// Copyright (C) 2015 The Android Open Source Project
//
// 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 com.googlesource.gerrit.plugins.manager;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.gerrit.extensions.registration.DynamicItem;
import com.google.gerrit.httpd.WebSession;
import com.google.gerrit.server.AccessPath;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Singleton
public class XAuthFilter implements Filter {
  private static final Logger log = LoggerFactory.getLogger(XAuthFilter.class);

  private DynamicItem<WebSession> webSession;

  @Inject
  public XAuthFilter(DynamicItem<WebSession> webSession) {
    this.webSession = webSession;
  }

  @Override
  public void destroy() {}

  @Override
  public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
      throws IOException, ServletException {
    HttpServletRequest httpReq = (HttpServletRequest) req;
    HttpServletResponse httpResp = (HttpServletResponse) resp;

    WebSession session = webSession.get();
    final String gerritAuth = session.getXGerritAuth();
    if (gerritAuth != null) {
      session.setAccessPathOk(AccessPath.REST_API, true);

      log.debug("Injecting X-Gerrit-Auth for {}", httpReq.getRequestURI());
      httpResp =
          new HttpServletResponseWrapper(httpResp) {

            private int origContentLength;

            @Override
            public void setHeader(String name, String value) {
              log.debug("{}: {}", name, value);
              if (name.equalsIgnoreCase("Content-Length")) {
                origContentLength = Integer.parseInt(value);
              } else {
                super.setHeader(name, value);
              }
            }

            @Override
            public PrintWriter getWriter() throws IOException {
              return super.getWriter();
            }

            @Override
            public ServletOutputStream getOutputStream() throws IOException {
              return new TokenReplaceOutputStream(
                  (HttpServletResponse) getResponse(),
                  origContentLength,
                  "@X-Gerrit-Auth".getBytes(UTF_8),
                  gerritAuth.getBytes(UTF_8));
            }
          };

      httpResp.setHeader(
          "Cache-Control", "private, no-cache, no-store, must-revalidate, max-age=0");
      httpResp.setHeader("Pragma", "no-cache");
      httpResp.setHeader("Expires", "0");

      chain.doFilter(req, httpResp);
    } else {
      HttpServletResponse res = (HttpServletResponse) resp;
      res.sendError(HttpServletResponse.SC_UNAUTHORIZED);
    }
  }

  @Override
  public void init(FilterConfig conf) throws ServletException {}
}