<?php

declare(strict_types=1);

require __DIR__.'/backend.php';

$project = (string) ($_GET['project'] ?? '');
$token = (string) ($_GET['token'] ?? '');
if (!bookingProjectIsValid($project) || !preg_match('/^[a-f0-9]{64}$/', $token)) {
    http_response_code(404);
    exit;
}

$database = bookingDatabase();
$settings = $database->prepare('SELECT feed_token FROM sufw_booking_project_settings WHERE project = :project');
$settings->execute(['project' => $project]);
if (!hash_equals((string) $settings->fetchColumn(), $token)) {
    http_response_code(404);
    exit;
}

$events = $database->prepare(<<<'SQL'
    SELECT e.id, e.title, e.starts_at, e.ends_at, e.format
    FROM sufw_booking_events e
    WHERE e.project = :project AND EXISTS (SELECT 1 FROM sufw_booking_registrations r WHERE r.event_id = e.id AND r.status = 'confirmed')
    ORDER BY e.starts_at
    SQL);
$events->execute(['project' => $project]);
$timezone = new DateTimeZone('Europe/Berlin');
$utc = new DateTimeZone('UTC');
$lines = ['BEGIN:VCALENDAR', 'VERSION:2.0', 'PRODID:-//SUFW//Terminbuchung//DE', 'CALSCALE:GREGORIAN', 'X-WR-CALNAME:'.bookingIcsEscape(bookingProjectTitle($project))];
foreach ($events as $event) {
    $start = new DateTimeImmutable($event['starts_at'], $timezone);
    $end = new DateTimeImmutable($event['ends_at'], $timezone);
    $lines[] = 'BEGIN:VEVENT';
    $lines[] = 'UID:'.bookingIcsEscape($event['id']).'@sufw-booking';
    $lines[] = 'DTSTAMP:'.gmdate('Ymd\\THis\\Z');
    $lines[] = 'DTSTART:'.$start->setTimezone($utc)->format('Ymd\\THis\\Z');
    $lines[] = 'DTEND:'.$end->setTimezone($utc)->format('Ymd\\THis\\Z');
    $lines[] = 'SUMMARY:'.bookingIcsEscape($event['title']);
    $lines[] = 'DESCRIPTION:'.bookingIcsEscape($event['format'] === 'telefonisch' ? 'Telefonischer Termin' : 'Termin vor Ort');
    $lines[] = 'END:VEVENT';
}
$lines[] = 'END:VCALENDAR';
header('Content-Type: text/calendar; charset=utf-8');
header('Content-Disposition: inline; filename="'.($project === 'produktionsschule' ? 'produktionsschule' : 'perspektivwerk').'-termine.ics"');
header('Cache-Control: no-store');
echo implode("\r\n", $lines)."\r\n";