@burglekitt/gmt/dist/plain/calculate/startOfTime.js

Temporal-based date and time utilities with timezone support and polyfill integration

import { Temporal } from "@js-temporal/polyfill";
import { isValidTime } from "../validate/index.js";
const supported = [
    "day",
    "hour",
    "minute",
    "second",
    "millisecond",
    "microsecond",
    "nanosecond",
];
/**
 * Return the start of the specified time `unit` for a given ISO 8601 time string.
 *
 * - Returns "" for invalid inputs.
 *
 * @param value ISO 8601 time string
 * @param unit StartOfTimeUnit to specify the unit for the start
 * @param optionsArg optional: fractionalSecondDigits (number)
 * @returns ISO 8601 string representing the start of the specified unit, or "" on invalid input
 *
 * @example startOfTime("12:34:56", "hour") // "12:00:00"
 * @example startOfTime("invalid", "hour") // ""
 */
export function startOfTime(value, unit, optionsArg) {
    const fractionalSecondDigits = optionsArg?.fractionalSecondDigits;
    if (!isValidTime(value) || !supported.includes(unit))
        return "";
    try {
        const source = Temporal.PlainTime.from(value);
        let result;
        switch (unit) {
            case "day":
                result = source.with({ hour: 0, minute: 0, second: 0 });
                break;
            case "hour":
                result = source.with({ minute: 0, second: 0 });
                break;
            case "minute":
                result = source.with({ second: 0 });
                break;
            case "second":
                result = source.with({ millisecond: 0, microsecond: 0, nanosecond: 0 });
                break;
            case "millisecond":
                result = source.with({ millisecond: 0, microsecond: 0, nanosecond: 0 });
                break;
            case "microsecond":
                result = source.with({ microsecond: 0, nanosecond: 0 });
                break;
            case "nanosecond":
                result = source.with({ nanosecond: 0 });
                break;
            default:
                return "";
        }
        // Handle default precision: 0 for > sec, 3 for ms, 6 for µs, 9 for ns
        const precisionMap = {
            millisecond: 3,
            microsecond: 6,
            nanosecond: 9,
        };
        const fractionalDigits = fractionalSecondDigits ?? (precisionMap[unit] || 0);
        return result.toString({ fractionalSecondDigits: fractionalDigits });
    }
    catch {
        return "";
    }
}