/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 * @flow strict-local
 * @emails oncall+draft_js
 */
'use strict';

const DraftModifier = require("./DraftModifier");

const EditorState = require("./EditorState");

const getContentStateFragment = require("./getContentStateFragment");
/**
 * Transpose the characters on either side of a collapsed cursor, or
 * if the cursor is at the end of the block, transpose the last two
 * characters.
 */


function keyCommandTransposeCharacters(editorState: EditorState): EditorState {
  const selection = editorState.getSelection();

  if (!selection.isCollapsed()) {
    return editorState;
  }

  const offset = selection.getAnchorOffset();

  if (offset === 0) {
    return editorState;
  }

  const blockKey = selection.getAnchorKey();
  const content = editorState.getCurrentContent();
  const block = content.getBlockForKey(blockKey);
  const length = block.getLength(); // Nothing to transpose if there aren't two characters.

  if (length <= 1) {
    return editorState;
  }

  let removalRange;
  let finalSelection;

  if (offset === length) {
    // The cursor is at the end of the block. Swap the last two characters.
    removalRange = selection.set('anchorOffset', offset - 1);
    finalSelection = selection;
  } else {
    removalRange = selection.set('focusOffset', offset + 1);
    finalSelection = removalRange.set('anchorOffset', offset + 1);
  } // Extract the character to move as a fragment. This preserves its
  // styling and entity, if any.


  const movedFragment = getContentStateFragment(content, removalRange);
  const afterRemoval = DraftModifier.removeRange(content, removalRange, 'backward'); // After the removal, the insertion target is one character back.

  const selectionAfter = afterRemoval.getSelectionAfter();
  const targetOffset = selectionAfter.getAnchorOffset() - 1;
  const targetRange = selectionAfter.merge({
    anchorOffset: targetOffset,
    focusOffset: targetOffset
  });
  const afterInsert = DraftModifier.replaceWithFragment(afterRemoval, targetRange, movedFragment);
  const newEditorState = EditorState.push(editorState, afterInsert, 'insert-fragment');
  return EditorState.acceptSelection(newEditorState, finalSelection);
}

module.exports = keyCommandTransposeCharacters;