✨ Basic message sending and listing

lib/providers/user_directory.dart

@@ -0,0 +1,50 @@
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+import 'package:surface/providers/sn_network.dart';
+import 'package:surface/types/account.dart';
+
+class UserDirectoryProvider {
+  late final SnNetworkProvider _sn;
+
+  UserDirectoryProvider(BuildContext context) {
+    _sn = context.read<SnNetworkProvider>();
+  }
+
+  final Map<String, int> _idCache = {};
+  final Map<int, SnAccount> _cache = {};
+
+  Future<List<SnAccount?>> listAccount(Iterable<dynamic> id) async {
+    final out = await Future.wait(
+      id.map((e) => getAccount(e)),
+    );
+    return out;
+  }
+
+  Future<SnAccount?> getAccount(dynamic id) async {
+    if (id is String && _idCache.containsKey(id)) {
+      id = _idCache[id];
+    }
+    if (_cache.containsKey(id)) {
+      return _cache[id];
+    }
+
+    try {
+      final resp = await _sn.client.get('/cgi/id/users/$id');
+      final account = SnAccount.fromJson(
+        resp.data as Map<String, dynamic>,
+      );
+      _cache[account.id] = account;
+      if (id is String) _idCache[id] = account.id;
+      return account;
+    } catch (err) {
+      return null;
+    }
+  }
+
+  SnAccount? getAccountFromCache(dynamic id) {
+    if (id is String && _idCache.containsKey(id)) {
+      id = _idCache[id];
+    }
+    return _cache[id];
+  }
+}