feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/features/channels/channel.dart

@@ -0,0 +1,239 @@
+import 'package:flutter/foundation.dart';
+
+const Object _sentinel = Object();
+
+/// Shown when a private-channel add is refused, so a missing Invite action
+/// reads as a rule rather than a bug.
+const privateChannelAddDeniedMessage =
+    'Only channel owners and admins can add people to a private channel.';
+
+@immutable
+class Channel {
+  final String id;
+  final String name;
+  final String channelType; // "stream", "forum", "dm"
+  final String visibility; // "open", "private"
+  final String description;
+  final String? topic;
+  final String? purpose;
+  final String createdBy;
+  final DateTime createdAt;
+  final int memberCount;
+  final DateTime? lastMessageAt;
+  final DateTime? archivedAt;
+  final List<String> participants;
+  final List<String> participantPubkeys;
+  final bool isMember;
+  final int? ttlSeconds;
+  final DateTime? ttlDeadline;
+
+  const Channel({
+    required this.id,
+    required this.name,
+    required this.channelType,
+    required this.visibility,
+    required this.description,
+    required this.createdBy,
+    required this.createdAt,
+    required this.memberCount,
+    this.topic,
+    this.purpose,
+    this.lastMessageAt,
+    this.archivedAt,
+    this.participants = const [],
+    this.participantPubkeys = const [],
+    this.isMember = false,
+    this.ttlSeconds,
+    this.ttlDeadline,
+  });
+
+  factory Channel.fromJson(Map<String, dynamic> json) => Channel(
+    id: json['id'] as String,
+    name: json['name'] as String,
+    channelType: json['channel_type'] as String,
+    visibility: json['visibility'] as String,
+    description: (json['description'] as String?) ?? '',
+    topic: json['topic'] as String?,
+    purpose: json['purpose'] as String?,
+    createdBy: json['created_by'] as String,
+    createdAt: DateTime.parse(json['created_at'] as String),
+    memberCount: json['member_count'] as int,
+    lastMessageAt: json['last_message_at'] != null
+        ? DateTime.parse(json['last_message_at'] as String)
+        : null,
+    archivedAt: json['archived_at'] != null
+        ? DateTime.parse(json['archived_at'] as String)
+        : null,
+    participants: (json['participants'] as List<dynamic>? ?? const [])
+        .cast<String>(),
+    participantPubkeys:
+        (json['participant_pubkeys'] as List<dynamic>? ?? const [])
+            .cast<String>(),
+    isMember: json['is_member'] as bool? ?? false,
+    ttlSeconds: json['ttl_seconds'] as int?,
+    ttlDeadline: json['ttl_deadline'] != null
+        ? DateTime.parse(json['ttl_deadline'] as String)
+        : null,
+  );
+
+  bool get isEphemeral => ttlSeconds != null || ttlDeadline != null;
+
+  bool get isStream => channelType == 'stream';
+  bool get isForum => channelType == 'forum';
+  bool get isDm => channelType == 'dm';
+  bool get isPrivate => visibility == 'private';
+
+  /// Whether [selfRole] may add *another* identity here, mirroring the relay's
+  /// kind:9000 authority (`validate_admin_event` + `add_member`): DMs never,
+  /// open channels always, private channels owners/admins only. An unknown
+  /// visibility fails closed — the relay is the authority.
