Cleanup (#98)

lib/custom_errors.dart

@@ -1,3 +1,15 @@
+import 'package:flutter/material.dart';
+import 'package:obtainium/providers/apps_provider.dart';
+
+class ObtainiumError {
+  late String message;
+  ObtainiumError(this.message);
+  @override
+  String toString() {
+    return message;
+  }
+}
+
 class RateLimitError {
   late int remainingMinutes;
   RateLimitError(this.remainingMinutes);
@@ -6,3 +18,81 @@ class RateLimitError {
   String toString() =>
       'Too many requests (rate limited) - try again in $remainingMinutes minutes';
 }
+
+class InvalidURLError extends ObtainiumError {
+  InvalidURLError(String sourceName) : super('Not a valid $sourceName App URL');
+}
+
+class NoReleasesError extends ObtainiumError {
+  NoReleasesError() : super('Could not find a suitable release');
+}
+
+class NoAPKError extends ObtainiumError {
+  NoAPKError() : super('Could not find a suitable release');
+}
+
+class NoVersionError extends ObtainiumError {
+  NoVersionError() : super('Could not determine release version');
+}
+
+class UnsupportedURLError extends ObtainiumError {
+  UnsupportedURLError() : super('URL does not match a known source');
+}
+
+class DowngradeError extends ObtainiumError {
+  DowngradeError() : super('Cannot install an older version of an App');
+}
+
+class IDChangedError extends ObtainiumError {
+  IDChangedError()
+      : super('Downloaded package ID does not match existing App ID');
+}
+
+class MultiAppMultiError extends ObtainiumError {
+  Map<String, List<String>> content = {};
+
+  MultiAppMultiError() : super('Multiple Errors Placeholder');
+
+  add(String appId, String string) {
+    var tempIds = content.remove(string);
+    tempIds ??= [];
+    tempIds.add(appId);
+    content.putIfAbsent(string, () => tempIds!);
+  }
+
+  @override
+  String toString() {
+    String finalString = '';
+    for (var e in content.keys) {
+      finalString += '$e: ${content[e].toString()}\n\n';
+    }
+    return finalString;
+  }
+}
+
+showError(dynamic e, BuildContext context) {
+  if (e is String || (e is ObtainiumError && e is! MultiAppMultiError)) {
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(content: Text(e.toString())),
+    );
+  } else {
+    showDialog(
+        context: context,
+        builder: (BuildContext ctx) {
+          return AlertDialog(
+            scrollable: true,
+            title: Text(e is MultiAppMultiError
+                ? 'Some Errors Occurred'
+                : 'Unexpected Error'),
+            content: Text(e.toString()),
+            actions: [
+              TextButton(
+                  onPressed: () {
+                    Navigator.of(context).pop(null);
+                  },
+                  child: const Text('Ok')),
+            ],
+          );
+        });
+  }
+}