/**
 * @copyright 2023 Christopher Ng <chrng8@gmail.com>
 *
 * @author Christopher Ng <chrng8@gmail.com>
 *
 * @license AGPL-3.0-or-later
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 */

import { getCanonicalLocale } from '@nextcloud/l10n'

export enum DateTimePreset {
	LaterToday = 'later-today',
	Tomorrow = 'tomorrow',
	ThisWeekend = 'this-weekend',
	NextWeek = 'next-week',
}

const getFirstWorkdayOfWeek = () => {
	const now = new Date()
	now.setHours(0, 0, 0, 0)
	now.setDate(now.getDate() - now.getDay() + 1)
	return new Date(now)
}

const getWeek = (date: Date) => {
	const dateClone = new Date(date)
	dateClone.setHours(0, 0, 0, 0)
	const firstDayOfYear = new Date(date.getFullYear(), 0, 1, 0, 0, 0, 0)
	const daysFromFirstDay = (date.getTime() - firstDayOfYear.getTime()) / 86400000
	return Math.ceil((daysFromFirstDay + firstDayOfYear.getDay() + 1) / 7)
}

const isSameWeek = (a: Date, b: Date) => {
	return getWeek(a) === getWeek(b)
		&& a.getFullYear() === b.getFullYear()
}

const isSameDate = (a: Date, b: Date) => {
	return a.getDate() === b.getDate()
		&& a.getMonth() === b.getMonth()
		&& a.getFullYear() === b.getFullYear()
}

export const getDateTime = (dateTime: DateTimePreset): null | Date => {
	const matchPreset: Record<DateTimePreset, () => null | Date> = {
		[DateTimePreset.LaterToday]: () => {
			const now = new Date()
			const evening = new Date()
			evening.setHours(18, 0, 0, 0)
			const cutoff = new Date()
			cutoff.setHours(17, 0, 0, 0)
			if (now >= cutoff) {
				return null
			}
			return evening
		},

		[DateTimePreset.Tomorrow]: () => {
			const now = new Date()
			const day = new Date()
			day.setDate(now.getDate() + 1)
			day.setHours(8, 0, 0, 0)
			return day
		},

		[DateTimePreset.ThisWeekend]: () => {
			const today = new Date()
			if (
				[
					5, // Friday
					6, // Saturday
					0, // Sunday
				].includes(today.getDay())
			) {
				return null
			}
			const saturday = new Date()
			const firstWorkdayOfWeek = getFirstWorkdayOfWeek()
			saturday.setDate(firstWorkdayOfWeek.getDate() + 5)
			saturday.setHours(8, 0, 0, 0)
			return saturday
		},

		[DateTimePreset.NextWeek]: () => {
			const today = new Date()
			if (today.getDay() === 0) { // Sunday
				return null
			}
			const workday = new Date()
			const firstWorkdayOfWeek = getFirstWorkdayOfWeek()
			workday.setDate(firstWorkdayOfWeek.getDate() + 7)
			workday.setHours(8, 0, 0, 0)
			return workday
		},
	}

	return matchPreset[dateTime]()
}

export const getInitialCustomDueDate = (): Date => {
	const now = new Date()
	const dueDate = new Date()
	dueDate.setHours(now.getHours() + 2, 0, 0, 0)
	return dueDate
}

export const getDateString = (dueDate: Date): string => {
	let formatOptions: Intl.DateTimeFormatOptions = {
		hour: 'numeric',
		minute: '2-digit',
	}

	const today = new Date()

	if (!isSameDate(dueDate, today)) {
		formatOptions = {
			...formatOptions,
			weekday: 'short',
		}
	}

	if (!isSameWeek(dueDate, today)) {
		formatOptions = {
			...formatOptions,
			month: 'short',
			day: 'numeric',
		}
	}

	if (dueDate.getFullYear() !== today.getFullYear()) {
		formatOptions = {
			...formatOptions,
			year: 'numeric',
		}
	}

	return dueDate.toLocaleString(
		getCanonicalLocale(),
		formatOptions,
	)
}

export const getVerboseDateString = (dueDate: Date): string => {
	let formatOptions: Intl.DateTimeFormatOptions = {
		month: 'long',
		day: 'numeric',
		weekday: 'long',
		hour: 'numeric',
		minute: '2-digit',
	}

	const today = new Date()

	if (dueDate.getFullYear() !== today.getFullYear()) {
		formatOptions = {
			...formatOptions,
			year: 'numeric',
		}
	}

	return dueDate.toLocaleString(
		getCanonicalLocale(),
		formatOptions,
	)
}