import dayjs from 'dayjs';
import duration from 'dayjs/plugin/duration';
import relativeTime from 'dayjs/plugin/relativeTime';
import isToday from 'dayjs/plugin/isToday';
import isYesterday from 'dayjs/plugin/isYesterday';
import utc from 'dayjs/plugin/utc';
import timezone from 'dayjs/plugin/timezone';
import weekOfYear from 'dayjs/plugin/weekOfYear';
import parse from 'parse-duration';

import { getUserTimezone, getWeekStart } from './settings';
import updateLocale from 'dayjs/plugin/updateLocale';
import { computed } from 'vue';
import { formatNumber } from './number';


export type DateFormat =
    | 'point-separated-d-m-yyyy'
    | 'slash-separated-mm-dd-yyyy'
    | 'slash-separated-dd-mm-yyyy'
    | 'hyphen-separated-dd-mm-yyyy'
    | 'hyphen-separated-mm-dd-yyyy'
    | 'hyphen-separated-yyyy-mm-dd';

const dateFormatMap: Record<DateFormat, string> = {
    'point-separated-d-m-yyyy': 'D.M.YYYY',
    'slash-separated-mm-dd-yyyy': 'MM/DD/YYYY',
    'slash-separated-dd-mm-yyyy': 'DD/MM/YYYY',
    'hyphen-separated-dd-mm-yyyy': 'DD-MM-YYYY',
    'hyphen-separated-mm-dd-yyyy': 'MM-DD-YYYY',
    'hyphen-separated-yyyy-mm-dd': 'YYYY-MM-DD'
};

export type TimeFormat = '12-hours' | '24-hours';
export type IntervalFormat =
    | 'decimal'
    | 'hours-minutes'
    | 'hours-minutes-colon-separated'
    | 'hours-minutes-seconds-colon-separated';
export type TimeInputUnit = 'minutes' | 'hours';

dayjs.extend(relativeTime);
dayjs.extend(isToday);
dayjs.extend(isYesterday);
dayjs.extend(duration);
dayjs.extend(utc);
dayjs.extend(timezone);
dayjs.extend(updateLocale);
dayjs.extend(weekOfYear);

export function getDayJsInstance() {
    dayjs.updateLocale('en', {
        weekStart: firstDayIndex.value,
    });
    return dayjs;
}

export const firstDayIndex = computed(() => {
    const apiDayOrder = [
        'sunday',
        'monday',
        'tuesday',
        'wednesday',
        'thursday',
        'friday',
        'saturday',
    ];
    return apiDayOrder.indexOf(getWeekStart());
});

export function formatHumanReadableDuration(
    duration: number,
    intervalFormat?: string,
    numberFormat?: string
): string {
    const dayJsDuration = dayjs.duration(duration, 's');
    const hours = Math.floor(dayJsDuration.asHours());
    const minutes = dayJsDuration.minutes();
    const seconds = dayJsDuration.seconds();

    switch (intervalFormat) {
        case 'decimal':
            return formatNumber(dayJsDuration.asHours(), numberFormat) + ' h';
        case 'hours-minutes':
            return `${hours}h ${minutes.toString().padStart(2, '0')}min`;
        case 'hours-minutes-colon-separated':
            return `${hours}:${minutes.toString().padStart(2, '0')}`;
        case 'hours-minutes-seconds-colon-separated':
            return `${hours}:${minutes.toString().padStart(2, '0')}:${seconds.toString().padStart(2, '0')}`;
        default:
            return `${hours}h ${minutes.toString().padStart(2, '0')}min`;
    }
}

export function formatDuration(duration: number): string {
    const dayJsDuration = dayjs.duration(duration, 's');
    const hours = Math.floor(dayJsDuration.asHours());
    const minutes = dayJsDuration.minutes();
    const seconds = dayJsDuration.seconds();
    return `${hours.toString().padStart(2, '0')}:${minutes.toString().padStart(2, '0')}:${seconds.toString().padStart(2, '0')}`;
}

export function calculateDifference(start: string, end: string | null) {
    if (end === null) {
        end = dayjs().utc().format();
    }
    return dayjs(end).diff(dayjs(start), 'second');
}

