<?php
require __DIR__ . '/common.php';

/**
 * Agenda : conversion de l'iCal officiel de silly.be en flux RSS.
 * Le calendrier annonce un TTL de 12 h (X-PUBLISHED-TTL:PT12H), on cache
 * donc aussi 12 h. Il ne contient que les evenements a venir (quelques
 * uns) ; l'API REST /wp-json/wp/v2/evenement liste plus d'evenements mais
 * sans aucune date (champ acf vide), donc inutilisable pour un agenda.
 * Les regles de recurrence (RRULE) ne sont pas developpees.
 */
const ICAL_URL = 'https://www.silly.be/agenda/?ics=1';
const AGENDA_SELF_URL = 'https://sillycone-village.be/silly-rss/agenda.php';
const AGENDA_TTL_SECONDS = 43200; // 12 heures
const DISPLAY_TZ = 'Europe/Brussels';

/**
 * Parse un texte iCal : deplie les lignes (RFC 5545 §3.1) et renvoie la
 * liste des VEVENT, chacun sous la forme NOM => [['params' => [...], 'value' => ...], ...].
 */
function parse_ical_events(string $ical): array
{
    $ical = str_replace(["\r\n", "\r"], "\n", $ical);
    $ical = preg_replace('/\n[ \t]/', '', $ical);

    $events = [];
    $current = null;
    foreach (explode("\n", $ical) as $line) {
        $line = rtrim($line);
        if ($line === 'BEGIN:VEVENT') {
            $current = [];
        } elseif ($line === 'END:VEVENT') {
            if ($current !== null) {
                $events[] = $current;
            }
            $current = null;
        } elseif ($current !== null && $line !== '') {
            // NOM[;PARAM=VAL...]:valeur (les valeurs de parametres peuvent
            // etre entre guillemets et contenir ':' ; on coupe sur le 1er
            // ':' hors guillemets)
            if (!preg_match('/^([A-Za-z0-9-]+)((?:;(?:[^:;"]|"[^"]*")*)*):(.*)$/s', $line, $m)) {
                continue;
            }
            $params = [];
            foreach (explode(';', ltrim($m[2], ';')) as $p) {
                if (strpos($p, '=') !== false) {
                    [$k, $v] = explode('=', $p, 2);
                    $params[strtoupper($k)] = trim($v, '"');
                }
            }
            $current[strtoupper($m[1])][] = ['params' => $params, 'value' => $m[3]];
        }
    }
    return $events;
}

/** Deséchappe une valeur TEXT iCal : \\ \, \; \n. */
function ical_unescape(string $text): string
{
    return preg_replace_callback('/\\\\([nN,;\\\\])/', function ($m) {
        return ($m[1] === 'n' || $m[1] === 'N') ? "\n" : $m[1];
    }, $text);
}

function ical_text(array $event, string $name): string
{
    return isset($event[$name][0]) ? trim(ical_unescape($event[$name][0]['value'])) : '';
}

/** Renvoie [DateTimeImmutable|null, bool $allDay] pour DTSTART/DTEND/CREATED. */
function ical_date(array $event, string $name): array
{
    if (!isset($event[$name][0])) {
        return [null, false];
    }
    $prop = $event[$name][0];
    $value = trim($prop['value']);
    $display = new DateTimeZone(DISPLAY_TZ);
    try {
        if (($prop['params']['VALUE'] ?? '') === 'DATE' || preg_match('/^\d{8}$/', $value)) {
            return [new DateTimeImmutable($value, $display), true];
        }
        if (substr($value, -1) === 'Z') {
            $dt = new DateTimeImmutable(substr($value, 0, -1), new DateTimeZone('UTC'));
        } else {
            $tz = new DateTimeZone($prop['params']['TZID'] ?? DISPLAY_TZ);
            $dt = new DateTimeImmutable($value, $tz);
        }
        return [$dt->setTimezone($display), false];
    } catch (Exception $e) {
        return [null, false];
    }
}

