/*
 * 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 jakarta.servlet;

import java.io.Serial;
import java.io.Serializable;
import java.util.Enumeration;

/**
 * Provides a base class that implements the Filter and FilterConfig interfaces to reduce boilerplate when writing new
 * filters.
 *
 * @see jakarta.servlet.Filter
 * @see jakarta.servlet.FilterConfig
 *
 * @since Servlet 4.0
 */
public abstract class GenericFilter implements Filter, FilterConfig, Serializable {

    @Serial
    private static final long serialVersionUID = 1L;

    /**
     * The filter configuration.
     */
    private volatile FilterConfig filterConfig;


    @Override
    public String getInitParameter(String name) {
        return getFilterConfig().getInitParameter(name);
    }


    @Override
    public Enumeration<String> getInitParameterNames() {
        return getFilterConfig().getInitParameterNames();
    }


    /**
     * Obtain the FilterConfig used to initialise this Filter instance.
     *
     * @return The config previously passed to the {@link #init(FilterConfig)} method
     */
    public FilterConfig getFilterConfig() {
        return filterConfig;
    }


    @Override
    public ServletContext getServletContext() {
        return getFilterConfig().getServletContext();
    }


    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
        init();
    }


    /**
     * Convenience method for subclasses to save them having to call <code>super.init(config)</code>. This is a NO-OP by
     * default.
     *
     * @throws ServletException If an exception occurs that interrupts the Filter's normal operation
     */
    public void init() throws ServletException {
        // NO-OP
    }


    @Override
    public String getFilterName() {
        return getFilterConfig().getFilterName();
    }
}
