feat(core): person-to-person ratings transport (kind 30778)

Wallapop-style reputation primitive next to trust: Rating (1..5 stars +
optional comment), RatingTransport (rate/retract/ratingsOf/myRatingOf)
and a Nostr implementation on the shared channel. Addressable kind
30778, d = subject: one live rating per (rater, subject) — re-rating
replaces (a single author can never pile up reviews) and retracting
overwrites in place. Client-side dedupe mirrors NIP-01 replacement
order for relays that keep history.

packages/commons_core/lib/commons_core.dart

@@ -21,11 +21,14 @@ export 'src/social/nostr/nostr_connection.dart';
 export 'src/social/nostr/nostr_message_transport.dart';
 export 'src/social/nostr/nostr_offer_transport.dart';
 export 'src/social/nostr/nostr_profile_transport.dart';
+export 'src/social/nostr/nostr_rating_transport.dart';
 export 'src/social/nostr/nostr_trust_transport.dart';
 export 'src/social/nostr/relay_pool.dart';
 export 'src/social/offer.dart';
 export 'src/social/offer_transport.dart';
 export 'src/social/profile_transport.dart';
+export 'src/social/rating.dart';
+export 'src/social/rating_transport.dart';
 export 'src/social/sync_transport.dart';
 export 'src/social/trust_transport.dart';
 export 'src/social/web_of_trust.dart';

packages/commons_core/lib/src/social/nostr/nostr_rating_transport.dart

@@ -0,0 +1,125 @@
+import 'package:nostr/nostr.dart';
+
+import '../rating.dart';
+import '../rating_transport.dart';
+import 'nostr_channel.dart';
+
+/// Ratings carried as Nostr events, on the shared [NostrConnection]. No settled
+/// NIP exists for person-to-person reviews, so this uses a custom addressable
+/// kind (next to the certification kind): one live rating per (rater, subject),
+/// so rating again replaces and retracting overwrites in place.
+class NostrRatingTransport implements RatingTransport {
+  NostrRatingTransport(this._conn);
+
+  final NostrChannel _conn;
+
+  /// Custom Tanemaki rating kind (addressable range, next to trust's 30777).
+  static const kindRating = 30778;
+
+  @override
+  Future<void> rate({
+    required String subjectPubkey,
+    required int stars,
+    String comment = '',
+  }) {
+    if (stars < Rating.minStars || stars > Rating.maxStars) {
+      throw ArgumentError.value(
+          stars, 'stars', 'must be ${Rating.minStars}..${Rating.maxStars}');
+    }
+    return _publish(subjectPubkey,
+        stars: stars, comment: comment, retracted: false);
+  }
+
+  @override
+  Future<void> retract({required String subjectPubkey}) =>
+      _publish(subjectPubkey, stars: Rating.minStars, comment: '',
+          retracted: true);
+
+  Future<void> _publish(
+    String subject, {
+    required int stars,
+    required String comment,
+    required bool retracted,
+  }) async {
+    final event = Event.from(
+      kind: kindRating,
+      content: comment,
+      tags: [
+        ['p', subject],
+        ['d', subject],
+        ['rating', '$stars'],
+        ['status', retracted ? 'retracted' : 'valid'],
+      ],
+      secretKey: _conn.privateKeyHex,
+    );
+    final r = await _conn.publish(event);
+    if (!r.accepted) throw StateError('relay rejected rating: ${r.message}');
+  }
+
+  @override
+  Future<List<Rating>> ratingsOf(String subjectPubkey) async {
+    final events = await _conn.reqOnce(
+      Filter(kinds: const [kindRating], pTags: [subjectPubkey]),
+    );
+    // One rating per rater: keep the newest event should a relay return
+    // several, then drop retractions.
+    final newestByRater = <String, Event>{};
+    for (final e in events) {
+      final prev = newestByRater[e.pubkey];
+      if (prev == null || _newer(e, prev)) newestByRater[e.pubkey] = e;
+    }
+    return newestByRater.values
+        .map(_toRating)
+        .whereType<Rating>()
+        .where((r) => r.subject == subjectPubkey && r.isActive)
+        .toList();
+  }
+
+  @override
+  Future<Rating?> myRatingOf(String subjectPubkey) async {
+    final mine = await _conn.reqOnce(Filter(
+      kinds: const [kindRating],
+      authors: [_conn.publicKeyHex],
+      pTags: [subjectPubkey],
+    ));
+    Event? newest;
+    for (final e in mine) {
+      if (newest == null || _newer(e, newest)) newest = e;
+    }
+    final rating = newest == null ? null : _toRating(newest);
+    return (rating != null && rating.isActive) ? rating : null;
+  }
+
+  /// NIP-01 replacement order: newer created_at wins; on a tie the
+  /// lexicographically smallest id does.
+  static bool _newer(Event a, Event b) =>
+      a.createdAt != b.createdAt
+          ? a.createdAt > b.createdAt
+          : a.id.compareTo(b.id) < 0;
+
+  /// Null for malformed events (missing/out-of-range stars).
+  Rating? _toRating(Event e) {
+    String? tag(String name) {
+      for (final t in e.tags) {
+        if (t.isNotEmpty && t[0] == name && t.length > 1) return t[1];
+      }
+      return null;
+    }
+
+    final stars = int.tryParse(tag('rating') ?? '');
+    if (stars == null || stars < Rating.minStars || stars > Rating.maxStars) {
+      return null;
+    }
+    return Rating(
+      rater: e.pubkey,
+      subject: tag('p') ?? tag('d') ?? '',
+      stars: stars,
+      ratedAt: DateTime.fromMillisecondsSinceEpoch(e.createdAt * 1000),
+      comment: e.content,
+      retracted: tag('status') == 'retracted',
+    );
+  }
+
+  @override
+  Future<void> close() => _conn.close();
+}

