Fix loading notes when approaching newest

lib/meilisearch.dart

@@ -348,10 +348,14 @@ Future<Note> createNote(String content) async {
     }
   }
 
-  final mostFrequentLetter =
-      letterFrequency.entries.reduce((a, b) => a.value > b.value ? a : b).key;
-  final mostFrequentLetterCount =
-      letterFrequency[mostFrequentLetter]! / trimmedContent.length;
+  // Handle the case where there are no alphanumeric characters
+  String mostFrequentLetter = 'a'; // Default value
+  double mostFrequentLetterCount = 0.0; // Default value
+  
+  if (letterFrequency.isNotEmpty) {
+    mostFrequentLetter = letterFrequency.entries.reduce((a, b) => a.value > b.value ? a : b).key;
+    mostFrequentLetterCount = letterFrequency[mostFrequentLetter]! / (trimmedContent.length > 0 ? trimmedContent.length : 1);
+  }
 
   final document = {
     'id': generateRandomString(32),
@@ -431,10 +435,14 @@ Future<void> updateNote(Note note) async {
     }
   }
 
-  final mostFrequentLetter =
-      letterFrequency.entries.reduce((a, b) => a.value > b.value ? a : b).key;
-  final mostFrequentLetterRatio =
-      letterFrequency[mostFrequentLetter]! / trimmedContent.length;
+  // Handle the case where there are no alphanumeric characters
+  String mostFrequentLetter = 'a'; // Default value
+  double mostFrequentLetterRatio = 0.0; // Default value
+  
+  if (letterFrequency.isNotEmpty) {
+    mostFrequentLetter = letterFrequency.entries.reduce((a, b) => a.value > b.value ? a : b).key;
+    mostFrequentLetterRatio = letterFrequency[mostFrequentLetter]! / (trimmedContent.length > 0 ? trimmedContent.length : 1);
+  }
 
   final document = {
     'id': note.id,
@@ -527,3 +535,101 @@ Future<Scratch> createScratch(String content) async {
     content: document['content'] as String,
   );
 }
+
+Future<List<Note>> getNotesBefore(int epochTime, {int limit = 50}) async {
+  final endpoint = await _getEndpoint();
+  final headers = await _getHeaders();
+  final searchCondition = MeilisearchQuery(
+    q: '',
+    filter: 'date < $epochTime',
+    sort: ['date:desc'],
+    limit: limit,
+  );
+  final response = await http.post(
+    Uri.parse('$endpoint/indexes/$noteIndex/search'),
+    headers: headers,
+    body: jsonEncode(searchCondition.toJson()),
+  );
+  if (response.statusCode != 200) {
+    throw Exception(
+      'Failed to get notes before timestamp, backend responded with ${response.statusCode}',
+    );
+  }
+  final responseJson = MeilisearchResponse.fromJson(jsonDecode(response.body));
+  return responseJson.hits
+      .map(
+        (hit) => Note(
+          id: hit['id'] as String,
+          epochTime: hit['date'] as int,
+          content: hit['content'] as String,
+        ),
+      )
+      .toList();
+}
+
+Future<List<Note>> getNotesAfter(int epochTime, {int limit = 50}) async {
+  final endpoint = await _getEndpoint();
+  final headers = await _getHeaders();
+  final searchCondition = MeilisearchQuery(
+    q: '',
+    filter: 'date > $epochTime',
+    sort: ['date:asc'],
+    limit: limit,
+  );
+  final response = await http.post(
+    Uri.parse('$endpoint/indexes/$noteIndex/search'),
+    headers: headers,
+    body: jsonEncode(searchCondition.toJson()),
+  );
+  if (response.statusCode != 200) {
+    throw Exception(
+      'Failed to get notes after timestamp, backend responded with ${response.statusCode}',
+    );
+  }
+  final responseJson = MeilisearchResponse.fromJson(jsonDecode(response.body));
+  return responseJson.hits
+      .map(
+        (hit) => Note(
+          id: hit['id'] as String,
+          epochTime: hit['date'] as int,
+          content: hit['content'] as String,
+        ),
+      )
+      .toList();
+}
+
+Future<Duration> getPopupInterval() async {
+  final value = await getSetting('popupInterval');
+  if (value == null) {
+    return const Duration(minutes: 20);
+  }
+  return Duration(minutes: int.parse(value));
+}
+
+Future<void> setPopupInterval(Duration interval) async {
+  await setSetting('popupInterval', interval.inMinutes.toString());
+}
+
+Future<int> getCacheSizeBefore() async {
+  final value = await getSetting('cacheSizeBefore');
+  if (value == null) {
+    return 50; // Default value
+  }
+  return int.parse(value);
+}
+
+Future<void> setCacheSizeBefore(int size) async {
+  await setSetting('cacheSizeBefore', size.toString());
+}
+
+Future<int> getCacheSizeAfter() async {
+  final value = await getSetting('cacheSizeAfter');
+  if (value == null) {
+    return 50; // Default value
+  }
+  return int.parse(value);
+}
+
+Future<void> setCacheSizeAfter(int size) async {
+  await setSetting('cacheSizeAfter', size.toString());
+}