function format_event_dates(?DateTimeImmutable $start, ?DateTimeImmutable $end, bool $allDay): string
{
    if (!$start) {
        return '';
    }
    if ($allDay) {
        // En iCal, DTEND d'un evenement "journee entiere" est exclusif.
        $last = $end ? $end->modify('-1 day') : $start;
        if ($last <= $start) {
            return 'Le ' . $start->format('d/m/Y');
        }
        return 'Du ' . $start->format('d/m/Y') . ' au ' . $last->format('d/m/Y');
    }
    if (!$end || $end == $start) {
        return 'Le ' . $start->format('d/m/Y à H:i');
    }
    if ($end->format('Y-m-d') === $start->format('Y-m-d')) {
        return 'Le ' . $start->format('d/m/Y') . ' de ' . $start->format('H:i') . ' à ' . $end->format('H:i');
    }
    return 'Du ' . $start->format('d/m/Y à H:i') . ' au ' . $end->format('d/m/Y à H:i');
}

/** Texte brut -> HTML : paragraphes sur lignes vides, <br> sur retours simples, URLs cliquables. */
function text_to_html(string $text): string
{
    $html = '';
    foreach (preg_split('/\n{2,}/', trim($text)) as $para) {
        $para = trim($para);
        if ($para === '') {
            continue;
        }
        $safe = htmlspecialchars($para, ENT_QUOTES, 'UTF-8');
        $safe = preg_replace('#(https?://[^\s<]+)#', '<a href="$1">$1</a>', $safe);
        $html .= '<p>' . nl2br($safe, false) . '</p>';
    }
    return $html;
}

function build_events_feed(): string
{
    $ical = http_get(ICAL_URL, ['Accept: text/calendar, */*']);
    if (strpos($ical, 'BEGIN:VCALENDAR') === false) {
        throw new RuntimeException('Reponse inattendue : pas un calendrier iCal');
    }

    $entries = [];
    $seen = [];
    foreach (parse_ical_events($ical) as $event) {
        [$start, $allDay] = ical_date($event, 'DTSTART');
        [$end] = ical_date($event, 'DTEND');
        [$created] = ical_date($event, 'CREATED');

        $title = ical_text($event, 'SUMMARY') ?: '(sans titre)';
        $uid = ical_text($event, 'UID') ?: $title . '-' . ($start ? $start->format('c') : '');
        $url = ical_text($event, 'URL');
        $location = ical_text($event, 'LOCATION');

        $guid = $uid;
        if (isset($seen[$guid])) { // occurrence d'un evenement repete : meme UID
            $guid .= '-' . ($start ? $start->format('YmdHi') : count($seen));
        }
        $seen[$guid] = true;

        $meta = format_event_dates($start, $end, $allDay);
        if ($location !== '') {
            $meta .= ($meta !== '' ? ' — ' : '') . 'Lieu : ' . $location;
        }
        $description = ($meta !== '' ? '<p>' . htmlspecialchars($meta, ENT_QUOTES, 'UTF-8') . '</p>' : '')
            . text_to_html(ical_text($event, 'DESCRIPTION'));

        $pub = $created ?? $start;
        $entries[] = [
            'sort' => $start ? $start->getTimestamp() : PHP_INT_MAX,
            'item' => [
                'title' => $title,
                'link' => $url !== '' ? $url : 'https://www.silly.be/agenda/',
                'guid' => $guid,
                'pubDate' => $pub ? $pub->format('c') : null,
                'description' => $description,
            ],
        ];
    }
    usort($entries, fn($a, $b) => $a['sort'] <=> $b['sort']);

    return build_rss(
        'Silly.be - Agenda',
        'https://www.silly.be/agenda/',
        'Agenda / événements de la commune de Silly (Belgique)',
        array_column($entries, 'item'),
        AGENDA_SELF_URL
    );
}

serve_cached_feed('agenda', 'build_events_feed', AGENDA_TTL_SECONDS);