/**
 * 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 ContentState from "./ContentState";
import type SelectionState from "./SelectionState";

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

const {
  Map
} = require("immutable");

const ContentStateInlineStyle = {
  add: function (contentState: ContentState, selectionState: SelectionState, inlineStyle: string): ContentState {
    return modifyInlineStyle(contentState, selectionState, inlineStyle, true);
  },
  remove: function (contentState: ContentState, selectionState: SelectionState, inlineStyle: string): ContentState {
    return modifyInlineStyle(contentState, selectionState, inlineStyle, false);
  }
};

function modifyInlineStyle(contentState: ContentState, selectionState: SelectionState, inlineStyle: string, addOrRemove: boolean): ContentState {
  const blockMap = contentState.getBlockMap();
  const startKey = selectionState.getStartKey();
  const startOffset = selectionState.getStartOffset();
  const endKey = selectionState.getEndKey();
  const endOffset = selectionState.getEndOffset();
  const newBlocks = blockMap.skipUntil((_, k) => k === startKey).takeUntil((_, k) => k === endKey).concat(Map([[endKey, blockMap.get(endKey)]])).map((block, blockKey) => {
    let sliceStart;
    let sliceEnd;

    if (startKey === endKey) {
      sliceStart = startOffset;
      sliceEnd = endOffset;
    } else {
      sliceStart = blockKey === startKey ? startOffset : 0;
      sliceEnd = blockKey === endKey ? endOffset : block.getLength();
    }

    let chars = block.getCharacterList();
    let current;

    while (sliceStart < sliceEnd) {
      current = chars.get(sliceStart);
      chars = chars.set(sliceStart, addOrRemove ? CharacterMetadata.applyStyle(current, inlineStyle) : CharacterMetadata.removeStyle(current, inlineStyle));
      sliceStart++;
    }

    return block.set('characterList', chars);
  });
  return contentState.merge({
    blockMap: blockMap.merge(newBlocks),
    selectionBefore: selectionState,
    selectionAfter: selectionState
  });
}

module.exports = ContentStateInlineStyle;