<?php

class CalDavClient
{
    private string $baseUrl;
    private string $username;
    private string $password;

    public function __construct(string $baseUrl, string $username, string $password)
    {
        $this->baseUrl = rtrim($baseUrl, '/') . '/';
        $this->username = $username;
        $this->password = $password;
    }

    public function getBaseUrl(): string { return $this->baseUrl; }

    public function request(string $method, string $url, string $body = '', array $headers = []): array
    {
        $ch = curl_init();
        curl_setopt_array($ch, [
            CURLOPT_URL => $url,
            CURLOPT_CUSTOMREQUEST => $method,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_HEADER => true,
            CURLOPT_USERPWD => $this->username . ':' . $this->password,
            CURLOPT_HTTPAUTH => CURLAUTH_BASIC,
            CURLOPT_TIMEOUT => 30,
            CURLOPT_SSL_VERIFYPEER => true,
        ]);
        if ($body !== '') {
            curl_setopt($ch, CURLOPT_POSTFIELDS, $body);
        }
        // Use caller's Content-Type if provided, otherwise default to XML
        $hasContentType = false;
        foreach ($headers as $h) { if (stripos($h, 'Content-Type:') === 0) { $hasContentType = true; break; } }
        $allHeaders = $hasContentType ? $headers : array_merge(['Content-Type: application/xml; charset=utf-8'], $headers);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $allHeaders);

        $response = curl_exec($ch);
        $error = curl_error($ch);
        $status = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $headerSize = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
        curl_close($ch);

        if ($response === false) {
            return ['status' => 0, 'headers' => '', 'body' => '', 'error' => $error];
        }

        $respHeaders = substr($response, 0, $headerSize);
        $respBody = substr($response, $headerSize);

        // Extract ETag from headers
        $etag = null;
        if (preg_match('/^ETag:\s*(.+)$/mi', $respHeaders, $m)) {
            $etag = trim($m[1]);
        }

        return ['status' => $status, 'headers' => $respHeaders, 'body' => $respBody, 'etag' => $etag, 'error' => null];
    }

    public function testConnection(): bool
    {
        $res = $this->request('PROPFIND', $this->baseUrl, '<?xml version="1.0"?><d:propfind xmlns:d="DAV:"><d:prop><d:resourcetype/></d:prop></d:propfind>', ['Depth: 0']);
        return $res['status'] === 207;
    }

    public function listCalendars(): array
    {
        // PROPFIND depth 1 on the base URL to find calendar collections underneath
        $body = '<?xml version="1.0"?><d:propfind xmlns:d="DAV:" xmlns:cs="http://calendarserver.org/ns/" xmlns:c="urn:ietf:params:xml:ns:caldav"><d:prop><d:displayname/><d:resourcetype/><cs:getctag/></d:prop></d:propfind>';
        $res = $this->request('PROPFIND', $this->baseUrl, $body, ['Depth: 1']);
        if ($res['status'] !== 207) return [];

        $baseHref = rtrim(parse_url($this->baseUrl, PHP_URL_PATH), '/');
        $calendars = [];
        try {
            $xml = new SimpleXMLElement($res['body']);
            $xml->registerXPathNamespace('d', 'DAV:');
            $xml->registerXPathNamespace('cs', 'http://calendarserver.org/ns/');
            $xml->registerXPathNamespace('c', 'urn:ietf:params:xml:ns:caldav');
            foreach ($xml->xpath('//d:response') as $resp) {
                $resp->registerXPathNamespace('d', 'DAV:');
                $resp->registerXPathNamespace('cs', 'http://calendarserver.org/ns/');
                $resp->registerXPathNamespace('c', 'urn:ietf:params:xml:ns:caldav');

                $href = (string) ($resp->xpath('.//d:href')[0] ?? '');
                // Skip the collection itself (same path as base)
                if (rtrim($href, '/') === $baseHref) continue;

                // Check for calendar resource type via namespace-aware xpath
                $isCal = $resp->xpath('.//d:resourcetype/c:calendar');
                if (!$isCal) {
                    // Fallback: check raw XML for 'calendar' string
                    $rtXml = $resp->xpath('.//d:resourcetype');
                    if (!$rtXml || strpos($rtXml[0]->asXML(), 'calendar') === false) continue;
                }

                $name = (string) ($resp->xpath('.//d:displayname')[0] ?? basename(rtrim($href, '/')));
                $ctag = (string) ($resp->xpath('.//cs:getctag')[0] ?? '');
                if ($href) $calendars[] = ['name' => $name, 'href' => $href, 'ctag' => $ctag];
            }
        } catch (Exception $e) {}
        return $calendars;
    }

    public function getCalendarCtag(): ?string
    {
        $body = '<?xml version="1.0"?><d:propfind xmlns:d="DAV:" xmlns:cs="http://calendarserver.org/ns/"><d:prop><cs:getctag/></d:prop></d:propfind>';
        $res = $this->request('PROPFIND', $this->baseUrl, $body, ['Depth: 0']);
        if ($res['status'] !== 207) return null;
        try {
            $xml = new SimpleXMLElement($res['body']);
            $xml->registerXPathNamespace('d', 'DAV:');
            $xml->registerXPathNamespace('cs', 'http://calendarserver.org/ns/');
            $ctag = $xml->xpath('//cs:getctag');
            return $ctag ? (string) $ctag[0] : null;
        } catch (Exception $e) {
            return null;
        }
    }

    public function listEvents(): array
    {
        $body = '<?xml version="1.0"?><c:calendar-query xmlns:d="DAV:" xmlns:c="urn:ietf:params:xml:ns:caldav"><d:prop><d:getetag/><c:calendar-data/></d:prop><c:filter><c:comp-filter name="VCALENDAR"><c:comp-filter name="VEVENT"/></c:comp-filter></c:filter></c:calendar-query>';
        $res = $this->request('REPORT', $this->baseUrl, $body, ['Depth: 1']);
        if ($res['status'] !== 207) return [];

