// Copyright 2026 The Nomulus Authors. All Rights Reserved.
//
// Licensed 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 google.registry.ui.server;

import jakarta.servlet.Filter;
import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;

/** Filter to inject security headers, including CSP, for defense-in-depth. */
public class CspFilter implements Filter {

  private static final String CSP_POLICY =
      "default-src 'self'; object-src 'none'; base-uri 'self';";

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    if (response instanceof HttpServletResponse httpResponse) {
      httpResponse.setHeader("Content-Security-Policy", CSP_POLICY);
      httpResponse.setHeader("X-Content-Type-Options", "nosniff");
      httpResponse.setHeader("X-Frame-Options", "DENY");
    }
    chain.doFilter(request, response);
  }
}
