/**
 * Some utils for manipulating dates
 *
 * **WARNING** experimental
 */

/**
 * Return the date to local ISO date, like YYYY-mm-dd
 *
 * The date is valid for the same timezone as the date's locale
 *
 * Do not take time into account
 *
 */
export const dateToISO = (date: Date | null): string | null => {
    if (null === date) {
        return null;
    }

    return [
        date.getFullYear(),
        (date.getMonth() + 1).toString().padStart(2, "0"),
        date.getDate().toString().padStart(2, "0"),
    ].join("-");
};

/**
 * Return a date object from iso string formatted as YYYY-mm-dd
 *
 * **Experimental**
 */
export const ISOToDate = (str: string | null): Date | null => {
    if (null === str) {
        return null;
    }
    if ("" === str.trim()) {
        return null;
    }

    // If the string already contains time info, use it directly
    if (str.includes('T') || str.includes(' ')) {
        return new Date(str);
    }

    // Otherwise, parse date only
    const [year, month, day] = str.split("-").map((p) => parseInt(p));
    return new Date(year, month - 1, day, 0, 0, 0, 0);
};

/**
 * Return a date object from iso string formatted as YYYY-mm-dd:HH:MM:ss+01:00
 *
 */
export const ISOToDatetime = (str: string | null): Date | null => {
    if (null === str) {
        return null;
    }

    const [cal, times] = str.split("T"),
        [year, month, date] = cal.split("-").map((s) => parseInt(s)),
        [time, timezone] = times.split(times.charAt(8)),
        [hours, minutes, seconds] = time.split(":").map((s) => parseInt(s));
    if ("0000" === timezone) {
        return new Date(
            Date.UTC(year, month - 1, date, hours, minutes, seconds),
        );
    }

    return new Date(year, month - 1, date, hours, minutes, seconds);
};

/**
 * Convert a date to ISO8601, valid for usage in api
 *
 */
export const datetimeToISO = (date: Date): string => {
    let cal, time, offset;
    cal = [
        date.getFullYear(),
        (date.getMonth() + 1).toString().padStart(2, "0"),
        date.getDate().toString().padStart(2, "0"),
    ].join("-");

    time = [
        date.getHours().toString().padStart(2, "0"),
        date.getMinutes().toString().padStart(2, "0"),
        date.getSeconds().toString().padStart(2, "0"),
    ].join(":");

    offset = [
        date.getTimezoneOffset() <= 0 ? "+" : "-",
        Math.abs(Math.floor(date.getTimezoneOffset() / 60))
            .toString()
            .padStart(2, "0"),
        ":",
        Math.abs(date.getTimezoneOffset() % 60)
            .toString()
            .padStart(2, "0"),
    ].join("");

    const x = cal + "T" + time + offset;

    return x;
};

export const intervalDaysToISO = (days: number | string | null): string => {
    if (null === days) {
        return "P0D";
    }

    return `P${days}D`;
};

export const intervalISOToDays = (str: string | null): number | null => {
    if (null === str) {
        return null;
    }

    if ("" === str.trim()) {
        return null;
    }

    let days = 0;
    let isDate = true;
    let vstring = "";
    for (let i = 0; i < str.length; i = i + 1) {
        if (!isDate) {
            continue;
        }
        switch (str.charAt(i)) {
            case "P":
                isDate = true;
                break;
            case "T":
                isDate = false;
                break;
            case "0":
            case "1":
            case "2":
            case "3":
            case "4":
            case "5":
            case "6":
            case "7":
            case "8":
            case "9":
                vstring = vstring + str.charAt(i);
                break;
            case "Y":
                days = days + Number.parseInt(vstring) * 365;
                vstring = "";
                break;
            case "M":
                days = days + Number.parseInt(vstring) * 30;
                vstring = "";
                break;
            case "D":
                days = days + Number.parseInt(vstring);
                vstring = "";
                break;
            default:
                throw Error(
                    "this character should not appears: " + str.charAt(i),
                );
        }
    }

    return days;
};