        $events = [];
        try {
            $xml = new SimpleXMLElement($res['body']);
            $xml->registerXPathNamespace('d', 'DAV:');
            $xml->registerXPathNamespace('c', 'urn:ietf:params:xml:ns:caldav');
            foreach ($xml->xpath('//d:response') as $resp) {
                $resp->registerXPathNamespace('d', 'DAV:');
                $resp->registerXPathNamespace('c', 'urn:ietf:params:xml:ns:caldav');
                $href = (string) ($resp->xpath('.//d:href')[0] ?? '');
                $etag = (string) ($resp->xpath('.//d:getetag')[0] ?? '');
                $ical = (string) ($resp->xpath('.//c:calendar-data')[0] ?? '');
                if ($href && $ical) {
                    $events[] = ['href' => $href, 'etag' => $etag, 'ical' => $ical];
                }
            }
        } catch (Exception $e) {}
        return $events;
    }

    public function createEvent(string $uid, string $icalData): array
    {
        // Use URL-safe filename (replace @ and other special chars)
        $filename = preg_replace('/[^a-zA-Z0-9._-]/', '-', $uid);
        $url = $this->baseUrl . $filename . '.ics';
        return $this->request('PUT', $url, $icalData, [
            'Content-Type: text/calendar; charset=utf-8',
            'If-None-Match: *',
        ]);
    }

    public function updateEvent(string $href, string $icalData, string $etag): array
    {
        $url = $this->resolveHref($href);
        return $this->request('PUT', $url, $icalData, [
            'Content-Type: text/calendar; charset=utf-8',
            'If-Match: ' . $etag,
        ]);
    }

    public function deleteEvent(string $href, string $etag): array
    {
        $url = $this->resolveHref($href);
        return $this->request('DELETE', $url, '', ['If-Match: ' . $etag]);
    }

    private function resolveHref(string $href): string
    {
        if (str_starts_with($href, 'http')) return $href;
        $parsed = parse_url($this->baseUrl);
        return $parsed['scheme'] . '://' . $parsed['host'] . (isset($parsed['port']) ? ':' . $parsed['port'] : '') . $href;
    }

    // ── iCalendar parsing ──

    public static function parseVEvent(string $ical): ?array
    {
        // Unfold RFC 5545 line continuations
        $ical = preg_replace('/\r\n[ \t]/', '', $ical);
        $ical = str_replace("\r\n", "\n", $ical);

        if (!preg_match('/BEGIN:VEVENT(.+?)END:VEVENT/s', $ical, $m)) return null;
        $block = $m[1];

        $get = function ($prop) use ($block) {
            // Match property value: everything after "PROP...:" until the next property or end
            if (preg_match('/^' . preg_quote($prop, '/') . '[^:]*:([\s\S]*?)(?=\n[A-Z][-A-Z]*[;:]|\z)/m', $block, $m)) return trim($m[1]);
            return null;
        };

        return [
            'uid' => $get('UID'),
            'summary' => $get('SUMMARY'),
            'dtstart' => $get('DTSTART'),
            'dtend' => $get('DTEND'),
            'location' => $get('LOCATION'),
            'description' => str_replace('\\n', "\n", $get('DESCRIPTION') ?? ''),
            'last_modified' => $get('LAST-MODIFIED'),
            'sequence' => (int) ($get('SEQUENCE') ?? 0),
            'rrule' => $get('RRULE'),
        ];
    }

    public static function buildVEvent(array $props): string
    {
        $fold = function ($line) {
            $out = '';
            while (strlen($line) > 75) {
                $out .= substr($line, 0, 75) . "\r\n ";
                $line = substr($line, 75);
            }
            return $out . $line;
        };

        $escape = function ($s) {
            return str_replace(["\n", ",", ";", "\\"], ["\\n", "\\,", "\\;", "\\\\"], $s ?? '');
        };

        $lines = [
            'BEGIN:VCALENDAR',
            'VERSION:2.0',
            'PRODID:-//hyprcrd//CalDAV Client//EN',
            'CALSCALE:GREGORIAN',
            'BEGIN:VEVENT',
            'UID:' . $props['uid'],
        ];

        // DTSTART / DTEND
        if (strlen($props['dtstart'] ?? '') === 8) {
            $lines[] = 'DTSTART;VALUE=DATE:' . $props['dtstart'];
            $lines[] = 'DTEND;VALUE=DATE:' . ($props['dtend'] ?? $props['dtstart']);
        } else {
            $lines[] = 'DTSTART:' . $props['dtstart'];
            if (!empty($props['dtend'])) $lines[] = 'DTEND:' . $props['dtend'];
        }

        $lines[] = $fold('SUMMARY:' . $escape($props['summary'] ?? ''));
        if (!empty($props['rrule'])) $lines[] = 'RRULE:' . $props['rrule'];
        if (!empty($props['location'])) $lines[] = $fold('LOCATION:' . $escape($props['location']));
        if (!empty($props['description'])) $lines[] = $fold('DESCRIPTION:' . $escape($props['description']));
        $lines[] = 'SEQUENCE:' . ($props['sequence'] ?? 0);
        $lines[] = 'LAST-MODIFIED:' . gmdate('Ymd\THis\Z');
        $lines[] = 'DTSTAMP:' . gmdate('Ymd\THis\Z');
        if (!empty($props['color'])) $lines[] = 'X-HYPRCRD-COLOR:' . $props['color'];
        $lines[] = 'END:VEVENT';
        $lines[] = 'END:VCALENDAR';

        return implode("\r\n", $lines) . "\r\n";
    }
}