/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.ambari.logsearch.web.filters;

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.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.ambari.logsearch.common.MessageEnums;
import org.apache.ambari.logsearch.common.VResponse;
import org.apache.ambari.logsearch.conf.global.LogSearchConfigState;
import org.apache.ambari.logsearch.util.RESTErrorUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.security.web.util.matcher.RequestMatcher;

import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * Filter to decide whether the server us ready to serve requests which require Log Search configuration available.
 */
public class LogSearchConfigStateFilter implements Filter {
  private static final Logger LOG = LoggerFactory.getLogger(LogSearchConfigStateFilter.class);

  private static final String CONFIG_NOT_AVAILABLE = "Configuration is not available";

  private final RequestMatcher requestMatcher;
  private final LogSearchConfigState logSearchConfigState;
  
  public LogSearchConfigStateFilter(RequestMatcher requestMatcher, LogSearchConfigState logSearchConfigState) {
    this.requestMatcher = requestMatcher;
    this.logSearchConfigState = logSearchConfigState;
  }

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

  @Override
  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
      throws IOException, ServletException {
    HttpServletRequest request = (HttpServletRequest) servletRequest;
    if (requestMatcher.matches(request)) {
      VResponse errorResponse = getErrorResponse();
      if (errorResponse != null) {
        LOG.info("{} request is filtered out: {}", request.getRequestURL(), errorResponse.getMsgDesc());
        HttpServletResponse resp = (HttpServletResponse) servletResponse;
        resp.setStatus(500);
        resp.setContentType("application/json");
        resp.getWriter().print(createStringFromErrorMessageObject(errorResponse));
        return;
      }
    }
    
    filterChain.doFilter(servletRequest, servletResponse);
  }

  private VResponse getErrorResponse() {
    if (!logSearchConfigState.isLogSearchConfigAvailable()) {
      return RESTErrorUtil.createMessageResponse(CONFIG_NOT_AVAILABLE, MessageEnums.CONFIGURATION_NOT_AVAILABLE);
    }
    
    return null;
  }

  private String createStringFromErrorMessageObject(VResponse responseObject) {
    try {
      ObjectMapper mapper = new ObjectMapper();
      return mapper.writeValueAsString(responseObject);
    } catch (Exception e) {
      throw RESTErrorUtil.createRESTException("Cannot parse response object on backend", MessageEnums.ERROR_CREATING_OBJECT);
    }
  }

  @Override
  public void destroy() {
  }
}