Database Connection Pool - إدارة الاتصالات

class ConnectionPool {
    private array $pool = [];
    private array $inUse = [];
    private int $maxConnections;
    private int $timeout;
    private $connectionFactory;

    public function __construct(
        int $maxConnections = 10,
        int $timeout = 30,
        callable $connectionFactory = null
    ) {
        $this->maxConnections = $maxConnections;
        $this->timeout = $timeout;
        $this->connectionFactory = $connectionFactory ?? function() {
            return new PDO(
                'mysql:host=localhost;dbname=test',
                'user',
                'pass',
                [PDO::ATTR_PERSISTENT => true]
            );
        };
    }

    public function acquire(): PDO {
        // Try to get from pool
        if (!empty($this->pool)) {
            $conn = array_pop($this->pool);
            $this->inUse[] = $conn;
            return $conn;
        }

        // Create new if under limit
        if (count($this->inUse) < $this->maxConnections) {
            $conn = ($this->connectionFactory)();
            $this->inUse[] = $conn;
            return $conn;
        }

        // Wait for available connection
        $startTime = time();
        while (empty($this->pool) && (time() - $startTime) < $this->timeout) {
            usleep(100000); // 100ms
        }

        if (empty($this->pool)) {
            throw new \RuntimeException('Connection pool timeout');
        }

        $conn = array_pop($this->pool);
        $this->inUse[] = $conn;
        return $conn;
    }

    public function release(PDO $connection): void {
        $key = array_search($connection, $this->inUse, true);
        if ($key !== false) {
            unset($this->inUse[$key]);
            $this->inUse = array_values($this->inUse);

            // Reset connection state
            $connection->exec('ROLLBACK');
            $this->pool[] = $connection;
        }
    }

    public function getStats(): array {
        return [
            'available' => count($this->pool),
            'in_use' => count($this->inUse),
            'total' => count($this->pool) + count($this->inUse),
            'max' => $this->maxConnections
        ];
    }
}

// Usage with try-finally
$pool = new ConnectionPool(10);
$conn = $pool->acquire();
try {
    $stmt = $conn->prepare('SELECT * FROM users WHERE id = ?');
    $stmt->execute([1]);
    $result = $stmt->fetchAll();
} finally {
    $pool->release($conn);
}