feat: import Chinese-localized Buzz source snapshot

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

mobile/lib/shared/custom_emoji/custom_emoji.dart

@@ -0,0 +1,139 @@
+import 'package:flutter/foundation.dart';
+
+import '../relay/nostr_models.dart';
+
+/// A community custom emoji: a `:shortcode:` mapped to an image URL.
+///
+/// Mirrors desktop's NIP-30 model (kind:30030, per-user sets unioned into one
+/// community palette). Identity downstream is shortcode-only — the palette must
+/// never carry two URLs under one shortcode.
+@immutable
+class CustomEmoji {
+  final String shortcode;
+  final String url;
+
+  const CustomEmoji({required this.shortcode, required this.url});
+
+  @override
+  bool operator ==(Object other) =>
+      other is CustomEmoji && other.shortcode == shortcode && other.url == url;
+
+  @override
+  int get hashCode => Object.hash(shortcode, url);
+
+  @override
+  String toString() => 'CustomEmoji($shortcode -> $url)';
+}
+
+/// NIP-30 emoji set kind (parameterized-replaceable).
+const int kindEmojiSet = 30030;
+
+/// d-tag for a member's own custom emoji set.
+const String customEmojiSetDTag = 'buzz:custom-emoji';
+
+final RegExp _shortcodeRe = RegExp(r'^[a-z0-9_-]+$');
+
+/// Normalize a shortcode the way the relay does: strip surrounding colons and
+/// lowercase. Returns null if the result is empty or has invalid chars.
+String? normalizeShortcode(String raw) {
+  final stripped = raw
+      .trim()
+      .replaceFirst(RegExp(r'^:+'), '')
+      .replaceFirst(RegExp(r':+$'), '');
+  final lower = stripped.toLowerCase();
+  return _shortcodeRe.hasMatch(lower) ? lower : null;
+}
+
+/// Parse NIP-30 `["emoji", shortcode, url]` tags from one event's tags into a
+/// custom-emoji list. Shortcodes are normalized; malformed/duplicate entries
+/// within the one event are skipped (first wins).
+List<CustomEmoji> customEmojiFromTags(List<List<String>> tags) {
+  final seen = <String>{};
+  final emoji = <CustomEmoji>[];
+
+  for (final tag in tags) {
+    if (tag.isEmpty || tag[0] != 'emoji') continue;
+    if (tag.length < 3) continue;
+    final rawShortcode = tag[1];
+    final url = tag[2];
+    if (rawShortcode.isEmpty || url.isEmpty) continue;
+    final shortcode = normalizeShortcode(rawShortcode);
+    if (shortcode == null) continue;
+    if (seen.contains(shortcode)) continue;
+    seen.add(shortcode);
+    emoji.add(CustomEmoji(shortcode: shortcode, url: url));
+  }
+
+  return emoji;
+}
+
+/// Union every member's kind:30030 set into the community palette, collapsed to
+/// one entry per shortcode. When members disagree on a shortcode's URL, the
+/// most recently published set wins (`created_at` is signed event data, so the
+/// result stays deterministic and fetch-order-independent); equal timestamps
+/// tie-break to the lexicographically-smallest URL. Output is sorted by
+/// shortcode.
+List<CustomEmoji> unionCustomEmoji(Iterable<NostrEvent> events) {
+  final byShortcode = <String, ({String url, int createdAt})>{};
+  for (final event in events) {
+    for (final e in customEmojiFromTags(event.tags)) {
+      final winner = byShortcode[e.shortcode];
+      if (winner == null ||
+          event.createdAt > winner.createdAt ||
+          (event.createdAt == winner.createdAt &&
+              e.url.compareTo(winner.url) < 0)) {
+        byShortcode[e.shortcode] = (url: e.url, createdAt: event.createdAt);
+      }
+    }
+  }
+  final result =
+      byShortcode.entries
+          .map((e) => CustomEmoji(shortcode: e.key, url: e.value.url))
+          .toList()
+        ..sort((a, b) => a.shortcode.compareTo(b.shortcode));
+  return result;
+}
+
+final RegExp _shortcodeScan = RegExp(r':([a-z0-9_-]+):', caseSensitive: false);
+
+/// Return one `["emoji", shortcode, url]` tag per *distinct* known custom emoji
+/// referenced in [content]. Matched case-insensitively; the canonical lowercase
+/// shortcode is emitted. Unknown `:foo:` are ignored. Order follows first
+/// appearance; each shortcode emitted at most once.
+///
+/// Mirrors how @mentions become `p` tags: derived from the final content at
+/// send time so the event is self-contained for any NIP-30 client.
+List<List<String>> buildCustomEmojiTags(
+  String content,
+  List<CustomEmoji> customEmoji,
+) {
+  if (customEmoji.isEmpty) return [];
+  final urlByShortcode = {for (final e in customEmoji) e.shortcode: e.url};
+
+  final emitted = <String>{};
+  final tags = <List<String>>[];
+
+  for (final match in _shortcodeScan.allMatches(content)) {
+    final shortcode = match.group(1)!.toLowerCase();
+    if (emitted.contains(shortcode)) continue;
+    final url = urlByShortcode[shortcode];
+    if (url == null) continue;
+    emitted.add(shortcode);
+    tags.add(['emoji', shortcode, url]);
+  }
+
+  return tags;
+}
+
+/// Resolve the image URL for a reaction whose content is a custom-emoji
+/// `:shortcode:`, from the community palette. Returns null for unicode
+/// reactions or unknown shortcodes.
+String? reactionEmojiUrl(String emoji, List<CustomEmoji>? palette) {
+  if (palette == null) return null;
+  if (!emoji.startsWith(':') || !emoji.endsWith(':')) return null;
+  final shortcode = emoji.substring(1, emoji.length - 1).toLowerCase();
+  for (final e in palette) {
+    if (e.shortcode == shortcode) return e.url;
+  }
+  return null;
+}