atom/src/cursor.js

const {Point, Range} = require('text-buffer')
const {Emitter} = require('event-kit')
const _ = require('underscore-plus')
const Model = require('./model')

const EmptyLineRegExp = /(\r\n[\t ]*\r\n)|(\n[\t ]*\n)/g

// Extended: The `Cursor` class represents the little blinking line identifying
// where text can be inserted.
//
// Cursors belong to {TextEditor}s and have some metadata attached in the form
// of a {DisplayMarker}.
module.exports =
class Cursor extends Model {
  // Instantiated by a {TextEditor}
  constructor (params) {
    super(params)
    this.editor = params.editor
    this.marker = params.marker
    this.emitter = new Emitter()
  }

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

  /*
  Section: Event Subscription
  */

  // Public: Calls your `callback` when the cursor has been moved.
  //
  // * `callback` {Function}
  //   * `event` {Object}
  //     * `oldBufferPosition` {Point}
  //     * `oldScreenPosition` {Point}
  //     * `newBufferPosition` {Point}
  //     * `newScreenPosition` {Point}
  //     * `textChanged` {Boolean}
  //     * `cursor` {Cursor} that triggered the event
  //
  // Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
  onDidChangePosition (callback) {
    return this.emitter.on('did-change-position', callback)
  }

  // Public: Calls your `callback` when the cursor is 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 Cursor Position
  */

  // Public: Moves a cursor to a given screen position.
  //
  // * `screenPosition` {Array} of two numbers: the screen row, and the screen column.
  // * `options` (optional) {Object} with the following keys:
  //   * `autoscroll` A Boolean which, if `true`, scrolls the {TextEditor} to wherever
  //     the cursor moves to.
  setScreenPosition (screenPosition, options = {}) {
    this.changePosition(options, () => {
      this.marker.setHeadScreenPosition(screenPosition, options)
    })
  }

  // Public: Returns the screen position of the cursor as a {Point}.
  getScreenPosition () {
    return this.marker.getHeadScreenPosition()
  }

  // Public: Moves a cursor to a given buffer position.
  //
  // * `bufferPosition` {Array} of two numbers: the buffer row, and the buffer column.
  // * `options` (optional) {Object} with the following keys:
  //   * `autoscroll` {Boolean} indicating whether to autoscroll to the new
  //     position. Defaults to `true` if this is the most recently added cursor,
  //     `false` otherwise.
  setBufferPosition (bufferPosition, options = {}) {
    this.changePosition(options, () => {
      this.marker.setHeadBufferPosition(bufferPosition, options)
    })
  }

  // Public: Returns the current buffer position as an Array.
  getBufferPosition () {
    return this.marker.getHeadBufferPosition()
  }

  // Public: Returns the cursor's current screen row.
  getScreenRow () {
    return this.getScreenPosition().row
  }

  // Public: Returns the cursor's current screen column.
  getScreenColumn () {
    return this.getScreenPosition().column
  }

  // Public: Retrieves the cursor's current buffer row.
  getBufferRow () {
    return this.getBufferPosition().row
  }

  // Public: Returns the cursor's current buffer column.
  getBufferColumn () {
    return this.getBufferPosition().column
  }

  // Public: Returns the cursor's current buffer row of text excluding its line
  // ending.
  getCurrentBufferLine () {
    return this.editor.lineTextForBufferRow(this.getBufferRow())
  }

  // Public: Returns whether the cursor is at the start of a line.
  isAtBeginningOfLine () {
    return this.getBufferPosition().column === 0
  }

  // Public: Returns whether the cursor is on the line return character.
  isAtEndOfLine () {
    return this.getBufferPosition().isEqual(this.getCurrentLineBufferRange().end)
  }

  /*
  Section: Cursor Position Details
  */

  // Public: Returns the underlying {DisplayMarker} for the cursor.
  // Useful with overlay {Decoration}s.
  getMarker () { return this.marker }

  // Public: Identifies if the cursor is surrounded by whitespace.
  //
  // "Surrounded" here means that the character directly before and after the
  // cursor are both whitespace.
  //
  // Returns a {Boolean}.
  isSurroundedByWhitespace () {
    const {row, column} = this.getBufferPosition()
    const range = [[row, column - 1], [row, column + 1]]
    return /^\s+$/.test(this.editor.getTextInBufferRange(range))
  }

