fix: prevent duplicate stream notifications

- add store that is singleton
  to keep track of last posted
  stream and prevent
  posting twice for same stream

src/src/StevesBot.Webhook/Program.cs

@@ -41,6 +41,8 @@ builder.Services.AddSingleton(TimeProvider.System);
 builder.Services.AddSingleton<ConcurrentQueue<SubscribeTask>>();
 builder.Services.AddHostedService<SubscriptionWorker>();
 
+builder.Services.AddSingleton<LastPostedStreamStore>();
+
 builder.Services.AddOptionsWithValidateOnStart<DiscordNotificationOptions>()
   .BindConfiguration(nameof(DiscordNotificationOptions))
   .ValidateDataAnnotations();

src/src/StevesBot.Webhook/YouTube/Handlers/NotificationHandler.cs

@@ -8,6 +8,7 @@ internal static class NotificationHandler
     [FromServices] IYouTubeDataApiClient youTubeDataApiClient,
     [FromServices] IDiscordRestClient discordRestClient,
     [FromServices] IOptionsMonitor<DiscordNotificationOptions> discordNotificationOptions,
+    [FromServices] LastPostedStreamStore lastPostedStream,
     CancellationToken cancellationToken
   )
   {
@@ -39,6 +40,14 @@ internal static class NotificationHandler
       return Results.Ok();
     }
 
+    if (lastPostedStream.Value == videoId)
+    {
+      logger.LogInformation("Video ID {VideoId} has already been posted. Skipping notification.", videoId);
+      return Results.Ok();
+    }
+
+    lastPostedStream.SetValue(videoId);
+
     logger.LogInformation(
       "Video ID {VideoId} is a live stream. Creating discord message in channel {ChannelId}",
       videoId,

src/src/StevesBot.Webhook/YouTube/LastPostedStreamStore.cs

@@ -0,0 +1,11 @@
+namespace StevesBot.Webhook.YouTube;
+
+internal class LastPostedStreamStore
+{
+  public string Value { get; private set; } = string.Empty;
+
+  public void SetValue(string value)
+  {
+    Value = value;
+  }
+}