console/src/lib/helpers/date.ts

import { browser } from '$app/environment';
import dayjs from 'dayjs';
import relativeTime from 'dayjs/plugin/relativeTime';

export type WeekDay =
    | 'Sunday'
    | 'Monday'
    | 'Tuesday'
    | 'Wednesday'
    | 'Thursday'
    | 'Friday'
    | 'Saturday';

if (browser) {
    dayjs.extend(relativeTime);
}

export const toLocaleDate = (datetime: string) => {
    const date = new Date(datetime);

    if (isNaN(date.getTime())) {
        return 'n/a';
    }

    const options: Intl.DateTimeFormatOptions = {
        year: 'numeric',
        month: 'short',
        day: 'numeric'
    };

    return date.toLocaleDateString('en', options);
};

export const toLocaleDateTime = (
    datetime: string | number,
    timeZone: string | undefined = undefined
) => {
    const date = new Date(datetime);

    if (isNaN(date.getTime())) {
        return 'n/a';
    }

    const options: Intl.DateTimeFormatOptions = {
        timeZone,
        year: 'numeric',
        month: 'short',
        day: 'numeric',
        hour: 'numeric',
        minute: 'numeric',
        hourCycle: 'h23'
    };

    return date.toLocaleDateString('en', options);
};

/**
 * Returns a date string using the local timezone in ISO format (yyyy-mm-dd)
 *
 * @param datetime date string or milliseconds since the epoch
 */
export const toLocaleDateISO = (datetime: string | number) => {
    const date = new Date(datetime);

    if (isNaN(date.getTime())) {
        return 'n/a';
    }

    // Use Sweden's locale (sv) since it matches ISO format
    return date.toLocaleDateString('sv');
};

/**
 * Returns a time string using the local timezone in ISO format (hh:mm:ss)
 *
 * @param datetime date string or milliseconds since the epoch
 */
export const toLocaleTimeISO = (datetime: string | number) => {
    const date = new Date(datetime);

    if (isNaN(date.getTime())) {
        return 'n/a';
    }

    // Use Sweden's locale (sv) since it matches ISO format
    return date.toLocaleTimeString('sv');
};

/**
 * Returns a local datetime string in ISO 8601 format (YYYY-MM-DDTHH:mm:ss.sss),
 * matching local time, without the 'Z' suffix.
 *
 * @returns Local ISO string (with ms) or 'n/a' if invalid
 */
export const toLocalDateTimeISO = (datetime: string | number): string => {
    const date = new Date(datetime);

    if (isNaN(date.getTime())) {
        return 'n/a';
    }

    // Get timezone offset in minutes, convert to ms
    const tzOffsetMs = date.getTimezoneOffset() * 60 * 1000;

    // Shift date to local time
    const local = new Date(date.getTime() - tzOffsetMs);

    // Drop the trailing 'Z' to keep it as local
    return local.toISOString().replace('Z', '');
};

export const utcHourToLocaleHour = (utcTimeString: string) => {
    const now = new Date();
    const [hours, minutes] = utcTimeString.split(':').map(Number);
    const customTime = Date.UTC(now.getFullYear(), now.getMonth(), now.getDate(), hours, minutes);

    const options: Intl.DateTimeFormatOptions = {
        hour: 'numeric',
        minute: 'numeric',
        hourCycle: 'h23'
    };

    return new Intl.DateTimeFormat('en', options).format(new Date(customTime));
};

export const utcWeekDayToLocaleWeekDay = (utcDay: WeekDay, utcTimeString: string) => {
    const now = new Date();

    const daysOfTheWeek = {
        Sunday: 0,
        Monday: 1,
        Tuesday: 2,
        Wednesday: 3,
        Thursday: 4,
        Friday: 5,
        Saturday: 6
    };

    const utcDayNumber = daysOfTheWeek[utcDay];
    const [hours, minutes] = utcTimeString.split(':').map(Number);

    const daysUntilNextUtcDay = (7 + utcDayNumber - now.getUTCDay()) % 7;
    now.setUTCDate(now.getUTCDate() + daysUntilNextUtcDay);
    now.setUTCHours(hours, minutes, 0, 0);

    return new Intl.DateTimeFormat('en', { weekday: 'short' }).format(now);
};

export const localeTimezoneName = () => {
    const options: Intl.DateTimeFormatOptions = {
        timeZoneName: 'longGeneric'
    };

    const dateWithTimezone = new Intl.DateTimeFormat('en', options).format(new Date());
    return dateWithTimezone.split(', ')[1];
};

/**
 * This function processes the timezone name using regex to:
 *
 * 1. Trim and simplify the text for UI display (e.g., IST, UST, etc.).
 * 2. Handle cases where `timeZoneName: 'shortGeneric'` returns names like `India Time`,
 *    which do not fit well in the support modal UI.
 * 3. Not using `timeZoneName: 'short'`, as it can display `GMT+-` formatted timezones,
 *    which may not be ideal.
 *
 * Refer to:
 * https://github.com/appwrite/console/pull/1564#discussion_r1913977798
 */
export const localeShortTimezoneName = () => {
    const timezone = localeTimezoneName();
    return timezone.match(/[A-Z]/g)?.join('') || timezone;
};

export const isSameDay = (date1: Date, date2: Date) => {
    return (
        date1.getFullYear() === date2.getFullYear() &&
        date1.getMonth() === date2.getMonth() &&
        date1.getDate() === date2.getDate()
    );
};

export const isValidDate = (date: string) => {
    return !isNaN(new Date(date).getTime());
};

export const diffDays = (date1: Date, date2: Date) => {
    const diffTime = Math.abs(date2.getTime() - date1.getTime());
    return Math.floor(diffTime / (1000 * 60 * 60 * 24));
};

export function timeFromNow(datetime: string): string {
    if (!datetime) {
        return 'unknown time';
    }
    if (!isValidDate(datetime)) {
        return 'invalid date';
    }

    return dayjs().to(dayjs(datetime));
}

export function hoursToDays(hours: number) {
    if (hours > 24) {
        return `${Math.floor(hours / 24)} days`;
    } else {
        return `${hours} hour`;
    }
}

export function getTomorrow(date: Date) {
    const tomorrow = new Date(date);
    tomorrow.setDate(tomorrow.getDate() + 2);
    tomorrow.setHours(0, 0, 0, 0);

    return tomorrow;
}

export function getUTCOffset(): string {
    const offsetMinutes = -new Date().getTimezoneOffset();
    const hours = Math.floor(offsetMinutes / 60);
    const minutes = Math.abs(offsetMinutes % 60);

    return `${hours >= 0 ? '+' : ''}${hours}${minutes ? `:${minutes.toString().padStart(2, '0')}` : ''}`;
}

export function toISOString(date: string): string {
    const d = new Date(date);

    if (isNaN(d.getTime())) {
        return 'n/a';
    }
    return d.toISOString();
}