interface Args {
    cron: string
    job: (fireDate: Date) => Promise<unknown>
    onError?: (err: any) => Promise<unknown> | unknown
    invokeNow?: true
}
export async function schedule(args: Args) {
    const nodeSchedule: typeof import('node-schedule') = require('node-schedule')

    let lock = false
    let runAfter = false

    const errorCallback = args.onError ?? ((err: any) => console.error(err))

    const call = async (fireDate: Date, skipLock?: true) => {
        if (lock === true && skipLock !== true) {
            runAfter = true
            return
        }

        lock = true

        await args.job(fireDate).catch(errorCallback)

        if (runAfter === true) {
            runAfter = false
            return setImmediate(() => call(new Date(), true))
        }

        lock = false   
    }

    const scheduled = nodeSchedule.scheduleJob(args.cron, call)

    if (args.invokeNow === true) {
        scheduled.invoke()
    }

    return scheduled
}