dotnet-cqrs/Svrnty.CQRS.Events.RabbitMQ/Configuration/RabbitMQTopologyManager.cs

using System;
using Svrnty.CQRS.Events.RabbitMQ.Configuration;
using Svrnty.CQRS.Events.Abstractions.Subscriptions;
using Svrnty.CQRS.Events.Abstractions.Configuration;
using Svrnty.CQRS.Events.Abstractions.EventStore;
using System.Collections.Generic;
using Microsoft.Extensions.Logging;
using RabbitMQ.Client;
using Svrnty.CQRS.Events.Abstractions;

namespace Svrnty.CQRS.Events.RabbitMQ.Configuration;

/// <summary>
/// Manages RabbitMQ topology (exchanges, queues, bindings).
/// </summary>
/// <remarks>
/// This class is responsible for creating and configuring RabbitMQ topology
/// based on the stream and subscription configuration.
/// </remarks>
public sealed class RabbitMQTopologyManager
{
    private readonly RabbitMQConfiguration _config;
    private readonly ILogger<RabbitMQTopologyManager> _logger;

    public RabbitMQTopologyManager(
        RabbitMQConfiguration config,
        ILogger<RabbitMQTopologyManager> logger)
    {
        _config = config ?? throw new ArgumentNullException(nameof(config));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <summary>
    /// Gets the exchange name for a stream.
    /// </summary>
    /// <param name="streamName">The stream name.</param>
    /// <returns>The full exchange name.</returns>
    public string GetExchangeName(string streamName)
    {
        if (string.IsNullOrWhiteSpace(streamName))
            throw new ArgumentException("Stream name cannot be null or whitespace.", nameof(streamName));

        return string.IsNullOrWhiteSpace(_config.ExchangePrefix)
            ? streamName
            : $"{_config.ExchangePrefix}.{streamName}";
    }

    /// <summary>
    /// Gets the queue name for a subscription.
    /// </summary>
    /// <param name="subscriptionId">The subscription ID.</param>
    /// <param name="consumerId">The consumer ID (for broadcast mode).</param>
    /// <param name="mode">The subscription mode.</param>
    /// <returns>The queue name.</returns>
    public string GetQueueName(string subscriptionId, string? consumerId, SubscriptionMode mode)
    {
        if (string.IsNullOrWhiteSpace(subscriptionId))
            throw new ArgumentException("Subscription ID cannot be null or whitespace.", nameof(subscriptionId));

        var queueName = mode switch
        {
            SubscriptionMode.Broadcast when !string.IsNullOrWhiteSpace(consumerId) =>
                // Each consumer gets its own queue
                $"{subscriptionId}.{consumerId}",

            SubscriptionMode.Exclusive or SubscriptionMode.ConsumerGroup =>
                // All consumers share one queue
                subscriptionId,

            _ => subscriptionId
        };

        return string.IsNullOrWhiteSpace(_config.ExchangePrefix)
            ? queueName
            : $"{_config.ExchangePrefix}.{queueName}";
    }

    /// <summary>
    /// Gets the routing key for an event based on the configured strategy.
    /// </summary>
    /// <param name="streamName">The stream name.</param>
    /// <param name="event">The event.</param>
    /// <returns>The routing key.</returns>
    public string GetRoutingKey(string streamName, ICorrelatedEvent @event)
    {
        if (string.IsNullOrWhiteSpace(streamName))
            throw new ArgumentException("Stream name cannot be null or whitespace.", nameof(streamName));
        if (@event == null)
            throw new ArgumentNullException(nameof(@event));

        return _config.DefaultRoutingKeyStrategy switch
        {
            "EventType" => @event.GetType().Name,
            "StreamName" => streamName,
            "Wildcard" => "#",
            _ => @event.GetType().Name
        };
    }

    /// <summary>
    /// Declares an exchange for a stream.
    /// </summary>
    /// <param name="channel">The RabbitMQ channel.</param>
    /// <param name="streamName">The stream name.</param>
    public void DeclareExchange(IChannel channel, string streamName)
    {
        if (channel == null)
            throw new ArgumentNullException(nameof(channel));
        if (string.IsNullOrWhiteSpace(streamName))
            throw new ArgumentException("Stream name cannot be null or whitespace.", nameof(streamName));

        if (!_config.AutoDeclareTopology)
        {
            _logger.LogDebug("Auto-declare topology is disabled, skipping exchange declaration for {StreamName}", streamName);
            return;
        }

        var exchangeName = GetExchangeName(streamName);

        try
        {
            channel.ExchangeDeclareAsync(
                exchange: exchangeName,
                type: _config.DefaultExchangeType,
                durable: _config.DurableExchanges,
                autoDelete: false,
                arguments: null).GetAwaiter().GetResult();

            _logger.LogInformation(
                "Declared exchange {ExchangeName} (type: {ExchangeType}, durable: {Durable})",
                exchangeName,
                _config.DefaultExchangeType,
                _config.DurableExchanges);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to declare exchange {ExchangeName}", exchangeName);
            throw;
        }
    }

