// ============================================================
// 居家上门服务预约时间工具
// 负责：动态日期生成、常用/自定义时间段生成、时间合法性校验
// 约束：所有计算基于真实当前时间，不写死任何展示文本
// ============================================================

export const BOOKING_DAYS_LIMIT = 7
export const MIN_ADVANCE_MINUTES = 30
export const CUSTOM_SLOT_DURATION_MINUTES = 60
export const CUSTOM_SLOT_STEP_MINUTES = 30

export const PRESET_SLOT_RANGES = [
	'09:00-10:00',
	'10:00-11:00',
	'14:00-15:00',
	'15:00-16:00',
	'18:00-19:00'
]

export type BookingDayOptionType = {
	id: string
	dateKey: string
	label: string
	dateText: string
	weekday: string
	timestamp: number
	available: boolean
	disabledReason: string
}

export type BookingTimeSlotType = {
	id: string
	label: string
	startAt: number
	endAt: number
	source: string
	available: boolean
	disabledReason: string
}

export type BookingValidationResultType = {
	valid: boolean
	message: string
}

const WEEKDAY_LABELS = ['周日', '周一', '周二', '周三', '周四', '周五', '周六']

function padLeft(num: number, length: number): string {
	let result = String(num)
	while (result.length < length) {
		result = '0' + result
	}
	return result
}

function parseDateKey(dateKey: string): { year: number, month: number, day: number } | null {
	if (dateKey.length != 10) {
		return null
	}
	const year = parseInt(dateKey.substring(0, 4))
	const month = parseInt(dateKey.substring(5, 7)) - 1
	const day = parseInt(dateKey.substring(8, 10))
	if (isNaN(year) || isNaN(month) || isNaN(day)) {
		return null
	}
	return { year, month, day }
}

function parseTimeRange(range: string): { startH: number, startM: number, endH: number, endM: number } | null {
	const parts = range.split('-')
	if (parts.length != 2) {
		return null
	}
	const startParts = parts[0].split(':')
	const endParts = parts[1].split(':')
	if (startParts.length != 2 || endParts.length != 2) {
		return null
	}
	const startH = parseInt(startParts[0])
	const startM = parseInt(startParts[1])
	const endH = parseInt(endParts[0])
	const endM = parseInt(endParts[1])
	if (isNaN(startH) || isNaN(startM) || isNaN(endH) || isNaN(endM)) {
		return null
	}
	return { startH, startM, endH, endM }
}

export function buildBookingDays(now: Date): Array<BookingDayOptionType> {
	const result: Array<BookingDayOptionType> = []
	const base = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 0, 0, 0, 0)

	for (let i = 0; i < BOOKING_DAYS_LIMIT; i++) {
		const d = new Date(base.getTime() + i * 24 * 60 * 60 * 1000)
		const year = d.getFullYear()
		const month = d.getMonth() + 1
		const day = d.getDate()
		const weekdayIndex = d.getDay()

		const dateKey = year + '-' + padLeft(month, 2) + '-' + padLeft(day, 2)
		let label = ''
		if (i == 0) {
			label = '今天'
		} else if (i == 1) {
			label = '明天'
		} else if (i == 2) {
			label = '后天'
		} else {
			label = WEEKDAY_LABELS[weekdayIndex]
		}

		const dateText = padLeft(month, 2) + '月' + padLeft(day, 2) + '日'
		const weekday = WEEKDAY_LABELS[weekdayIndex]

		result.push({
			id: 'day-' + String(i),
			dateKey,
			label,
			dateText,
			weekday,
			timestamp: d.getTime(),
			available: true,
			disabledReason: ''
		})
	}
	return result
}

export function buildPresetSlots(selectedDateKey: string, now: Date): Array<BookingTimeSlotType> {
	const result: Array<BookingTimeSlotType> = []
	const parsed = parseDateKey(selectedDateKey)
	if (parsed == null) {
		return result
	}

	const minStartTime = now.getTime() + MIN_ADVANCE_MINUTES * 60 * 1000

	for (let i = 0; i < PRESET_SLOT_RANGES.length; i++) {
		const range = PRESET_SLOT_RANGES[i]
		const time = parseTimeRange(range)
		if (time == null) {
			continue
		}

		const startDate = new Date(parsed.year, parsed.month, parsed.day, time.startH, time.startM, 0, 0)
		const endDate = new Date(parsed.year, parsed.month, parsed.day, time.endH, time.endM, 0, 0)
		const startAt = startDate.getTime()
		const endAt = endDate.getTime()