  // Public: Returns whether the cursor is currently between a word and non-word
  // character. The non-word characters are defined by the
  // `editor.nonWordCharacters` config value.
  //
  // This method returns false if the character before or after the cursor is
  // whitespace.
  //
  // Returns a Boolean.
  isBetweenWordAndNonWord () {
    if (this.isAtBeginningOfLine() || this.isAtEndOfLine()) return false

    const {row, column} = this.getBufferPosition()
    const range = [[row, column - 1], [row, column + 1]]
    const text = this.editor.getTextInBufferRange(range)
    if (/\s/.test(text[0]) || /\s/.test(text[1])) return false

    const nonWordCharacters = this.getNonWordCharacters()
    return nonWordCharacters.includes(text[0]) !== nonWordCharacters.includes(text[1])
  }

  // Public: Returns whether this cursor is between a word's start and end.
  //
  // * `options` (optional) {Object}
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //     (default: {::wordRegExp}).
  //
  // Returns a {Boolean}
  isInsideWord (options) {
    const {row, column} = this.getBufferPosition()
    const range = [[row, column], [row, Infinity]]
    const text = this.editor.getTextInBufferRange(range)
    return text.search((options && options.wordRegex) || this.wordRegExp()) === 0
  }

  // Public: Returns the indentation level of the current line.
  getIndentLevel () {
    if (this.editor.getSoftTabs()) {
      return this.getBufferColumn() / this.editor.getTabLength()
    } else {
      return this.getBufferColumn()
    }
  }

  // Public: Retrieves the scope descriptor for the cursor's current position.
  //
  // Returns a {ScopeDescriptor}
  getScopeDescriptor () {
    return this.editor.scopeDescriptorForBufferPosition(this.getBufferPosition())
  }

  // Public: Returns true if this cursor has no non-whitespace characters before
  // its current position.
  hasPrecedingCharactersOnLine () {
    const bufferPosition = this.getBufferPosition()
    const line = this.editor.lineTextForBufferRow(bufferPosition.row)
    const firstCharacterColumn = line.search(/\S/)

    if (firstCharacterColumn === -1) {
      return false
    } else {
      return bufferPosition.column > firstCharacterColumn
    }
  }

  // Public: Identifies if this cursor is the last in the {TextEditor}.
  //
  // "Last" is defined as the most recently added cursor.
  //
  // Returns a {Boolean}.
  isLastCursor () {
    return this === this.editor.getLastCursor()
  }

  /*
  Section: Moving the Cursor
  */

  // Public: Moves the cursor up one screen row.
  //
  // * `rowCount` (optional) {Number} number of rows to move (default: 1)
  // * `options` (optional) {Object} with the following keys:
  //   * `moveToEndOfSelection` if true, move to the left of the selection if a
  //     selection exists.
  moveUp (rowCount = 1, {moveToEndOfSelection} = {}) {
    let row, column
    const range = this.marker.getScreenRange()
    if (moveToEndOfSelection && !range.isEmpty()) {
      ({row, column} = range.start)
    } else {
      ({row, column} = this.getScreenPosition())
    }

    if (this.goalColumn != null) column = this.goalColumn
    this.setScreenPosition({row: row - rowCount, column}, {skipSoftWrapIndentation: true})
    this.goalColumn = column
  }

  // Public: Moves the cursor down one screen row.
  //
  // * `rowCount` (optional) {Number} number of rows to move (default: 1)
  // * `options` (optional) {Object} with the following keys:
  //   * `moveToEndOfSelection` if true, move to the left of the selection if a
  //     selection exists.
  moveDown (rowCount = 1, {moveToEndOfSelection} = {}) {
    let row, column
    const range = this.marker.getScreenRange()
    if (moveToEndOfSelection && !range.isEmpty()) {
      ({row, column} = range.end)
    } else {
      ({row, column} = this.getScreenPosition())
    }

    if (this.goalColumn != null) column = this.goalColumn
    this.setScreenPosition({row: row + rowCount, column}, {skipSoftWrapIndentation: true})
    this.goalColumn = column
  }

