Implement Max Queue and Max Batch size when publishing

MaxPublishBatchSize must be set, but MaxQueueSize can be set to 0 to disable check of the rabbitmq queue size

src/producer/Services/TorrentPublisher.cs

@@ -1,12 +1,24 @@
 namespace Producer.Services;
 
-public class TorrentPublisher(ISendEndpointProvider sendEndpointProvider, RabbitMqConfiguration configuration) : IMessagePublisher
+public class TorrentPublisher(
+    ISendEndpointProvider sendEndpointProvider,
+    RabbitMqConfiguration configuration,
+    IHttpClientFactory httpClientFactory,
+    ILogger<TorrentPublisher> logger) : IMessagePublisher
 {
-    public async Task PublishAsync(IEnumerable<Torrent> torrents, CancellationToken cancellationToken = default)
+    public async Task<bool> PublishAsync(IReadOnlyCollection<Torrent> torrents, CancellationToken cancellationToken = default)
     {
         var queueAddress = ConstructQueue();
         var sendEndpoint = await sendEndpointProvider.GetSendEndpoint(new(queueAddress));
+
+        if (!await CanPublishToRabbitMq(torrents, cancellationToken))
+        {
+            logger.LogWarning("Queue is full or not accessible, not publishing this time.");   
+            return false;
+        }
+        
         await sendEndpoint.SendBatch(torrents, cancellationToken: cancellationToken);
+        return true;
     }
     
     private string ConstructQueue()
@@ -19,4 +31,48 @@ public class TorrentPublisher(ISendEndpointProvider sendEndpointProvider, Rabbit
 
         return queueBuilder.ToString();
     }
+    
+    private async Task<bool> CanPublishToRabbitMq(IReadOnlyCollection<Torrent> torrents, CancellationToken cancellationToken)
+    {
+        if (configuration.MaxQueueSize == 0)
+        {
+            return true;
+        }
+        
+        var client = httpClientFactory.CreateClient("RabbitMq");
+        
+        client.DefaultRequestHeaders.Authorization = 
+            new("Basic", Convert.ToBase64String(Encoding.UTF8.GetBytes($"{configuration.Username}:{configuration.Password}")));
+        
+        var url = $"http://{configuration.Host}:15672/api/queues/{Uri.EscapeDataString("/")}/{configuration.QueueName}";
+        
+        var response = await client.GetAsync(url, cancellationToken);
+        
+        var body = await response.Content.ReadAsStringAsync(cancellationToken);
+        var doc = JsonDocument.Parse(body);
+
+        if (!doc.RootElement.TryGetProperty("messages", out var messages))
+        {
+            logger.LogWarning("Failed to get message count from RabbitMq");
+            return false;
+        }
+
+        if (!messages.TryGetInt32(out var messageCount))
+        {
+            logger.LogWarning("Failed to get message count from RabbitMq");
+            return false;
+        }
+        
+        logger.LogInformation("Current queue message count: {MessageCount}", messageCount);
+        
+        var canPublish = messageCount < configuration.MaxQueueSize + torrents.Count;
+        
+        if (!canPublish)
+        {
+            logger.LogWarning("You have configured a max queue size of {MaxQueueSize}.", configuration.MaxQueueSize);
+            logger.LogWarning("Not publishing this time.");
+        }
+        
+        return canPublish;
+    }
 }