Add kanji page

lib/service/tangocard_files.dart

@@ -0,0 +1,50 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter/services.dart';
+import 'package:tangocard_reader/models/data_entry.dart';
+
+// TODO: merge
+
+Future<Map<File, List<YokutangoEntry>>> get tangocardFilePaths => rootBundle
+    .loadString('AssetManifest.json')
+    .then(
+      (json) => jsonDecode(json)
+          .keys
+          .where((String key) =>
+              key.contains('yokutango/json/') && key.contains('.json'))
+          .toList(),
+    )
+    .then(
+      (l) async => Map.fromIterables(
+        l.map<File>((f) => File(f)),
+        await Future.wait<List<YokutangoEntry>>(
+            l.map<Future<List<YokutangoEntry>>>(
+          (String t) => rootBundle.loadString(t).then<List<YokutangoEntry>>(
+              (s) => jsonDecode(s)
+                  .map<YokutangoEntry>((e) => YokutangoEntry.fromJson(e))
+                  .toList()),
+        )),
+      ),
+    );
+
+Future<Map<File, List<KanjiEntry>>> get kanjicardFilePaths => rootBundle
+    .loadString('AssetManifest.json')
+    .then(
+      (json) => jsonDecode(json)
+          .keys
+          .where((String key) =>
+              key.contains(RegExp(r'yokutango/kanji/kanji_\d+.json')))
+          .toList(),
+    )
+    .then(
+      (l) async => Map.fromIterables(
+        l.map<File>((f) => File(f)),
+        await Future.wait<List<KanjiEntry>>(l.map<Future<List<KanjiEntry>>>(
+          (String t) => rootBundle.loadString(t).then<List<KanjiEntry>>((s) =>
+              jsonDecode(s)
+                  .map<KanjiEntry>((e) => KanjiEntry.fromJson(e))
+                  .toList()),
+        )),
+      ),
+    );