/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.nifi.dbcp;

import com.zaxxer.hikari.HikariDataSource;
import org.apache.commons.lang3.StringUtils;
import org.apache.nifi.annotation.behavior.DynamicProperty;
import org.apache.nifi.annotation.behavior.RequiresInstanceClassLoading;
import org.apache.nifi.annotation.behavior.Restricted;
import org.apache.nifi.annotation.behavior.Restriction;
import org.apache.nifi.annotation.behavior.SupportsSensitiveDynamicProperties;
import org.apache.nifi.annotation.documentation.CapabilityDescription;
import org.apache.nifi.annotation.documentation.Tags;
import org.apache.nifi.annotation.lifecycle.OnDisabled;
import org.apache.nifi.annotation.lifecycle.OnEnabled;
import org.apache.nifi.annotation.lifecycle.OnRemoved;
import org.apache.nifi.components.ConfigVerificationResult;
import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.PropertyValue;
import org.apache.nifi.components.RequiredPermission;
import org.apache.nifi.components.resource.ResourceCardinality;
import org.apache.nifi.components.resource.ResourceReference;
import org.apache.nifi.components.resource.ResourceReferences;
import org.apache.nifi.components.resource.ResourceType;
import org.apache.nifi.controller.AbstractControllerService;
import org.apache.nifi.controller.ConfigurationContext;
import org.apache.nifi.controller.VerifiableControllerService;
import org.apache.nifi.dbcp.utils.DriverUtils;
import org.apache.nifi.expression.AttributeExpression;
import org.apache.nifi.expression.ExpressionLanguageScope;
import org.apache.nifi.kerberos.KerberosUserService;
import org.apache.nifi.logging.ComponentLog;
import org.apache.nifi.migration.PropertyConfiguration;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.processor.util.StandardValidators;
import org.apache.nifi.security.krb.KerberosAction;
import org.apache.nifi.security.krb.KerberosLoginException;
import org.apache.nifi.security.krb.KerberosUser;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.TimeUnit;
import javax.security.auth.login.LoginException;

import static org.apache.nifi.components.ConfigVerificationResult.Outcome.FAILED;
import static org.apache.nifi.components.ConfigVerificationResult.Outcome.SUCCESSFUL;

/**
 * Implementation of Database Connection Pooling Service. HikariCP is used for connection pooling functionality.
 */
@RequiresInstanceClassLoading
@Tags({"dbcp", "hikari", "jdbc", "database", "connection", "pooling", "store"})
@CapabilityDescription("Provides Database Connection Pooling Service based on HikariCP. Connections can be asked from pool and returned after usage.")
@SupportsSensitiveDynamicProperties
@DynamicProperty(name = "JDBC property name", value = "JDBC property value", expressionLanguageScope = ExpressionLanguageScope.ENVIRONMENT,
        description = "Specifies a property name and value to be set on the JDBC connection(s). "
                + "If Expression Language is used, evaluation will be performed upon the controller service being enabled. "
                + "Note that no flow file input (attributes, e.g.) is available for use in Expression Language constructs for these properties.")
@Restricted(
        restrictions = {
                @Restriction(
                        requiredPermission = RequiredPermission.REFERENCE_REMOTE_RESOURCES,
                        explanation = "Database Driver Location can reference resources over HTTP"
                )
        }
)
public class HikariCPConnectionPool extends AbstractControllerService implements DBCPService, VerifiableControllerService {
    /**
     * Property Name Prefix for Sensitive Dynamic Properties
     */
    protected static final String SENSITIVE_PROPERTY_PREFIX = "SENSITIVE.";
    protected static final long INFINITE_MILLISECONDS = -1L;

    private static final String DEFAULT_TOTAL_CONNECTIONS = "10";
    private static final String DEFAULT_MAX_CONN_LIFETIME = "-1";

    private static final int DEFAULT_MIN_VALIDATION_TIMEOUT = 250;