  // Public: Moves the cursor left one screen column.
  //
  // * `columnCount` (optional) {Number} number of columns to move (default: 1)
  // * `options` (optional) {Object} with the following keys:
  //   * `moveToEndOfSelection` if true, move to the left of the selection if a
  //     selection exists.
  moveLeft (columnCount = 1, {moveToEndOfSelection} = {}) {
    const range = this.marker.getScreenRange()
    if (moveToEndOfSelection && !range.isEmpty()) {
      this.setScreenPosition(range.start)
    } else {
      let {row, column} = this.getScreenPosition()

      while (columnCount > column && row > 0) {
        columnCount -= column
        column = this.editor.lineLengthForScreenRow(--row)
        columnCount-- // subtract 1 for the row move
      }

      column = column - columnCount
      this.setScreenPosition({row, column}, {clipDirection: 'backward'})
    }
  }

  // Public: Moves the cursor right one screen column.
  //
  // * `columnCount` (optional) {Number} number of columns to move (default: 1)
  // * `options` (optional) {Object} with the following keys:
  //   * `moveToEndOfSelection` if true, move to the right of the selection if a
  //     selection exists.
  moveRight (columnCount = 1, {moveToEndOfSelection} = {}) {
    const range = this.marker.getScreenRange()
    if (moveToEndOfSelection && !range.isEmpty()) {
      this.setScreenPosition(range.end)
    } else {
      let {row, column} = this.getScreenPosition()
      const maxLines = this.editor.getScreenLineCount()
      let rowLength = this.editor.lineLengthForScreenRow(row)
      let columnsRemainingInLine = rowLength - column

      while (columnCount > columnsRemainingInLine && row < maxLines - 1) {
        columnCount -= columnsRemainingInLine
        columnCount-- // subtract 1 for the row move

        column = 0
        rowLength = this.editor.lineLengthForScreenRow(++row)
        columnsRemainingInLine = rowLength
      }

      column = column + columnCount
      this.setScreenPosition({row, column}, {clipDirection: 'forward'})
    }
  }

  // Public: Moves the cursor to the top of the buffer.
  moveToTop () {
    this.setBufferPosition([0, 0])
  }

  // Public: Moves the cursor to the bottom of the buffer.
  moveToBottom () {
    this.setBufferPosition(this.editor.getEofBufferPosition())
  }

  // Public: Moves the cursor to the beginning of the line.
  moveToBeginningOfScreenLine () {
    this.setScreenPosition([this.getScreenRow(), 0])
  }

  // Public: Moves the cursor to the beginning of the buffer line.
  moveToBeginningOfLine () {
    this.setBufferPosition([this.getBufferRow(), 0])
  }

  // Public: Moves the cursor to the beginning of the first character in the
  // line.
  moveToFirstCharacterOfLine () {
    let targetBufferColumn
    const screenRow = this.getScreenRow()
    const screenLineStart = this.editor.clipScreenPosition([screenRow, 0], {skipSoftWrapIndentation: true})
    const screenLineEnd = [screenRow, Infinity]
    const screenLineBufferRange = this.editor.bufferRangeForScreenRange([screenLineStart, screenLineEnd])

    let firstCharacterColumn = null
    this.editor.scanInBufferRange(/\S/, screenLineBufferRange, ({range, stop}) => {
      firstCharacterColumn = range.start.column
      stop()
    })

    if (firstCharacterColumn != null && firstCharacterColumn !== this.getBufferColumn()) {
      targetBufferColumn = firstCharacterColumn
    } else {
      targetBufferColumn = screenLineBufferRange.start.column
    }

    this.setBufferPosition([screenLineBufferRange.start.row, targetBufferColumn])
  }

  // Public: Moves the cursor to the end of the line.
  moveToEndOfScreenLine () {
    this.setScreenPosition([this.getScreenRow(), Infinity])
  }

  // Public: Moves the cursor to the end of the buffer line.
  moveToEndOfLine () {
    this.setBufferPosition([this.getBufferRow(), Infinity])
  }

  // Public: Moves the cursor to the beginning of the word.
  moveToBeginningOfWord () {
    this.setBufferPosition(this.getBeginningOfCurrentWordBufferPosition())
  }

