tout-doux/resources/ts/lib/recurrence.ts

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

const ONE_TIME_VALUE = "@one-time";

export function parseCron(cron: string | null): {
    type: CronType;
    value: number;
    date: Date | null;
} {
    let value: RegExpMatchArray | null;
    if (cron === null) {
        return {
            type: CronType.MANUAL,
            value: 0,
            date: null,
        };
    } else if (cron === ONE_TIME_VALUE) {
        return {
            type: CronType.ONE_TIME,
            value: 0,
            date: null,
        };
    } else if (cron.startsWith("RRULE:") || cron.startsWith("DTSTART:")) {
        return parseRrule(cron);
    } else if ((value = /^0 (\d+) \* \* \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_DAY,
            value: parseInt(value[1] ?? ""),
            date: null,
        };
    } else if ((value = /^0 0 \* \* (\d+)$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_WEEK,
            value: parseInt(value[1] ?? ""),
            date: null,
        };
    } else if ((value = /^0 0 (\d+) \* \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_MONTH,
            value: parseInt(value[1] ?? ""),
            date: null,
        };
    } else if ((value = /^0 0 L \* \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_MONTH,
            value: 32,
            date: null,
        };
    } else if ((value = /^0 0 \* \* (\d+)#1$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_MONTH,
            value: -parseInt(value[1] ?? ""),
            date: null,
        };
    } else if ((value = /^0 0 \* \* (\d+)L$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_MONTH,
            value: -parseInt(value[1] ?? "") - 7,
            date: null,
        };
    } else if ((value = /^0 0 1 (\d+) \*$/i.exec(cron)) !== null) {
        return {
            type: CronType.EVERY_YEAR,
            value: parseInt(value[1] ?? ""),
            date: null,
        };
    } else {
        return {
            type: CronType.CUSTOM,
            value: 0,
            date: null,
        };
    }
}

export function parseRrule(rule: string): {
    type: CronType;
    value: number;
    date: Date | null;
} {
    try {
        const rrule = RRule.parseString(rule);
        switch (rrule.freq) {
            case RRule.YEARLY:
                return {
                    type: CronType.EVERY_N_MONTHS,
                    value: (rrule.interval ?? 1) * 12,
                    date: rrule.dtstart ?? null,
                };
            case RRule.MONTHLY:
                return {
                    type: CronType.EVERY_N_MONTHS,
                    value: rrule.interval ?? 1,
                    date: rrule.dtstart ?? null,
                };
            case RRule.WEEKLY:
                return {
                    type: CronType.EVERY_N_WEEKS,
                    value: rrule.interval ?? 1,
                    date: rrule.dtstart ?? null,
                };
            case RRule.DAILY:
                return {
                    type: CronType.EVERY_N_DAYS,
                    value: rrule.interval ?? 1,
                    date: rrule.dtstart ?? null,
                };
        }
    } catch {
        // ignore
    }
    return {
        type: CronType.MANUAL,
        value: 0,
        date: null,
    };
}

export function getCron(
    type: CronType,
    value: number,
    date: Date,
    fallback: string,
): string | null {
    switch (type) {
        case CronType.ONE_TIME:
            return ONE_TIME_VALUE;
        case CronType.EVERY_DAY:
            return `0 0 * * *`;
        case CronType.EVERY_WEEK:
            return `0 0 * * ${value.toFixed(0)}`;
        case CronType.EVERY_MONTH:
            if (value === 32) {
                return `0 0 L * *`;
            }
            if (value < 0 && value >= -7) {
                return `0 0 * * ${(-value).toFixed(0)}#1`;
            }
            if (value < -7 && value >= -14) {
                return `0 0 * * ${(-value - 7).toFixed(0)}L`;
            }
            return `0 0 ${value.toFixed(0)} * *`;
        case CronType.EVERY_YEAR:
            return `0 0 1 ${value.toFixed(0)} *`;
        case CronType.EVERY_N_MONTHS:
            return new RRule({
                freq: RRule.MONTHLY,
                interval: value,
                dtstart: date,
            }).toString();
        case CronType.EVERY_N_WEEKS:
            return new RRule({
                freq: RRule.WEEKLY,
                interval: value,
                dtstart: date,
            }).toString();
        case CronType.EVERY_N_DAYS:
            return new RRule({
                freq: RRule.DAILY,
                interval: value,
                dtstart: date,
            }).toString();
        case CronType.CUSTOM:
            if (validCron(fallback)) {
                return fallback;
            }
    }

    return null;
}

export function isOneTime(cron: string | null): boolean {
    return cron === ONE_TIME_VALUE;
}

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

export function nextCronReset(
    date: Date,
    cron: string | null,
    hash: string,
): Date | null {
    if (cron === null || isOneTime(cron)) {
        return null;
    }
    try {
        if (cron.startsWith("RRULE:")) {
            try {
                const rule = new RRule({
                    ...RRule.parseString(cron),
                    count: 2,
                });

                return rule.after(date) ?? null;
            } catch {
                // ignore
            }
        }

        const interval = CronExpressionParser.parse(cron, {
            currentDate: date,
            hashSeed: hash,
        });
        return interval.next().toDate();
    } catch {
        return null;
    }
}