import {
    toDate,
    format as dateFnsFormat,
    utcToZonedTime as dateFnsUtcToZonedTime,
    zonedTimeToUtc as dateFnsZonedTimeToUtc,
    OptionsWithTZ
} from 'date-fns-tz';
import { parse as dateFnsParse } from 'date-fns';

/**
 * Need to be IANA logo without daylight saving time
 */
export const IANAOffsetMap = [
    [-11, ['Pacific/Midway']],
    [-10, ['Pacific/Honolulu']],
    [-9.5, ['Pacific/Marquesas']],
    [-9, ['Pacific/Gambier']],
    [-8, ['Pacific/Pitcairn']],
    [-7, ['America/Phoenix']],
    [-6, ['America/Tegucigalpa']],
    [-5, ['America/Bogota']],
    [-4, ['America/Puerto_Rico']],
    [-3.5, ['America/St_Johns']], // No alternative daylight saving time zone
    [-3, ['America/Montevideo']],
    [-2, ['Atlantic/South_Georgia']],
    [-1, ['Atlantic/Cape_Verde']],
    [0, ['Africa/Accra']],
    [1, ['Africa/Bangui']],
    [2, ['Africa/Cairo']],
    [3, ['Asia/Bahrain', 'Indian/Antananarivo']],
    [3.5, ['Asia/Tehran']], // No alternative daylight saving time zone
    [4, ['Asia/Dubai', 'Asia/Muscat']],
    [4.5, ['Asia/Kabul']],
    [5, ['Asia/Samarkand', 'Asia/Karachi']],
    [5.5, ['Asia/Kolkata']],
    [5.75, ['Asia/Kathmandu']],
    [6, ['Asia/Dhaka']],
    [6.5, ['Asia/Rangoon', 'Asia/Rangoon']],
    [7, ['Asia/Jakarta', 'Asia/Phnom_Penh', 'Asia/Bangkok']],
    [8, ['Asia/Shanghai', 'Asia/Singapore']],
    [8.75, ['Australia/Eucla']],
    [9, ['Asia/Tokyo', 'Asia/Seoul', 'Asia/Pyongyang']],
    [9.5, ['Australia/Darwin']],
    [10, ['Pacific/Guam']],
    [10.5, ['Australia/Adelaide']], // No alternative daylight saving time zone
    [11, ['Pacific/Guadalcanal']],
    [12, ['Pacific/Funafuti']],
    [13, ['Pacific/Enderbury']],
    [13.75, ['Pacific/Chatham']], // No alternative daylight saving time zone
    [14, ['Pacific/Kiritimati']],
];

/**
 * Etc/GMT* no DST
 * @see https://data.iana.org/time-zones/tzdb/etcetera
 */
const IANAEtcGMTOffsetMap = {
    '0': 'Etc/GMT',
    '1': 'Etc/GMT-1',
    '2': 'Etc/GMT-2',
    '3': 'Etc/GMT-3',
    '4': 'Etc/GMT-4',
    '5': 'Etc/GMT-5',
    '6': 'Etc/GMT-6',
    '7': 'Etc/GMT-7',
    '8': 'Etc/GMT-8',
    '9': 'Etc/GMT-9',
    '10': 'Etc/GMT-10',
    '11': 'Etc/GMT-11',
    '12': 'Etc/GMT-12',
    '13': 'Etc/GMT-13',
    '14': 'Etc/GMT-14',
    '-1': 'Etc/GMT+1',
    '-2': 'Etc/GMT+2',
    '-3': 'Etc/GMT+3',
    '-4': 'Etc/GMT+4',
    '-5': 'Etc/GMT+5',
    '-6': 'Etc/GMT+6',
    '-7': 'Etc/GMT+7',
    '-8': 'Etc/GMT+8',
    '-9': 'Etc/GMT+9',
    '-10': 'Etc/GMT+10',
    '-11': 'Etc/GMT+11',
    '-12': 'Etc/GMT+12',
};

const GMTStringReg = /([\-\+]{1})(\d{2})\:(\d{2})/;