    public static final PropertyDescriptor DATABASE_URL = new PropertyDescriptor.Builder()
            .name("Database Connection URL")
            .description("A database connection URL used to connect to a database. May contain database system name, host, port, database name and some parameters."
                    + " The exact syntax of a database connection URL is specified by your DBMS.")
            .addValidator(new ConnectionUrlValidator())
            .required(true)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor DB_DRIVERNAME = new PropertyDescriptor.Builder()
            .name("Database Driver Class Name")
            .description("The fully-qualified class name of the JDBC driver. Example: com.mysql.jdbc.Driver")
            .required(true)
            .addValidator(new DriverClassValidator())
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor DB_DRIVER_LOCATION = new PropertyDescriptor.Builder()
            .name("Database Driver Locations")
            .description("Comma-separated list of files/folders and/or URLs containing the driver JAR and its dependencies (if any). For example '/var/tmp/mariadb-java-client-1.1.7.jar'")
            .required(false)
            .identifiesExternalResource(ResourceCardinality.MULTIPLE, ResourceType.FILE, ResourceType.DIRECTORY, ResourceType.URL)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .dynamicallyModifiesClasspath(true)
            .build();

    public static final PropertyDescriptor DB_USER = new PropertyDescriptor.Builder()
            .name("Database User")
            .description("Database user name")
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor DB_PASSWORD = new PropertyDescriptor.Builder()
            .name("Password")
            .description("The password for the database user")
            .required(false)
            .sensitive(true)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor MAX_WAIT_TIME = new PropertyDescriptor.Builder()
            .name("Max Wait Time")
            .description("The maximum amount of time that the pool will wait (when there are no available connections) "
                    + " for a connection to be returned before failing, or 0 <time units> to wait indefinitely. ")
            .defaultValue("500 millis")
            .required(true)
            .addValidator(StandardValidators.TIME_PERIOD_VALIDATOR)
            .sensitive(false)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor MAX_TOTAL_CONNECTIONS = new PropertyDescriptor.Builder()
            .name("Max Total Connections")
            .description("This property controls the maximum size that the pool is allowed to reach, including both idle and in-use connections. Basically this value will determine the "
                    + "maximum number of actual connections to the database backend. A reasonable value for this is best determined by your execution environment. When the pool reaches "
                    + "this size, and no idle connections are available, the service will block for up to connectionTimeout milliseconds before timing out.")
            .defaultValue(DEFAULT_TOTAL_CONNECTIONS)
            .required(true)
            .addValidator(StandardValidators.INTEGER_VALIDATOR)
            .sensitive(false)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor VALIDATION_QUERY = new PropertyDescriptor.Builder()
            .name("Validation Query")
            .description("Validation Query used to validate connections before returning them. "
                    + "When connection is invalid, it gets dropped and new valid connection will be returned. "
                    + "NOTE: Using validation might have some performance penalty.")
            .required(false)
            .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor MIN_IDLE = new PropertyDescriptor.Builder()
            .name("Minimum Idle Connections")
            .description("This property controls the minimum number of idle connections that HikariCP tries to maintain in the pool. If the idle connections dip below this value and total "
                    + "connections in the pool are less than 'Max Total Connections', HikariCP will make a best effort to add additional connections quickly and efficiently. It is recommended "
                    + "that this property to be set equal to 'Max Total Connections'.")
            .defaultValue(DEFAULT_TOTAL_CONNECTIONS)
            .required(true)
            .addValidator(StandardValidators.NON_NEGATIVE_INTEGER_VALIDATOR)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor MAX_CONN_LIFETIME = new PropertyDescriptor.Builder()
            .name("Max Connection Lifetime")
            .description("The maximum lifetime of a connection. After this time is exceeded the " +
                    "connection will fail the next activation, passivation or validation test. A value of zero or less " +
                    "means the connection has an infinite lifetime.")
            .defaultValue(DEFAULT_MAX_CONN_LIFETIME)
            .required(false)
            .addValidator(DBCPValidator.CUSTOM_TIME_PERIOD_VALIDATOR)
            .expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT)
            .build();

