import {EventEmitter} from 'node:events';
import {onMessage, onDisconnect} from './incoming.js';
import {undoAddedReferences} from './reference.js';

// Forward the `message` and `disconnect` events from the process and subprocess to a proxy emitter.
// This prevents the `error` event from stopping IPC.
// This also allows debouncing the `message` event.
export const getIpcEmitter = (anyProcess, channel, isSubprocess) => {
	if (IPC_EMITTERS.has(anyProcess)) {
		return IPC_EMITTERS.get(anyProcess);
	}

	// Use an `EventEmitter`, like the `process` that is being proxied
	// eslint-disable-next-line unicorn/prefer-event-target
	const ipcEmitter = new EventEmitter();
	ipcEmitter.connected = true;
	IPC_EMITTERS.set(anyProcess, ipcEmitter);
	forwardEvents({
		ipcEmitter,
		anyProcess,
		channel,
		isSubprocess,
	});
	return ipcEmitter;
};

const IPC_EMITTERS = new WeakMap();

// The `message` and `disconnect` events are buffered in the subprocess until the first listener is setup.
// However, unbuffering happens after one tick, so this give enough time for the caller to setup the listener on the proxy emitter first.
// See https://github.com/nodejs/node/blob/2aaeaa863c35befa2ebaa98fb7737ec84df4d8e9/lib/internal/child_process.js#L721
const forwardEvents = ({ipcEmitter, anyProcess, channel, isSubprocess}) => {
	const boundOnMessage = onMessage.bind(undefined, {
		anyProcess,
		channel,
		isSubprocess,
		ipcEmitter,
	});
	anyProcess.on('message', boundOnMessage);
	anyProcess.once('disconnect', onDisconnect.bind(undefined, {
		anyProcess,
		channel,
		isSubprocess,
		ipcEmitter,
		boundOnMessage,
	}));
	undoAddedReferences(channel, isSubprocess);
};

// Check whether there might still be some `message` events to receive
export const isConnected = anyProcess => {
	const ipcEmitter = IPC_EMITTERS.get(anyProcess);
	return ipcEmitter === undefined
		? anyProcess.channel !== null
		: ipcEmitter.connected;
};