Module System

The Module System provides a structured, type-safe way to organize CQRS/ES applications by domain.

Why Modules?

Instead of manually wiring handlers with scattered bus.register() calls:

// Before: Manual wiring
const commandBus = new CommandBus();
commandBus.register('CreateUser', new CreateUserHandler(userRepo));
commandBus.register('UpdateUser', new UpdateUserHandler(userRepo));
commandBus.register('PlaceOrder', new PlaceOrderHandler(orderRepo));
// ... dozens more registrations

Organize handlers into cohesive domain modules:

// After: Module-based organization
const app = createEventFlowsApp({
  eventStore,
  eventBus,
  modules: [userModule, orderModule] as const,
});

// Full intellisense for all commands and queries
await app.commands.CreateUser({ userId: '123', name: 'John' });

Key Benefits

• Domain Organization: Group related handlers by bounded context
• Type-Safe Execution: Full TypeScript intellisense for commands and queries
• Dependency Injection: Modules receive infrastructure via setup function
• Automatic Wiring: Event store publishes to event bus automatically
• Cross-Module Events: Modules communicate through domain events

When to Use

Use modules when your application has:

• Multiple bounded contexts or domains
• Many command and query handlers to organize
• Need for type-safe command/query execution with intellisense
• Desire for cleaner dependency injection patterns

Quick Example

import { createModule, createEventFlowsApp } from '@eventflows/core';

// Define a module
const userModule = createModule({
  name: 'users',
  setup: ({ eventStore }) => {
    const userRepository = new UserRepository(eventStore);
    return {
      commandHandlers: {
        CreateUser: new CreateUserCommandHandler(userRepository),
      },
      queryHandlers: {
        GetUserById: new GetUserByIdQueryHandler(),
      },
    };
  },
});

// Create the application
const app = createEventFlowsApp({
  eventStore: myEventStore,
  eventBus: new InMemoryEventBus({}),
  modules: [userModule] as const,
});

// Execute with full type inference
await app.commands.CreateUser({ userId: '123', name: 'John' });
const user = await app.queries.GetUserById({ userId: '123' });

Next Steps

• createModule() - Define domain modules with handlers
• createEventFlowsApp() - Compose modules into an application