import { CronType } from "@/enums";
import CronExpressionParser from "cron-parser";

export function parseCron(cron: string | null): { type: CronType, value: number } {
    let value: RegExpMatchArray | null;
    if (cron === null) {
        return {
            type: CronType.ONE_TIME,
            value: 0
        }
    } else if ((value = /^0 (\d+) \* \* \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_DAY,
            value: parseInt(value[1] ?? '')
        }
    } else if ((value = /^0 0 \* \* (\d+)$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_WEEK,
            value: parseInt(value[1] ?? '')
        }
    } else if ((value = /^0 0 (\d+) \* \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_MONTH,
            value: parseInt(value[1] ?? '')
        }
    } else if ((value = /^0 0 1 (\d+) \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_YEAR,
            value: parseInt(value[1] ?? '')
        }
    } else {
        return {
            type: CronType.SPECIFIC,
            value: 0
        }
    }
}

export function getCron(type: CronType, value: number, fallback: string): string | null {
    switch(type) {
        case CronType.EVERY_DAY:
            return `0 ${value.toFixed(0)} * * *`;
        case CronType.EVERY_WEEK:
            return `0 0 * * ${value.toFixed(0)}`
        case CronType.EVERY_MONTH:
            return `0 0 ${value.toFixed(0)} * *`;
        case CronType.EVERY_YEAR:
            return `0 0 1 ${value.toFixed(0)} *`;
        case CronType.SPECIFIC:
            if (validCron(fallback)) {
                return fallback;
            }
    }

    return null;
}

export function validCron(cron: string): boolean {
    try {
        CronExpressionParser.parse(cron);
        return true;
    } catch {
        return false;
    }
}