<?php
declare(strict_types=1);

/**
 * Snapshots of projects (#231): `data/snapshots/{projectId}/{snapshotId}.json`, each a copy of the
 * project as it was stored, with { id, name, revision, createdAt, project }.
 *
 * A copy of the project document is all a snapshot needs: images, fonts, sounds and cels are
 * content-addressed, and a file a snapshot names cannot be deleted (#344, see FileUsage), so
 * whatever the copy names is still there to load.
 *
 * The store checks nothing about who asks. The router reaches it only after `Store::load` found
 * the project for that user, so the snapshots of a project are seen by exactly those who see it.
 */
final class SnapshotStore
{
    public function __construct(private readonly string $dir)
    {
    }

    /** @return list<array{id:string,name:string,revision:int,createdAt:string}>, newest first */
    public function list(string $projectId): array
    {
        $items = [];
        foreach (glob($this->folder($projectId) . '/*.json') ?: [] as $file) {
            $snapshot = $this->readFile($file);
            if ($snapshot !== null) {
                $items[] = self::summary($snapshot);
            }
        }
        usort($items, static fn(array $a, array $b): int => strcmp($b['createdAt'], $a['createdAt']));
        return $items;
    }

    /**
     * Copies a stored project document into a new snapshot.
     *
     * @param array{revision:int,project:array} $doc
     * @return array{id:string,name:string,revision:int,createdAt:string}
     */
    public function create(string $projectId, array $doc, string $name): array
    {
        $folder = $this->folder($projectId);
        if (!is_dir($folder) && !mkdir($folder, 0775, true) && !is_dir($folder)) {
            throw new RuntimeException("Cannot create snapshot directory {$folder}");
        }
        do {
            $id = Store::newId();
        } while (file_exists($this->path($projectId, $id)));

        $snapshot = [
            'id' => $id,
            'name' => $name,
            'revision' => $doc['revision'],
            // Microseconds, so two snapshots made within one second still list in the order made.
            'createdAt' => (new DateTimeImmutable('now', new DateTimeZone('UTC')))->format('Y-m-d\TH:i:s.uP'),
            'project' => $doc['project'],
        ];
        $json = json_encode($snapshot, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
        if ($json === false) {
            throw new RuntimeException('Cannot encode snapshot');
        }
        AtomicFile::write($this->path($projectId, $id), $json, AtomicFile::HIDDEN, 'snapshot file');
        return self::summary($snapshot);
    }

    /** @return array{id:string,name:string,revision:int,createdAt:string,project:array}|null */
    public function load(string $projectId, string $id): ?array
    {
        return $this->readFile($this->path($projectId, $id));
    }

    public function delete(string $projectId, string $id): bool
    {
        $path = $this->path($projectId, $id);
        return is_file($path) && unlink($path);
    }

    /** What deleting the project does to its snapshots. */
    public function deleteAll(string $projectId): void
    {
        $folder = $this->folder($projectId);
        foreach (glob($folder . '/*.json') ?: [] as $file) {
            unlink($file);
        }
        if (is_dir($folder)) {
            @rmdir($folder);
        }
    }

    /** @return array{id:string,name:string,revision:int,createdAt:string} */
    private static function summary(array $snapshot): array
    {
        return [
            'id' => $snapshot['id'],
            'name' => $snapshot['name'],
            'revision' => $snapshot['revision'],
            'createdAt' => $snapshot['createdAt'],
        ];
    }

    private function folder(string $projectId): string
    {
        return $this->dir . '/' . $projectId;
    }

    private function path(string $projectId, string $id): string
    {
        return $this->folder($projectId) . '/' . $id . '.json';
    }

    private function readFile(string $path): ?array
    {
        if (!is_file($path)) {
            return null;
        }
        $raw = file_get_contents($path);
        $snapshot = $raw === false ? null : json_decode($raw, true);
        if (!is_array($snapshot) || !isset($snapshot['id'], $snapshot['project']) || !is_array($snapshot['project'])) {
            return null;
        }
        $snapshot['name'] = is_string($snapshot['name'] ?? null) ? $snapshot['name'] : '';
        $snapshot['revision'] = (int) ($snapshot['revision'] ?? 0);
        $snapshot['createdAt'] = is_string($snapshot['createdAt'] ?? null) ? $snapshot['createdAt'] : '';
        return $snapshot;
    }
}