@graphql-yoga/redis-event-target/esm/index.js

Do distributed GraphQL subscriptions over Redis.

import { CustomEvent } from '@whatwg-node/events';
export function createRedisEventTarget(args) {
    const { publishClient, subscribeClient } = args;
    const serializer = args.serializer ?? JSON;
    const callbacksForTopic = new Map();
    function onMessage(channel, message) {
        const callbacks = callbacksForTopic.get(channel);
        if (callbacks === undefined) {
            return;
        }
        const event = new CustomEvent(channel, {
            detail: message === '' ? null : serializer.parse(message),
        });
        for (const callback of callbacks) {
            callback(event);
        }
    }
    subscribeClient.on('message', onMessage);
    function addCallback(topic, callback) {
        let callbacks = callbacksForTopic.get(topic);
        if (callbacks === undefined) {
            callbacks = new Set();
            callbacksForTopic.set(topic, callbacks);
            subscribeClient.subscribe(topic);
        }
        callbacks.add(callback);
    }
    function removeCallback(topic, callback) {
        const callbacks = callbacksForTopic.get(topic);
        if (callbacks === undefined) {
            return;
        }
        callbacks.delete(callback);
        if (callbacks.size > 0) {
            return;
        }
        callbacksForTopic.delete(topic);
        subscribeClient.unsubscribe(topic);
    }
    return {
        addEventListener(topic, callbackOrOptions) {
            if (callbackOrOptions != null) {
                const callback = 'handleEvent' in callbackOrOptions ? callbackOrOptions.handleEvent : callbackOrOptions;
                addCallback(topic, callback);
            }
        },
        dispatchEvent(event) {
            publishClient.publish(event.type, event.detail === undefined ? '' : serializer.stringify(event.detail));
            return true;
        },
        removeEventListener(topic, callbackOrOptions) {
            if (callbackOrOptions != null) {
                const callback = 'handleEvent' in callbackOrOptions ? callbackOrOptions.handleEvent : callbackOrOptions;
                removeCallback(topic, callback);
            }
        },
    };
}