<?php

declare(strict_types=1);

/**
 * SPDX-FileCopyrightText: Sebastian Krupinski <krupinski01@gmail.com>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

namespace KTXM\ChronoManager\Export;

use Generator;
use KTXF\Chrono\Entity\EventObject;
use KTXF\Chrono\Entity\JournalObject;
use KTXF\Chrono\Entity\TaskObject;
use KTXF\Resource\Identifier\CollectionIdentifier;
use KTXF\Resource\Identifier\EntityIdentifier;
use KTXF\Resource\Identifier\ResourceIdentifiers;
use KTXM\ChronoManager\Manager;
use KTXM\ChronoManager\Conversion\IcalEncoder;
use Psr\Log\LoggerInterface;
use Throwable;

/** Exports Chrono entities as a streamed RFC 5545 iCalendar document. */
class ExportService {

    public function __construct(
        private readonly Manager $manager,
        private readonly IcalEncoder $encoder,
        private readonly LoggerInterface $logger,
    ) {}

    /**
     * @param ResourceIdentifiers $sources collection and/or entity identifiers
     * @return Generator<string> iCalendar document chunks
     */
    public function export(ResourceIdentifiers $sources, string $tenantId, string $userId): Generator {
        yield from $this->encoder->toIcs($this->entities($sources, $tenantId, $userId));
    }

    /** @return Generator<EventObject|TaskObject|JournalObject> */
    private function entities(ResourceIdentifiers $sources, string $tenantId, string $userId): Generator {
        $collections = [];
        $entities = [];
        foreach ($sources as $source) {
            if ($source instanceof EntityIdentifier) {
                $entities[] = $source;
            } elseif ($source instanceof CollectionIdentifier) {
                $collections[] = $source;
            }
        }

        if ($collections !== []) {
            $listed = $this->manager->entityListBulk($tenantId, $userId, new ResourceIdentifiers($collections));
            foreach ($listed as $services) {
                foreach ($services as $collectionSets) {
                    foreach ($collectionSets as $set) {
                        foreach ((array)$set as $entity) {
                            if (($hydrated = $this->hydrate($entity)) !== null) {
                                yield $hydrated;
                            }
                        }
                    }
                }
            }
        }

        if ($entities !== []) {
            foreach ($this->manager->entityFetchBulk($tenantId, $userId, ...$entities) as $entity) {
                if (($hydrated = $this->hydrate($entity)) !== null) {
                    yield $hydrated;
                }
            }
        }
    }

    /** Skip-and-continue on per-entity failure, matching import's error-tolerant posture. */
    private function hydrate(mixed $entity): EventObject|TaskObject|JournalObject|null {
        if (!is_object($entity)) {
            return null;
        }
        try {
            $hydrated = $entity->getProperties();
            // DAV-created entities may carry no urid; the provider identifier
            // keeps exported UIDs stable in that case.
            $hydrated->urid ??= (string)$entity->identifier();
            return $hydrated;
        } catch (Throwable $t) {
            $this->logger->warning('Skipping entity during export', ['exception' => $t]);
            return null;
        }
    }
}