cqrs-eda/dist/queries/handler.js

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

import { getQueryRegistry } from "./decorators";
/**
 * Handles the registration and execution of query handlers.
 * Supports instantiation of query classes, optionally via a custom factory.
 *
 * @template Q - A mapping of query names to their parameter types.
 * @template R - A mapping of query names to their return types.
 *
 * @example
 * ```ts
 * interface Queries {
 *   GET_USER: { id: number };
 * }
 * interface Results {
 *   GET_USER: User | null;
 * }
 *
 * const queryHandler = new QueryHandler<Queries, Results>();
 * const user = await queryHandler.fire("GET_USER", { id: 1 });
 * ```
 */
export class QueryHandler {
    /**
     * @param factory Optional factory function to instantiate query classes.
     * Useful for integrating with DI containers or custom initialization.
     *
     * Example:
     * ```ts
     * const handler = new QueryHandler((cls) => container.resolve(cls));
     * ```
     */
    constructor(factory) {
        this.factory = factory;
        // Map of query names to query instances
        this.queries = new Map();
        const registry = getQueryRegistry();
        for (const [name, QueryClass] of registry.entries()) {
            const instance = this.factory
                ? this.factory(QueryClass)
                : new QueryClass();
            this.queries.set(name, instance);
        }
    }
    /**
     * Executes a query by name with the given parameters.
     *
     * @param queryName - The query name to execute.
     * @param params - The parameters to pass to the query.
     * @returns The result of the query execution.
     * @throws Error if the query is not registered.
     */
    async fire(queryName, params) {
        const query = this.queries.get(queryName);
        if (!query) {
            throw new Error(`Query "${String(queryName)}" not found.`);
        }
        return await query.execute(params);
    }
}