class ZookeeperStore

class ZookeeperStore implements PersistingStoreInterface {
    use ExpiringStoreTrait;
    public function __construct(\Zookeeper $zookeeper) {
    }
    public static function createConnection(string $dsn) : \Zookeeper {
        if (!str_starts_with($dsn, 'zookeeper:')) {
            throw new InvalidArgumentException('Unsupported DSN for Zookeeper.');
        }
        if (false === ($params = parse_url($dsn))) {
            throw new InvalidArgumentException('Invalid Zookeeper DSN.');
        }
        $host = $params['host'] ?? '';
        $hosts = explode(',', $host);
        foreach ($hosts as $index => $host) {
            if (isset($params['port'])) {
                $hosts[$index] = $host . ':' . $params['port'];
            }
        }
        return new \Zookeeper(implode(',', $hosts));
    }
    public function save(Key $key) : void {
        if ($this->exists($key)) {
            return;
        }
        $resource = $this->getKeyResource($key);
        $token = $this->getUniqueToken($key);
        $this->createNewLock($resource, $token);
        $key->markUnserializable();
        $this->checkNotExpired($key);
    }
    public function delete(Key $key) : void {
        if (!$this->exists($key)) {
            return;
        }
        $resource = $this->getKeyResource($key);
        try {
            $this->zookeeper
                ->delete($resource);
        } catch (\ZookeeperException $exception) {
            // For Zookeeper Ephemeral Nodes, the node will be deleted upon session death. But, if we want to unlock
            // the lock before proceeding further in the session, the client should be aware of this
            throw new LockReleasingException($exception);
        }
    }
    public function exists(Key $key) : bool {
        $resource = $this->getKeyResource($key);
        try {
            return $this->zookeeper
                ->get($resource) === $this->getUniqueToken($key);
        } catch (\ZookeeperException) {
            return false;
        }
    }
    public function putOffExpiration(Key $key, float $ttl) : void {
        // do nothing, zookeeper locks forever.
    }
    
    /**
     * Creates a zookeeper node.
     *
     * @param string $node  The node which needs to be created
     * @param string $value The value to be assigned to a zookeeper node
     *
     * @throws LockConflictedException
     * @throws LockAcquiringException
     */
    private function createNewLock(string $node, string $value) : void {
        // Default Node Permissions
        $acl = [
            [
                'perms' => \Zookeeper::PERM_ALL,
                'scheme' => 'world',
                'id' => 'anyone',
            ],
        ];
        // This ensures that the nodes are deleted when the client session to zookeeper server ends.
        $type = \Zookeeper::EPHEMERAL;
        try {
            $this->zookeeper
                ->create($node, $value, $acl, $type);
        } catch (\ZookeeperException $ex) {
            if (\Zookeeper::NODEEXISTS === $ex->getCode()) {
                throw new LockConflictedException($ex);
            }
            throw new LockAcquiringException($ex);
        }
    }
    private function getKeyResource(Key $key) : string {
        // Since we do not support storing locks as multi-level nodes, we convert them to be stored at root level.
        // For example: foo/bar will become /foo-bar and /foo/bar will become /-foo-bar
        $resource = (string) $key;
        if (str_contains($resource, '/')) {
            $resource = strtr($resource, [
                '/' => '-',
            ]) . '-' . sha1($resource);
        }
        if ('' === $resource) {
            $resource = sha1($resource);
        }
        return '/' . $resource;
    }
    private function getUniqueToken(Key $key) : string {
        if (!$key->hasState(self::class)) {
            $token = base64_encode(random_bytes(32));
            $key->setState(self::class, $token);
        }
        return $key->getState(self::class);
    }

}