/**
 * 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 encodeInlineStyleRanges
 * @format
 * @flow
 */

'use strict';

import type { BlockNodeRecord } from './BlockNodeRecord';
import type { DraftInlineStyle } from './DraftInlineStyle';
import type { InlineStyleRange } from './InlineStyleRange';
import type { List } from 'immutable';

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

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

var areEqual = (a, b) => a === b;
var isTruthy = a => !!a;
var EMPTY_ARRAY = [];

/**
 * Helper function for getting encoded styles for each inline style. Convert
 * to UTF-8 character counts for storage.
 */
function getEncodedInlinesForType(block: BlockNodeRecord, styleList: List<DraftInlineStyle>, styleToEncode: string): Array<InlineStyleRange> {
  var ranges = [];

  // Obtain an array with ranges for only the specified style.
  var filteredInlines = styleList.map(style => style.has(styleToEncode)).toList();

  findRangesImmutable(filteredInlines, areEqual,
  // We only want to keep ranges with nonzero style values.
  isTruthy, (start, end) => {
    var text = block.getText();
    ranges.push({
      offset: UnicodeUtils.strlen(text.slice(0, start)),
      length: UnicodeUtils.strlen(text.slice(start, end)),
      style: styleToEncode
    });
  });

  return ranges;
}

/*
 * Retrieve the encoded arrays of inline styles, with each individual style
 * treated separately.
 */
function encodeInlineStyleRanges(block: BlockNodeRecord): Array<InlineStyleRange> {
  var styleList = block.getCharacterList().map(c => c.getStyle()).toList();
  var ranges = styleList.flatten().toSet().map(style => getEncodedInlinesForType(block, styleList, style));

  return Array.prototype.concat.apply(EMPTY_ARRAY, ranges.toJS());
}

module.exports = encodeInlineStyleRanges;