/**
 *
 * @param {string|number} tz
 * @returns {number|undefined}
 */
export const toIANA = (tz: string | number) => {
    let matches = null;
    if (typeof tz === 'string') {
        matches = tz.match(GMTStringReg);
        if (!matches) {
            return tz;
        }

        const symbol = parseInt(matches[1] + 1, 10); // => -1 or 1
        const hourOffset = parseInt(matches[2], 10);
        const minuteOffset = parseInt(matches[3], 10);
        tz = symbol * (hourOffset + minuteOffset / 60);
    }

    if (typeof tz === 'number') {
        // if tz can be transformed to a Etc/GMT* and browser supports it
        if (tz in IANAEtcGMTOffsetMap) {
            const etcGMTtimeZone = IANAEtcGMTOffsetMap[tz];
            if (isValidTimezoneIANAString(etcGMTtimeZone)) {
                return etcGMTtimeZone;
            }
        }
        const found = IANAOffsetMap.find(item => item[0] === tz);
        return found && found[1][0];
    }
};

const validIANATimezoneCache = {};
/**
 * @see https://github.com/marnusw/date-fns-tz/blob/a92e0ad017d101a0c50e39a63ef5d322b4d849f6/src/_lib/tzParseTimezone/index.js#L137
 */
export function isValidTimezoneIANAString(timeZoneString: string) {
    if (validIANATimezoneCache[timeZoneString]) return true;
    try {
        new Intl.DateTimeFormat(undefined, { timeZone: timeZoneString });
        validIANATimezoneCache[timeZoneString] = true;
        return true;
    } catch (error) {
        return false;
    }
}

/**
 *
 * @param {string | number | Date} date
 * @param {string} formatToken
 * @param {object} [options]
 * @param {string} [options.timeZone]
 * @returns {Date}
 */
/* istanbul ignore next */
const parse = (date: string | number | Date, formatToken: string, options?: any) => {
    if (typeof date === 'string') {
        date = dateFnsParse(date, formatToken, new Date(), options);
    }
    if (options && options.timeZone != null && options.timeZone !== '') {
        const timeZone = toIANA(options.timeZone);
        options = { ...options, timeZone };
    }

    return toDate(date, options);
};

/* istanbul ignore next */
const format = (date: number | Date, formatToken: string, options?: any) => {
    if (options && options.timeZone != null && options.timeZone !== '') {
        const timeZone = toIANA(options.timeZone);
        options = { ...options, timeZone };

        date = dateFnsUtcToZonedTime(date, timeZone, options);
    }

    return dateFnsFormat(date, formatToken, options);
};

/**
 * Returns a Date which will format as the local time of any time zone from a specific UTC time
 * 
 * @example
 * ```javascript
 * import { utcToZonedTime } from 'date-fns-tz'
 * const { isoDate, timeZone } = fetchInitialValues() // 2014-06-25T10:00:00.000Z, America/New_York
 * const date = utcToZonedTime(isoDate, timeZone) // In June 10am UTC is 6am in New York (-04:00)
 * renderDatePicker(date) // 2014-06-25 06:00:00 (in the system time zone)
 * renderTimeZoneSelect(timeZone) // America/New_York
 * ```
 * 
 * @see https://github.com/marnusw/date-fns-tz#utctozonedtime
 */
const utcToZonedTime = (date: string | number | Date, timeZone: string | number, options?: OptionsWithTZ) => dateFnsUtcToZonedTime(date, toIANA(timeZone), options);

/**
 * Given a date and any time zone, returns a Date with the equivalent UTC time
 * 
 * @example
 * ```
 * import { zonedTimeToUtc } from 'date-fns-tz'
 * const date = getDatePickerValue() // e.g. 2014-06-25 10:00:00 (picked in any time zone)
 * const timeZone = getTimeZoneValue() // e.g. America/Los_Angeles
 * const utcDate = zonedTimeToUtc(date, timeZone) // In June 10am in Los Angeles is 5pm UTC
 * postToServer(utcDate.toISOString(), timeZone) // post 2014-06-25T17:00:00.000Z, America/Los_Angeles
 * ```
 * 
 * @see https://github.com/marnusw/date-fns-tz#zonedtimetoutc
 */
const zonedTimeToUtc = (date: string | number | Date, timeZone: string | number, options?: OptionsWithTZ) => dateFnsZonedTimeToUtc(date, toIANA(timeZone), options);

/**
 * return current system hour offset based on utc:
 *
 * ```
 * 8 => "GMT+08:00"
 * -9.5 => "GMT-09:30"
 * -8 => "GMT-08:00"
 * ```
 */
const getCurrentTimeZone = () => new Date().getTimezoneOffset() / 60;

export { format, parse, utcToZonedTime, zonedTimeToUtc, getCurrentTimeZone };