/*
    * Copyright 2012-2025 CodeLibs Project and the Others.
    *
    * 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 org.codelibs.fess.filter;
  
  import java.io.IOException;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  import org.codelibs.core.lang.StringUtil;
  import org.codelibs.fess.cors.CorsHandler;
  import org.codelibs.fess.cors.CorsHandlerFactory;
  import org.codelibs.fess.util.ComponentUtil;
  
  import jakarta.servlet.Filter;
  import jakarta.servlet.FilterChain;
  import jakarta.servlet.ServletException;
  import jakarta.servlet.ServletRequest;
  import jakarta.servlet.ServletResponse;
  import jakarta.servlet.http.HttpServletRequest;
  import jakarta.servlet.http.HttpServletResponse;
  
  /**
   * Filter for handling Cross-Origin Resource Sharing (CORS) requests.
   * Processes CORS headers and handles preflight OPTIONS requests.
   */
  public class CorsFilter implements Filter {
  
      /**
       * Creates a new instance of CorsFilter.
       */
      public CorsFilter() {
          // Default constructor
      }
  
      private static final Logger logger = LogManager.getLogger(CorsFilter.class);
  
      /**
       * HTTP OPTIONS method constant used for CORS preflight requests.
       */
      protected static final String OPTIONS = "OPTIONS";
  
      @Override
      public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
              throws IOException, ServletException {
          final HttpServletRequest httpRequest = (HttpServletRequest) request;
          final String origin = httpRequest.getHeader("Origin");
          if (StringUtil.isNotBlank(origin)) {
              if (logger.isDebugEnabled()) {
                  logger.debug("HTTP Request: method={}", httpRequest.getMethod());
              }
              final CorsHandlerFactory factory = ComponentUtil.getCorsHandlerFactory();
              final CorsHandler handler = factory.get(origin);
              if (handler != null) {
                  handler.process(origin, request, response);
  
                  if (OPTIONS.equals(httpRequest.getMethod())) {
                      final HttpServletResponse httpResponse = (HttpServletResponse) response;
                      httpResponse.setStatus(HttpServletResponse.SC_ACCEPTED);
                      return;
                  }
              } else if (logger.isDebugEnabled()) {
                  logger.debug("No CorsHandler: origin={}", origin);
              }
          }
  
          chain.doFilter(request, response);
      }
  
  }