<?php

declare(strict_types=1);

namespace KTXM\ServiceDav\Backends;

use KTXC\SessionIdentity;
use KTXC\SessionTenant;
use KTXM\ChronoManager\Manager as ChronoManager;
use KTXM\ServiceDav\DavProperties;
use KTXM\ServiceDav\DavUriMap;
use KTXF\Resource\Identifier\CollectionIdentifier;
use KTXF\Resource\Identifier\EntityIdentifier;
use KTXF\Resource\Identifier\ResourceIdentifiers;
use Sabre\CalDAV\Backend\AbstractBackend;
use Sabre\CalDAV\Xml\Property\SupportedCalendarComponentSet;
use Sabre\VObject\Component\VCalendar;
use Sabre\VObject\Reader;

/**
 * CalDAV backend bridging sabre/dav to the KTXM ChronoManager.
 *
 * Calendar  <=> Collection  (within a provider service)
 * Calendar object <=> Entity  (VEVENT / VTODO)
 *
 * Calendar identifiers use the composite key "{providerId}:{serviceId}:{collectionId}".
 * Object URIs are client-chosen names (e.g. "event-uid.ics") mapped to provider
 * entity identifiers via DavUriMap.
 */
class CalDavBackend extends AbstractBackend
{
    private const ID_SEP = ':';

    public function __construct(
        private readonly ChronoManager $manager,
        private readonly SessionIdentity $identity,
        private readonly SessionTenant $tenant,
        private readonly DavUriMap $uriMap,
    ) {}

    public function getCalendarsForUser($principalUri): array
    {
        $result   = [];
        
        $allCollections = $this->manager->collectionList($this->tenant->identifier(), $this->identity->identifier());

        foreach ($allCollections as $providerId => $providerServices) {
            foreach ($providerServices as $serviceId => $collections) {
                foreach ($collections as $collectionId => $collection) {
                    if (!is_object($collection)) {
                        continue;
                    }
                    $props = $collection->getProperties();
                    $label = $props->getLabel();
                    $calId = implode(self::ID_SEP, [(string) $providerId, (string) $serviceId, (string) $collectionId]);

                    $result[] = [
                        DavProperties::ID                 => $calId,
                        DavProperties::URI                => $this->slugify($label),
                        DavProperties::DISPLAYNAME        => $label,
                        DavProperties::CALDAV_DESCRIPTION => $props->getDescription() ?? '',
                        DavProperties::APPLE_COLOR        => $props->getColor() ?? '#3a87ad',
                        DavProperties::CALDAV_COMPONENTS  => new SupportedCalendarComponentSet(['VEVENT', 'VTODO']),
                        DavProperties::CS_CTAG            => md5($calId . (string) ($collection->modified()?->getTimestamp() ?? 0)),
                        DavProperties::SYNC_TOKEN         => '1',
                        DavProperties::PRINCIPAL_URI      => $principalUri,
                    ];
                }
            }
        }

        return $result;
    }

    public function createCalendar($principalUri, $calendarUri, array $properties): string
    {
        throw new \Sabre\DAV\Exception\Forbidden('Calendar creation is not supported via DAV');
    }

    public function deleteCalendar($calendarId): void
    {
        throw new \Sabre\DAV\Exception\Forbidden('Calendar deletion is not supported via DAV');
    }

    public function getCalendarObjects($calendarId): array
    {
        [$providerId, $serviceId, $collectionId] = $this->parseId($calendarId);
        $tenantId = $this->tenant->identifier();
        $userId   = $this->identity->identifier();

        $targets  = ResourceIdentifiers::fromArray([$calendarId]);
        $all      = $this->manager->entityListBulk($tenantId, $userId, $targets);
        $entities = $all[(string) $providerId][(string) $serviceId][(string) $collectionId] ?? [];

        $mapId   = $this->mapId($tenantId, $userId, $calendarId);
        $objects = [];
        foreach ($entities as $entity) {
            if (!is_object($entity)) {
                continue;
            }
            $entityId  = (string) $entity->identifier();
            $objectUri = $this->uriMap->getObjectUri($mapId, $entityId) ?? ($entityId . '.ics');
            $data      = $this->entityToIcal($entity);

