example typesafe job handlers for bullmq

bullmq.ts

import type { Job } from "bullmq";
import { Queue } from "bullmq";

const queue = new Queue("general");

interface Handler<Name extends string, Data> {
    name: Name;
    handler: (job: Job<Data, unknown, Name>) => void;
}

const welcomeMessage = {
    name: "WelcomeMessage",
    handler: (job) => {
        console.log(job.data.name);
    },
} satisfies Handler<"WelcomeMessage", { name: string }>;

const ping = {
    name: "Ping",
    handler: (job) => {
        console.log(job.data.ip);
    },
} satisfies Handler<"Ping", { ip: string }>;

const handlers = [welcomeMessage, ping] as const;

async function addJob<
    T extends (typeof handlers)[number],
    Name extends T["name"],
    Data extends Parameters<Extract<T, { name: Name }>["handler"]>[0]["data"],
>(name: Name, data: Data) {
    return await queue.add(name, data);
}

await addJob("WelcomeMessage", { name: "" });
await addJob("Ping", { ip: "" });

// @ts-expect-error these are passing the wrong data fields, so we want them to be invalid
await addJob("WelcomeMessage", { ip: "" });
// @ts-expect-error these are passing the wrong data fields, so we want them to be invalid
await addJob("Ping", { name: "" });