/*
 * Copyright (C) 2010, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.http.server;

import static org.eclipse.jgit.util.HttpSupport.HDR_CACHE_CONTROL;
import static org.eclipse.jgit.util.HttpSupport.HDR_EXPIRES;
import static org.eclipse.jgit.util.HttpSupport.HDR_PRAGMA;

import java.io.IOException;

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.HttpServletResponse;

/** Add HTTP response headers to prevent caching by proxies/browsers. */
class NoCacheFilter implements Filter {
	/** {@inheritDoc} */
	@Override
	public void init(FilterConfig config) throws ServletException {
		// Do nothing.
	}

	/** {@inheritDoc} */
	@Override
	public void destroy() {
		// Do nothing.
	}

	/** {@inheritDoc} */
	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletResponse rsp = (HttpServletResponse) response;

		rsp.setHeader(HDR_EXPIRES, "Fri, 01 Jan 1980 00:00:00 GMT");
		rsp.setHeader(HDR_PRAGMA, "no-cache");

		final String nocache = "no-cache, max-age=0, must-revalidate";
		rsp.setHeader(HDR_CACHE_CONTROL, nocache);

		chain.doFilter(request, response);
	}
}