import * as mqtt from 'mqtt-packet';

import { MqttClient } from './client.js';

import { logger } from './util/logger.js';

export async function write(client: MqttClient, packet: mqtt.Packet): Promise<void> {

/* TODO: Enforce maximum packet size */

logger.trace(`writing packet: ${JSON.stringify(packet)}`);

if (!client.connected && !client.connecting) throw new Error('connection closed');

/**

* If writeToStream returns true, we can immediately continue. Otherwise,

* either we need to wait for the 'drain' event or the client has errored.

*/

if (mqtt.writeToStream(packet, client.conn)) return;

// if we get an error while writing to the packet stream in mqtt-packet v8, then the stream will synchronously be set to 'destroyed' immediately, so we can

// check for errors by checking if the connection is destroyed after writing to stream.

if (client.conn.destroyed) throw new Error('stream destroyed while attempting to write');

/** TODO: if there is an issue, write could potentially stall forever

* We should look into if we should have a timeout here or if the timeout should be

*/

/**

* TODO: Need to make sure that this promise settles if the client errors

* before the 'drain' event is emitted. Aedes does a weird hack to make it

* work, but it's not clear if it's the right thing to do. See Aedes:

* https://github.com/moscajs/aedes/blob/39ccdb554d9e32113216e5f7180d3297314e5e12/lib/client.js#L193-L196

*/

if (!client.errored) return new Promise((resolve) => client.conn.once('drain', resolve));

}