Add sheet view page

lib/sheet.dart

@@ -0,0 +1,65 @@
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:path/path.dart' as p;
+
+class Sheet {
+  final String author;
+  final String name;
+
+  Sheet(this.author, this.name);
+}
+
+Future<List<Sheet>> loadSheetsSorted() async {
+  var sheets = await _loadSheets();
+  sheets.sort((left, right) => left.name.compareTo(right.name));
+  return sheets;
+}
+
+Future<List<Sheet>> _loadSheets() async {
+  // TODO: Handle directory not found
+  var dir = Directory("/home/julian/Nextcloud/jhome/Klavier-Noten/");
+  final List<Sheet> sheets = List.empty(growable: true);
+  if (dir.existsSync()) {
+    await for (final FileSystemEntity x in dir.list()) {
+      if (x is Directory) {
+        var authorName = p.basename(x.path);
+        await for (final FileSystemEntity a in x.list()) {
+          if (a is File) {
+            var sheetName = p.basenameWithoutExtension(a.path);
+            sheetName = sheetName.capitalize();
+            sheets.add(Sheet(authorName, sheetName));
+          }
+        }
+      }
+    }
+  }
+  return sheets;
+}
+
+extension StringExtension on String {
+  String capitalize() {
+    return "${this[0].toUpperCase()}${substring(1).toLowerCase()}";
+  }
+}
+
+class SheetsWidget extends StatelessWidget {
+  final List<Sheet> sheets;
+  final ValueSetter<Sheet> callback;
+
+  const SheetsWidget({super.key, required this.sheets, required this.callback});
+
+  @override
+  Widget build(context) {
+    return ListView.builder(
+        itemCount: sheets.length,
+        itemBuilder: (context, index) {
+          var sheet = sheets[index];
+          return ListTile(
+            title: Text(sheet.name),
+            subtitle: Text(sheet.author),
+            onTap: () => callback(sheet),
+          );
+        });
+  }
+}