+  bool canAddMembers(String? selfRole) {
+    if (isDm) return false;
+    if (visibility == 'open') return true;
+    return selfRole == 'owner' || selfRole == 'admin';
+  }
+
+  bool get isArchived => archivedAt != null;
+
+  String displayLabel({String? currentPubkey}) {
+    if (!isDm || participants.isEmpty) {
+      return name;
+    }
+
+    final normalizedCurrent = currentPubkey?.toLowerCase();
+    final labels = <String>[];
+    for (var index = 0; index < participants.length; index++) {
+      final participantPubkey = index < participantPubkeys.length
+          ? participantPubkeys[index].toLowerCase()
+          : null;
+      if (participantPubkey != null && participantPubkey == normalizedCurrent) {
+        continue;
+      }
+      labels.add(participants[index]);
+    }
+
+    if (labels.isEmpty) {
+      labels.addAll(participants);
+    }
+
+    return labels.join(', ');
+  }
+
+  Channel mergeDetails(ChannelDetails details) => Channel(
+    id: id,
+    name: details.name,
+    channelType: details.channelType,
+    visibility: details.visibility,
+    description: details.description,
+    topic: details.topic,
+    purpose: details.purpose,
+    createdBy: details.createdBy,
+    createdAt: details.createdAt,
+    memberCount: memberCount,
+    lastMessageAt: lastMessageAt,
+    archivedAt: details.archivedAt,
+    participants: participants,
+    participantPubkeys: participantPubkeys,
+    isMember: isMember,
+    ttlSeconds: details.ttlSeconds,
+    ttlDeadline: details.ttlDeadline,
+  );
+
+  Channel copyWith({
+    Object? lastMessageAt = _sentinel,
+    Object? archivedAt = _sentinel,
+    int? memberCount,
+    bool? isMember,
+  }) => Channel(
+    id: id,
+    name: name,
+    channelType: channelType,
+    visibility: visibility,
+    description: description,
+    topic: topic,
+    purpose: purpose,
+    createdBy: createdBy,
+    createdAt: createdAt,
+    memberCount: memberCount ?? this.memberCount,
+    lastMessageAt: identical(lastMessageAt, _sentinel)
+        ? this.lastMessageAt
+        : lastMessageAt as DateTime?,
+    archivedAt: identical(archivedAt, _sentinel)
+        ? this.archivedAt
+        : archivedAt as DateTime?,
+    participants: participants,
+    participantPubkeys: participantPubkeys,
+    isMember: isMember ?? this.isMember,
+    ttlSeconds: ttlSeconds,
+    ttlDeadline: ttlDeadline,
+  );
+}
+
+@immutable
+class ChannelDetails {
+  final String id;
+  final String name;
+  final String channelType;
+  final String visibility;
+  final String description;
+  final String? topic;
+  final String? purpose;
+  final String createdBy;
+  final DateTime createdAt;
+  final int memberCount;
+  final DateTime? archivedAt;
+  final int? ttlSeconds;
+  final DateTime? ttlDeadline;
+
+  const ChannelDetails({
+    required this.id,
+    required this.name,
+    required this.channelType,
+    required this.visibility,
+    required this.description,
+    required this.createdBy,
+    required this.createdAt,
+    required this.memberCount,
+    this.topic,
+    this.purpose,
+    this.archivedAt,
+    this.ttlSeconds,
+    this.ttlDeadline,
+  });
+
+  factory ChannelDetails.fromJson(Map<String, dynamic> json) => ChannelDetails(
+    id: json['id'] as String,
+    name: json['name'] as String,
+    channelType: json['channel_type'] as String,
+    visibility: json['visibility'] as String,
+    description: (json['description'] as String?) ?? '',
+    topic: json['topic'] as String?,
+    purpose: json['purpose'] as String?,
+    createdBy: json['created_by'] as String,
+    createdAt: DateTime.parse(json['created_at'] as String),
+    memberCount: json['member_count'] as int,
+    archivedAt: json['archived_at'] != null
+        ? DateTime.parse(json['archived_at'] as String)
+        : null,
+    ttlSeconds: json['ttl_seconds'] as int?,
+    ttlDeadline: json['ttl_deadline'] != null
+        ? DateTime.parse(json['ttl_deadline'] as String)
+        : null,
+  );
+
+  factory ChannelDetails.fromChannel(Channel channel) => ChannelDetails(
+    id: channel.id,
+    name: channel.name,
+    channelType: channel.channelType,
+    visibility: channel.visibility,
+    description: channel.description,
+    topic: channel.topic,
+    purpose: channel.purpose,
+    createdBy: channel.createdBy,
+    createdAt: channel.createdAt,
+    memberCount: channel.memberCount,
+    archivedAt: channel.archivedAt,
+    ttlSeconds: channel.ttlSeconds,
+    ttlDeadline: channel.ttlDeadline,
+  );
+}