date-fns-tz/dist/esm/_lib/tzParseTimezone/index.js

Time zone support for date-fns v3 with the Intl API

import { tzTokenizeDate } from '../tzTokenizeDate/index.js';
import { newDateUTC } from '../newDateUTC/index.js';
const MILLISECONDS_IN_HOUR = 3600000;
const MILLISECONDS_IN_MINUTE = 60000;
const patterns = {
    timezone: /([Z+-].*)$/,
    timezoneZ: /^(Z)$/,
    timezoneHH: /^([+-]\d{2})$/,
    timezoneHHMM: /^([+-])(\d{2}):?(\d{2})$/,
};
// Parse constious time zone offset formats to an offset in milliseconds
export function tzParseTimezone(timezoneString, date, isUtcDate) {
    // Empty string
    if (!timezoneString) {
        return 0;
    }
    // Z
    let token = patterns.timezoneZ.exec(timezoneString);
    if (token) {
        return 0;
    }
    let hours;
    let absoluteOffset;
    // ±hh
    token = patterns.timezoneHH.exec(timezoneString);
    if (token) {
        hours = parseInt(token[1], 10);
        if (!validateTimezone(hours)) {
            return NaN;
        }
        return -(hours * MILLISECONDS_IN_HOUR);
    }
    // ±hh:mm or ±hhmm
    token = patterns.timezoneHHMM.exec(timezoneString);
    if (token) {
        hours = parseInt(token[2], 10);
        const minutes = parseInt(token[3], 10);
        if (!validateTimezone(hours, minutes)) {
            return NaN;
        }
        absoluteOffset = Math.abs(hours) * MILLISECONDS_IN_HOUR + minutes * MILLISECONDS_IN_MINUTE;
        return token[1] === '+' ? -absoluteOffset : absoluteOffset;
    }
    // IANA time zone
    if (isValidTimezoneIANAString(timezoneString)) {
        date = new Date(date || Date.now());
        const utcDate = isUtcDate ? date : toUtcDate(date);
        const offset = calcOffset(utcDate, timezoneString);
        const fixedOffset = isUtcDate ? offset : fixOffset(date, offset, timezoneString);
        return -fixedOffset;
    }
    return NaN;
}
function toUtcDate(date) {
    return newDateUTC(date.getFullYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds(), date.getMilliseconds());
}
function calcOffset(date, timezoneString) {
    const tokens = tzTokenizeDate(date, timezoneString);
    // ms dropped because it's not provided by tzTokenizeDate
    const asUTC = newDateUTC(tokens[0], tokens[1] - 1, tokens[2], tokens[3] % 24, tokens[4], tokens[5], 0).getTime();
    let asTS = date.getTime();
    const over = asTS % 1000;
    asTS -= over >= 0 ? over : 1000 + over;
    return asUTC - asTS;
}
function fixOffset(date, offset, timezoneString) {
    const localTS = date.getTime();
    // Our UTC time is just a guess because our offset is just a guess
    let utcGuess = localTS - offset;
    // Test whether the zone matches the offset for this ts
    const o2 = calcOffset(new Date(utcGuess), timezoneString);
    // If so, offset didn't change, and we're done
    if (offset === o2) {
        return offset;
    }
    // If not, change the ts by the difference in the offset
    utcGuess -= o2 - offset;
    // If that gives us the local time we want, we're done
    const o3 = calcOffset(new Date(utcGuess), timezoneString);
    if (o2 === o3) {
        return o2;
    }
    // If it's different, we're in a hole time. The offset has changed, but we don't adjust the time
    return Math.max(o2, o3);
}
function validateTimezone(hours, minutes) {
    return -23 <= hours && hours <= 23 && (minutes == null || (0 <= minutes && minutes <= 59));
}
const validIANATimezoneCache = {};
function isValidTimezoneIANAString(timeZoneString) {
    if (validIANATimezoneCache[timeZoneString])
        return true;
    try {
        new Intl.DateTimeFormat(undefined, { timeZone: timeZoneString });
        validIANATimezoneCache[timeZoneString] = true;
        return true;
    }
    catch (error) {
        return false;
    }
}