cqrs-eda/dist/commands/handler.js

Lightweight CQRS and Event-Driven Architecture library using TypeScript decorators, handlers and typings. Perfect for scalable event-driven apps.

import { getCommandRegistry } from "./decorators";
/**
 * Handles the registration and execution of command handlers.
 * Supports instantiation of command classes, optionally via a custom factory.
 *
 * @template C - A mapping of command names to their payload types.
 *
 * @example
 * ```ts
 * interface CommandsPayloads {
 *   CREATE_USER: { name: string };
 * }
 *
 * const commandHandler = new CommandHandler<CommandsPayloads>();
 * await commandHandler.fire("CREATE_USER", { name: "Leandro" });
 * ```
 */
export class CommandHandler {
    /**
     * @param factory Optional factory function to instantiate command classes.
     * Useful for integrating with DI containers or custom initialization.
     *
     * Example:
     * ```ts
     * const handler = new CommandHandler((cls) => container.resolve(cls));
     * ```
     */
    constructor(factory) {
        this.factory = factory;
        // Map of command names to command instances
        this.commands = new Map();
        const registry = getCommandRegistry();
        for (const [name, CommandClass] of registry.entries()) {
            const instance = this.factory
                ? this.factory(CommandClass)
                : new CommandClass();
            this.commands.set(name, instance);
        }
    }
    /**
     * Executes a command by name with the given payload.
     *
     * @param commandName - The command name to execute.
     * @param payload - The data to pass to the command.
     * @throws Error if the command is not registered.
     */
    async fire(commandName, payload) {
        const command = this.commands.get(commandName);
        if (!command) {
            throw new Error(`Command "${String(commandName)}" not found.`);
        }
        await command.execute(payload);
    }
}