packages/commons_core/lib/src/social/rating.dart

@@ -0,0 +1,44 @@
+import 'package:equatable/equatable.dart';
+
+/// One "A rates B" review: stars plus an optional short comment. Public by
+/// design and signed by the rater. One live rating per (rater, subject) pair —
+/// re-rating replaces, so a single author can never pile up reviews. Generic
+/// core type — no seed specifics.
+class Rating extends Equatable {
+  Rating({
+    required this.rater,
+    required this.subject,
+    required this.stars,
+    required this.ratedAt,
+    this.comment = '',
+    this.retracted = false,
+  }) {
+    if (stars < minStars || stars > maxStars) {
+      throw ArgumentError.value(stars, 'stars', 'must be $minStars..$maxStars');
+    }
+  }
+
+  static const minStars = 1;
+  static const maxStars = 5;
+
+  /// Rater public key (hex).
+  final String rater;
+
+  /// Rated public key (hex).
+  final String subject;
+
+  /// 1..5, Wallapop style.
+  final int stars;
+
+  final DateTime ratedAt;
+  final String comment;
+
+  /// A rater can take their rating back; a retracted rating doesn't count.
+  final bool retracted;
+
+  bool get isActive => !retracted;
+
+  @override
+  List<Object?> get props =>
+      [rater, subject, stars, ratedAt, comment, retracted];
+}

packages/commons_core/lib/src/social/rating_transport.dart

@@ -0,0 +1,25 @@
+import 'rating.dart';
+
+/// The reputation contract over the shared connection: rate / retract / read
+/// ratings. Ratings are public signed events (like certifications), so this
+/// transport publishes and discovers rather than encrypts. One live rating per
+/// (rater, subject) pair — rating again replaces the previous one.
+abstract interface class RatingTransport {
+  /// Publishes (or replaces) this identity's rating of [subjectPubkey].
+  Future<void> rate({
+    required String subjectPubkey,
+    required int stars,
+    String comment = '',
+  });
+
+  /// Takes back this identity's rating of [subjectPubkey].
+  Future<void> retract({required String subjectPubkey});
+
+  /// Active ratings of [subjectPubkey], one per rater.
+  Future<List<Rating>> ratingsOf(String subjectPubkey);
+
+  /// This identity's active rating of [subjectPubkey], or null.
+  Future<Rating?> myRatingOf(String subjectPubkey);
+
+  Future<void> close();
+}