feat(mobile): add channel sections with relay sync

mobile/lib/features/channels/channel_sections/channel_sections_manager.dart

@@ -0,0 +1,347 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:flutter/foundation.dart';
+import 'package:nostr/nostr.dart' as nostr;
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:uuid/uuid.dart';
+
+import '../../../shared/crypto/nip44.dart';
+import '../../../shared/relay/relay.dart';
+import '../read_state/read_state_time.dart';
+import 'channel_sections_storage.dart';
+
+const _uuid = Uuid();
+
+class ChannelSectionsCrypto {
+  final Uint8List _conversationKey;
+
+  ChannelSectionsCrypto(String nsec, String pubkey)
+    : _conversationKey = _deriveKey(nsec, pubkey);
+
+  static Uint8List _deriveKey(String nsec, String pubkey) {
+    final privkeyHex = nostr.Nip19.decode(payload: nsec).data;
+    return getConversationKey(privkeyHex, pubkey);
+  }
+
+  String encrypt(String plaintext) => nip44Encrypt(_conversationKey, plaintext);
+
+  String decrypt(String ciphertext) =>
+      nip44Decrypt(_conversationKey, ciphertext);
+}
+
+class ChannelSectionsManager {
+  final String pubkey;
+  final ChannelSectionsStorage _storage;
+  final ChannelSectionsCrypto _crypto;
+  final RelaySessionNotifier? _relaySession;
+  final SignedEventRelay? _signedEventRelay;
+  final bool _remoteEnabled;
+  final VoidCallback _onChanged;
+
+  ChannelSectionStore _store;
+  Timer? _publishDebounce;
+  int _lastRemoteCreatedAt = 0;
+  void Function()? _unsubscribe;
+  bool _disposed = false;
+
+  ChannelSectionsManager({
+    required this.pubkey,
+    required SharedPreferences prefs,
+    required ChannelSectionsCrypto crypto,
+    required RelaySessionNotifier? relaySession,
+    required SignedEventRelay? signedEventRelay,
+    required bool remoteEnabled,
+    required VoidCallback onChanged,
+  }) : _storage = ChannelSectionsStorage(prefs),
+       _crypto = crypto,
+       _relaySession = relaySession,
+       _signedEventRelay = signedEventRelay,
+       _remoteEnabled = remoteEnabled,
+       _onChanged = onChanged,
+       _store = ChannelSectionsStorage(prefs).read(pubkey);
+
+  ChannelSectionStore get store => _store;
+
+  Future<void> initialize() async {
+    if (_disposed) return;
+
+    if (!_remoteEnabled || _relaySession == null) {
+      _onChanged();
+      return;
+    }
+
+    await _fetchAndMerge();
+    await _startLiveSubscription();
+    _onChanged();
+  }
+
+  void dispose({bool flushPending = true}) {
+    if (_disposed) return;
+    _disposed = true;
+
+    final hadPending = _publishDebounce != null;
+    _publishDebounce?.cancel();
+    _publishDebounce = null;
+
+    if (flushPending && hadPending && _remoteEnabled) {
+      unawaited(_publish(allowDisposed: true));
+    }
+
+    _unsubscribe?.call();
+    _unsubscribe = null;
+  }
+
+  // -------------------------------------------------------------------------
+  // CRUD
+  // -------------------------------------------------------------------------
+
+  void createSection(String name) {
+    if (_disposed) return;
+    final maxOrder = _store.sections.fold<int>(
+      -1,
+      (max, s) => s.order > max ? s.order : max,
+    );
+    final section = ChannelSection(
+      id: _uuid.v4(),
+      name: name.trim(),
+      order: maxOrder + 1,
+    );
+    _store = ChannelSectionStore(
+      sections: [..._store.sections, section],
+      assignments: _store.assignments,
+    );
+    _persist();
+    markDirty();
+  }
+
+  void renameSection(String sectionId, String newName) {
+    if (_disposed) return;
+    _store = ChannelSectionStore(
+      sections: [
+        for (final s in _store.sections)
+          if (s.id == sectionId)
+            ChannelSection(id: s.id, name: newName.trim(), order: s.order)
+          else
+            s,
+      ],
+      assignments: _store.assignments,
+    );
+    _persist();
+    markDirty();
+  }
+
+  void deleteSection(String sectionId) {
+    if (_disposed) return;
+    final updatedAssignments = Map<String, String>.from(_store.assignments)
+      ..removeWhere((_, sid) => sid == sectionId);
+    _store = ChannelSectionStore(
+      sections: [
+        for (final s in _store.sections)
+          if (s.id != sectionId) s,
+      ],
+      assignments: updatedAssignments,
+    );
+    _persist();
+    markDirty();
+  }
+
+  void moveSectionUp(String sectionId) {
+    if (_disposed) return;
+    final sorted = _sortedSections();
+    final idx = sorted.indexWhere((s) => s.id == sectionId);
+    if (idx <= 0) return;
+    _swapOrders(sorted, idx, idx - 1);
+    markDirty();
+  }
+
+  void moveSectionDown(String sectionId) {
+    if (_disposed) return;
+    final sorted = _sortedSections();
+    final idx = sorted.indexWhere((s) => s.id == sectionId);
+    if (idx < 0 || idx >= sorted.length - 1) return;
+    _swapOrders(sorted, idx, idx + 1);
+    markDirty();
+  }
+
+  void assignChannel(String channelId, String sectionId) {
+    if (_disposed) return;
+    final updated = Map<String, String>.from(_store.assignments)
+      ..[channelId] = sectionId;
+    _store = ChannelSectionStore(
+      sections: _store.sections,
+      assignments: updated,
+    );
+    _persist();
+    markDirty();
+  }
+
+  void unassignChannel(String channelId) {
+    if (_disposed) return;
+    final updated = Map<String, String>.from(_store.assignments)
+      ..remove(channelId);
+    _store = ChannelSectionStore(
+      sections: _store.sections,
+      assignments: updated,
+    );
+    _persist();
+    markDirty();
+  }
+
+  void markDirty() {
+    if (!_remoteEnabled || _disposed) return;
+    _publishDebounce?.cancel();
+    _publishDebounce = Timer(const Duration(seconds: 5), () {
+      _publishDebounce = null;
+      unawaited(_publish());
+    });
+  }
+
+  // -------------------------------------------------------------------------
+  // Remote sync
+  // -------------------------------------------------------------------------
+
+  Future<void> _fetchAndMerge() async {
+    if (_relaySession == null) return;
+    try {
+      final events = await _relaySession.fetchHistory(
+        NostrFilter(
+          kinds: const [EventKind.readState],
+          authors: [pubkey],
+          tags: const {
+            '#d': ['channel-sections'],
+          },
+          limit: 1,
+        ),
+      );
+      _mergeEvents(events);
+      _persist();
+      if (!_disposed) _onChanged();
+    } catch (_) {
+      // Local state remains usable when relay is unavailable.
