package at.gv.egovernment.moa.id.configuration.filter;

import java.io.IOException;
import java.nio.charset.Charset;

import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.builder.ToStringBuilder;

import lombok.extern.slf4j.Slf4j;

/**
 * @author <a href="mailto:thomas.knall@iaik.tugraz.at">Thomas Knall</a>
 */
@Slf4j
public class EncodingFilter implements javax.servlet.Filter {

   private static final String SERVLET_INIT_PARAM_ENCODING = "encoding";
   
   private static final String SERVLET_INIT_PARAM_SET_REQUEST_ENCODING    = "setRequestEncoding";
   private static final String SERVLET_INIT_PARAM_FORCE_REQUEST_ENCODING  = "forceRequestEncoding";

   private static final String SERVLET_INIT_PARAM_SET_RESPONSE_ENCODING   = "setResponseEncoding";
   private static final String SERVLET_INIT_PARAM_FORCE_RESPONSE_ENCODING = "forceResponseEncoding";
   
   private static final boolean DEFAULT_SET_REQUEST_ENCODING_VALUE    = true;
   private static final boolean DEFAULT_FORCE_REQUEST_ENCODING_VALUE  = true;
   private static final boolean DEFAULT_SET_RESPONSE_ENCODING_VALUE   = false;
   private static final boolean DEFAULT_FORCE_RESPONSE_ENCODING_VALUE = false;

   private String encoding = null;
   
   private boolean setRequestEncoding;
   private boolean forceRequestEncoding;

   private boolean setResponseEncoding;
   private boolean forceResponseEncoding;
   
   private boolean enabled = false;
   
   private boolean parseBooleanInitParameter(final FilterConfig filterConfig, String parameterName, boolean defaultValue) {
      String paramValue = filterConfig.getInitParameter(parameterName);
      if (paramValue == null) {
         return defaultValue;
      }
      paramValue = paramValue.trim();
      if (paramValue.equalsIgnoreCase("true")) {
         return true;
      } else if (paramValue.equalsIgnoreCase("false")){
         return false;
      } else {
         log.warn("Unknown value \"" + paramValue + "\" for init parameter \"" + parameterName + "\" detected. Should be \"true\" or \"false\". Using default value \"" + defaultValue + "\".");
         return defaultValue;
      }
   }

   public void init(final FilterConfig filterConfig) throws ServletException {
      log.debug("Initializing encoding filter (" + getClass().getName() + ").");

      // mandatory parameter encoding
      String desiredEncoding = filterConfig.getInitParameter(SERVLET_INIT_PARAM_ENCODING);
      if (StringUtils.isEmpty(desiredEncoding)) {
         log.warn("Unable to initialize encoding filter (" + getClass().getName() + "). Init parameter \"" + SERVLET_INIT_PARAM_ENCODING + "\" empty or not supplied.");
      } else if (!Charset.isSupported(desiredEncoding)) {
         log.warn("Unable to initialize encoding filter (" + getClass().getName() + "). Encoding \"" + desiredEncoding + "\" is not supported.");
      } else {
         this.encoding = desiredEncoding;
         this.enabled = true;
         this.setRequestEncoding    = this.parseBooleanInitParameter(filterConfig, SERVLET_INIT_PARAM_SET_REQUEST_ENCODING,    DEFAULT_SET_REQUEST_ENCODING_VALUE);
         this.forceRequestEncoding  = this.parseBooleanInitParameter(filterConfig, SERVLET_INIT_PARAM_FORCE_REQUEST_ENCODING,  DEFAULT_FORCE_REQUEST_ENCODING_VALUE);
         this.setResponseEncoding   = this.parseBooleanInitParameter(filterConfig, SERVLET_INIT_PARAM_SET_RESPONSE_ENCODING,   DEFAULT_SET_RESPONSE_ENCODING_VALUE);
         this.forceResponseEncoding = this.parseBooleanInitParameter(filterConfig, SERVLET_INIT_PARAM_FORCE_RESPONSE_ENCODING, DEFAULT_FORCE_RESPONSE_ENCODING_VALUE);
         log.debug("Encoding filter \"" + getClass().getName() + "\" configured: " + this.toString(true));
         
      }
   }
   
   public String toString(boolean verbose) {
      if (verbose) {
         return new ToStringBuilder(this)
            .append(SERVLET_INIT_PARAM_ENCODING, this.encoding)
            .append(SERVLET_INIT_PARAM_SET_REQUEST_ENCODING, this.setRequestEncoding)
            .append(SERVLET_INIT_PARAM_FORCE_REQUEST_ENCODING, this.forceRequestEncoding)
            .append(SERVLET_INIT_PARAM_SET_RESPONSE_ENCODING, this.setResponseEncoding)
            .append(SERVLET_INIT_PARAM_FORCE_RESPONSE_ENCODING, this.forceResponseEncoding)
         .toString();
      } else {
         return super.toString();
      }
   }

   public void doFilter(ServletRequest request, ServletResponse response, final FilterChain filterChain) throws IOException, ServletException {
      if (this.enabled) {
         if (this.setRequestEncoding) {
            if (this.forceRequestEncoding) {
               log.trace("Forcing request encoding \"" + this.encoding + "\".");
               request.setCharacterEncoding(this.encoding);
            } else if (request.getCharacterEncoding() == null) {
               log.trace("Request character encoding not set. Setting to \"" + this.encoding + "\".");
               request.setCharacterEncoding(this.encoding);
            }
         }
         if (this.setResponseEncoding) {
            if (this.forceResponseEncoding) {
               log.trace("Forcing response encoding \"" + this.encoding + "\".");
               response.setCharacterEncoding(this.encoding);
            } else if (response.getCharacterEncoding() == null) {
               log.trace("Response character encoding not set. Setting to \"" + this.encoding + "\".");
               response.setCharacterEncoding(this.encoding);
            }
         }
      }
      filterChain.doFilter(request, response);
   }

   public void destroy() {
   }
}