seyfert/vendor/gateway/shard/startHeartbeating.ts

import { GatewayOpcodes } from "../../types/shared.ts";
import { Shard, ShardSocketCloseCodes, ShardState } from "./types.ts";

export function startHeartbeating(shard: Shard, interval: number) {
    //   gateway.debug("GW HEARTBEATING_STARTED", { shardId, interval });

    shard.heart.interval = interval;

    // Only set the shard's state to `Unidentified`
    // if heartbeating has not been started due to an identify or resume action.
    if ([ShardState.Disconnected, ShardState.Offline].includes(shard.state)) {
        shard.state = ShardState.Unidentified;
    }

    // The first heartbeat needs to be send with a random delay between `0` and `interval`
    // Using a `setTimeout(_, jitter)` here to accomplish that.
    // `Math.random()` can be `0` so we use `0.5` if this happens
    // Reference: https://discord.com/developers/docs/topics/gateway#heartbeating
    const jitter = Math.ceil(shard.heart.interval * (Math.random() || 0.5));
    shard.heart.timeoutId = setTimeout(() => {
        // Using a direct socket.send call here because heartbeat requests are reserved by us.
        shard.socket?.send(JSON.stringify({
            op: GatewayOpcodes.Heartbeat,
            d: shard.previousSequenceNumber,
        }));

        shard.heart.lastBeat = Date.now();
        shard.heart.acknowledged = false;

        // After the random heartbeat jitter we can start a normal interval.
        shard.heart.intervalId = setInterval(async () => {
            // gateway.debug("GW DEBUG", `Running setInterval in heartbeat file. Shard: ${shardId}`);

            // gateway.debug("GW HEARTBEATING", { shardId, shard: currentShard });

            // The Shard did not receive a heartbeat ACK from Discord in time,
            // therefore we have to assume that the connection has failed or got "zombied".
            // The Shard needs to start a re-identify action accordingly.
            // Reference: https://discord.com/developers/docs/topics/gateway#heartbeating-example-gateway-heartbeat-ack
            if (!shard.heart.acknowledged) {
                shard.close(
                    ShardSocketCloseCodes.ZombiedConnection,
                    "Zombied connection, did not receive an heartbeat ACK in time.",
                );

                return await shard.identify();
            }

            shard.heart.acknowledged = false;

            // Using a direct socket.send call here because heartbeat requests are reserved by us.
            shard.socket?.send(
                JSON.stringify({
                    op: GatewayOpcodes.Heartbeat,
                    d: shard.previousSequenceNumber,
                }),
            );

            shard.heart.lastBeat = Date.now();

            shard.events.heartbeat?.(shard);
        }, shard.heart.interval);
    }, jitter);
}