import { ChildProcess } from 'child_process'

export interface QueuedSender {
	send: (msg: any) => void
}

const isWindows = /^win/.test(process.platform)
const logOnError = error => {
	if (error) {
		console.error(error)
	}
}

// Wrapper around process.send() that will queue any messages if the internal node.js
// queue is filled with messages and only continue sending messages when the internal
// queue is free again to consume messages.
// On Windows we always wait for the send() method to return before sending the next message
// to workaround https://github.com/nodejs/node/issues/7657 (IPC can freeze process)
export function createQueuedSender(childProcess: ChildProcess): QueuedSender {
	if (isWindows) {
		let msgQueue = []
		let isSending = false

		const cb = error => {
			logOnError(error)
			if (msgQueue.length > 0) {
				setImmediate(doSendLoop)
			} else {
				isSending = false
			}
		}

		const doSendLoop = function(): void {
			;(childProcess.send as any)(msgQueue.shift(), cb)
		}

		const send = function(msg: any): void {
			msgQueue.push(msg) // add to the queue if the process cannot handle more messages
			if (isSending) {
				return
			}

			isSending = true
			doSendLoop()
		}

		return { send }
	} else {
		const send = function(msg: any): void {
			;(childProcess.send as any)(msg, logOnError)
		}

		return { send }
	}
}