feat: import Chinese-localized Buzz source snapshot

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

mobile/lib/shared/read_state/read_state_format.dart

@@ -0,0 +1,193 @@
+import 'dart:convert';
+
+import 'package:flutter/foundation.dart';
+
+import '../relay/nostr_models.dart';
+
+const readStateDTagPrefix = 'read-state:';
+const readStateFetchLimit = 500;
+const readStateHorizonSeconds = 7 * 24 * 60 * 60;
+const _maxContexts = 10000;
+const msgContextPrefix = 'msg:';
+const threadContextPrefix = 'thread:';
+
+String msgContextKey(String messageId) => '$msgContextPrefix$messageId';
+String threadContextKey(String rootId) => '$threadContextPrefix$rootId';
+
+int? maxReadAt(Iterable<int?> markers) {
+  int? latest;
+  for (final marker in markers) {
+    if (marker == null) continue;
+    if (latest == null || marker > latest) {
+      latest = marker;
+    }
+  }
+  return latest;
+}
+
+typedef ReadStateDecrypt = String Function(String ciphertext);
+
+class ReadStateBlob {
+  final String clientId;
+  final Map<String, int> contexts;
+
+  ReadStateBlob({required this.clientId, required Map<String, int> contexts})
+    : contexts = Map.unmodifiable(contexts);
+
+  Map<String, dynamic> toJson() => {
+    'v': 1,
+    'client_id': clientId,
+    'contexts': contexts,
+  };
+}
+
+class DecodedReadStateEvent {
+  final NostrEvent event;
+  final String dTag;
+  final ReadStateBlob blob;
+
+  const DecodedReadStateEvent({
+    required this.event,
+    required this.dTag,
+    required this.blob,
+  });
+}
+
+bool isPlainJsonObject(Object? value) {
+  if (value is! Map) return false;
+  return value.keys.every((key) => key is String);
+}
+
+Map<String, Object?>? asStringObjectMap(Object? value) {
+  if (!isPlainJsonObject(value)) return null;
+  return (value as Map).cast<String, Object?>();
+}
+
+bool isValidReadStateDTag(String? value) {
+  if (value == null || !value.startsWith(readStateDTagPrefix)) {
+    return false;
+  }
+
+  final slotId = value.substring(readStateDTagPrefix.length);
+  if (slotId.isEmpty || slotId.length > 64) {
+    return false;
+  }
+
+  for (var index = 0; index < slotId.length; index++) {
+    if (slotId.codeUnitAt(index) > 0x7f) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool hasValidReadStateTags(NostrEvent event) {
+  final dTags = event.tags.where((tag) => tag.isNotEmpty && tag[0] == 'd');
+  if (dTags.length != 1) {
+    return false;
+  }
+  final dTag = dTags.single;
+  if (dTag.length < 2 || !isValidReadStateDTag(dTag[1])) {
+    return false;
+  }
+
+  final tTags = event.tags.where(
+    (tag) => tag.length >= 2 && tag[0] == 't' && tag[1] == 'read-state',
+  );
+  return tTags.length == 1;
+}
+
+ReadStateBlob? decodeReadStateBlob(String plaintext) {
+  final Object? parsed;
+  try {
+    parsed = jsonDecode(plaintext);
+  } catch (_) {
+    return null;
+  }
+
+  final record = asStringObjectMap(parsed);
+  if (record == null) return null;
+
+  if (record['v'] != 1) return null;
+
+  final clientId = record['client_id'];
+  if (clientId is! String || clientId.isEmpty || clientId.runes.length > 64) {
+    return null;
+  }
+
+  final contexts = asStringObjectMap(record['contexts']);
+  if (contexts == null || contexts.length > _maxContexts) {
+    return null;
+  }
+
+  return ReadStateBlob(
+    clientId: clientId,
+    contexts: sanitizeReadStateContexts(contexts),
+  );
+}
+
+Map<String, int> sanitizeReadStateContexts(Map<String, Object?> contexts) {
+  final sanitized = <String, int>{};
+  for (final entry in contexts.entries) {
+    if (utf8.encode(entry.key).length > 256) continue;
+
+    final value = entry.value;
+    if (value is! int) continue;
+    if (value < 0 || value > 4294967295) continue;
+
+    sanitized[entry.key] = value;
+  }
+  return sanitized;
+}
+
+DecodedReadStateEvent? decodeReadStateEvent(
+  NostrEvent event, {
+  required String pubkey,
+  required ReadStateDecrypt decrypt,
+}) {
+  if (event.pubkey.toLowerCase() != pubkey.toLowerCase()) {
+    return null;
+  }
+  if (!hasValidReadStateTags(event)) {
+    return null;
+  }
+
+  final dTag = event.tags.firstWhere(
+    (tag) => tag.isNotEmpty && tag[0] == 'd',
+  )[1];
+
+  final String plaintext;
+  try {
+    plaintext = decrypt(event.content);
+  } catch (e) {
+    debugPrint(
+      '[ReadStateManager] decrypt failed for event ${event.id.substring(0, 8)}…: $e',
+    );
+    return null;
+  }
+
+  final blob = decodeReadStateBlob(plaintext);
+  if (blob == null) {
+    debugPrint(
+      '[ReadStateManager] blob decode failed for event ${event.id.substring(0, 8)}…',
+    );
+    return null;
+  }
+
+  return DecodedReadStateEvent(event: event, dTag: dTag, blob: blob);
+}
+
+Map<String, int> mergeReadStateContexts(
+  Iterable<Map<String, int>> contextSets,
+) {
+  final merged = <String, int>{};
+  for (final contexts in contextSets) {
+    for (final entry in contexts.entries) {
+      final current = merged[entry.key] ?? 0;
+      if (entry.value > current) {
+        merged[entry.key] = entry.value;
+      }
+    }
+  }
+  return merged;
+}