Add kanji page

lib/models/data_entry.dart

@@ -0,0 +1,6 @@
+part 'yokutango_entry.dart';
+part 'kanji_entry.dart';
+
+abstract class DataEntry {
+  const DataEntry();
+}

lib/models/kanji_entry.dart

@@ -0,0 +1,53 @@
+part of 'data_entry.dart';
+
+class KanjiEntry extends DataEntry {
+  final String kanji;
+  final List<WordConstruct> kana;
+
+  KanjiEntry.fromJson(Map<String, dynamic> json)
+      : kanji = json['kanji'] as String,
+        kana = [
+          for (final j in json['kana'] as List) WordConstruct.fromJson(j)
+        ];
+
+        @override
+        String toString() {
+          return '$kanji - ${kana.join('、')}';
+        }
+}
+
+class WordConstruct {
+  final List<WordPiece> pieces;
+
+  WordConstruct({required this.pieces});
+
+  WordConstruct.fromJson(dynamic json)
+      : pieces = (json is String)
+            ? [WordPiece(word: json, isActive: true)]
+            : [for (final j in json as List) WordPiece.fromJson(j)];
+  
+  @override
+  String toString() {
+    return pieces.map((p) => p.isActive ? p.word : '(${p.word})').join('');
+  }
+}
+
+class WordPiece {
+  final String? kana;
+  final String? romaji;
+  final String word;
+  final bool isActive;
+
+  const WordPiece({
+    required this.word,
+    this.kana,
+    this.romaji,
+    this.isActive = false,
+  });
+
+  WordPiece.fromJson(Map<String, dynamic> json)
+      : kana = json['kana'] as String?,
+        romaji = json['romaji'] as String?,
+        word = json['text'] as String,
+        isActive = json['active'] as bool? ?? false;
+}

lib/models/router_args.dart

@@ -1,7 +1,7 @@
-import 'package:tangocard_reader/models/yokutango_entry.dart';
+import 'data_entry.dart';
 
 class BenkyouArgs {
-  final List<YokutangoEntry> cards;
+  final List<DataEntry> cards;
   final int? index;
 
   const BenkyouArgs({required this.cards, this.index});

lib/models/yokutango_entry.dart

@@ -1,4 +1,6 @@
-class YokutangoEntry {
+part of 'data_entry.dart';
+
+class YokutangoEntry extends DataEntry {
   final List<JapaneseWord> japanese;
   final List<NorwegianWord> norwegian;