		const available = startAt >= minStartTime
		result.push({
			id: 'preset-' + String(i),
			label: range,
			startAt,
			endAt,
			source: 'preset',
			available,
			disabledReason: available ? '' : '该时段距离当前不足30分钟，无法保证服务人员按时到达'
		})
	}
	return result
}

export function buildCustomSlots(selectedDateKey: string, now: Date): Array<BookingTimeSlotType> {
	const result: Array<BookingTimeSlotType> = []
	const parsed = parseDateKey(selectedDateKey)
	if (parsed == null) {
		return result
	}

	const minStartTime = now.getTime() + MIN_ADVANCE_MINUTES * 60 * 1000

	for (let h = 0; h < 24; h++) {
		for (let m = 0; m < 60; m += CUSTOM_SLOT_STEP_MINUTES) {
			const startDate = new Date(parsed.year, parsed.month, parsed.day, h, m, 0, 0)
			const endDate = new Date(parsed.year, parsed.month, parsed.day, h, m + CUSTOM_SLOT_DURATION_MINUTES, 0, 0)

			const startAt = startDate.getTime()
			const endAt = endDate.getTime()
			const available = startAt >= minStartTime

			const startLabel = padLeft(h, 2) + ':' + padLeft(m, 2)
			const endLabel = padLeft(endDate.getHours(), 2) + ':' + padLeft(endDate.getMinutes(), 2)

			result.push({
				id: 'custom-' + startLabel + '-' + endLabel,
				label: startLabel + '-' + endLabel,
				startAt,
				endAt,
				source: 'custom',
				available,
				disabledReason: available ? '' : '该时段距离当前不足30分钟，无法保证服务人员按时到达'
			})
		}
	}
	return result
}

export function hasAnyAvailableSlots(dateKey: string, now: Date): boolean {
	const presets = buildPresetSlots(dateKey, now)
	for (let i = 0; i < presets.length; i++) {
		if (presets[i].available) {
			return true
		}
	}
	const customs = buildCustomSlots(dateKey, now)
	for (let i = 0; i < customs.length; i++) {
		if (customs[i].available) {
			return true
		}
	}
	return false
}

export function validateSelectedAppointmentTime(
	selectedDay: BookingDayOptionType | null,
	selectedSlot: BookingTimeSlotType | null,
	now: Date
): BookingValidationResultType {
	if (selectedDay == null) {
		return { valid: false, message: '请选择预约日期' }
	}
	if (selectedSlot == null) {
		return { valid: false, message: '请选择预约时间段' }
	}

	const slotStartDate = new Date(selectedSlot.startAt)
	const dayDate = new Date(selectedDay.timestamp)
	const sameDay = slotStartDate.getFullYear() == dayDate.getFullYear()
		&& slotStartDate.getMonth() == dayDate.getMonth()
		&& slotStartDate.getDate() == dayDate.getDate()
	if (!sameDay) {
		return { valid: false, message: '所选时间段不属于当前选中的日期' }
	}

	const minStartTime = now.getTime() + MIN_ADVANCE_MINUTES * 60 * 1000
	if (selectedSlot.startAt < minStartTime) {
		return { valid: false, message: '当前选择的上门时间已失效，请重新选择稍晚的时间段' }
	}

	const maxDate = new Date(now.getTime() + BOOKING_DAYS_LIMIT * 24 * 60 * 60 * 1000)
	const maxDateStart = new Date(maxDate.getFullYear(), maxDate.getMonth(), maxDate.getDate(), 0, 0, 0, 0)
	if (selectedDay.timestamp > maxDateStart.getTime()) {
		return { valid: false, message: '预约日期超出可预约范围' }
	}

	return { valid: true, message: '' }
}

export function formatAppointmentDisplayText(
	day: BookingDayOptionType | null,
	slot: BookingTimeSlotType | null
): string {
	if (day == null || slot == null) {
		return '请选择上门时间'
	}
	return day.label + ' ' + day.dateText + ' ' + day.weekday + ' ' + slot.label
}

export function formatStandardAppointmentTime(
	day: BookingDayOptionType | null,
	slot: BookingTimeSlotType | null
): string {
	if (day == null || slot == null) {
		return ''
	}
	return new Date(slot.startAt).toISOString()
}