Move into mobile/

mobile/lib/extensions/string_ext.dart

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+const List<String> connectWords = [
+  'a', 'an', 'the', // Articles
+
+  'about', 'above', 'across', 'after', 'against', 'along', 'amid', 'among',
+  'around', 'as', 'at', 'before', 'behind', 'below', 'beneath', 'beside',
+  'between', 'beyond', 'by', 'concerning', 'considering', 'despite', 'down',
+  'during', 'except', 'for', 'from', 'in', 'inside', 'into', 'like', 'near',
+  'of', 'off', 'on', 'onto', 'out', 'outside', 'over', 'past', 'regarding',
+  'round', 'since', 'through', 'to', 'toward', 'under', 'underneath', 'until',
+  'unto', 'up', 'upon', 'with', 'within', 'without', // Prepositions
+
+  'and', 'as', 'because', 'but', 'for', 'if', 'nor', 'or', 'since', 'so',
+  'that', 'though', 'unless', 'until', 'when', 'whenever', 'where', 'whereas',
+  'wherever', 'while', 'yet', // Conjunctions
+
+  'i', 'you', 'he', 'she', 'it', 'we', 'they', 'me', 'him', 'her', 'us', 'them',
+  'my', 'your', 'his', 'its', 'our', 'their', 'mine', 'yours', 'hers', 'ours',
+  'theirs', 'who', 'whom', 'whose', 'which', 'what', // Pronouns
+
+  'am', 'is', 'are', 'was', 'were', 'be', 'being', 'been', 'have', 'has', 'had',
+  'do', 'does', 'did', 'will', 'would', 'shall', 'should', 'can', 'could',
+  'may', 'might', 'must', // Auxiliary Verbs
+];
+
+extension StringExtensionsNullSafe on String? {
+  int get sumAsciiValues {
+    if (this == null) {
+      return -1;
+    }
+    int sum = 0;
+    for (int i = 0; i < this!.length; i++) {
+      sum += this!.codeUnitAt(i);
+    }
+    return sum;
+  }
+}
+
+extension DescriptionString on String? {
+  bool get isAllConnectWords {
+    if (this == null) {
+      throw AssertionError("String cannot be null");
+    }
+    final subDescWords = this!.split(" ");
+    return subDescWords.every(
+      (subDescWord) => connectWords.any(
+        (connectWord) => subDescWord.toLowerCase() == connectWord,
+      ),
+    );
+  }
+
+  bool get isLastWordConnectWord {
+    if (this == null) {
+      throw AssertionError("String cannot be null");
+    }
+    final subDescWords = this!.split(" ");
+    return connectWords
+        .any((element) => element == subDescWords.last.toLowerCase());
+  }
+}