buffer} = this.editor
    const leadingTabRegex = new RegExp(`^( {1,${this.editor.getTabLength()}}|\t)`)
    for (let row = start; row <= end; row++) {
      const match = buffer.lineForRow(row).match(leadingTabRegex)
      if (match && match[0].length > 0) {
        buffer.delete([[row, 0], [row, match[0].length]])
      }
    }
  }

  // Public: Sets the indentation level of all selected rows to values suggested
  // by the relevant grammars.
  autoIndentSelectedRows () {
    const [start, end] = this.getBufferRowRange()
    return this.editor.autoIndentBufferRows(start, end)
  }

  // Public: Wraps the selected lines in comments if they aren't currently part
  // of a comment.
  //
  // Removes the comment if they are currently wrapped in a comment.
  toggleLineComments () {
    this.editor.toggleLineCommentsForBufferRows(...(this.getBufferRowRange() || []))
  }

  // Public: Cuts the selection until the end of the screen line.
  cutToEndOfLine (maintainClipboard) {
    if (this.isEmpty()) this.selectToEndOfLine()
    return this.cut(maintainClipboard)
  }

  // Public: Cuts the selection until the end of the buffer line.
  cutToEndOfBufferLine (maintainClipboard) {
    if (this.isEmpty()) this.selectToEndOfBufferLine()
    this.cut(maintainClipboard)
  }

  // Public: Copies the selection to the clipboard and then deletes it.
  //
  // * `maintainClipboard` {Boolean} (default: false) See {::copy}
  // * `fullLine` {Boolean} (default: false) See {::copy}
  cut (maintainClipboard = false, fullLine = false) {
    this.copy(maintainClipboard, fullLine)
    this.delete()
  }

  // Public: Copies the current selection to the clipboard.
  //
  // * `maintainClipboard` {Boolean} if `true`, a specific metadata property
  //   is created to store each content copied to the clipboard. The clipboard
  //   `text` still contains the concatenation of the clipboard with the
  //   current selection. (default: false)
  // * `fullLine` {Boolean} if `true`, the copied text will always be pasted
  //   at the beginning of the line containing the cursor, regardless of the
  //   cursor's horizontal position. (default: false)
  copy (maintainClipboard = false, fullLine = false) {
    if (this.isEmpty()) return
    const {start, end} = this.getBufferRange()
    const selectionText = this.editor.getTextInRange([start, end])
    const precedingText = this.editor.getTextInRange([[start.row, 0], start])
    const startLevel = this.editor.indentLevelForLine(precedingText)

    if (maintainClipboard) {
      let {text: clipboardText, metadata} = this.editor.constructor.clipboard.readWithMetadata()
      if (!metadata) metadata = {}
      if (!metadata.selections) {
        metadata.selections = [{
          text: clipboardText,
          indentBasis: metadata.indentBasis,
          fullLine: metadata.fullLine
        }]
      }
      metadata.selections.push({
        text: selectionText,
        indentBasis: startLevel,
        fullLine
      })
      this.editor.constructor.clipboard.write([clipboardText, selectionText].join('\n'), metadata)
    } else {
      this.editor.constructor.clipboard.write(selectionText, {
        indentBasis: startLevel,
        fullLine
      })
    }
  }

  // Public: Creates a fold containing the current selection.
  fold () {
    const range = this.getBufferRange()
    if (!range.isEmpty()) {
      this.editor.foldBufferRange(range)
      this.cursor.setBufferPosition(range.end)
    }
  }

  // Private: Increase the indentation level of the given text by given number
  // of levels. Leaves the first line unchanged.
  adjustIndent (lines, indentAdjustment) {
    for (let i = 0; i < lines.length; i++) {
      const line = lines[i]
      if (indentAdjustment === 0 || line === '') {
        continue
      } else if (indentAdjustment > 0) {
        lines[i] = this.editor.buildIndentString(indentAdjustment) + line
      } else {
        const currentIndentLevel = this.editor.indentLevelForLine(lines[i])
        const indentLevel = Math.max(0, currentIndentLevel + indentAdjustment)
        lines[i] = line.replace(/^[\t ]+/, this.editor.buildIndentString(indentLevel))
      }
    }
  }

  // Indent the current line(s).
  //
  // If the selection is empty, indents the current line if the cursor precedes
  // non-whitespace characters, and otherwise inserts a tab. If the selection is
  // non empty, calls {::indentSelectedRows}.
  //
  // * `options` (optional) {Object} with the keys:
  //   * `autoIndent` If `true`, the line is indented to an automatically-inferred
  //     level. Otherwise, {TextEditor::getTabText} is inserted.
  indent ({autoIndent} = {}) {
    const {row} = this.cursor.getBufferPosition()

    if (this.isEmpty()) {
      this.cursor.skipLeadingWhitespace()
      const desiredIndent = this.editor.suggestedIndentForBufferRow(row)
      let delta = desiredIndent - this.cursor.getIndentLevel()

      if (autoIndent && delta > 0) {
        if (!this.editor.getSoftTabs()) delta = Math.max(delta, 1)
        this.insertText(this.editor.buildIndentString(delta))
      } else {
        this.insertText(this.editor.buildIndentString(1, this.cursor.getBufferColumn()))
      }
    } else {
      this.indentSelectedRows()
    }
  }

  // Public: If the selection spans multiple rows, indent all of them.
  indentSelectedRows () {
    const [start, end] = this.getBufferRowRange()
    for (let row = start; row <= end; row++) {
      if (this.editor.buffer.lineLengthForRow(row) !== 0) {
        this.editor.buffer.insert([row, 0], this.editor.getTabText())
      }
    }
  }

