/**
 * 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';

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

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

const nullthrows = require("fbjs/lib/nullthrows");

function getUpdatedSelectionState(editorState: EditorState, anchorKey: string, anchorOffset: number, focusKey: string, focusOffset: number): SelectionState {
  const selection: SelectionState = nullthrows(editorState.getSelection());

  if (!anchorKey || !focusKey) {
    // If we cannot make sense of the updated selection state, stick to the current one.
    if (__DEV__) {
      /* eslint-disable-next-line */
      console.warn('Invalid selection state.', arguments, editorState.toJS());
    }

    return selection;
  }

  const anchorPath = DraftOffsetKey.decode(anchorKey);
  const anchorBlockKey = anchorPath.blockKey;
  const anchorLeafBlockTree = editorState.getBlockTree(anchorBlockKey);
  const anchorLeaf = anchorLeafBlockTree && anchorLeafBlockTree.getIn([anchorPath.decoratorKey, 'leaves', anchorPath.leafKey]);
  const focusPath = DraftOffsetKey.decode(focusKey);
  const focusBlockKey = focusPath.blockKey;
  const focusLeafBlockTree = editorState.getBlockTree(focusBlockKey);
  const focusLeaf = focusLeafBlockTree && focusLeafBlockTree.getIn([focusPath.decoratorKey, 'leaves', focusPath.leafKey]);

  if (!anchorLeaf || !focusLeaf) {
    // If we cannot make sense of the updated selection state, stick to the current one.
    if (__DEV__) {
      /* eslint-disable-next-line */
      console.warn('Invalid selection state.', arguments, editorState.toJS());
    }

    return selection;
  }

  const anchorLeafStart: number = anchorLeaf.get('start');
  const focusLeafStart: number = focusLeaf.get('start');
  const anchorBlockOffset = anchorLeaf ? anchorLeafStart + anchorOffset : null;
  const focusBlockOffset = focusLeaf ? focusLeafStart + focusOffset : null;
  const areEqual = selection.getAnchorKey() === anchorBlockKey && selection.getAnchorOffset() === anchorBlockOffset && selection.getFocusKey() === focusBlockKey && selection.getFocusOffset() === focusBlockOffset;

  if (areEqual) {
    return selection;
  }

  let isBackward = false;

  if (anchorBlockKey === focusBlockKey) {
    const anchorLeafEnd: number = anchorLeaf.get('end');
    const focusLeafEnd: number = focusLeaf.get('end');

    if (focusLeafStart === anchorLeafStart && focusLeafEnd === anchorLeafEnd) {
      isBackward = focusOffset < anchorOffset;
    } else {
      isBackward = focusLeafStart < anchorLeafStart;
    }
  } else {
    const 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;