<?php
declare(strict_types=1);

/**
 * Released games (#266): a frozen copy of a project that anybody with the link can play.
 *
 *   data/releases/{token}.json            { token, projectId, name, revision, publishedAt, project }
 *   data/releases/projects/{projectId}.json  { token }   which link a project has
 *
 * One link per project: publishing again replaces the copy and keeps the token, so a link handed out
 * stays good. The token is 128 random bits and is the only secret, so both kinds of file are written
 * 0640 – the web server serves `data/` as static files and must not hand them out by name.
 *
 * Like the snapshots, the store checks nothing about who asks: the router reaches the project half
 * only after `Store::load` found the project for that user.
 */
final class ReleaseStore
{
    public function __construct(private readonly string $dir)
    {
    }

    public static function isValidToken(string $token): bool
    {
        return (bool) preg_match('/^[a-f0-9]{32}$/', $token);
    }

    /** @return array{token:string,revision:int,publishedAt:string}|null */
    public function of(string $projectId): ?array
    {
        $token = $this->tokenOf($projectId);
        $release = $token === null ? null : $this->load($token);
        return $release === null ? null : self::summary($release);
    }

    /**
     * Copies a stored project document into the project's release, under the token it already has.
     *
     * @param array{id:string,name:string,revision:int,project:array} $doc
     * @return array{token:string,revision:int,publishedAt:string}
     */
    public function publish(array $doc): array
    {
        $token = $this->tokenOf($doc['id']);
        if ($token === null) {
            do {
                $token = bin2hex(random_bytes(16));
            } while (file_exists($this->path($token)));
        }
        $release = [
            'token' => $token,
            'projectId' => $doc['id'],
            'name' => $doc['name'],
            'revision' => $doc['revision'],
            'publishedAt' => gmdate('Y-m-d\TH:i:s\Z'),
            'project' => $doc['project'],
        ];
        // The copy first, the pointer to it second: a crash in between leaves an unused file, never
        // a project pointing at nothing.
        $this->write($this->path($token), $release);
        $this->write($this->indexPath($doc['id']), ['token' => $token]);
        return self::summary($release);
    }

    /** @return array{token:string,projectId:string,name:string,revision:int,publishedAt:string,project:array}|null */
    public function load(string $token): ?array
    {
        if (!self::isValidToken($token)) {
            return null;
        }
        $release = $this->read($this->path($token));
        if ($release === null || !is_array($release['project'] ?? null) || !is_string($release['projectId'] ?? null)) {
            return null;
        }
        return [
            'token' => $token,
            'projectId' => $release['projectId'],
            'name' => is_string($release['name'] ?? null) ? $release['name'] : '',
            'revision' => (int) ($release['revision'] ?? 0),
            'publishedAt' => is_string($release['publishedAt'] ?? null) ? $release['publishedAt'] : '',
            'project' => $release['project'],
        ];
    }

    /** Makes the link dead. False when the project had none. */
    public function takeDown(string $projectId): bool
    {
        $token = $this->tokenOf($projectId);
        $index = $this->indexPath($projectId);
        if (is_file($index)) {
            unlink($index);
        }
        if ($token === null) {
            return false;
        }
        $path = $this->path($token);
        if (is_file($path)) {
            unlink($path);
        }
        return true;
    }

    private function tokenOf(string $projectId): ?string
    {
        $token = $this->read($this->indexPath($projectId))['token'] ?? null;
        return is_string($token) && self::isValidToken($token) ? $token : null;
    }

    /** @return array{token:string,revision:int,publishedAt:string} */
    private static function summary(array $release): array
    {
        return [
            'token' => $release['token'],
            'revision' => $release['revision'],
            'publishedAt' => $release['publishedAt'],
        ];
    }

    private function path(string $token): string
    {
        return $this->dir . '/' . $token . '.json';
    }

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

    private function read(string $path): ?array
    {
        if (!is_file($path)) {
            return null;
        }
        $raw = file_get_contents($path);
        $data = $raw === false ? null : json_decode($raw, true);
        return is_array($data) ? $data : null;
    }

    private function write(string $path, array $data): void
    {
        $folder = dirname($path);
        if (!is_dir($folder) && !mkdir($folder, 0775, true) && !is_dir($folder)) {
            throw new RuntimeException("Cannot create release directory {$folder}");
        }
        $json = json_encode($data, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
        if ($json === false) {
            throw new RuntimeException('Cannot encode release');
        }
        AtomicFile::write($path, $json, AtomicFile::HIDDEN, 'release file');
    }
}