applyDictionaryCorrectionOnSingleSentence function

String applyDictionaryCorrectionOnSingleSentence(String inputSentence, Map<String, List<String>> correctionLetters)

Applies dictionary-based correction to inputSentence. It first tries to match words directly in the dictionary, then attempts to substitute commonly confused characters correctionLetters, and finally finds the closest match in the dictionary if no direct match is found. The original casing of the input words is preserved in the corrected output.

Implementation

String applyDictionaryCorrectionOnSingleSentence(
  final String inputSentence,
  final Map<String, List<String>> correctionLetters,
) {
  final regex = RegExp(
    r'(\s+|[.,!?;:])',
  ); // Matches spaces or single punctuation marks

  final words = inputSentence
      .splitMapJoin(
        regex,
        onMatch: (m) => '¤${m[0]}¤', // Tag matched pieces
        onNonMatch: (n) => '¤$n¤', // Tag non-matched parts (i.e., words)
      )
      .split('¤')
      .where((s) => s.isNotEmpty)
      .toList();

  for (int i = 0; i < words.length; i++) {
    String word = words[i];
    if (word.length > 1 &&
        !['.', ',', '!', '?', ';', ':', ' '].contains(word)) {
      // No need to process numbers
      if (!CharacterStats(word).mostlyDigits()) {
        //
        // Try direct dictionary match first
        //
        if (!englishWords.contains(word.toLowerCase())) {
          //
          // Try substituting commonly confused characters
          //
          String modifiedWord = word;
          bool foundMatch = false;

          for (final MapEntry<String, List<String>> entry
              in correctionLetters.entries) {
            if (word.contains(entry.key)) {
              for (final String substitute in entry.value) {
                final String testWord = word.replaceAll(entry.key, substitute);

                if (englishWords.contains(testWord.toLowerCase())) {
                  modifiedWord = testWord;
                  foundMatch = true;
                  break;
                }
              }
              if (foundMatch) {
                break;
              }
            }
          }

          if (!foundMatch) {
            // If no direct match after substitutions, find closest match
            modifiedWord = findClosestMatchingWordInDictionary(word);
          }

          words[i] = modifiedWord;
        }
      }
    }
  }

  return normalizeCasingOfParagraph(words.join(''));
}