<?php

function calendar_next_events(int $n = 5): array {
    $url   = 'https://alpinux.org/public-calendars/n5BWPYsxw7FCYozM?p=webcal';
    $cache = sys_get_temp_dir() . '/alpinux_calendar.ics';
    $ttl   = 3600;

    if (!file_exists($cache) || (time() - filemtime($cache)) >= $ttl) {
        $data = @file_get_contents($url);
        if ($data !== false) file_put_contents($cache, $data);
    }

    if (!file_exists($cache)) return [];

    return _ical_upcoming(file_get_contents($cache), $n);
}

function _ical_upcoming(string $ical, int $n): array {
    $events = [];
    $now    = time();

    preg_match_all('/BEGIN:VEVENT(.+?)END:VEVENT/s', $ical, $blocks);

    foreach ($blocks[1] as $b) {
        $e = [];

        if (preg_match('/^SUMMARY[^:]*:(.+)$/m', $b, $m))
            $e['title'] = trim($m[1]);

        if (preg_match('/^LOCATION[^:]*:(.+)$/m', $b, $m))
            $e['location'] = trim($m[1]);

        if (preg_match('/^DTSTART[^:]*:(\d+)/m', $b, $m)) {
            $r = $m[1];
            $e['start'] = strlen($r) === 8
                ? mktime(0, 0, 0, substr($r, 4, 2), substr($r, 6, 2), substr($r, 0, 4))
                : strtotime($r);
        }

        if (isset($e['start'], $e['title']) && $e['start'] >= $now)
            $events[] = $e;
    }

    usort($events, fn($a, $b) => $a['start'] - $b['start']);

    return array_slice($events, 0, $n);
}