/*
 * Copyright 2009-2010 Markus KARG
 *
 * This file is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This file is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * For a copy of the GNU Lesser General Public License
 * see <http://www.gnu.org/licenses/>.
 */

package eu.headcrashing.javax.servlet;

import java.io.IOException;
import java.util.Collections;
import java.util.Enumeration;
import java.util.logging.Logger;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Implementation of {@link Filter} logging request and response.
 * 
 * @author Markus KARG (markus@headcrashing.eu)
 */
@SuppressWarnings("deprecation")
/*
 * When using Servlet API 3.0, replace ReadableHttpServletResponseWrapper by
 * HttpServletResponseWrapper
 */
public final class LoggingFilter implements Filter {

	private static final Logger LOGGER = Logger.getLogger(LoggingFilter.class.getPackage().getName());

	@Override
	public void init(final FilterConfig config) throws ServletException {
		// Intentionally left blank.
	}

	@Override
	public final void destroy() {
		// Intentionally left blank.
	}

	@Override
	public final void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain) throws IOException, ServletException {
		/*
		 * This filter is only able to handle HTTP, so we bypass anything else.
		 */
		if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
			chain.doFilter(request, response);
			return;
		}

		this.doFilter((HttpServletRequest) request, (HttpServletResponse) response, chain);
	}

	private final void doFilter(final HttpServletRequest request, final HttpServletResponse response, final FilterChain chain) throws IOException,
			ServletException {
		this.log(request);

		final ReadableHttpServletResponseWrapper wrapper = new ReadableHttpServletResponseWrapper(response);

		chain.doFilter(request, wrapper);

		this.log(wrapper);
	}

	@SuppressWarnings("unchecked")
	/*
	 * When using Servlet API 3.0, remove casting to Enumeration<String>, as
	 * this is the actual return type already.
	 */
	private final void log(final HttpServletRequest request) {
		final StringBuilder message = new StringBuilder();

		message.append(String.format("--> %1$s %2$s", request.getMethod(), request.getPathInfo()));

		for (final String headerName : Collections.list((Enumeration<String>) request.getHeaderNames()))
			for (final String headerValue : Collections.list((Enumeration<String>) request.getHeaders(headerName)))
				message.append(String.format(" %s=%s", headerName, headerValue));

		LOGGER.fine(message.toString());
	}

	private final void log(final ReadableHttpServletResponseWrapper response) {
		final StringBuilder message = new StringBuilder();

		message.append(String.format("<-- %1$d", response.getStatus()));

		for (final String headerName : response.getHeaderNames())
			for (final String headerValue : response.getHeaders(headerName))
				message.append(String.format(" %s=%s", headerName, headerValue));

		LOGGER.fine(message.toString());
	}
}