// Program.cs
builder.Host.UseWolverine(opts =>
{
    // Auto-discover handlers from this assembly
    opts.Discovery.IncludeAssembly(typeof(Program).Assembly);

    // RabbitMQ transport
    opts.UseRabbitMq(rabbit =>
    {
        rabbit.HostName = "localhost";
        // Or from configuration:
        // rabbit.HostName = builder.Configuration["RabbitMq:Host"]!;
    })
    .AutoProvision()   // Create queues/exchanges automatically
    .AutoPurgeOnStartup(); // Dev only — clear queues on startup

    // Enable transactional outbox with EF Core
    opts.Services.AddDbContextWithWolverineIntegration<AppDbContext>(x =>
        x.UseNpgsql(builder.Configuration.GetConnectionString("Default")));

    opts.Policies.AutoApplyTransactions(); // Wrap handlers in DB transactions
});

// Message contract (in shared Contracts project)
public record OrderCreated(Guid OrderId, string CustomerId, decimal Total, DateTimeOffset CreatedAt);

// Style 1: Cascading messages — return the event from the handler
// Wolverine automatically publishes returned messages after the handler completes.
public static class CreateOrder
{
    public record Command(string CustomerId, List<OrderItem> Items);
    public record Response(Guid OrderId, decimal Total);

    public static async Task<(Response, OrderCreated)> HandleAsync(
        Command command, AppDbContext db, TimeProvider clock, CancellationToken ct)
    {
        var order = Order.Create(command.CustomerId, command.Items, clock.GetUtcNow());
        db.Orders.Add(order);
        await db.SaveChangesAsync(ct);

        var response = new Response(order.Id, order.Total);
        var @event = new OrderCreated(order.Id, order.CustomerId, order.Total, order.CreatedAt);

        return (response, @event); // Both are published automatically
    }
}

// Style 2: Explicit publishing via IMessageBus
public static class CreateOrder
{
    public record Command(string CustomerId, List<OrderItem> Items);
    public record Response(Guid OrderId, decimal Total);

    public static async Task<Response> HandleAsync(
        Command command, AppDbContext db, IMessageBus bus, TimeProvider clock, CancellationToken ct)
    {
        var order = Order.Create(command.CustomerId, command.Items, clock.GetUtcNow());
        db.Orders.Add(order);
        await db.SaveChangesAsync(ct);

        await bus.PublishAsync(new OrderCreated(
            order.Id, order.CustomerId, order.Total, order.CreatedAt));

        return new Response(order.Id, order.Total);
    }
}

// Notifications module — handles OrderCreated from Orders module
public static class OrderCreatedHandler
{
    public static async Task HandleAsync(
        OrderCreated message, NotificationsDbContext db, ILogger logger, CancellationToken ct)
    {
        logger.LogInformation("Processing OrderCreated: {OrderId}", message.OrderId);

        var notification = new OrderNotification(message.OrderId, message.CustomerId);
        db.Notifications.Add(notification);
        await db.SaveChangesAsync(ct);
    }
}

// 1. Register DbContext with Wolverine integration
builder.Host.UseWolverine(opts =>
{
    opts.Services.AddDbContextWithWolverineIntegration<AppDbContext>(x =>
        x.UseNpgsql(builder.Configuration.GetConnectionString("Default")));

    opts.Policies.AutoApplyTransactions();
});

// 2. DbContext — add Wolverine outbox tables
public class AppDbContext(DbContextOptions<AppDbContext> options) : DbContext(options)
{
    public DbSet<Order> Orders => Set<Order>();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        // Wolverine inbox/outbox tables — required for transactional messaging
        modelBuilder.AddIncomingWolverineMessageTable();
        modelBuilder.AddOutgoingWolverineMessageTable();
    }
}

public record OrderSagaState(Guid Id)
{
    public string? CustomerId { get; set; }
    public bool PaymentReceived { get; set; }
}

public class OrderSaga : Saga<OrderSagaState>
{
    public Guid Id { get; set; }

    // Start the saga when an OrderCreated event arrives
    public static (OrderSagaState, ProcessPayment) Start(OrderCreated message)
    {
        var state = new OrderSagaState(message.OrderId)
        {
            CustomerId = message.CustomerId
        };

        var command = new ProcessPayment(message.OrderId, message.Total);
        return (state, command); // State is persisted, command is sent
    }

    // Handle payment result
    public CompleteOrder Handle(PaymentCompleted message)
    {
        PaymentReceived = true;
        MarkCompleted(); // Ends the saga
        return new CompleteOrder(Id);
    }

    // Compensating action on failure
    public CancelOrder Handle(PaymentFailed message)
    {
        MarkCompleted();
        return new CancelOrder(Id);
    }
}

// Setup
builder.Services.AddMassTransit(x =>
{
    x.SetKebabCaseEndpointNameFormatter();
    x.AddConsumers(typeof(Program).Assembly);
    x.UsingRabbitMq((context, cfg) =>
    {
        cfg.Host(builder.Configuration.GetConnectionString("RabbitMq"));
        cfg.ConfigureEndpoints(context);
    });
});

// Publishing
await publishEndpoint.Publish(new OrderCreated(...), ct);

// Consuming — requires IConsumer<T> interface
public class OrderCreatedConsumer(AppDbContext db) : IConsumer<OrderCreated>
{
    public async Task Consume(ConsumeContext<OrderCreated> context)
    {
        var message = context.Message;
        // Handle event...
    }
}

// Outbox
x.AddEntityFrameworkOutbox<AppDbContext>(o =>
{
    o.UsePostgres();
    o.UseBusOutbox();
});

// Saga — uses MassTransitStateMachine<TState>
public class OrderSaga : MassTransitStateMachine<OrderSagaState> { /* ... */ }

// BAD — if SaveChanges succeeds but Publish fails, data is inconsistent
await db.SaveChangesAsync(ct);
await bus.PublishAsync(new OrderCreated(...));

// GOOD — use transactional outbox (messages are in the same transaction)
// Configure AddDbContextWithWolverineIntegration() + AutoApplyTransactions()
// Wolverine handles this automatically

// BAD — behavior in a message
public record OrderCreated(Guid OrderId)
{
    public decimal CalculateShipping() => /* logic */; // DON'T
}

// GOOD — messages are pure data
public record OrderCreated(Guid OrderId, string CustomerId, decimal Total, DateTimeOffset CreatedAt);

// BAD — no guarantee of delivery
_ = Task.Run(() => bus.PublishAsync(new OrderCreated(...)));

// GOOD — await the publish (with outbox, this is transactional)
await bus.PublishAsync(new OrderCreated(...));