opt: danmaku filter (#486)

lib/models/user/danmaku_rule.dart

@@ -0,0 +1,44 @@
+import 'package:PiliPlus/grpc/dm/v1/dm.pb.dart';
+
+class RuleFilter {
+  static final _regExp = RegExp(r'^/(.*)/$');
+
+  List<String> dmFilterString = [];
+  List<RegExp> dmRegExp = [];
+  Set<String> dmUid = {};
+
+  int count = 0;
+
+  RuleFilter(this.dmFilterString, this.dmRegExp, this.dmUid, [int? count]) {
+    this.count =
+        count ?? dmFilterString.length + dmRegExp.length + dmUid.length;
+  }
+
+  RuleFilter.fromRuleTypeEntires(
+      Iterable<MapEntry<int, Map<int, String>>> rules) {
+    for (var rule in rules) {
+      switch (rule.key) {
+        case 0:
+          dmFilterString.addAll(rule.value.values);
+          break;
+        case 1:
+          dmRegExp.addAll(rule.value.values.map((i) => RegExp(
+              _regExp.matchAsPrefix(i)?.group(1) ?? i,
+              caseSensitive: false)));
+          break;
+        case 2:
+          dmUid.addAll(rule.value.values);
+          break;
+      }
+    }
+    count = dmFilterString.length + dmRegExp.length + dmUid.length;
+  }
+
+  RuleFilter.empty();
+
+  bool retain(DanmakuElem elem) {
+    return !(dmUid.contains(elem.midHash) ||
+        dmFilterString.any((i) => elem.content.contains(i)) ||
+        dmRegExp.any((i) => i.hasMatch(elem.content)));
+  }
+}