Advanced Patterns

<Matrix xmlns="http://schemas.matrix.com/network/2024">
    <Pipeline Name="OrderProcessing">
        <Transformer Name="Validation">
            <Rules>
                <Required Path="order.customerId" />
                <Required Path="order.items[*].productId" />
            </Rules>
        </Transformer>
        
        <Processor Name="Enrichment">
            <Lookups>
                <ServiceLookup Path="customer" 
                             Source="CustomerService" />
                <ServiceLookup Path="inventory" 
                             Source="InventoryService" />
            </Lookups>
        </Processor>
        
        <Router Name="Distribution">
            <Routes>
                <Route When="order.type == 'standard'"
                       To="StandardProcessor" />
                <Route When="order.type == 'express'"
                       To="ExpressProcessor" />
            </Routes>
        </Router>
    </Pipeline>
</Matrix>

public class StateReplication
{
    public enum ConsistencyModel
    {
        Eventual,
        Strong,
        Causal
    }

    private readonly IStateStore _store;
    private readonly IMessageBus _bus;
    private readonly ConsistencyModel _model;

    public async Task ReplicateStateAsync(
        string path, 
        object value, 
        ConsistencyModel model)
    {
        switch (model)
        {
            case ConsistencyModel.Strong:
                await ReplicateStronglyConsistentAsync(path, value);
                break;
                
            case ConsistencyModel.Eventual:
                await ReplicateEventuallyConsistentAsync(path, value);
                break;
                
            case ConsistencyModel.Causal:
                await ReplicateCausallyConsistentAsync(path, value);
                break;
        }
    }

    private async Task ReplicateStronglyConsistentAsync(
        string path, 
        object value)
    {
        // Acquire distributed lock
        using var @lock = await _lockProvider.AcquireAsync(path);

        // Update all replicas
        var replicas = await _topology.GetReplicasAsync(path);
        
        foreach (var replica in replicas)
        {
            await replica.UpdateStateAsync(path, value);
            await replica.ConfirmUpdateAsync(path);
        }

        // Release lock only after all replicas confirm
    }
}

public class CircuitBreaker
{
    private readonly IHealthMonitor _monitor;
    private readonly TimeSpan _resetTimeout;
    private readonly int _failureThreshold;

    public async Task<TResult> ExecuteAsync<TResult>(
        Func<Task<TResult>> operation)
    {
        if (_monitor.IsOpen)
            throw new CircuitBreakerOpenException();

        try
        {
            var result = await operation();
            _monitor.RecordSuccess();
            return result;
        }
        catch (Exception ex)
        {
            _monitor.RecordFailure(ex);
            
            if (_monitor.FailureCount >= _failureThreshold)
                _monitor.OpenCircuit();
                
            throw;
        }
    }
}

public class ServiceDiscovery
{
    private readonly IServiceRegistry _registry;
    private readonly ILoadBalancer _loadBalancer;

    public async Task<ServiceEndpoint> LocateServiceAsync(
        string serviceName, 
        ServiceRequirements requirements)
    {
        // Find all matching services
        var candidates = await _registry.FindServicesAsync(
            serviceName, 
            requirements);

        // Filter by health status
        var healthy = candidates.Where(
            s => s.Health.Status == HealthStatus.Healthy);

        // Apply load balancing
        return _loadBalancer.SelectEndpoint(healthy);
    }

    public async Task RegisterServiceAsync(
        ServiceDefinition definition)
    {
        // Register service
        await _registry.RegisterAsync(definition);

        // Start health checks
        await _healthChecker.StartAsync(definition);

        // Begin metrics collection
        await _metrics.StartCollectionAsync(definition);
    }
}

public class ServiceStateMachine
{
    private readonly Dictionary<string, StateTransition> _transitions;
    private readonly IStateStore _store;

    public async Task TransitionAsync(
        string currentState, 
        string trigger)
    {
        var transition = _transitions[currentState];
        
        if (!transition.CanHandle(trigger))
            throw new InvalidTransitionException();

        // Execute pre-transition actions
        await transition.BeforeAsync();

        // Perform state change
        var newState = transition.Execute(trigger);
        await _store.SaveStateAsync(newState);

        // Execute post-transition actions
        await transition.AfterAsync();

        // Notify observers
        await NotifyStateChangeAsync(currentState, newState);
    }
}

public class RetryPolicy
{
    private readonly int _maxAttempts;
    private readonly TimeSpan _delay;
    private readonly IBackoffStrategy _backoff;

    public async Task<TResult> ExecuteWithRetryAsync<TResult>(
        Func<Task<TResult>> operation)
    {
        var attempts = 0;
        var delay = _delay;

        while (true)
        {
            try
            {
                return await operation();
            }
            catch (Exception ex) when (ShouldRetry(ex))
            {
                if (++attempts >= _maxAttempts)
                    throw;

                await Task.Delay(delay);
                delay = _backoff.NextDelay(delay);
            }
        }
    }
}

public class Bulkhead
{
    private readonly SemaphoreSlim _semaphore;
    private readonly int _maxParallelism;
    private readonly TimeSpan _timeout;

    public async Task ExecuteAsync(
        Func<Task> operation)
    {
        if (!await _semaphore.WaitAsync(_timeout))
            throw new BulkheadRejectedException();

        try
        {
            await operation();
        }
        finally
        {
            _semaphore.Release();
        }
    }
}