+    }
+  }
+
+  Future<void> _startLiveSubscription() async {
+    if (_relaySession == null) return;
+    try {
+      _unsubscribe = await _relaySession.subscribe(
+        NostrFilter(
+          kinds: const [EventKind.readState],
+          authors: [pubkey],
+          tags: const {
+            '#d': ['channel-sections'],
+          },
+          limit: 1,
+        ),
+        _handleIncomingEvent,
+      );
+    } catch (_) {
+      // Non-fatal — local state and history still work.
+    }
+  }
+
+  void _mergeEvents(List<NostrEvent> events) {
+    for (final event in events) {
+      if (event.pubkey != pubkey) continue;
+      _mergeEvent(event);
+    }
+  }
+
+  void _mergeEvent(NostrEvent event) {
+    // Only process channel-sections d-tag events.
+    final dTag = event.getTagValue('d');
+    if (dTag != 'channel-sections') return;
+
+    try {
+      final plaintext = _crypto.decrypt(event.content);
+      final parsed = jsonDecode(plaintext);
+      if (parsed is! Map<String, dynamic>) return;
+
+      final incoming = ChannelSectionStore.fromJson(parsed);
+
+      // Last-write-wins: newer createdAt wins; tie-break by event ID.
+      final isNewer =
+          event.createdAt > _lastRemoteCreatedAt ||
+          (event.createdAt == _lastRemoteCreatedAt &&
+              event.id.compareTo(_lastRemoteEventId ?? '') > 0);
+
+      if (isNewer) {
+        _lastRemoteCreatedAt = event.createdAt;
+        _lastRemoteEventId = event.id;
+        _store = incoming;
+        _persist();
+      }
+    } catch (_) {
+      // Decryption failure or parse error — keep existing state.
+    }
+  }
+
+  String? _lastRemoteEventId;
+
+  void _handleIncomingEvent(NostrEvent event) {
+    if (_disposed) return;
+    _mergeEvent(event);
+    if (!_disposed) _onChanged();
+  }
+
+  Future<void> _publish({bool allowDisposed = false}) async {
+    if ((!allowDisposed && _disposed) ||
+        !_remoteEnabled ||
+        _signedEventRelay == null) {
+      return;
+    }
+
+    try {
+      final payload = jsonEncode(_store.toJson());
+      final ciphertext = _crypto.encrypt(payload);
+      final createdAt = max(currentUnixSeconds(), _lastRemoteCreatedAt + 1);
+
+      await _signedEventRelay.submit(
+        kind: EventKind.readState,
+        content: ciphertext,
+        tags: [
+          ['d', 'channel-sections'],
+          ['t', 'channel-sections'],
+        ],
+        createdAt: createdAt,
+      );
+
+      _lastRemoteCreatedAt = max(_lastRemoteCreatedAt, createdAt);
+    } catch (error) {
+      debugPrint('[ChannelSectionsManager] publish failed: $error');
+    }
+  }
+
+  void _persist() {
+    _storage.write(pubkey, _store);
+  }
+
+  List<ChannelSection> _sortedSections() {
+    final sorted = _store.sections.toList()
+      ..sort((a, b) => a.order.compareTo(b.order));
+    return sorted;
+  }
+
+  void _swapOrders(List<ChannelSection> sorted, int indexA, int indexB) {
+    final orderA = sorted[indexA].order;
+    final orderB = sorted[indexB].order;
+    final idA = sorted[indexA].id;
+    final idB = sorted[indexB].id;
+
+    _store = ChannelSectionStore(
+      sections: [
+        for (final s in _store.sections)
+          if (s.id == idA)
+            ChannelSection(id: s.id, name: s.name, order: orderB)
+          else if (s.id == idB)
+            ChannelSection(id: s.id, name: s.name, order: orderA)
+          else
+            s,
+      ],
+      assignments: _store.assignments,
+    );
+    _persist();
+  }
+}