/**
 * Returns a formatted time.
 * @param date - A UTC date time string.
 * @param timeFormat - The time format to use ('12-hours' or '24-hours')
 */
export function formatTime(date: string, timeFormat: TimeFormat = '24-hours') {
    const format = timeFormat === '12-hours' ? 'hh:mm A' : 'HH:mm';
    return dayjs.utc(date).tz(getUserTimezone()).format(format);
}

export function getLocalizedDayJs(timestamp?: string | null) {
    return dayjs.utc(timestamp).tz(getUserTimezone());
}

export function getLocalizedDateFromTimestamp(timestamp: string) {
    return getLocalizedDayJs(timestamp).format('YYYY-MM-DD');
}

/*
 * Returns a formatted date.
 * @param date - date in the format of 'YYYY-MM-DD'
 */
export function formatDate(date: string, format: DateFormat = 'point-separated-d-m-yyyy'): string {
    if (date?.includes('+')) {
        console.warn(
            'Date contains timezone information, use formatDateLocalized instead'
        );
    }
    return getDayJsInstance()(date).format(dateFormatMap[format]);
}

/*
 * Returns a formatted date.
 * @param date - date in the format of 'YYYY-MM-DD'
 */
export function formatDateLocalized(date: string, format: DateFormat = 'point-separated-d-m-yyyy'): string {
    return getLocalizedDayJs(date).format(dateFormatMap[format]);
}

export function formatDateTimeLocalized(date: string, dateFormat?: DateFormat, timeFormat?: TimeFormat): string {
    const format = `${dateFormatMap[dateFormat ?? 'point-separated-d-m-yyyy']} ${timeFormat === '12-hours' ? 'hh:mm A' : 'HH:mm'}`;
    return getLocalizedDayJs(date).format(format);
}

export function formatWeek(date: string | null): string {
    return 'Week ' + getDayJsInstance()(date).week();
}

/*
 * Returns a human readable date format.
 * @param date - date in the format of 'YYYY-MM-DD'
 */
export function formatHumanReadableDate(date: string) {
    if (dayjs(date).isToday()) {
        return 'Today';
    } else if (dayjs(date).isYesterday()) {
        return 'Yesterday';
    }
    return dayjs(date).fromNow();
}

export function formatWeekday(date: string) {
    return dayjs(date).format('dddd');
}

export function formatStartEnd(start: string, end: string | null, timeFormat: TimeFormat = '24-hours') {
    if (end) {
        return `${formatTime(start, timeFormat)} - ${formatTime(end, timeFormat)}`;
    } else {
        return `${formatTime(start, timeFormat)} - ...`;
    }
}

export function parseTimeInput(
    input: string,
    defaultUnit: TimeInputUnit = 'minutes'
): {
    seconds: number | null;
    isHHMM: boolean;
} {
    // Check if input is a decimal number (hours)
    const decimalRegex = /^-?\d+[.,]\d+$/;
    if (decimalRegex.test(input)) {
        const hours = parseFloat(input.replace(',', '.'));
        return { seconds: Math.round(hours * 3600), isHHMM: false };
    }

    // Check if input is just a number (minutes or hours based on defaultUnit)
    if (/^-?\d+$/.test(input)) {
        const value = parseInt(input);
        const seconds = defaultUnit === 'minutes' ? value * 60 : value * 3600;
        return { seconds, isHHMM: false };
    }

    // Check if input is in HH:MM format
    const HHMMtimeRegex = /^([0-9]{1,2}):([0-5]?[0-9])$/;
    if (HHMMtimeRegex.test(input)) {
        const match = input.match(HHMMtimeRegex);
        if (match) {
            const hours = parseInt(match[1]);
            const minutes = parseInt(match[2]);
            return { seconds: (hours * 60 + minutes) * 60, isHHMM: true };
        }
    }

    // Try to parse natural language like "1h 30m"
    const parsedDuration = parse(input, 's');
    if (parsedDuration && parsedDuration > 0) {
        return { seconds: parsedDuration, isHHMM: false };
    }

    return { seconds: null, isHHMM: false };
}