package com.atlassian.plugin.servlet.filter;
   
   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 java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  
  public final class FilterTestUtils {
      public static class FilterAdapter implements Filter {
          public void init(FilterConfig filterConfig) throws ServletException {
          }
  
          public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
          }
  
          public void destroy() {
          }
      }
  
      public final static class SoundOffFilter extends FilterAdapter {
          private final List<Integer> filterCallOrder;
          private final int filterId;
  
          public SoundOffFilter(List<Integer> filterCallOrder, int filterId) {
              this.filterCallOrder = filterCallOrder;
              this.filterId = filterId;
          }
  
          @Override
          public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
                  throws IOException, ServletException {
              filterCallOrder.add(filterId);
              chain.doFilter(request, response);
              filterCallOrder.add(filterId);
          }
      }
  
      public static final FilterChain emptyChain = new FilterChain() {
          public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
          }
      };
  
      static <T> List<T> newList(T first, T... rest) {
          List<T> list = new LinkedList<>();
          list.add(first);
          for (T element : rest) {
              list.add(element);
          }
          return list;
      }
  
      /**
       * Creates a filter chain from the single filter. When this filter is called once, the filter chain is finished.
       */
      static FilterChain singletonFilterChain(final Filter filter) {
          return new FilterChain() {
              boolean called = false;
  
              public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException {
                  if (!called) {
                      called = true;
                      filter.doFilter(request, response, this);
                  }
              }
          };
      }
  
      public static <T> List<T> immutableList(List<T> list) {
          List<T> copy = new ArrayList<T>(list.size());
          copy.addAll(list);
          return Collections.unmodifiableList(copy);
      }
  }