{ComposerExtension, AccountStore, DOMUtils, NylasSpellchecker} = require 'nylas-exports'
_ = require 'underscore'
remote = require('remote')
MenuItem = remote.require('menu-item')
spellchecker = NylasSpellchecker

SpellcheckCache = {}

class SpellcheckComposerExtension extends ComposerExtension

  @isMisspelled: (word) ->
    SpellcheckCache[word] ?= spellchecker.isMisspelled(word)
    SpellcheckCache[word]

  @onContentChanged: ({editor}) =>
    @update(editor)

  @onShowContextMenu: ({editor, event, menu}) =>
    selection = editor.currentSelection()
    range = DOMUtils.Mutating.getRangeAtAndSelectWord(selection, 0)
    word = range.toString()
    if @isMisspelled(word)
      corrections = spellchecker.getCorrectionsForMisspelling(word)
      if corrections.length > 0
        corrections.forEach (correction) =>
          menu.append(new MenuItem({
            label: correction,
            click: @applyCorrection.bind(@, editor, range, selection, correction)
          }))
      else
        menu.append(new MenuItem({ label: 'No Guesses Found', enabled: false}))

      menu.append(new MenuItem({ type: 'separator' }))
      menu.append(new MenuItem({
        label: 'Learn Spelling',
        click: @learnSpelling.bind(@, editor, word)
      }))
      menu.append(new MenuItem({ type: 'separator' }))

  @applyCorrection: (editor, range, selection, correction) =>
    DOMUtils.Mutating.applyTextInRange(range, selection, correction)
    @update(editor)

  @learnSpelling: (editor, word) =>
    spellchecker.add(word)
    delete SpellcheckCache[word]
    @update(editor)

  @update: (editor) =>
    @_unwrapWords(editor)
    @_wrapMisspelledWords(editor)

  # Creates a shallow copy of a selection object where anchorNode / focusNode
  # can be changed, and provides it to the callback provided. After the callback
  # runs, it applies the new selection if `snapshot.modified` has been set.
  #
  # Note: This is different from ExposedSelection because the nodes are not cloned.
  # In the callback functions, we need to check whether the anchor/focus nodes
  # are INSIDE the nodes we're adjusting.
  #
  @_whileApplyingSelectionChanges: (cb) =>
    selection = document.getSelection()
    selectionSnapshot =
      anchorNode: selection.anchorNode
      anchorOffset: selection.anchorOffset
      focusNode: selection.focusNode
      focusOffset: selection.focusOffset
      modified: false

    cb(selectionSnapshot)

    if selectionSnapshot.modified
      selection.setBaseAndExtent(selectionSnapshot.anchorNode, selectionSnapshot.anchorOffset, selectionSnapshot.focusNode, selectionSnapshot.focusOffset)

  # Removes all of the <spelling> nodes found in the provided `editor`.
  # It normalizes the DOM after removing spelling nodes to ensure that words
  # are not split between text nodes. (ie: doesn, 't => doesn't)
  @_unwrapWords: (editor) =>
    @_whileApplyingSelectionChanges (selectionSnapshot) =>
      spellingNodes = editor.rootNode.querySelectorAll('spelling')

      for node in spellingNodes
        if selectionSnapshot.anchorNode is node
          selectionSnapshot.anchorNode = node.firstChild
        if selectionSnapshot.focusNode is node
          selectionSnapshot.focusNode = node.firstChild

        selectionSnapshot.modified = true
        node.parentNode.insertBefore(node.firstChild, node) while (node.firstChild)
        node.parentNode.removeChild(node)

    editor.rootNode.normalize()

  # Traverses all of the text nodes within the provided `editor`. If it finds a
  # text node with a misspelled word, it splits it, wraps the misspelled word
  # with a <spelling> node and updates the selection to account for the change.
  @_wrapMisspelledWords: (editor) =>
    @_whileApplyingSelectionChanges (selectionSnapshot) =>
      treeWalker = document.createTreeWalker(editor.rootNode, NodeFilter.SHOW_TEXT)
      nodeList = []
      nodeMisspellingsFound = 0

      while (treeWalker.nextNode())
        nodeList.push(treeWalker.currentNode)

      # Note: As a performance optimization, we stop spellchecking after encountering
      # 30 misspelled words. This keeps the runtime of this method bounded!

      while (node = nodeList.shift())
        break if nodeMisspellingsFound > 30
        str = node.textContent

        # https://regex101.com/r/bG5yC4/1
        wordRegexp = /(\w[\w'’-]*\w|\w)/g

        while ((match = wordRegexp.exec(str)) isnt null)
          break if nodeMisspellingsFound > 30
          misspelled = @isMisspelled(match[0])

          if misspelled
            # The insertion point is currently at the end of this misspelled word.
            # Do not mark it until the user types a space or leaves.
            if selectionSnapshot.focusNode is node and selectionSnapshot.focusOffset is match.index + match[0].length
              continue

            if match.index is 0
              matchNode = node
            else
              matchNode = node.splitText(match.index)
            afterMatchNode = matchNode.splitText(match[0].length)

            spellingSpan = document.createElement('spelling')
            spellingSpan.classList.add('misspelled')
            spellingSpan.innerText = match[0]
            matchNode.parentNode.replaceChild(spellingSpan, matchNode)

            for prop in ['anchor', 'focus']
              if selectionSnapshot["#{prop}Node"] is node
                if selectionSnapshot["#{prop}Offset"] > match.index + match[0].length
                  selectionSnapshot.modified = true
                  selectionSnapshot["#{prop}Node"] = afterMatchNode
                  selectionSnapshot["#{prop}Offset"] -= match.index + match[0].length
                else if selectionSnapshot["#{prop}Offset"] > match.index
                  selectionSnapshot.modified = true
                  selectionSnapshot["#{prop}Node"] = spellingSpan.childNodes[0]
                  selectionSnapshot["#{prop}Offset"] -= match.index

            nodeMisspellingsFound += 1
            nodeList.unshift(afterMatchNode)
            break

  @finalizeSessionBeforeSending: ({session}) ->
    body = session.draft().body
    clean = body.replace(/<\/?spelling[^>]*>/g, '')
    if body != clean
      return session.changes.add(body: clean)

SpellcheckComposerExtension.SpellcheckCache = SpellcheckCache

module.exports = SpellcheckComposerExtension