transform method

@override String transform(String input, String locale)

Transforms input into an instance of U using the provided locale.

Implementation

@override
String transform(String input, String locale) {
  assert(length >= 0);

  if (length == 0) {
    return truncationIndicator;
  }

  final isTruncatedAtStart = truncateAt == TruncateAt.start;
  final wordExpression = isTruncatedAtStart
      ? _wordWithTrailingWhitespaceExpression
      : _wordWithLeadingWhitespaceExpression;
  final wordMatches = wordExpression.allMatches(input).toList();
  final wordMatchIndexes = Iterable<int>.generate(
    wordMatches.length,
    (i) => isTruncatedAtStart ? wordMatches.length - 1 - i : i,
  );

  final buffer = <int>[];
  var wordCount = 0;

  for (final i in wordMatchIndexes) {
    final wordMatch = wordMatches[i];
    final word = isTruncatedAtStart ? wordMatch.group(1) : wordMatch.group(2);
    final wordWithOptionalWhitespace = wordMatch.group(0);

    if (isTruncatedAtStart && word != null && wordCount == length) {
      buffer.insertAll(0, truncationIndicator.runes);
      break;
    } else if (!isTruncatedAtStart && word != null && wordCount == length) {
      buffer.addAll(truncationIndicator.runes);
      break;
    }

    if (wordWithOptionalWhitespace != null) {
      if (isTruncatedAtStart) {
        buffer.insertAll(0, wordWithOptionalWhitespace.runes);
      } else {
        buffer.addAll(wordWithOptionalWhitespace.runes);
      }

      if (word != null) {
        ++wordCount;
      }
    }
  }

  final result = String.fromCharCodes(buffer);
  return result;
}