import * as EventsService from '../../calendar/events/events.service';
import logger from '../../../middleware/logger';
import {NachklangTicketsDB} from '../Tickets.db';
import {getEventTicketState} from '../tickets.capacity';
import {recordConfirmationEmailResult, sendRedemptionConfirmation} from '../tickets.confirmation-email';
import {EligibleEvent, RedeemRequest, VoucherValidation} from '../tickets.interface';
import {isValidEmail} from '../tickets.validation';

/**
 * Builds the eligible-events list for a code: for each event it's linked
 * to, merges live Calendar event details with the Tickets module's own
 * capacity/deadline state. Events deleted from the calendar since the code
 * was generated are silently skipped rather than erroring. DRAFT events are
 * deliberately still eligible - vouchers are sometimes sent out before a
 * concert is publicly announced (see docs/plan-ticket-shop.md), so only
 * DELETED is excluded here, not draft/unpublished status.
 */
export const validateVoucher = async (code: string): Promise<VoucherValidation | null> => {
	let conn = await NachklangTicketsDB.getConnection();
	try {
		const voucherRows = await conn.query('SELECT * FROM voucher_codes WHERE code = ?', [code]);
		if (voucherRows.length === 0) {
			return null;
		}
		const voucher = voucherRows[0];

		const eventIdRows = await conn.query('SELECT event_id FROM voucher_code_events WHERE code = ?', [code]);
		const eligibleEvents: EligibleEvent[] = [];
		const now = new Date();

		for (const row of eventIdRows) {
			const eventId = row.event_id;
			const event = await EventsService.getEventById(eventId);
			if (!event || event.status === 'DELETED') continue;

			const ticketState = await getEventTicketState(conn, eventId);
			eligibleEvents.push({
				eventId,
				name: event.name,
				startDateTime: event.startDateTime,
				location: event.location,
				deadlinePassed: ticketState.redemptionDeadline !== null && now > new Date(ticketState.redemptionDeadline),
				isFull: ticketState.spotsRemaining !== null && ticketState.spotsRemaining <= 0,
				spotsRemaining: ticketState.spotsRemaining,
				collectAddress: ticketState.collectAddress,
				requireAddress: ticketState.requireAddress
			});
		}

		eligibleEvents.sort((a, b) => a.startDateTime.getTime() - b.startDateTime.getTime());

		return {
			code: voucher.code,
			status: voucher.status,
			maxGuests: voucher.max_guests,
			prefillName: voucher.prefill_name,
			prefillEmail: voucher.prefill_email,
			eligibleEvents
		};
	} finally {
		await conn.end();
	}
};

export type RedeemResult =
	| {status: 'OK'; redemptionId: number}
	| {status: 'NOT_FOUND'}
	| {status: 'ALREADY_USED'}
	| {status: 'INVALID_EVENT'}
	| {status: 'DEADLINE_PASSED'}
	| {status: 'CAPACITY_EXCEEDED'; spotsRemaining: number}
	| {status: 'ADDRESS_REQUIRED'};

export const redeemVoucher = async (code: string, request: RedeemRequest): Promise<RedeemResult> => {
	if (!request.contactName || !request.contactEmail || !Array.isArray(request.guests) || request.guests.length === 0) {
		throw new Error('contactName, contactEmail, and at least one guest are required');
	}
	if (!isValidEmail(request.contactEmail)) {
		throw new Error('contactEmail does not look like a valid email address');
	}
	for (const guest of request.guests) {
		if (!guest.name) {
			throw new Error('every guest requires a name');
		}
	}

	let conn = await NachklangTicketsDB.getConnection();
	let redemptionId: number;
	let eventId: number;
	try {
		await conn.beginTransaction();

		// Locks the code row so two concurrent requests for the same code
		// can't both pass the "still UNUSED" check.
		const voucherRows = await conn.query('SELECT * FROM voucher_codes WHERE code = ? FOR UPDATE', [code]);
		if (voucherRows.length === 0) {
			await conn.rollback();
			return {status: 'NOT_FOUND'};
		}
		const voucher = voucherRows[0];
		if (voucher.status !== 'UNUSED') {
			await conn.rollback();
			return {status: 'ALREADY_USED'};
		}

		const eligibleRows = await conn.query('SELECT 1 FROM voucher_code_events WHERE code = ? AND event_id = ?', [code, request.eventId]);
		if (eligibleRows.length === 0) {
			await conn.rollback();
			return {status: 'INVALID_EVENT'};
		}

		// A concert can be canceled/deleted from the calendar after codes were
		// issued - without this, such a code would stay silently redeemable.
		// DRAFT is deliberately still allowed (see validateVoucher's comment).
		const event = await EventsService.getEventById(request.eventId);
		if (!event || event.status === 'DELETED') {
			await conn.rollback();
			return {status: 'INVALID_EVENT'};
		}

		if (request.guests.length > voucher.max_guests) {
			await conn.rollback();
			throw new Error(`this code allows at most ${voucher.max_guests} guests`);
		}

		// forUpdate=true serializes concurrent redemptions against this event
		// so the capacity check below can't race past a hard cap.
		const ticketState = await getEventTicketState(conn, request.eventId, true);
		const now = new Date();
		if (ticketState.redemptionDeadline !== null && now > new Date(ticketState.redemptionDeadline)) {
			await conn.rollback();
			return {status: 'DEADLINE_PASSED'};
		}
		if (ticketState.spotsRemaining !== null && request.guests.length > ticketState.spotsRemaining) {
			await conn.rollback();
			return {status: 'CAPACITY_EXCEEDED', spotsRemaining: ticketState.spotsRemaining};
		}
		if (ticketState.requireAddress && !request.contactAddress?.trim()) {
			await conn.rollback();
			return {status: 'ADDRESS_REQUIRED'};
		}

		const contactAddress = ticketState.collectAddress ? (request.contactAddress || null) : null;

		const redemptionRes = await conn.query(
			'INSERT INTO redemptions (code, event_id, contact_name, contact_email, contact_address, guest_count) VALUES (?,?,?,?,?,?) RETURNING redemption_id',
			[code, request.eventId, request.contactName, request.contactEmail, contactAddress, request.guests.length]
		);
		redemptionId = redemptionRes[0].redemption_id;
		eventId = request.eventId;

		for (let i = 0; i < request.guests.length; i++) {
			await conn.query('INSERT INTO redemption_guests (redemption_id, name, position) VALUES (?,?,?)', [redemptionId, request.guests[i].name, i]);
		}

		await conn.query('UPDATE voucher_codes SET status = ? WHERE code = ?', ['REDEEMED', code]);

		await conn.commit();
	} catch (err) {
		await conn.rollback();
		throw err;
	} finally {
		await conn.end();
	}

	// Sent after commit, mirroring the Calendar/Feedback convention: a mail
	// delivery failure shouldn't roll back a successful redemption, and the
	// guest has in fact already secured their spot. The send itself no longer
	// throws on a delivery problem; its result is recorded on the redemption
	// so staff can spot and resend a failed confirmation from the admin UI.
	try {
		const sent = await sendRedemptionConfirmation({
			eventId,
			contactName: request.contactName,
			contactEmail: request.contactEmail,
			guestNames: request.guests.map(g => g.name)
		});
		await recordConfirmationEmailResult(redemptionId, sent);
	} catch (e: any) {
		logger.error('Redemption ' + redemptionId + ' committed but the confirmation email step failed: ' + e.message);
	}

	return {status: 'OK', redemptionId};
};