            $objects[] = [
                DavProperties::ID            => $entityId,
                DavProperties::URI           => $objectUri,
                DavProperties::LAST_MODIFIED => $entity->modified()?->getTimestamp() ?? time(),
                DavProperties::ETAG          => '"' . md5($data) . '"',
                DavProperties::SIZE          => strlen($data),
                DavProperties::COMPONENT     => 'VEVENT',
                DavProperties::CALENDAR_DATA => null, // lazy - fetched on demand
            ];
        }

        return $objects;
    }

    public function getCalendarObject($calendarId, $objectUri): ?array
    {
        [$providerId, $serviceId, $collectionId] = $this->parseId($calendarId);
        $tenantId = $this->tenant->identifier();
        $userId   = $this->identity->identifier();
        $mapId    = $this->mapId($tenantId, $userId, $calendarId);

        // Resolve URI => entityId via the map; fall back to treating stripped URI as entityId
        $entityId = $this->uriMap->getEntityId($mapId, $objectUri)
                 ?? preg_replace('/\.ics$/i', '', $objectUri);

        $identifier = new EntityIdentifier($providerId, $serviceId, $collectionId, $entityId);
        $fetched    = $this->manager->entityFetchBulk($tenantId, $userId, $identifier);
        $entity     = reset($fetched) ?: null;

        if ($entity === null) {
            return null;
        }

        $data = $this->entityToIcal($entity);

        return [
            DavProperties::ID            => $entityId,
            DavProperties::URI           => $objectUri,
            DavProperties::LAST_MODIFIED => $entity->modified()?->getTimestamp() ?? time(),
            DavProperties::ETAG          => '"' . md5($data) . '"',
            DavProperties::SIZE          => strlen($data),
            DavProperties::COMPONENT     => 'VEVENT',
            DavProperties::CALENDAR_DATA => $data,
        ];
    }

    public function getMultipleCalendarObjects($calendarId, array $uris): array
    {
        return array_values(array_filter(array_map(
            fn($uri) => $this->getCalendarObject($calendarId, $uri),
            $uris,
        )));
    }

    public function createCalendarObject($calendarId, $objectUri, $calendarData): ?string
    {
        [$providerId, $serviceId, $collectionId] = $this->parseId($calendarId);
        $tenantId = $this->tenant->identifier();
        $userId   = $this->identity->identifier();

        $vcal   = Reader::read($calendarData);
        $props  = $this->icalToEntityProps($vcal);
        $target = new CollectionIdentifier($providerId, $serviceId, $collectionId);
        $entity = $this->manager->entityCreate($tenantId, $userId, $target, $props);

        // Persist the client-chosen URI => provider entityId mapping
        $this->uriMap->set(
            $this->mapId($tenantId, $userId, $calendarId),
            $objectUri,
            (string) $entity->identifier(),
        );

        return '"' . md5($this->entityToIcal($entity)) . '"';
    }

    public function updateCalendarObject($calendarId, $objectUri, $calendarData): ?string
    {
        [$providerId, $serviceId, $collectionId] = $this->parseId($calendarId);
        $tenantId = $this->tenant->identifier();
        $userId   = $this->identity->identifier();
        $mapId    = $this->mapId($tenantId, $userId, $calendarId);

        $entityId = $this->uriMap->getEntityId($mapId, $objectUri)
                 ?? preg_replace('/\.ics$/i', '', $objectUri);

        $vcal   = Reader::read($calendarData);
        $props  = $this->icalToEntityProps($vcal);
        $target = new EntityIdentifier($providerId, $serviceId, $collectionId, $entityId);
        $entity = $this->manager->entityModify($tenantId, $userId, $target, $props);

        return '"' . md5($this->entityToIcal($entity)) . '"';
    }

    public function deleteCalendarObject($calendarId, $objectUri): void
    {
        [$providerId, $serviceId, $collectionId] = $this->parseId($calendarId);
        $tenantId = $this->tenant->identifier();
        $userId   = $this->identity->identifier();
        $mapId    = $this->mapId($tenantId, $userId, $calendarId);

        $entityId = $this->uriMap->getEntityId($mapId, $objectUri)
                 ?? preg_replace('/\.ics$/i', '', $objectUri);

        $target = new EntityIdentifier($providerId, $serviceId, $collectionId, $entityId);
        $this->manager->entityDelete($tenantId, $userId, $target);
        $this->uriMap->delete($mapId, $objectUri);
    }

