code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC 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.openqa.selenium.remote.http;
  
  import java.io.UncheckedIOException;
  import java.util.function.Function;
  import org.openqa.selenium.internal.Require;
  
  /**
   * Can be wrapped around an {@link HttpHandler} in order to either modify incoming {@link
   * HttpRequest}s or outgoing {@link HttpResponse}s using the well-known "Filter" pattern. This is
   * very similar to the Servlet spec's {@code javax.servlet.Filter}, but takes advantage of lambdas:
   *
   * <pre><code>
   * Filter filter = next -&gt; {
   *   return req -&gt; {
   *     req.addHeader("cheese", "brie");
   *     HttpResponse res = next.apply(req);
   *     res.addHeader("vegetable", "peas");
   *     return res;
   *   };
   * }
   * </code></pre>
   *
   * <p>Because each filter returns an {@link HttpHandler}, it's easy to do processing before, or
   * after each request, as well as short-circuit things if necessary.
   */
  @FunctionalInterface
  public interface Filter extends Function<HttpHandler, HttpHandler> {
  
    default Filter andThen(Filter next) {
      Require.nonNull("Next filter", next);
  
      return req -> apply(next.apply(req));
    }
  
    default HttpHandler andFinally(HttpHandler end) {
      Require.nonNull("HTTP handler", end);
  
      return request -> Filter.this.apply(end).execute(request);
    }
  
    default Routable andFinally(Routable end) {
      return new Routable() {
  
        @Override
        public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
          return Filter.this.apply(end).execute(req);
        }
  
        @Override
        public boolean matches(HttpRequest req) {
          return end.matches(req);
        }
      };
    }
  }
  