  /*
  Section: Managing multiple selections
  */

  // Public: Moves the selection down one row.
  addSelectionBelow () {
    const range = this.getGoalScreenRange().copy()
    const nextRow = range.end.row + 1

    for (let row = nextRow, end = this.editor.getLastScreenRow(); row <= end; row++) {
      range.start.row = row
      range.end.row = row
      const clippedRange = this.editor.clipScreenRange(range, {skipSoftWrapIndentation: true})

      if (range.isEmpty()) {
        if (range.end.column > 0 && clippedRange.end.column === 0) continue
      } else {
        if (clippedRange.isEmpty()) continue
      }

      const selection = this.editor.addSelectionForScreenRange(clippedRange)
      selection.setGoalScreenRange(range)
      break
    }
  }

  // Public: Moves the selection up one row.
  addSelectionAbove () {
    const range = this.getGoalScreenRange().copy()
    const previousRow = range.end.row - 1

    for (let row = previousRow; row >= 0; row--) {
      range.start.row = row
      range.end.row = row
      const clippedRange = this.editor.clipScreenRange(range, {skipSoftWrapIndentation: true})

      if (range.isEmpty()) {
        if (range.end.column > 0 && clippedRange.end.column === 0) continue
      } else {
        if (clippedRange.isEmpty()) continue
      }

      const selection = this.editor.addSelectionForScreenRange(clippedRange)
      selection.setGoalScreenRange(range)
      break
    }
  }

  // Public: Combines the given selection into this selection and then destroys
  // the given selection.
  //
  // * `otherSelection` A {Selection} to merge with.
  // * `options` (optional) {Object} options matching those found in {::setBufferRange}.
  merge (otherSelection, options = {}) {
    const myGoalScreenRange = this.getGoalScreenRange()
    const otherGoalScreenRange = otherSelection.getGoalScreenRange()

    if (myGoalScreenRange && otherGoalScreenRange) {
      options.goalScreenRange = myGoalScreenRange.union(otherGoalScreenRange)
    } else {
      options.goalScreenRange = myGoalScreenRange || otherGoalScreenRange
    }

    const bufferRange = this.getBufferRange().union(otherSelection.getBufferRange())
    this.setBufferRange(bufferRange, Object.assign({autoscroll: false}, options))
    otherSelection.destroy()
  }

  /*
  Section: Comparing to other selections
  */

  // Public: Compare this selection's buffer range to another selection's buffer
  // range.
  //
  // See {Range::compare} for more details.
  //
  // * `otherSelection` A {Selection} to compare against
  compare (otherSelection) {
    return this.marker.compare(otherSelection.marker)
  }

  /*
  Section: Private Utilities
  */

  setGoalScreenRange (range) {
    this.goalScreenRange = Range.fromObject(range)
  }

  getGoalScreenRange () {
    return this.goalScreenRange || this.getScreenRange()
  }

  markerDidChange (e) {
    const {oldHeadBufferPosition, oldTailBufferPosition, newHeadBufferPosition} = e
    const {oldHeadScreenPosition, oldTailScreenPosition, newHeadScreenPosition} = e
    const {textChanged} = e

    if (!oldHeadScreenPosition.isEqual(newHeadScreenPosition)) {
      this.cursor.goalColumn = null
      const cursorMovedEvent = {
        oldBufferPosition: oldHeadBufferPosition,
        oldScreenPosition: oldHeadScreenPosition,
        newBufferPosition: newHeadBufferPosition,
        newScreenPosition: newHeadScreenPosition,
        textChanged,
        cursor: this.cursor
      }
      this.cursor.emitter.emit('did-change-position', cursorMovedEvent)
      this.editor.cursorMoved(cursorMovedEvent)
    }

    this.emitter.emit('did-change-range')
    this.editor.selectionRangeChanged({
      oldBufferRange: new Range(oldHeadBufferPosition, oldTailBufferPosition),
      oldScreenRange: new Range(oldHeadScreenPosition, oldTailScreenPosition),
      newBufferRange: this.getBufferRange(),
      newScreenRange: this.getScreenRange(),
      selection: this
    })
  }

  markerDidDestroy () {
    if (this.editor.isDestroyed()) return

    this.destroyed = true
    this.cursor.destroyed = true

    this.editor.removeSelection(this)

    this.cursor.emitter.emit('did-destroy')
    this.emitter.emit('did-destroy')

    this.cursor.emitter.dispose()
    this.emitter.dispose()
  }

  finalize () {
    if (!this.initialScreenRange || !this.initialScreenRange.isEqual(this.getScreenRange())) {
      this.initialScreenRange = null
    }
    if (this.isEmpty()) {
      this.wordwise = false
      this.linewise = false
    }
  }

  autoscroll (options) {
    if (this.marker.hasTail()) {
      this.editor.scrollToScreenRange(this.getScreenRange(), Object.assign({reversed: this.isReversed()}, options))
    } else {
      this.cursor.autoscroll(options)
    }
  }

  clearAutoscroll () {}

  modifySelection (fn) {
    this.retainSelection = true
    this.plantTail()
    fn()
    this.retainSelection = false
  }

  // Sets the marker's tail to the same position as the marker's head.
  //
  // This only works if there isn't already a tail position.
  //
  // Returns a {Point} representing the new tail position.
  plantTail () {
    this.marker.plantTail()
  }
}