    public static final PropertyDescriptor KERBEROS_USER_SERVICE = new PropertyDescriptor.Builder()
            .name("Kerberos User Service")
            .description("Specifies the Kerberos User Controller Service that should be used for authenticating with Kerberos")
            .identifiesControllerService(KerberosUserService.class)
            .required(false)
            .build();

    private static final List<PropertyDescriptor> PROPERTY_DESCRIPTORS = List.of(
        DATABASE_URL,
        DB_DRIVERNAME,
        DB_DRIVER_LOCATION,
        KERBEROS_USER_SERVICE,
        DB_USER,
        DB_PASSWORD,
        MAX_WAIT_TIME,
        MAX_TOTAL_CONNECTIONS,
        VALIDATION_QUERY,
        MIN_IDLE,
        MAX_CONN_LIFETIME
    );

    private volatile HikariDataSource dataSource;
    private volatile KerberosUser kerberosUser;
    // Hold an instance of the driver so we can properly de-register it.
    private volatile Driver registeredDriver;

    @Override
    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return PROPERTY_DESCRIPTORS;
    }

    @Override
    protected PropertyDescriptor getSupportedDynamicPropertyDescriptor(final String propertyDescriptorName) {
        final PropertyDescriptor.Builder builder = new PropertyDescriptor.Builder()
                .name(propertyDescriptorName)
                .required(false)
                .dynamic(true)
                .addValidator(StandardValidators.createAttributeExpressionLanguageValidator(AttributeExpression.ResultType.STRING, true))
                .addValidator(StandardValidators.ATTRIBUTE_KEY_PROPERTY_NAME_VALIDATOR);

        if (propertyDescriptorName.startsWith(SENSITIVE_PROPERTY_PREFIX)) {
            builder.sensitive(true).expressionLanguageSupported(ExpressionLanguageScope.NONE);
        } else {
            builder.expressionLanguageSupported(ExpressionLanguageScope.ENVIRONMENT);
        }

        return builder.build();
    }

    /**
     * Configures connection pool by creating an instance of the
     * {@link HikariDataSource} based on configuration provided with
     * {@link ConfigurationContext}.
     * <p>
     * This operation makes no guarantees that the actual connection could be
     * made since the underlying system may still go off-line during normal
     * operation of the connection pool.
     *
     * @param context the configuration context
     */
    @OnEnabled
    public void onConfigured(final ConfigurationContext context) {
        dataSource = new HikariDataSource();
        configureDataSource(context, dataSource);
    }

    private long extractMillisWithInfinite(PropertyValue prop) {
        return "-1".equals(prop.getValue()) ? INFINITE_MILLISECONDS : prop.asTimePeriod(TimeUnit.MILLISECONDS);
    }

    /**
     * Shutdown pool, close all open connections.
     * If a principal is authenticated with a KDC, that principal is logged out.
     * <p>
     * If a @{@link LoginException} occurs while attempting to log out the @{@link org.apache.nifi.security.krb.KerberosUser},
     * an attempt will still be made to shut down the pool and close open connections.
     *
     */
    @OnDisabled
    public void shutdown() {
        try {
            if (kerberosUser != null) {
                kerberosUser.logout();
            }
        } finally {
            kerberosUser = null;
            try {
                if (dataSource != null) {
                    dataSource.close();
                }
            } finally {
                dataSource = null;
            }
        }
    }

    @Override
    public Connection getConnection() throws ProcessException {
        try {
            final Connection con;
            if (kerberosUser != null) {
                KerberosAction<Connection> kerberosAction = new KerberosAction<>(kerberosUser, dataSource::getConnection, getLogger());
                con = kerberosAction.execute();
            } else {
                con = dataSource.getConnection();
            }
            return con;
        } catch (final SQLException e) {
            // If using Kerberos,  attempt to re-login
            if (kerberosUser != null) {
                getLogger().info("Error getting connection, performing Kerberos re-login");
                kerberosUser.login();
            }
            throw new ProcessException("Connection retrieval failed", e);
        }
    }

