lock.js

const { promises: { stat, writeFile, unlink } } = require('fs')
const { settings } = require('./settings')

class LockError extends Error {
    constructor(name, message) {
        super(message || `Already locked by ${name}`)
        this.name = name
    }
}

async function fileLock(lockFile = settings.lockFile()) {
    if (lockFile) {
        try {
            await stat(lockFile)
            throw new LockError(lockFile)
        } catch (err) {
            if ('ENOENT' === err.code) {
                await writeFile(lockFile, (process.pid).toString(), 'utf8');
                // console.log(`Lock file ${lockFile} created`)
            } else {
                throw err;
            }
        }
    }
}

async function fileUnlock(lockFile = settings.lockFile()) {
    if (lockFile) {
        try {
            await unlink(lockFile)
        } catch (err) {
            if ('ENOENT' === err.code) {
                console.error(`Lock file ${lockFile} does not exists`)
            }
        }
    }
}

module.exports = { fileLock, fileUnlock, LockError }