Improve charting UI for error cases

Web/Controllers/ChartController.cs

@@ -4,6 +4,7 @@ using System.Drawing;
 using System.Drawing.Imaging;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Web.Mvc;
 using System.Web.UI.DataVisualization.Charting;
 using System.Web.UI.WebControls;
@@ -57,7 +58,7 @@ namespace LeafWeb.Web.Controllers
 		    var curveData = GetCurveData(leafOutputFile.FileContents.Contents, curveId);
 
 		    if (curveData == null)
-			    return File("/Content/favicon/apple-icon-57x57.png", "image/png"); // TODO: different image ?
+			    return new HttpStatusCodeResult(HttpStatusCode.NotFound);
 
 		    var charts = GetChartBitmaps(curveData).ToList();
 
@@ -75,11 +76,18 @@ namespace LeafWeb.Web.Controllers
 
 		private CurveData GetCurveData(byte[] fileContents, string curveId)
 		{
-			LeafGasComparison[] leafGasComparisons;
-			using (var parser = new LeafGasComparisonParser(fileContents))
-				leafGasComparisons = parser.Parse(curveId);
-
-			return CurveDataConverter.Convert(leafGasComparisons).First();
+			try
+			{
+				LeafGasComparison[] leafGasComparisons;
+				using (var parser = new LeafGasComparisonParser(fileContents))
+					leafGasComparisons = parser.Parse(curveId);
+				return CurveDataConverter.Convert(leafGasComparisons).First();
+			}
+			catch (Exception e)
+			{
+				LogManager.GetCurrentClassLogger().Warn(e);
+			}
+			return null;
 		}
 
 		private string[] GetCurveIds(byte[] fileContents)

Web/Views/Chart/Index.cshtml

@@ -1,13 +1,17 @@
 @model LeafWeb.Web.ViewModels.Chart.ChartViewModel
 @{
     ViewBag.Title = "Chart";
+    var selectText = "Select CurveId";
 }
 <h1>@ViewBag.Title</h1>
 <h3>Identifier: <strong>@Model.LeafInputIdentifier</strong></h3>
 
-@Html.DropDownList("CurveId", new SelectList(Model.AvailableCurveId, Model.CurveId), "Select CurveId")
+@Html.DropDownList("CurveId", new SelectList(Model.AvailableCurveId, Model.CurveId), selectText)
 
 <img id="chart"/>
+<span class="help-block">
+    <span id="chart-error"></span>
+</span>
 
 @section Scripts
 {
@@ -15,17 +19,27 @@
         $(function () {
             $('#CurveId')
                 .change(function () {
+                    $('#chart-error').removeClass('text-danger').text('');
                     var $chart = $("#chart");
-                    var $spinner = $(this).after('<i class="fa fa-spinner fa-spin"></i>').next('i');
-                    $chart.attr('src', "");
+                    $chart.removeAttr('src');
+
                     var curveId = $("option:selected", this).text();
+                    if (curveId === "@Html.Raw(selectText)") {
+                        return;
+                    }
+                    var $spinner = $(this).after('<i class="fa fa-spinner fa-spin"></i>').next('i');
                     var url =
                         "@Html.Raw(Url.Action("ChartCurve", new {leafInputId = Model.LeafInputId, curveId="curveId"}))";
                     url = url.replace("=curveId", "=" + curveId);
-                    $chart.attr('src', url)
-                        .load(function() {
+                    $chart.load(function () {
                             $spinner.remove();
-                        });
+                        })
+                        .error(function () {
+                            $chart.removeAttr('src');
+                            $spinner.remove();
+                            $('#chart-error').addClass('text-danger').text('A problem was encountered loading this chart.');
+                        })
+                        .attr('src', url);
                 });
         });
     </script>