    @Override
    public List<ConfigVerificationResult> verify(final ConfigurationContext context, final ComponentLog verificationLogger, final Map<String, String> variables) {
        List<ConfigVerificationResult> results = new ArrayList<>();
        final KerberosUserService kerberosUserService = context.getProperty(KERBEROS_USER_SERVICE).asControllerService(KerberosUserService.class);
        KerberosUser kerberosUser = null;
        try {
            if (kerberosUserService != null) {
                kerberosUser = kerberosUserService.createKerberosUser();
                if (kerberosUser != null) {
                    results.add(new ConfigVerificationResult.Builder()
                            .verificationStepName("Configure Kerberos User")
                            .outcome(SUCCESSFUL)
                            .explanation("Successfully configured Kerberos user")
                            .build());
                }
            }
        } catch (final Exception e) {
            verificationLogger.error("Failed to configure Kerberos user", e);
            results.add(new ConfigVerificationResult.Builder()
                    .verificationStepName("Configure Kerberos User")
                    .outcome(FAILED)
                    .explanation("Failed to configure Kerberos user: " + e.getMessage())
                    .build());
        }

        final HikariDataSource hikariDataSource = new HikariDataSource();
        try {
            configureDataSource(context, hikariDataSource);
            results.add(new ConfigVerificationResult.Builder()
                    .verificationStepName("Configure Data Source")
                    .outcome(SUCCESSFUL)
                    .explanation("Successfully configured data source")
                    .build());

            try (final Connection ignored = getConnection(hikariDataSource, kerberosUser)) {
                results.add(new ConfigVerificationResult.Builder()
                        .verificationStepName("Establish Connection")
                        .outcome(SUCCESSFUL)
                        .explanation("Successfully established Database Connection")
                        .build());
            } catch (final Exception e) {
                verificationLogger.error("Failed to establish Database Connection", e);
                results.add(new ConfigVerificationResult.Builder()
                        .verificationStepName("Establish Connection")
                        .outcome(FAILED)
                        .explanation("Failed to establish Database Connection: " + e.getMessage())
                        .build());
            }
        } catch (final Exception e) {
            StringBuilder messageBuilder = new StringBuilder("Failed to configure Data Source.");
            verificationLogger.error(messageBuilder.toString(), e);

            final String driverName = context.getProperty(DB_DRIVERNAME).evaluateAttributeExpressions().getValue();
            final ResourceReferences driverResources = context.getProperty(DB_DRIVER_LOCATION).evaluateAttributeExpressions().asResources();

            if (StringUtils.isNotBlank(driverName) && driverResources.getCount() != 0) {
                List<String> availableDrivers = DriverUtils.findDriverClassNames(driverResources);
                if (!availableDrivers.isEmpty() && !availableDrivers.contains(driverName)) {
                    messageBuilder.append(" Driver class [%s] not found in provided resources. Available driver classes found: %s".formatted(driverName, String.join(", ", availableDrivers)));
                } else if (e.getCause() instanceof ClassNotFoundException && availableDrivers.contains(driverName)) {
                    messageBuilder.append(" Driver Class found but not loaded: Apply configuration before verifying.");
                } else {
                    messageBuilder.append(" Exception: %s".formatted(e.getMessage()));
                }
            } else {
                messageBuilder.append(" No driver name specified or no driver resources provided. Exception: %s".formatted(e.getMessage()));
            }

            results.add(new ConfigVerificationResult.Builder()
                    .verificationStepName("Configure Data Source")
                    .outcome(FAILED)
                    .explanation(messageBuilder.toString())
                    .build());
        } finally {
            try {
                shutdown(dataSource, kerberosUser);
            } catch (final SQLException e) {
                verificationLogger.error("Failed to shut down data source", e);
            }
        }
        return results;
    }

