package at.gv.egiz.eaaf.utils.springboot.ajp.logging;

import java.io.IOException;
import java.util.HashMap;
import java.util.Optional;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;

import org.apache.commons.lang3.StringUtils;
import org.slf4j.MDC;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.stereotype.Component;

import lombok.Getter;

@Component
@EnableConfigurationProperties(LoggingProperties.class)
public class MdcEnhancerFilter implements Filter {

  /**
   * Logging properties.
   */
  private LoggingProperties loggingProperties;

  /**
   * To reduce the overhead of building the final "headerMap".
   * 
   * <p>
   * The map is to be built when the object is initiated.
   * </p>
   */
  private final HashMap<String, String> headerMap;

  /**
   * Create a new instance of {@link MdcEnhancerFilter}.
   * 
   * @param loggingProperties an instance of {@link LoggingProperties}
   */
  public MdcEnhancerFilter(LoggingProperties loggingProperties) {
    this.loggingProperties = loggingProperties;
    this.headerMap = new HashMap<>(this.loggingProperties.getMdc().getHeaderMap());

    // add TXID into map (no overrides)
    for (final Txid txid : Txid.values()) {
      this.headerMap.putIfAbsent(txid.getFieldName(), txid.getHeaderName());
    }
  }

  /**
   * Filter the request headers based on the configured MDC properties.
   *
   * @param request incoming {@link HttpServletRequest}
   */
  private void filterHeader(final HttpServletRequest request) {
    this.headerMap.forEach((field, header) -> {
      // to provide backwards compatibility we have to put the "null-value" into the
      // MDC if it is not present
      final String value = Optional.ofNullable(request.getHeader(header))
          .orElse(this.loggingProperties.getMdc().getNullValue());
      MDC.put(field, value);
    });
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse,
      final FilterChain filterChain) throws IOException, ServletException {
    final HttpServletRequest request = (HttpServletRequest) servletRequest;

    filterHeader(request);

    String key;
    String value;
    for (final String cookie : loggingProperties.getMdc().getCookies()) {
      key = loggingProperties.getMdc().getCookiePrefix() + cookie + loggingProperties.getMdc()
          .getCookiePostfix();
      value = getCookie(cookie, request.getCookies());
      if (StringUtils.isNotBlank(value)) {
        MDC.put(key, value);
      } else if (loggingProperties.getMdc().getNullValue() != null) {
        MDC.put(key, loggingProperties.getMdc().getNullValue());
      }
    }

    Object object;
    for (final String attribute : loggingProperties.getMdc().getSessionAttributes()) {
      key = loggingProperties.getMdc().getSessionAttributePrefix() + attribute + loggingProperties.getMdc()
          .getSessionAttributePostfix();
      object = request.getSession(true).getAttribute(attribute);
      if (object != null) {
        MDC.put(key, object.toString());
      } else if (loggingProperties.getMdc().getNullValue() != null) {
        MDC.put(key, loggingProperties.getMdc().getNullValue());
      }
    }

    try {
      filterChain.doFilter(servletRequest, servletResponse);
    } finally {
      for (final String field : this.headerMap.keySet()) {
        MDC.remove(field);
      }
      for (final String cookie : loggingProperties.getMdc().getCookies()) {
        MDC.remove(cookie);
      }
      for (final String attribute : loggingProperties.getMdc().getSessionAttributes()) {
        MDC.remove(attribute);
      }
    }
  }

  private static String getCookie(final String cookie, final Cookie[] cookies) {
    if (cookies == null || !StringUtils.isNotBlank(cookie)) {
      return null;
    }
    for (final Cookie c : cookies) {
      if (c.getName().equals(cookie)) {
        return c.getValue();
      }
    }
    return null;
  }

  /**
   * Enumeration of default TXIDs handled by the auto-configuration.
   */
  @Getter
  private enum Txid {
    HTTP_REQUEST("AM-TXID-HTTP-Request", "amTxidHttpRequest"),
    BROWSER("AM-TXID-Browser-Session", "amTxidBrowserSession"),
    IDP("AM-TXID-IdP-Session", "amTxidIdpSession"),
    SP("AM-TXID-SP-Session", "amTxidSpSession");

    private final String headerName;
    private final String fieldName;

    Txid(final String headerName, final String fieldName) {
      this.headerName = headerName;
      this.fieldName = fieldName;
    }

  }

}