first implementation finished

app/lib/utils/lru_cache.dart

@@ -0,0 +1,48 @@
+import 'dart:collection';
+
+class LRUCache<K, V> {
+  int _capacity;
+  final LinkedHashMap<K, V> _cache;
+
+  LRUCache(
+    this._capacity, {
+    bool Function(K, K)? equals,
+    int Function(K)? hashCode,
+    bool Function(dynamic)? isValidKey,
+  }) : _cache = LinkedHashMap<K, V>(
+          equals: equals,
+          hashCode: hashCode,
+          isValidKey: isValidKey,
+        );
+
+  void resize(int capacity) {
+    if (_capacity > capacity) {
+      _cache.keys.take(_capacity - capacity).forEach(_cache.remove);
+    }
+
+    _capacity = capacity;
+  }
+
+  V? get(K key) {
+    final value = _cache.remove(key); // Temporarily remove the item.
+
+    if (value != null) {
+      _cache[key] =
+          value; // Re-inserting the item makes it the most-recently used.
+    }
+
+    return value;
+  }
+
+  void set(K key, V value) {
+    if (_cache.containsKey(key)) {
+      _cache.remove(key); // Remove the existing item before updating.
+    } else if (_cache.length == _capacity) {
+      _cache.remove(
+        _cache.keys.first,
+      ); // Explicitly remove the least recently used item if at capacity.
+    }
+
+    _cache[key] = value; // Inserting or updating the item.
+  }
+}

app/lib/utils/platform_util.dart

@@ -0,0 +1,9 @@
+import 'package:flutter/foundation.dart';
+
+bool isAndroid() {
+  return !kIsWeb && defaultTargetPlatform == TargetPlatform.android;
+}
+
+bool isIOS() {
+  return !kIsWeb && defaultTargetPlatform == TargetPlatform.iOS;
+}

app/lib/utils/ui_helper.dart

@@ -0,0 +1,14 @@
+import 'package:flutter/material.dart';
+
+void showErrorMessage(BuildContext context, String message) {
+  final snackBar = SnackBar(
+    content: Text(
+      message,
+      style: TextStyle(
+        color: Theme.of(context).colorScheme.error,
+      ),
+    ),
+    backgroundColor: Theme.of(context).colorScheme.onError,
+  );
+  ScaffoldMessenger.of(context).showSnackBar(snackBar);
+}

app/lib/utils/uri_parser.dart

@@ -0,0 +1,12 @@
+Uri? tryParseUrl(String? input) {
+  if (input != null) {
+    final uri = Uri.tryParse(input);
+    if (uri != null &&
+        uri.hasAuthority &&
+        (uri.isScheme('http') || uri.isScheme('https') || !uri.hasScheme)) {
+      return uri;
+    }
+  }
+
+  return null;
+}