    @Override
    public void migrateProperties(PropertyConfiguration config) {
        config.renameProperty("hikaricp-connection-url", DATABASE_URL.getName());
        config.renameProperty("hikaricp-driver-classname", DB_DRIVERNAME.getName());
        config.renameProperty("hikaricp-driver-locations", DB_DRIVER_LOCATION.getName());
        config.renameProperty("hikaricp-username", DB_USER.getName());
        config.renameProperty("hikaricp-password", DB_PASSWORD.getName());
        config.renameProperty("hikaricp-max-wait-time", MAX_WAIT_TIME.getName());
        config.renameProperty("hikaricp-max-total-conns", MAX_TOTAL_CONNECTIONS.getName());
        config.renameProperty("hikaricp-validation-query", VALIDATION_QUERY.getName());
        config.renameProperty("hikaricp-min-idle-conns", MIN_IDLE.getName());
        config.renameProperty("hikaricp-max-conn-lifetime", MAX_CONN_LIFETIME.getName());
        config.renameProperty("hikaricp-kerberos-user-service", KERBEROS_USER_SERVICE.getName());
    }

    protected void configureDataSource(final ConfigurationContext context, final HikariDataSource dataSource) {
        final String driverName = context.getProperty(DB_DRIVERNAME).evaluateAttributeExpressions().getValue();
        final String user = context.getProperty(DB_USER).evaluateAttributeExpressions().getValue();
        final String passw = context.getProperty(DB_PASSWORD).evaluateAttributeExpressions().getValue();
        final String dburl = context.getProperty(DATABASE_URL).evaluateAttributeExpressions().getValue();
        final Integer maxTotal = context.getProperty(MAX_TOTAL_CONNECTIONS).evaluateAttributeExpressions().asInteger();
        final String validationQuery = context.getProperty(VALIDATION_QUERY).evaluateAttributeExpressions().getValue();
        final long maxWaitMillis = extractMillisWithInfinite(context.getProperty(MAX_WAIT_TIME).evaluateAttributeExpressions());
        final int minIdle = context.getProperty(MIN_IDLE).evaluateAttributeExpressions().asInteger();
        final long maxConnLifetimeMillis = extractMillisWithInfinite(context.getProperty(MAX_CONN_LIFETIME).evaluateAttributeExpressions());

        final KerberosUserService kerberosUserService = context.getProperty(KERBEROS_USER_SERVICE).asControllerService(KerberosUserService.class);

        if (kerberosUserService != null) {
            kerberosUser = kerberosUserService.createKerberosUser();
            if (kerberosUser != null) {
                kerberosUser.login();
            }
        }

        // We load the driver here so we can keep a reference to it if it was loaded in the InstanceClassLoader.
        // This allows us to deregister it to prevent a memory leak.
        loadDriver(driverName, dburl);
        dataSource.setConnectionTimeout(maxWaitMillis);
        dataSource.setValidationTimeout(Math.max(maxWaitMillis, DEFAULT_MIN_VALIDATION_TIMEOUT));
        dataSource.setMaximumPoolSize(maxTotal);
        dataSource.setMinimumIdle(minIdle);
        dataSource.setMaxLifetime(maxConnLifetimeMillis);

        if (validationQuery != null && !validationQuery.isEmpty()) {
            dataSource.setConnectionTestQuery(validationQuery);
        }

        dataSource.setDriverClassName(driverName);
        dataSource.setJdbcUrl(dburl);
        dataSource.setUsername(user);
        dataSource.setPassword(passw);

        final List<PropertyDescriptor> dynamicProperties = context.getProperties()
                .keySet()
                .stream()
                .filter(PropertyDescriptor::isDynamic)
                .toList();

        Properties properties = dataSource.getDataSourceProperties();
        dynamicProperties.forEach((descriptor) -> {
            final PropertyValue propertyValue = context.getProperty(descriptor);
            if (descriptor.isSensitive()) {
                final String propertyName = StringUtils.substringAfter(descriptor.getName(), SENSITIVE_PROPERTY_PREFIX);
                properties.setProperty(propertyName, propertyValue.getValue());
            } else {
                properties.setProperty(descriptor.getName(), propertyValue.evaluateAttributeExpressions().getValue());
            }
        });
        dataSource.setDataSourceProperties(properties);
        dataSource.setPoolName(toString());
    }

