/*
 * Copyright @ 2013 CurisTEC, S.A.S. All Rights Reserved.
 */
package net.curisit.securis;

import java.io.IOException;

import jakarta.enterprise.context.ApplicationScoped;
import jakarta.servlet.Filter;
import jakarta.servlet.FilterChain;
import jakarta.servlet.FilterConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.annotation.WebFilter;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import net.curisit.securis.utils.GZipServletResponseWrapper;

/**
* GzipFilter
* <p>
* Servlet filter that compresses <code>*.js</code> responses with GZIP when the client
* advertises <code>Accept-Encoding: gzip</code>.
*/
@ApplicationScoped
@WebFilter(urlPatterns = "*.js")
public class GzipFilter implements Filter {

	@SuppressWarnings("unused")
	private static final Logger LOG = LogManager.getLogger(GzipFilter.class);

	/** init<p>Filter init hook (unused). */
	@Override
	public void init(FilterConfig fc) throws ServletException {
	}

	/**
	* doFilter
	* <p>
	* Wrap the response with a GZIP-compressing wrapper if supported by the client.
	*/
	@Override
	public void doFilter(ServletRequest sreq, ServletResponse sres, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest httpRequest = (HttpServletRequest) sreq;
		HttpServletResponse httpResponse = (HttpServletResponse) sres;

		if (acceptsGZipEncoding(httpRequest)) {
			httpResponse.addHeader("Content-Encoding", "gzip");
			GZipServletResponseWrapper gzipResponse = new GZipServletResponseWrapper(httpResponse);
			chain.doFilter(sreq, gzipResponse);
			gzipResponse.close();
		} else {
			chain.doFilter(sreq, sres);
		}
	}

	/**
	* acceptsGZipEncoding
	* <p>
	* @return {@code true} when request header contains "gzip" in <code>Accept-Encoding</code>.
	*/
	private boolean acceptsGZipEncoding(HttpServletRequest httpRequest) {
		String acceptEncoding = httpRequest.getHeader("Accept-Encoding");

		return acceptEncoding != null && acceptEncoding.indexOf("gzip") != -1;
	}

	/** destroy<p>Filter destroy hook (unused). */
	@Override
	public void destroy() {
	}

}