    // -------------------------------------------------------------------------
    // Helpers
    // -------------------------------------------------------------------------

    private function parseId(string $calendarId): array
    {
        return explode(self::ID_SEP, $calendarId, 3);
    }

    private function mapId(string $tenantId, string $userId, string $calendarId): string
    {
        return 'cal:' . $tenantId . ':' . $userId . ':' . $calendarId;
    }

    private function slugify(string $label): string
    {
        return strtolower(preg_replace('/[^a-z0-9]+/i', '-', trim($label)));
    }

    /**
     * Serialize a domain entity to an iCalendar string.
     *
     * The raw data from getDataRaw() is a serialized EventObject array
     * with fields matching EventCommonObject property names (label, startsOn, endsOn, ...).
     */
    private function entityToIcal(object $entity): string
    {
        $raw  = (array) ($entity->getProperties()->getDataRaw() ?? []);
        $utc  = new \DateTimeZone('UTC');
        $vcal = new VCalendar();

        // Create the VEVENT without sabre's auto-generated UID/DTSTAMP defaults,
        // otherwise they appear twice (we set our own below), which is invalid.
        /** @var \Sabre\VObject\Component $vevent */
        $vevent = $vcal->add('VEVENT', [], false);
        $vevent->add('UID',     (string) $entity->identifier());
        // Always emit date-times in UTC ("...Z"). A DateTime carrying a fixed
        // numeric offset (e.g. from an RFC3339 string) would otherwise serialize
        // as TZID=-04:00 with no matching VTIMEZONE, which clients reject.
        // DTSTAMP participates in the serialized data used for the ETag. Using
        // the current time here made an unchanged entity produce a different
        // ETag on every PROPFIND/REPORT and triggered perpetual client syncs.
        $stamp = $entity->modified() ?? $entity->created();
        $vevent->add(
            'DTSTAMP',
            $stamp !== null
                ? \DateTime::createFromImmutable($stamp)->setTimezone($utc)
                : (new \DateTime('@0'))->setTimezone($utc),
        );

        if ($created = $entity->created()) {
            $vevent->add('CREATED', \DateTime::createFromImmutable($created)->setTimezone($utc));
        }
        if ($modified = $entity->modified()) {
            $vevent->add('LAST-MODIFIED', \DateTime::createFromImmutable($modified)->setTimezone($utc));
        }
        if (!empty($raw['label'])) {
            $vevent->add('SUMMARY', (string) $raw['label']);
        }
        if (!empty($raw['description'])) {
            $vevent->add('DESCRIPTION', (string) $raw['description']);
        }
        if (!empty($raw['startsOn'])) {
            $vevent->add('DTSTART', (new \DateTime((string) $raw['startsOn']))->setTimezone($utc));
        }
        if (!empty($raw['endsOn'])) {
            $vevent->add('DTEND', (new \DateTime((string) $raw['endsOn']))->setTimezone($utc));
        }
        // iCal supports one LOCATION property; use first physical location
        if (!empty($raw['locationsPhysical']) && is_array($raw['locationsPhysical'])) {
            foreach ($raw['locationsPhysical'] as $loc) {
                $addr = $loc['address'] ?? $loc['name'] ?? $loc['label'] ?? null;
                if ($addr) {
                    $vevent->add('LOCATION', (string) $addr);
                    break;
                }
            }
        }

        return $vcal->serialize();
    }

    /**
     * Convert a parsed VCALENDAR to an array for entityCreate/entityUpdate.
     * Field names match EventCommonObject property names used in serialization.
     */
    private function icalToEntityProps(VCalendar $vcal): array
    {
        $comp = $vcal->VEVENT ?? $vcal->VTODO ?? $vcal->VJOURNAL ?? null;
        if ($comp === null) {
            return [];
        }

        $props = [];
        if ($summary = (string) ($comp->SUMMARY ?? '')) {
            $props['label'] = $summary;
        }
        if ($description = (string) ($comp->DESCRIPTION ?? '')) {
            $props['description'] = $description;
        }
        if ($dtstart = $comp->DTSTART ?? null) {
            $props['startsOn'] = $dtstart->getDateTime()->format(\DateTime::RFC3339);
        }
        if ($dtend = $comp->DTEND ?? $comp->DUE ?? null) {
            $props['endsOn'] = $dtend->getDateTime()->format(\DateTime::RFC3339);
        }
        if ($location = (string) ($comp->LOCATION ?? '')) {
            $props['locationsPhysical'] = [['label' => $location]];
        }

        return $props;
    }
}