decoupled business logic from ui

lib/src/util/checks.dart

@@ -0,0 +1,56 @@
+import 'dart:io';
+
+import '../model/fortnite_version.dart';
+
+String? checkVersion(String? text, List<FortniteVersion> versions) {
+  if (text == null || text.isEmpty) {
+    return 'Empty version name';
+  }
+
+  if (versions.any((element) => element.name == text)) {
+    return 'This version already exists';
+  }
+
+  return null;
+}
+
+String? checkGameFolder(text) {
+  if (text == null || text.isEmpty) {
+    return 'Empty game path';
+  }
+
+  var directory = Directory(text);
+  if (!directory.existsSync()) {
+    return "Directory doesn't exist";
+  }
+
+  if (FortniteVersion.findExecutable(directory, "FortniteClient-Win64-Shipping.exe") == null) {
+    return "Invalid game path";
+  }
+
+  return null;
+}
+
+String? checkDownloadDestination(text) {
+  if (text == null || text.isEmpty) {
+    return 'Invalid download path';
+  }
+
+  return null;
+}
+
+String? checkDll(String? text) {
+  if (text == null || text.isEmpty) {
+    return "Empty dll path";
+  }
+
+  if (!File(text).existsSync()) {
+    return "This dll doesn't exist";
+  }
+
+  if (!text.endsWith(".dll")) {
+    return "This file is not a dll";
+  }
+
+  return null;
+}