lib/search/filter_kanji: init

lib/search.dart

@@ -1,5 +1,6 @@
 import 'package:jadb/models/word_search/word_search_result.dart';
 import 'package:jadb/models/kanji_search/kanji_search_result.dart';
+import 'package:jadb/search/filter_kanji.dart';
 import 'package:jadb/search/radical_search.dart';
 import 'package:jadb/search/word_search/word_search.dart';
 
@@ -16,6 +17,13 @@ class JaDBConnection {
   Future<KanjiSearchResult?> searchKanji(String kanji) =>
       searchKanjiWithDbConnection(this._connection, kanji);
 
+  /// Filter a list of characters, and return the ones that are listed in the kanji dictionary.
+  Future<List<String>> filterKanji(
+    List<String> kanji, {
+    bool deduplicate = false,
+  }) =>
+      filterKanjiWithDbConnection(this._connection, kanji, deduplicate);
+
   /// Search for a word in the database.
   Future<List<WordSearchResult>?> searchWord(
     String word, {

lib/search/filter_kanji.dart

@@ -0,0 +1,23 @@
+import 'package:jadb/_data_ingestion/kanjidic/table_names.dart';
+import 'package:sqflite_common/sqflite.dart';
+
+Future<List<String>> filterKanjiWithDbConnection(
+  DatabaseExecutor connection,
+  List<String> kanji,
+  bool deduplicate,
+) async {
+  final Set<String> filteredKanji = await connection.rawQuery(
+    '''
+      SELECT "literal"
+      FROM "${KANJIDICTableNames.character}"
+      WHERE "literal" IN (${kanji.map((_) => '?').join(',')})
+    ''',
+    kanji,
+  ).then((value) => value.map((e) => e['literal'] as String).toSet());
+
+  if (deduplicate) {
+    return filteredKanji.toList();
+  } else {
+    return kanji.where((k) => !filteredKanji.contains(k)).toList();
+  }
+}