/**
 * 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';

import type { BlockMap } from "./BlockMap";
import type ContentState from "./ContentState";
import type SelectionState from "./SelectionState";

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

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

const getContentStateFragment = (contentState: ContentState, selectionState: SelectionState): BlockMap => {
  const startKey = selectionState.getStartKey();
  const startOffset = selectionState.getStartOffset();
  const endKey = selectionState.getEndKey();
  const endOffset = selectionState.getEndOffset(); // Edge entities should be stripped to ensure that we don't preserve
  // invalid partial entities when the fragment is reused. We do, however,
  // preserve entities that are entirely within the selection range.

  const contentWithoutEdgeEntities = removeEntitiesAtEdges(contentState, selectionState);
  const blockMap = contentWithoutEdgeEntities.getBlockMap();
  const blockKeys = blockMap.keySeq();
  const startIndex = blockKeys.indexOf(startKey);
  const endIndex = blockKeys.indexOf(endKey) + 1;
  return randomizeBlockMapKeys(blockMap.slice(startIndex, endIndex).map((block, blockKey) => {
    const text = block.getText();
    const chars = block.getCharacterList();

    if (startKey === endKey) {
      return block.merge({
        text: text.slice(startOffset, endOffset),
        characterList: chars.slice(startOffset, endOffset)
      });
    }

    if (blockKey === startKey) {
      return block.merge({
        text: text.slice(startOffset),
        characterList: chars.slice(startOffset)
      });
    }

    if (blockKey === endKey) {
      return block.merge({
        text: text.slice(0, endOffset),
        characterList: chars.slice(0, endOffset)
      });
    }

    return block;
  }));
};

module.exports = getContentStateFragment;