109 lines
2.9 KiB
Dart
109 lines
2.9 KiB
Dart
class Word {
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final int start;
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final int end;
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final String text;
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Word({required this.start, required this.end, required this.text});
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}
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class WordDelta {
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Word? old;
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Word? modified;
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WordDelta({this.old, this.modified});
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}
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class TextDelta {
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final List<WordDelta> wordDeltas = [];
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}
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class Utility {
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static List<Word> splitToWords(String text) {
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List<Word> words = [];
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String currentWord = "";
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for (int i = 0; i < text.length; i++) {
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if (text[i] == " " ||
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text[i] == "\n" ||
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text[i] == "\r" ||
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text[i] == "\t") {
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if (currentWord.isNotEmpty) {
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words.add(
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Word(start: i - currentWord.length, end: i, text: currentWord));
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currentWord = "";
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}
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} else {
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currentWord += text[i];
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}
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}
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if (currentWord.isNotEmpty) {
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words.add(Word(
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start: text.length - currentWord.length,
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end: text.length,
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text: currentWord));
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}
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return words;
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}
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static List<TextDelta> compare(String oldText, String newText) {
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var oldWords = splitToWords(oldText);
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var newWords = splitToWords(newText);
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int oldIndex = 0;
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int newIndex = 0;
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List<TextDelta> textDeltas = [];
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while ((oldIndex < oldWords.length) && (newIndex < newWords.length)) {
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var oldWord = oldWords[oldIndex];
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var newWord = newWords[newIndex];
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if (oldWord.text == newWord.text) {
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oldIndex++;
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newIndex++;
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} else {
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var delta = TextDelta();
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delta.wordDeltas.add(WordDelta(old: oldWord, modified: newWord));
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textDeltas.add(delta);
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oldIndex++;
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newIndex++;
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if (oldIndex < oldWords.length && newIndex < newWords.length) {
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var newSubIndex = newIndex;
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var oldSubIndex = oldIndex;
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while (newSubIndex < newWords.length &&
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newWords[newSubIndex].text != oldWords[oldSubIndex].text) {
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//nextOldWord was not incremented in the loop hence used indexing for nextOldWord
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WordDelta wordDelta =
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WordDelta(old: oldWords[oldSubIndex], modified: newWords[newSubIndex]);
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delta.wordDeltas.add(wordDelta);
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newSubIndex++;
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oldSubIndex++;
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}
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if (newIndex != newSubIndex) {
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newIndex = newSubIndex;
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oldIndex = oldSubIndex;
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}
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}
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}
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}
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if (newIndex < newWords.length) {
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var delta = TextDelta();
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while (newIndex < newWords.length) {
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delta.wordDeltas.add(WordDelta(modified: newWords[newIndex]));
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newIndex++;
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}
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textDeltas.add(delta);
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}
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if (oldIndex < oldWords.length) {
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var delta = TextDelta();
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while (oldIndex < oldWords.length) {
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delta.wordDeltas.add(WordDelta(old: oldWords[oldIndex]));
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oldIndex++;
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}
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textDeltas.add(delta);
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}
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return textDeltas;
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}
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}
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