/**
 * Copyright (c) 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule getUpdatedSelectionState
 * @format
 * @flow
 */

'use strict';

declare var __DEV__: boolean;
import type EditorState from './EditorState';
import type SelectionState from './SelectionState';

var DraftOffsetKey = require('./DraftOffsetKey');

var nullthrows = require('fbjs/lib/nullthrows');

function getUpdatedSelectionState(editorState: EditorState, anchorKey: string, anchorOffset: number, focusKey: string, focusOffset: number): SelectionState {
  var selection: SelectionState = nullthrows(editorState.getSelection());
  if (__DEV__) {
    if (!anchorKey || !focusKey) {
      /*eslint-disable no-console */
      console.warn('Invalid selection state.', arguments, editorState.toJS());
      /*eslint-enable no-console */
      return selection;
    }
  }

  var anchorPath = DraftOffsetKey.decode(anchorKey);
  var anchorBlockKey = anchorPath.blockKey;
  var anchorLeaf = editorState.getBlockTree(anchorBlockKey).getIn([anchorPath.decoratorKey, 'leaves', anchorPath.leafKey]);

  var focusPath = DraftOffsetKey.decode(focusKey);
  var focusBlockKey = focusPath.blockKey;
  var focusLeaf = editorState.getBlockTree(focusBlockKey).getIn([focusPath.decoratorKey, 'leaves', focusPath.leafKey]);

  var anchorLeafStart: number = anchorLeaf.get('start');
  var focusLeafStart: number = focusLeaf.get('start');

  var anchorBlockOffset = anchorLeaf ? anchorLeafStart + anchorOffset : null;
  var focusBlockOffset = focusLeaf ? focusLeafStart + focusOffset : null;

  var areEqual = selection.getAnchorKey() === anchorBlockKey && selection.getAnchorOffset() === anchorBlockOffset && selection.getFocusKey() === focusBlockKey && selection.getFocusOffset() === focusBlockOffset;

  if (areEqual) {
    return selection;
  }

  var isBackward = false;
  if (anchorBlockKey === focusBlockKey) {
    var anchorLeafEnd: number = anchorLeaf.get('end');
    var focusLeafEnd: number = focusLeaf.get('end');
    if (focusLeafStart === anchorLeafStart && focusLeafEnd === anchorLeafEnd) {
      isBackward = focusOffset < anchorOffset;
    } else {
      isBackward = focusLeafStart < anchorLeafStart;
    }
  } else {
    var startKey = editorState.getCurrentContent().getBlockMap().keySeq().skipUntil(v => v === anchorBlockKey || v === focusBlockKey).first();
    isBackward = startKey === focusBlockKey;
  }

  return selection.merge({
    anchorKey: anchorBlockKey,
    anchorOffset: anchorBlockOffset,
    focusKey: focusBlockKey,
    focusOffset: focusBlockOffset,
    isBackward
  });
}

module.exports = getUpdatedSelectionState;