Fix invalid ICS and PDF export returning validation errors as file content (#33)

* Initial plan

* Fix client-side export error handling and identify validation root cause

Co-authored-by: clayschaad <11883505+clayschaad@users.noreply.github.com>

* Complete fix for invalid ICS and PDF export issue

Co-authored-by: clayschaad <11883505+clayschaad@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: clayschaad <11883505+clayschaad@users.noreply.github.com>

Client/Pages/Index.razor

@@ -10,6 +10,22 @@
 
 <h3>Shift Scheduler - @CurrentMonthYear</h3>
 
+@if (!string.IsNullOrEmpty(_errorMessage))
+{
+    <div class="alert alert-danger" role="alert">
+        @_errorMessage
+        <button type="button" class="btn-close" @onclick="() => _errorMessage = string.Empty"></button>
+    </div>
+}
+
+@if (!string.IsNullOrEmpty(_successMessage))
+{
+    <div class="alert alert-success" role="alert">
+        @_successMessage
+        <button type="button" class="btn-close" @onclick="() => _successMessage = string.Empty"></button>
+    </div>
+}
+
 @if (_isLoadingInitial)
 {
     <div class="loading-overlay">

Client/Pages/Index.razor.cs

@@ -20,6 +20,8 @@ namespace ShiftScheduler.Client.Pages
         private int EditYear { get; set; }
         private bool _isLoadingTransport = false;
         private bool _isLoadingInitial = false;
+        private string _errorMessage = string.Empty;
+        private string _successMessage = string.Empty;
 
         private string CurrentMonthYear => new DateTime(EditYear, EditMonth, 1).ToString("MMMM yyyy");
 
@@ -98,21 +100,67 @@ namespace ShiftScheduler.Client.Pages
 
         private async Task ExportToIcs()
         {
+            try
+            {
+                _errorMessage = string.Empty;
+                _successMessage = string.Empty;
+                StateHasChanged();
+
                 var shiftsWithTransportList = SelectedShiftsWithTransport.Values.ToList();
                 var response = await HttpClient.PostAsJsonAsync("api/shift/export_ics", shiftsWithTransportList);
+                
+                if (response.IsSuccessStatusCode)
+                {
                     var bytes = await response.Content.ReadAsByteArrayAsync();
                     var base64 = Convert.ToBase64String(bytes);
                     var fileUrl = $"data:text/calendar;base64,{base64}";
                     NavigationManager.NavigateTo(fileUrl, true);
+                    _successMessage = "ICS file exported successfully!";
+                }
+                else
+                {
+                    var errorContent = await response.Content.ReadAsStringAsync();
+                    _errorMessage = $"Failed to export ICS file: {response.StatusCode}. {errorContent}";
+                }
+            }
+            catch (Exception ex)
+            {
+                _errorMessage = $"Error exporting ICS file: {ex.Message}";
+            }
+            
+            StateHasChanged();
         }
 
         private async Task ExportToPdf()
         {
+            try
+            {
+                _errorMessage = string.Empty;
+                _successMessage = string.Empty;
+                StateHasChanged();
+
                 var shiftsWithTransportList = SelectedShiftsWithTransport.Values.ToList();
                 var response = await HttpClient.PostAsJsonAsync("api/shift/export_pdf", shiftsWithTransportList);
+                
+                if (response.IsSuccessStatusCode)
+                {
                     var bytes = await response.Content.ReadAsByteArrayAsync();
                     var base64 = Convert.ToBase64String(bytes);
                     await JSRuntime.InvokeVoidAsync("downloadFile", $"Schedule {EditYear}-{EditMonth:D2}.pdf", "application/pdf", base64);
+                    _successMessage = "PDF file exported successfully!";
+                }
+                else
+                {
+                    var errorContent = await response.Content.ReadAsStringAsync();
+                    _errorMessage = $"Failed to export PDF file: {response.StatusCode}. {errorContent}";
+                }
+            }
+            catch (Exception ex)
+            {
+                _errorMessage = $"Error exporting PDF file: {ex.Message}";
+            }
+            
+            StateHasChanged();
         }
 
         private async Task SaveScheduleToStorage()

Shared/TransportModels.cs

@@ -17,7 +17,7 @@ namespace ShiftScheduler.Shared
         public string DepartureTime { get; set; } = string.Empty;
         public string ArrivalTime { get; set; } = string.Empty;
         public string Duration { get; set; } = string.Empty;
-        public string Platform { get; set; } = string.Empty;
+        public string? Platform { get; set; } = string.Empty;
         public List<TransportSection> Sections { get; set; } = new();
     }
 
@@ -38,9 +38,9 @@ namespace ShiftScheduler.Shared
     public class TransportCheckpoint
     {
         public TransportStation? Station { get; set; }
-        public string Departure { get; set; } = string.Empty;
+        public string? Departure { get; set; } = string.Empty;
-        public string Arrival { get; set; } = string.Empty;
+        public string? Arrival { get; set; } = string.Empty;
-        public string Platform { get; set; } = string.Empty;
+        public string? Platform { get; set; } = string.Empty;
     }
 
     public class TransportStation