@setu-ts/cqrs-plugin — command and query dispatch

Add it: setu add cqrs adds it and wires CqrsPlugin() in a recognized functional config. It provides CAPABILITIES.CQRS (ICqrsFacade), CAPABILITIES.COMMAND_BUS (ICommandBus) and CAPABILITIES.QUERY_BUS (IQueryBus).

Register a handler in setu.config.ts

import { CqrsPlugin } from '@setu-ts/cqrs-plugin';
import type { CqrsCommand, ICommandHandler } from '@setu-ts/common';

type Echo = CqrsCommand<{ text: string }>;
const echo: ICommandHandler<Echo, string> = {
  handle: (command) => command.data.text,
};
export const cqrs = CqrsPlugin({
  commandHandlers: [{ type: 'echo', handler: echo }],
});

Execute a command from a route

import { CAPABILITIES } from '@setu-ts/common';
import type { ICqrsFacade, IRouterApi } from '@setu-ts/common';

export function registerEchoRoutes(router: IRouterApi): void {
  router.get('/echo', {
    handler: async (ctx) => {
      const cqrs = ctx.services.get<ICqrsFacade>(CAPABILITIES.CQRS);
      const text = await cqrs.commandBus.execute<string>({
        type: 'echo', data: { text: 'hello' },
      });
      return ctx.response.json({ text });
    },
  });
}

Behaviour the types do not show

• Routing uses the string type, not class identity; plain objects work.
• Registering the same type again replaces its previous handler.
• An unregistered type rejects with HandlerNotFoundError; a non-string type rejects with TypeError.
• behaviors run in declared order on both buses. Returning without calling the continuation skips the remaining behaviors and handler.
• Handler and behavior factories resolve at onInit, after capabilities are registered.

Other options

• queryHandlers registers read handlers; execute them through queryBus.execute.
• behaviors accepts instances or factories receiving the service registry.
• CommandBus and QueryBus can also be constructed directly without the plugin.