Handle argument exceptions on client side

src/Podsync/Controllers/DownloadController.cs

@@ -1,5 +1,6 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc;
+using Podsync.Helpers;
 using Podsync.Services.Links;
 using Podsync.Services.Resolver;
 using Podsync.Services.Storage;
@@ -7,6 +8,7 @@ using Podsync.Services.Storage;
 namespace Podsync.Controllers
 {
     [Route("download")]
+    [HandleException]
     public class DownloadController : Controller
     {
         private readonly IResolverService _resolverService;

src/Podsync/Controllers/FeedController.cs

@@ -16,6 +16,7 @@ using Podsync.Services.Storage;
 namespace Podsync.Controllers
 {
     [Route("feed")]
+    [HandleException]
     public class FeedController : Controller
     {
         private const int DefaultPageSize = 50;

src/Podsync/Helpers/HandleExceptionAttribute.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Net;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
+
+namespace Podsync.Helpers
+{
+    public class HandleExceptionAttribute : ExceptionFilterAttribute
+    {
+        public override void OnException(ExceptionContext context)
+        {
+            var exception = context.Exception;
+            if (exception is ArgumentNullException || exception is ArgumentException)
+            {
+                context.Result = new BadRequestObjectResult(exception.Message);
+            }
+            else
+            {
+                context.Result = new StatusCodeResult((int)HttpStatusCode.InternalServerError);
+            }
+        }
+    }
+}

src/Podsync/Services/Links/LinkService.cs

@@ -173,7 +173,7 @@ namespace Podsync.Services.Links
 
             if (string.IsNullOrWhiteSpace(id) || linkType == LinkType.Unknown || provider == Provider.Unknown)
             {
-                throw new ArgumentException("Failed to parse URL");
+                throw new ArgumentException("This provider is not supported");
             }
             
             return new LinkInfo

src/Podsync/wwwroot/js/site.js

@@ -24,12 +24,16 @@ $(function () {
             error: function (xhr, status, error) {
                 if (xhr.status === 400) {
                     // Bad request
-                    var json = JSON.parse(xhr.responseText);
-
                     var text = '';
-                    $.each(json, function (key, value) {
-                        text += value + '\r\n';
-                    });
+
+                    try {
+                        var json = JSON.parse(xhr.responseText);
+                        $.each(json, function (key, value) {
+                            text += value + '\r\n';
+                        });
+                    } catch (e) {
+                        text = xhr.responseText;
+                    } 
 
                     err(text);
                 } else {