    /// <summary>
    /// Declares a queue for a subscription.
    /// </summary>
    /// <param name="channel">The RabbitMQ channel.</param>
    /// <param name="subscriptionId">The subscription ID.</param>
    /// <param name="consumerId">The consumer ID (for broadcast mode).</param>
    /// <param name="mode">The subscription mode.</param>
    /// <returns>The declared queue name.</returns>
    public string DeclareQueue(
        IChannel channel,
        string subscriptionId,
        string? consumerId,
        SubscriptionMode mode)
    {
        if (channel == null)
            throw new ArgumentNullException(nameof(channel));
        if (string.IsNullOrWhiteSpace(subscriptionId))
            throw new ArgumentException("Subscription ID cannot be null or whitespace.", nameof(subscriptionId));

        if (!_config.AutoDeclareTopology)
        {
            var queueName = GetQueueName(subscriptionId, consumerId, mode);
            _logger.LogDebug("Auto-declare topology is disabled, skipping queue declaration for {QueueName}", queueName);
            return queueName;
        }

        var queue = GetQueueName(subscriptionId, consumerId, mode);
        var arguments = new Dictionary<string, object?>();

        // Add dead letter exchange if configured
        if (!string.IsNullOrWhiteSpace(_config.DeadLetterExchange))
        {
            arguments["x-dead-letter-exchange"] = _config.DeadLetterExchange;
        }

        // Add message TTL if configured
        if (_config.MessageTTL.HasValue)
        {
            arguments["x-message-ttl"] = (int)_config.MessageTTL.Value.TotalMilliseconds;
        }

        // Add max queue length if configured
        if (_config.MaxQueueLength.HasValue)
        {
            arguments["x-max-length"] = _config.MaxQueueLength.Value;
        }

        try
        {
            channel.QueueDeclareAsync(
                queue: queue,
                durable: _config.DurableQueues,
                exclusive: false,
                autoDelete: mode == SubscriptionMode.Broadcast, // Auto-delete broadcast queues
                arguments: arguments.Count > 0 ? arguments : null).GetAwaiter().GetResult();

            _logger.LogInformation(
                "Declared queue {QueueName} (durable: {Durable}, mode: {Mode})",
                queue,
                _config.DurableQueues,
                mode);

            return queue;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to declare queue {QueueName}", queue);
            throw;
        }
    }

    /// <summary>
    /// Binds a queue to an exchange with routing keys.
    /// </summary>
    /// <param name="channel">The RabbitMQ channel.</param>
    /// <param name="streamName">The stream name.</param>
    /// <param name="queueName">The queue name.</param>
    /// <param name="routingKeys">The routing keys for binding.</param>
    public void BindQueue(
        IChannel channel,
        string streamName,
        string queueName,
        IEnumerable<string> routingKeys)
    {
        if (channel == null)
            throw new ArgumentNullException(nameof(channel));
        if (string.IsNullOrWhiteSpace(streamName))
            throw new ArgumentException("Stream name cannot be null or whitespace.", nameof(streamName));
        if (string.IsNullOrWhiteSpace(queueName))
            throw new ArgumentException("Queue name cannot be null or whitespace.", nameof(queueName));
        if (routingKeys == null)
            throw new ArgumentNullException(nameof(routingKeys));

        if (!_config.AutoDeclareTopology)
        {
            _logger.LogDebug("Auto-declare topology is disabled, skipping queue binding for {QueueName}", queueName);
            return;
        }

        var exchangeName = GetExchangeName(streamName);

        foreach (var routingKey in routingKeys)
        {
            try
            {
                channel.QueueBindAsync(
                    queue: queueName,
                    exchange: exchangeName,
                    routingKey: routingKey,
                    arguments: null).GetAwaiter().GetResult();

                _logger.LogInformation(
                    "Bound queue {QueueName} to exchange {ExchangeName} with routing key {RoutingKey}",
                    queueName,
                    exchangeName,
                    routingKey);
            }
            catch (Exception ex)
            {
                _logger.LogError(
                    ex,
                    "Failed to bind queue {QueueName} to exchange {ExchangeName} with routing key {RoutingKey}",
                    queueName,
                    exchangeName,
                    routingKey);
                throw;
            }
        }
    }

    /// <summary>
    /// Declares the dead letter exchange if configured.
    /// </summary>
    /// <param name="channel">The RabbitMQ channel.</param>
    public void DeclareDeadLetterExchange(IChannel channel)
    {
        if (channel == null)
            throw new ArgumentNullException(nameof(channel));

        if (string.IsNullOrWhiteSpace(_config.DeadLetterExchange))
            return;

        if (!_config.AutoDeclareTopology)
        {
            _logger.LogDebug("Auto-declare topology is disabled, skipping dead letter exchange declaration");
            return;
        }

        try
        {
            channel.ExchangeDeclareAsync(
                exchange: _config.DeadLetterExchange,
                type: "topic",
                durable: true,
                autoDelete: false,
                arguments: null).GetAwaiter().GetResult();

            _logger.LogInformation("Declared dead letter exchange {ExchangeName}", _config.DeadLetterExchange);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to declare dead letter exchange {ExchangeName}", _config.DeadLetterExchange);
            throw;
        }
    }
}