class DriverSpecificConnectionUnitTestBase

abstract class DriverSpecificConnectionUnitTestBase extends DriverSpecificKernelTestBase {
    
    /**
     * A target connection identifier to be used for testing.
     */
    const TEST_TARGET_CONNECTION = 'DatabaseConnectionUnitTest';
    
    /**
     * A database connection used for monitoring processes.
     */
    protected $monitor;
    
    /**
     * The connection ID of the current test connection.
     */
    protected $id;
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        // Create an additional connection to monitor the connections being opened
        // and closed in this test.
        $connection_info = Database::getConnectionInfo();
        Database::addConnectionInfo('default', 'monitor', $connection_info['default']);
        $this->monitor = Database::getConnection('monitor');
        // Add a new target to the connection, by cloning the current connection.
        $connection_info = Database::getConnectionInfo();
        Database::addConnectionInfo('default', static::TEST_TARGET_CONNECTION, $connection_info['default']);
        // Verify that the new target exists.
        $info = Database::getConnectionInfo();
        // New connection info found.
        $this->assertSame($connection_info['default'], $info[static::TEST_TARGET_CONNECTION]);
        // Add and open a new connection.
        Database::getConnection(static::TEST_TARGET_CONNECTION);
        // Verify that there is a new connection.
        $this->id = $this->getConnectionId();
        $this->assertConnection($this->id);
    }
    
    /**
     * Returns a set of queries specific for the database in testing.
     */
    protected abstract function getQuery() : array;
    
    /**
     * Returns the connection ID of the current test connection.
     *
     * @return int
     */
    protected function getConnectionId() : int {
        return (int) Database::getConnection(static::TEST_TARGET_CONNECTION)->query($this->getQuery()['connection_id'])
            ->fetchField();
    }
    
    /**
     * Asserts that a connection ID exists.
     *
     * @param int $id
     *   The connection ID to verify.
     *
     * @internal
     */
    protected function assertConnection(int $id) : void {
        $this->assertArrayHasKey($id, $this->monitor
            ->query($this->getQuery()['processlist'])
            ->fetchAllKeyed(0, 0));
    }
    
    /**
     * Asserts that a connection ID does not exist.
     *
     * @param int $id
     *   The connection ID to verify.
     *
     * @internal
     */
    protected function assertNoConnection(int $id) : void {
        $this->assertArrayNotHasKey($id, $this->monitor
            ->query($this->getQuery()['processlist'])
            ->fetchAllKeyed(0, 0));
    }
    
    /**
     * Tests Database::closeConnection() without query.
     *
     * @todo getConnectionId() executes a query.
     */
    public function testOpenClose() : void {
        // Close the connection.
        Database::closeConnection(static::TEST_TARGET_CONNECTION);
        // Wait 20ms to give the database engine sufficient time to react.
        usleep(20000);
        // Verify that we are back to the original connection count.
        $this->assertNoConnection($this->id);
    }
    
    /**
     * Tests Database::closeConnection() with a query.
     */
    public function testOpenQueryClose() : void {
        // Execute a query.
        Database::getConnection(static::TEST_TARGET_CONNECTION)->query($this->getQuery()['show_tables']);
        // Close the connection.
        Database::closeConnection(static::TEST_TARGET_CONNECTION);
        // Wait 20ms to give the database engine sufficient time to react.
        usleep(20000);
        // Verify that we are back to the original connection count.
        $this->assertNoConnection($this->id);
    }
    
    /**
     * Tests Database::closeConnection() with a query and custom prefetch method.
     */
    public function testOpenQueryPrefetchClose() : void {
        // Execute a query.
        Database::getConnection(static::TEST_TARGET_CONNECTION)->query($this->getQuery()['show_tables'])
            ->fetchCol();
        // Close the connection.
        Database::closeConnection(static::TEST_TARGET_CONNECTION);
        // Wait 20ms to give the database engine sufficient time to react.
        usleep(20000);
        // Verify that we are back to the original connection count.
        $this->assertNoConnection($this->id);
    }
    
    /**
     * Tests Database::closeConnection() with a select query.
     */
    public function testOpenSelectQueryClose() : void {
        // Create a table.
        $name = 'foo';
        Database::getConnection(static::TEST_TARGET_CONNECTION)->schema()
            ->createTable($name, [
            'fields' => [
                'name' => [
                    'type' => 'varchar',
                    'length' => 255,
                ],
            ],
        ]);
        // Execute a query.
        Database::getConnection(static::TEST_TARGET_CONNECTION)->select('foo', 'f')
            ->fields('f', [
            'name',
        ])
            ->execute()
            ->fetchAll();
        // Drop the table.
        Database::getConnection(static::TEST_TARGET_CONNECTION)->schema()
            ->dropTable($name);
        // Close the connection.
        Database::closeConnection(static::TEST_TARGET_CONNECTION);
        // Wait 20ms to give the database engine sufficient time to react.
        usleep(20000);
        // Verify that we are back to the original connection count.
        $this->assertNoConnection($this->id);
    }
    
    /**
     * Tests pdo options override.
     */
    public function testConnectionOpen() {
        $reflection = new \ReflectionObject($this->connection);
        $connection_property = $reflection->getProperty('connection');
        $connection_property->setAccessible(TRUE);
        $error_mode = $connection_property->getValue($this->connection)
            ->getAttribute(\PDO::ATTR_ERRMODE);
        // Ensure the default error mode is set to exception.
        $this->assertSame(\PDO::ERRMODE_EXCEPTION, $error_mode);
        $connection_info = Database::getConnectionInfo();
        $connection_info['default']['pdo'][\PDO::ATTR_ERRMODE] = \PDO::ERRMODE_SILENT;
        Database::addConnectionInfo('test', 'default', $connection_info['default']);
        $test_connection = Database::getConnection('default', 'test');
        $reflection = new \ReflectionObject($test_connection);
        $connection_property = $reflection->getProperty('connection');
        $connection_property->setAccessible(TRUE);
        $error_mode = $connection_property->getValue($test_connection)
            ->getAttribute(\PDO::ATTR_ERRMODE);
        // Ensure PDO connection options can be overridden.
        $this->assertSame(\PDO::ERRMODE_SILENT, $error_mode);
        Database::removeConnection('test');
    }

}