import { fail, redirect } from '@sveltejs/kit';
import type { Actions, PageServerLoad } from './$types';
import { requireUser } from '#lib/server/auth.js';
import { createShow, listShows, listShowTemplates } from '#lib/server/shows.js';

function berlinLocalToUtc(value: string): string | null {
	if (!value) return null;
	const match = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})$/.exec(value);
	if (!match) throw new Error('INVALID_TIMESTAMP');
	const parts = match.slice(1).map(Number);
	const localMilliseconds = Date.UTC(parts[0], parts[1] - 1, parts[2], parts[3], parts[4]);
	let candidate = localMilliseconds;
	for (let attempt = 0; attempt < 2; attempt += 1) {
		const formatted = new Intl.DateTimeFormat('en-CA', {
			timeZone: 'Europe/Berlin',
			year: 'numeric',
			month: '2-digit',
			day: '2-digit',
			hour: '2-digit',
			minute: '2-digit',
			hourCycle: 'h23'
		}).formatToParts(new Date(candidate));
		const read = (type: Intl.DateTimeFormatPartTypes) =>
			Number(formatted.find((part) => part.type === type)?.value);
		const represented = Date.UTC(
			read('year'),
			read('month') - 1,
			read('day'),
			read('hour'),
			read('minute')
		);
		candidate += localMilliseconds - represented;
	}
	return new Date(candidate).toISOString();
}

export const load: PageServerLoad = ({ locals }) => {
	requireUser(locals.user);
	return { shows: listShows(), templates: listShowTemplates() };
};

export const actions = {
	create: async ({ locals, request }) => {
		requireUser(locals.user);
		const data = await request.formData();
		const title = String(data.get('title') || '');
		const startsAt = String(data.get('startsAt') || '');
		const templateId = String(data.get('templateId') || '') || null;
		let id: string;
		try {
			id = createShow({ title, startsAtUtc: berlinLocalToUtc(startsAt), templateId }).id;
		} catch (cause) {
			const code = cause instanceof Error ? cause.message : '';
			if (code === 'INVALID_TITLE') {
				return fail(400, { error: 'Bitte einen Titel eingeben.', title, startsAt, templateId });
			}
			if (code === 'INVALID_TIMESTAMP') {
				return fail(400, {
					error: 'Bitte einen gültigen Termin eingeben.',
					title,
					startsAt,
					templateId
				});
			}
			return fail(400, {
				error: 'Die Sendung konnte nicht angelegt werden.',
				title,
				startsAt,
				templateId
			});
		}
		redirect(303, `/sendungen/${id}`);
	}
} satisfies Actions;