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lib/helpers/serialization/base_serialization_helper.dart

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+import 'dart:convert';
+import 'dart:io';
+
+import 'package:comunic/constants.dart';
+import 'package:path/path.dart' as path;
+import 'package:path_provider/path_provider.dart';
+
+/// Base serialization helper
+///
+/// @author Pierre Hubert
+
+abstract class SerializableElement<T> extends Comparable<T> {
+  Map<String, dynamic> toJson();
+}
+
+abstract class BaseSerializationHelper<T extends SerializableElement> {
+  /// List cache
+  List<T> _cache;
+
+  /// The name of the type of data to serialise
+  String get type;
+
+  /// Parse an json entry into a [T] object
+  T parse(Map<String, dynamic> m);
+
+  /// Get the file where data should be stored
+  Future<File> _getFilePath() async {
+    final dir = await getApplicationDocumentsDirectory();
+    final targetDir =
+        Directory(path.join(dir.absolute.path, SERIALIZATION_DIRECTORY));
+
+    targetDir.create(recursive: true);
+
+    return File(path.join(targetDir.absolute.path, type));
+  }
+
+  /// Load the cache
+  Future<void> _loadCache() async {
+    if (_cache != null) return;
+
+    try {
+      final file = await _getFilePath();
+
+      if (!await file.exists()) return _cache = List();
+
+      final List<dynamic> json = jsonDecode(await file.readAsString());
+      _cache = json.cast<Map<String, dynamic>>().map(parse).toList();
+
+      _cache.sort();
+    } catch (e, s) {
+      print("Failed to read serialized data! $e => $s");
+      _cache = List();
+    }
+  }
+
+  /// Save the cache to the persistent memory
+  Future<void> _saveCache() async {
+    final file = await _getFilePath();
+    await file.writeAsString(jsonEncode(
+        _cache.map((e) => e.toJson()).toList().cast<Map<String, dynamic>>()));
+  }
+
+  /// Get the current list of elements
+  Future<List<T>> getList() async {
+    await _loadCache();
+    return List.from(_cache);
+  }
+
+  /// Set a new list of conversations
+  Future<void> setList(List<T> list) async {
+    _cache = List.from(list);
+    await _saveCache();
+  }
+
+  /// Insert new element
+  Future<void> insert(T el) async {
+    await _loadCache();
+    _cache.add(el);
+    _cache.sort();
+    await _saveCache();
+  }
+
+  /// Insert new element
+  Future<void> insertMany(List<T> els) async {
+    await _loadCache();
+    _cache.addAll(els);
+    _cache.sort();
+    await _saveCache();
+  }
+
+  /// Check if any entry in the last match the predicate
+  Future<bool> any(bool isContained(T t)) async {
+    await _loadCache();
+    return _cache.any((element) => isContained(element));
+  }
+
+  /// Check if any entry in the last match the predicate
+  Future<T> first(bool filter(T t)) async {
+    await _loadCache();
+    return _cache.firstWhere((element) => filter(element));
+  }
+
+  /// Replace an element with another one
+  Future<void> insertOrReplaceElement(bool isToReplace(T t), T newEl) async {
+    await _loadCache();
+
+    // Insert or replace the element
+    _cache.where((element) => !isToReplace(element)).toList();
+    _cache.add(newEl);
+
+    _cache.sort();
+    await _saveCache();
+  }
+
+  /// Remove elements
+  Future<void> removeElement(bool isToRemove(T t)) async {
+    await _loadCache();
+    _cache.removeWhere((element) => isToRemove(element));
+    await _saveCache();
+  }
+}

lib/helpers/serialization/conversation_message_serialization_helper.dart

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+import 'dart:collection';
+
+import 'package:comunic/helpers/serialization/base_serialization_helper.dart';
+import 'package:comunic/lists/conversation_messages_list.dart';
+import 'package:comunic/models/conversation_message.dart';
+
+/// Conversations serialization helper
+///
+/// @author Pierre Hubert
+
+final HashMap<int, ConversationsMessagesSerializationHelper> _instances =
+    HashSet() as HashMap<int, ConversationsMessagesSerializationHelper>;
+
+class ConversationsMessagesSerializationHelper
+    extends BaseSerializationHelper<ConversationMessage> {
+  final int convID;
+
+  ConversationsMessagesSerializationHelper._(int convID)
+      : convID = convID,
+        assert(convID != null);
+
+  factory ConversationsMessagesSerializationHelper(int convID) {
+    if (!_instances.containsKey(convID))
+      _instances[convID] = ConversationsMessagesSerializationHelper._(convID);
+
+    return _instances[convID];
+  }
+
+  @override
+  ConversationMessage parse(Map<String, dynamic> m) =>
+      ConversationMessage.fromJson(m);
+
+  @override
+  String get type => "conv-messages-$convID";
+
+  Future<ConversationMessagesList> getList() async =>
+      ConversationMessagesList()..addAll(await super.getList());
+
+  Future<void> insertOrReplace(ConversationMessage msg) async =>
+      await insertOrReplaceElement((t) => t.id == msg.id, msg);
+
+  Future<void> remove(ConversationMessage msg) async =>
+      await removeElement((t) => t.id == msg.id);
+
+  /// Insert or replace a list of messages
+  Future<void> insertOrReplaceAll(List<ConversationMessage> list) async {
+    for (var message in list)
+      await insertOrReplaceElement((t) => t.id == message.id, message);
+  }
+}

lib/helpers/serialization/conversations_serialization_helper.dart

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+import 'package:comunic/helpers/serialization/base_serialization_helper.dart';
+import 'package:comunic/lists/conversations_list.dart';
+import 'package:comunic/models/conversation.dart';
+
+/// Conversations serialization helper
+///
+/// @author Pierre Hubert
+
+var _cache;
+
+class ConversationsSerializationHelper
+    extends BaseSerializationHelper<Conversation> {
+  /// Singleton
+  factory ConversationsSerializationHelper() {
+    if (_cache == null) _cache = ConversationsSerializationHelper._();
+    return _cache;
+  }
+
+  ConversationsSerializationHelper._();
+
+  @override
+  Conversation parse(Map<String, dynamic> m) => Conversation.fromJson(m);
+
+  @override
+  String get type => "conversations";
+
+  Future<ConversationsList> getList() async =>
+      ConversationsList()..addAll(await super.getList());
+
+  /// Get a conversation
+  Future<Conversation> get(int id) => first((t) => t.id == id);
+}