Add support for offline storage of errors to Raygun4Net Core

Mindscape.Raygun4Net.NetCore.Common/Offline/CrashReportStoreEntry.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace Mindscape.Raygun4Net.Offline;
+
+public sealed class CrashReportStoreEntry
+{
+  /// <summary>
+  /// Unique ID for the record
+  /// </summary>
+  public Guid Id { get; set; }
+
+  /// <summary>
+  /// The application api key that the payload was intended for
+  /// </summary>
+  public string ApiKey { get; set; }
+
+  /// <summary>
+  /// The JSON serialized payload of the error
+  /// </summary>
+  public string MessagePayload { get; set; }
+}

Mindscape.Raygun4Net.NetCore.Common/Offline/IBackgroundSendStrategy.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Mindscape.Raygun4Net.Offline;
+
+public interface IBackgroundSendStrategy : IDisposable
+{
+  public event Func<Task> OnSendAsync;
+  public void Start();
+  public void Stop();
+}

Mindscape.Raygun4Net.NetCore.Common/Offline/OfflineStoreBase.cs

@@ -0,0 +1,61 @@
+#nullable enable
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Mindscape.Raygun4Net.Offline;
+
+public delegate Task SendHandler(string messagePayload, string apiKey, CancellationToken cancellationToken);
+
+public abstract class OfflineStoreBase
+{
+  private readonly IBackgroundSendStrategy _backgroundSendStrategy;
+  protected SendHandler? SendCallback { get; set; }
+
+  protected OfflineStoreBase(IBackgroundSendStrategy backgroundSendStrategy)
+  {
+    _backgroundSendStrategy = backgroundSendStrategy ?? throw new ArgumentNullException(nameof(backgroundSendStrategy));
+    _backgroundSendStrategy.OnSendAsync += ProcessOfflineCrashReports;
+  }
+
+  public virtual void SetSendCallback(SendHandler sendHandler)
+  {
+    SendCallback = sendHandler;
+  }
+
+  protected virtual async Task ProcessOfflineCrashReports()
+  {
+    if (SendCallback is null)
+    {
+      return;
+    }
+
+    try
+    {
+      var cachedCrashReports = await GetAll(CancellationToken.None);
+      foreach (var crashReport in cachedCrashReports)
+      {
+        try
+        {
+          await SendCallback(crashReport.MessagePayload, crashReport.ApiKey, CancellationToken.None);
+          await Remove(crashReport.Id, CancellationToken.None);
+        }
+        catch (Exception ex)
+        {
+          Debug.WriteLine($"Exception sending offline error [{crashReport.Id}]: {ex}");
+          throw;
+        }
+      }
+    }
+    catch (Exception ex)
+    {
+      Debug.WriteLine($"Exception sending offline errors: {ex}");
+    }
+  }
+
+  public abstract Task<List<CrashReportStoreEntry>> GetAll(CancellationToken cancellationToken);
+  public abstract Task<bool> Save(string crashPayload, string apiKey, CancellationToken cancellationToken);
+  public abstract Task<bool> Remove(Guid cacheEntryId, CancellationToken cancellationToken);
+}

Mindscape.Raygun4Net.NetCore.Common/Offline/TimerBasedSendStrategy.cs

@@ -0,0 +1,62 @@
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Mindscape.Raygun4Net.Offline;
+
+public class TimerBasedSendStrategy : IBackgroundSendStrategy
+{
+  private static readonly TimeSpan DefaultInternal = TimeSpan.FromSeconds(30);
+
+  private readonly Timer _backgroundTimer;
+  public event Func<Task> OnSendAsync;
+
+  public TimeSpan Interval { get; }
+
+  public TimerBasedSendStrategy(TimeSpan? interval = null)
+  {
+    Interval = interval ?? DefaultInternal;
+    _backgroundTimer = new Timer(SendOfflineErrors);
+    Start();
+  }
+
+  ~TimerBasedSendStrategy()
+  {
+    Dispose();
+  }
+
+  private async void SendOfflineErrors(object state)
+  {
+    try
+    {
+      var invocationList = OnSendAsync?.GetInvocationList();
+      if (invocationList != null)
+      {
+        var tasks = invocationList.OfType<Func<Task>>().Select(handler => handler());
+        await Task.WhenAll(tasks);
+      }
+    }
+    finally
+    {
+      Start();
+    }
+  }
+
+  public void Start()
+  {
+    // This sets the timer to trigger once at the interval, and then "never again".
+    // This inherently prevents the timer from being re-entrant 
+    _backgroundTimer.Change(Interval, TimeSpan.FromMilliseconds(int.MaxValue));
+  }
+
+  public void Stop()
+  {
+    _backgroundTimer.Change(Timeout.Infinite, 0);
+  }
+
+  public void Dispose()
+  {
+    _backgroundTimer?.Dispose();
+  }
+}