  // Public: Moves the cursor to the end of the word.
  moveToEndOfWord () {
    const position = this.getEndOfCurrentWordBufferPosition()
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the beginning of the next word.
  moveToBeginningOfNextWord () {
    const position = this.getBeginningOfNextWordBufferPosition()
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the previous word boundary.
  moveToPreviousWordBoundary () {
    const position = this.getPreviousWordBoundaryBufferPosition()
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the next word boundary.
  moveToNextWordBoundary () {
    const position = this.getNextWordBoundaryBufferPosition()
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the previous subword boundary.
  moveToPreviousSubwordBoundary () {
    const options = {wordRegex: this.subwordRegExp({backwards: true})}
    const position = this.getPreviousWordBoundaryBufferPosition(options)
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the next subword boundary.
  moveToNextSubwordBoundary () {
    const options = {wordRegex: this.subwordRegExp()}
    const position = this.getNextWordBoundaryBufferPosition(options)
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the beginning of the buffer line, skipping all
  // whitespace.
  skipLeadingWhitespace () {
    const position = this.getBufferPosition()
    const scanRange = this.getCurrentLineBufferRange()
    let endOfLeadingWhitespace = null
    this.editor.scanInBufferRange(/^[ \t]*/, scanRange, ({range}) => {
      endOfLeadingWhitespace = range.end
    })

    if (endOfLeadingWhitespace.isGreaterThan(position)) this.setBufferPosition(endOfLeadingWhitespace)
  }

  // Public: Moves the cursor to the beginning of the next paragraph
  moveToBeginningOfNextParagraph () {
    const position = this.getBeginningOfNextParagraphBufferPosition()
    if (position) this.setBufferPosition(position)
  }

  // Public: Moves the cursor to the beginning of the previous paragraph
  moveToBeginningOfPreviousParagraph () {
    const position = this.getBeginningOfPreviousParagraphBufferPosition()
    if (position) this.setBufferPosition(position)
  }

  /*
  Section: Local Positions and Ranges
  */

  // Public: Returns buffer position of previous word boundary. It might be on
  // the current word, or the previous word.
  //
  // * `options` (optional) {Object} with the following keys:
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //      (default: {::wordRegExp})
  getPreviousWordBoundaryBufferPosition (options = {}) {
    const currentBufferPosition = this.getBufferPosition()
    const previousNonBlankRow = this.editor.buffer.previousNonBlankRow(currentBufferPosition.row)
    const scanRange = Range(Point(previousNonBlankRow || 0, 0), currentBufferPosition)

    const ranges = this.editor.buffer.findAllInRangeSync(
      options.wordRegex || this.wordRegExp(),
      scanRange
    )

    const range = ranges[ranges.length - 1]
    if (range) {
      if (range.start.row < currentBufferPosition.row && currentBufferPosition.column > 0) {
        return Point(currentBufferPosition.row, 0)
      } else if (currentBufferPosition.isGreaterThan(range.end)) {
        return Point.fromObject(range.end)
      } else {
        return Point.fromObject(range.start)
      }
    } else {
      return currentBufferPosition
    }
  }

  // Public: Returns buffer position of the next word boundary. It might be on
  // the current word, or the previous word.
  //
  // * `options` (optional) {Object} with the following keys:
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //      (default: {::wordRegExp})
  getNextWordBoundaryBufferPosition (options = {}) {
    const currentBufferPosition = this.getBufferPosition()
    const scanRange = Range(currentBufferPosition, this.editor.getEofBufferPosition())

    const range = this.editor.buffer.findInRangeSync(
      options.wordRegex || this.wordRegExp(),
      scanRange
    )

    if (range) {
      if (range.start.row > currentBufferPosition.row) {
        return Point(range.start.row, 0)
      } else if (currentBufferPosition.isLessThan(range.start)) {
        return Point.fromObject(range.start)
      } else {
        return Point.fromObject(range.end)
      }
    } else {
      return currentBufferPosition
    }
  }