    private Connection getConnection(final HikariDataSource dataSource, final KerberosUser kerberosUser) {
        try {
            final Connection con;
            if (kerberosUser != null) {
                KerberosAction<Connection> kerberosAction = new KerberosAction<>(kerberosUser, dataSource::getConnection, getLogger());
                con = kerberosAction.execute();
            } else {
                con = dataSource.getConnection();
            }
            return con;
        } catch (final SQLException e) {
            // If using Kerberos,  attempt to re-login
            if (kerberosUser != null) {
                try {
                    getLogger().info("Error getting connection, performing Kerberos re-login", e);
                    kerberosUser.login();
                } catch (KerberosLoginException le) {
                    throw new ProcessException("Unable to authenticate Kerberos principal", le);
                }
            }
            throw new ProcessException(e);
        }
    }

    private void shutdown(final HikariDataSource dataSource, final KerberosUser kerberosUser) throws SQLException {
        try {
            if (kerberosUser != null) {
                kerberosUser.logout();
            }
        } finally {
            if (dataSource != null) {
                dataSource.close();
            }
        }
    }

    protected void loadDriver(final String driverClassName, final String url) {
        final Class<?> clazz;

        try {
            clazz = Class.forName(driverClassName);
        } catch (final ClassNotFoundException e) {
            // Enhanced error message with discovery
            ResourceReferences driverResources = null;
            try {
                // Try to get driver resources from current context if available
                if (getConfigurationContext() != null) {
                    driverResources = getConfigurationContext().getProperty(DB_DRIVER_LOCATION).evaluateAttributeExpressions().asResources();
                }
            } catch (Exception ignored) {
                // Context might not be available, continue without it
            }

            final List<String> availableDrivers = (driverResources != null && driverResources.getCount() != 0) ? DriverUtils.discoverDriverClasses(driverResources) : List.of();

            StringBuilder errorMessage = new StringBuilder("JDBC driver class '%s' not found.".formatted(driverClassName));

            if (!availableDrivers.isEmpty()) {
                errorMessage.append(" Available driver classes found in resources: %s.".formatted(String.join(", ", availableDrivers)));
            } else if (driverResources != null && driverResources.getCount() != 0) {
                final List<ResourceReference> resourcesList = driverResources.asList();
                if (resourcesList.stream().filter(r -> r.getResourceType() != ResourceType.URL).count() != 0) {
                    errorMessage.append(" No JDBC driver classes found in the provided resources.");
                }
            } else if (driverResources == null) {
                errorMessage.append(" The property 'Database Driver Location(s)' should be set.");
            }

            throw new IllegalStateException(errorMessage.toString(), e);
        }

        try {
            final Driver driver = DriverManager.getDriver(url);
            // Ensure drivers that register themselves during class loading can be set as the registeredDriver.
            // This ensures drivers that register themselves can be deregisterd when the componet is removed.
            // These drivers should be loaded in the same InstanceClassloader that load this component
            if (driver != registeredDriver
                    && driver.getClass().getClassLoader().equals(getClass().getClassLoader())) {
                DriverManager.deregisterDriver(registeredDriver);
                registeredDriver = driver;
            }
        } catch (final SQLException e) {
            // In case the driver is not registered by the implementation, we explicitly try to register it.
            try {
                if (registeredDriver != null) {
                    DriverManager.deregisterDriver(registeredDriver);
                }
                registeredDriver = (Driver) clazz.getDeclaredConstructor().newInstance();

                DriverManager.registerDriver(registeredDriver);
                DriverManager.getDriver(url);
            } catch (final SQLException e2) {
                throw new IllegalStateException("No suitable driver for the given Database Connection URL", e2);
            } catch (final Exception e2) {
                throw new IllegalStateException("Creating driver instance is failed", e2);
            }
        }
    }

    @OnRemoved
    public void onRemove() {
        try {
            // We need to deregister the driver to allow the InstanceClassLoader to be garbage collected.
            DriverManager.deregisterDriver(registeredDriver);
        } catch (final SQLException e) {
            getLogger().warn("Failed to deregister driver [{}]", registeredDriver, e);
        }
    }

    @Override
    public String toString() {
        return String.format("%s[id=%s]", getClass().getSimpleName(), getIdentifier());
    }

    HikariDataSource getDataSource() {
        return dataSource;
    }
}