  // Public: Retrieves the buffer position of where the current word starts.
  //
  // * `options` (optional) An {Object} with the following keys:
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //     (default: {::wordRegExp}).
  //   * `includeNonWordCharacters` A {Boolean} indicating whether to include
  //     non-word characters in the default word regex.
  //     Has no effect if wordRegex is set.
  //   * `allowPrevious` A {Boolean} indicating whether the beginning of the
  //     previous word can be returned.
  //
  // Returns a {Range}.
  getBeginningOfCurrentWordBufferPosition (options = {}) {
    const allowPrevious = options.allowPrevious !== false
    const position = this.getBufferPosition()

    const scanRange = allowPrevious
      ? new Range(new Point(position.row - 1, 0), position)
      : new Range(new Point(position.row, 0), position)

    const ranges = this.editor.buffer.findAllInRangeSync(
      options.wordRegex || this.wordRegExp(),
      scanRange
    )

    let result
    for (let range of ranges) {
      if (position.isLessThanOrEqual(range.start)) break
      if (allowPrevious || position.isLessThanOrEqual(range.end)) result = Point.fromObject(range.start)
    }

    return result || (allowPrevious ? new Point(0, 0) : position)
  }

  // Public: Retrieves the buffer position of where the current word ends.
  //
  // * `options` (optional) {Object} with the following keys:
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //      (default: {::wordRegExp})
  //   * `includeNonWordCharacters` A Boolean indicating whether to include
  //     non-word characters in the default word regex. Has no effect if
  //     wordRegex is set.
  //
  // Returns a {Range}.
  getEndOfCurrentWordBufferPosition (options = {}) {
    const allowNext = options.allowNext !== false
    const position = this.getBufferPosition()

    const scanRange = allowNext
      ? new Range(position, new Point(position.row + 2, 0))
      : new Range(position, new Point(position.row, Infinity))

    const ranges = this.editor.buffer.findAllInRangeSync(
      options.wordRegex || this.wordRegExp(),
      scanRange
    )

    for (let range of ranges) {
      if (position.isLessThan(range.start) && !allowNext) break
      if (position.isLessThan(range.end)) return Point.fromObject(range.end)
    }

    return allowNext ? this.editor.getEofBufferPosition() : position
  }

  // Public: Retrieves the buffer position of where the next word starts.
  //
  // * `options` (optional) {Object}
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //     (default: {::wordRegExp}).
  //
  // Returns a {Range}
  getBeginningOfNextWordBufferPosition (options = {}) {
    const currentBufferPosition = this.getBufferPosition()
    const start = this.isInsideWord(options) ? this.getEndOfCurrentWordBufferPosition(options) : currentBufferPosition
    const scanRange = [start, this.editor.getEofBufferPosition()]

    let beginningOfNextWordPosition
    this.editor.scanInBufferRange(options.wordRegex || this.wordRegExp(), scanRange, ({range, stop}) => {
      beginningOfNextWordPosition = range.start
      stop()
    })

    return beginningOfNextWordPosition || currentBufferPosition
  }

  // Public: Returns the buffer Range occupied by the word located under the cursor.
  //
  // * `options` (optional) {Object}
  //   * `wordRegex` A {RegExp} indicating what constitutes a "word"
  //     (default: {::wordRegExp}).
  getCurrentWordBufferRange (options = {}) {
    const position = this.getBufferPosition()
    const ranges = this.editor.buffer.findAllInRangeSync(
      options.wordRegex || this.wordRegExp(options),
      new Range(new Point(position.row, 0), new Point(position.row, Infinity))
    )
    const range = ranges.find(range =>
      range.end.column >= position.column && range.start.column <= position.column
    )
    return range ? Range.fromObject(range) : new Range(position, position)
  }

  // Public: Returns the buffer Range for the current line.
  //
  // * `options` (optional) {Object}
  //   * `includeNewline` A {Boolean} which controls whether the Range should
  //     include the newline.
  getCurrentLineBufferRange (options) {
    return this.editor.bufferRangeForBufferRow(this.getBufferRow(), options)
  }

  // Public: Retrieves the range for the current paragraph.
  //
  // A paragraph is defined as a block of text surrounded by empty lines or comments.
  //
  // Returns a {Range}.
  getCurrentParagraphBufferRange () {
    return this.editor.rowRangeForParagraphAtBufferRow(this.getBufferRow())
  }

  // Public: Returns the characters preceding the cursor in the current word.
  getCurrentWordPrefix () {
    return this.editor.getTextInBufferRange([this.getBeginningOfCurrentWordBufferPosition(), this.getBufferPosition()])
  }

  /*
  Section: Visibility
  */

  /*
  Section: Comparing to another cursor
  */

  // Public: Compare this cursor's buffer position to another cursor's buffer position.
  //
  // See {Point::compare} for more details.
  //
  // * `otherCursor`{Cursor} to compare against
  compare (otherCursor) {
    return this.getBufferPosition().compare(otherCursor.getBufferPosition())
  }

  /*
  Section: Utilities
  */

  // Public: Deselects the current selection.
  clearSelection (options) {
    if (this.selection) this.selection.clear(options)
  }

  // Public: Get the RegExp used by the cursor to determine what a "word" is.
  //
  // * `options` (optional) {Object} with the following keys:
  //   * `includeNonWordCharacters` A {Boolean} indicating whether to include
  //     non-word characters in the regex. (default: true)
  //
  // Returns a {RegExp}.
  wordRegExp (options) {
    const nonWordCharacters = _.escapeRegExp(this.getNonWordCharacters())
    let source = `^[\t\r ]*$|[^\\s${nonWordCharacters}]+`
    if (!options || options.includeNonWordCharacters !== false) {
      source += `|${`[${nonWordCharacters}]+`}`
    }
    return new RegExp(source, 'g')
  }

  // Public: Get the RegExp used by the cursor to determine what a "subword" is.
  //
  // * `options` (optional) {Object} with the following keys:
  //   * `backwards` A {Boolean} indicating whether to look forwards or backwards
  //     for the next subword. (default: false)
  //
  // Returns a {RegExp}.
  subwordRegExp (options = {}) {
    const nonWordCharacters = this.getNonWordCharacters()
    const lowercaseLetters = 'a-z\\u00DF-\\u00F6\\u00F8-\\u00FF'
    const uppercaseLetters = 'A-Z\\u00C0-\\u00D6\\u00D8-\\u00DE'
    const snakeCamelSegment = `[${uppercaseLetters}]?[${lowercaseLetters}]+`
    const segments = [
      '^[\t ]+',
      '[\t ]+$',
      `[${uppercaseLetters}]+(?![${lowercaseLetters}])`,
      '\\d+'
    ]
    if (options.backwards) {
      segments.push(`${snakeCamelSegment}_*`)
      segments.push(`[${_.escapeRegExp(nonWordCharacters)}]+\\s*`)
    } else {
      segments.push(`_*${snakeCamelSegment}`)
      segments.push(`\\s*[${_.escapeRegExp(nonWordCharacters)}]+`)
    }
    segments.push('_+')
    return new RegExp(segments.join('|'), 'g')
  }

  /*
  Section: Private
  */

  getNonWordCharacters () {
    return this.editor.getNonWordCharacters(this.getBufferPosition())
  }

  changePosition (options, fn) {
    this.clearSelection({autoscroll: false})
    fn()
    const autoscroll = (options && options.autoscroll != null)
      ? options.autoscroll
      : this.isLastCursor()
    if (autoscroll) this.autoscroll()
  }

  getScreenRange () {
    const {row, column} = this.getScreenPosition()
    return new Range(new Point(row, column), new Point(row, column + 1))
  }

  autoscroll (options = {}) {
    options.clip = false
    this.editor.scrollToScreenRange(this.getScreenRange(), options)
  }

  getBeginningOfNextParagraphBufferPosition () {
    const start = this.getBufferPosition()
    const eof = this.editor.getEofBufferPosition()
    const scanRange = [start, eof]

    const {row, column} = eof
    let position = new Point(row, column - 1)

    this.editor.scanInBufferRange(EmptyLineRegExp, scanRange, ({range, stop}) => {
      position = range.start.traverse(Point(1, 0))
      if (!position.isEqual(start)) stop()
    })
    return position
  }

  getBeginningOfPreviousParagraphBufferPosition () {
    const start = this.getBufferPosition()

    const {row, column} = start
    const scanRange = [[row - 1, column], [0, 0]]
    let position = new Point(0, 0)
    this.editor.backwardsScanInBufferRange(EmptyLineRegExp, scanRange, ({range, stop}) => {
      position = range.start.traverse(Point(1, 0))
      if (!position.isEqual(start)) stop()
    })
    return position
  }
}