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.grid.sessionmap;
  
  import static org.openqa.selenium.remote.http.Route.combine;
  import static org.openqa.selenium.remote.http.Route.delete;
  import static org.openqa.selenium.remote.http.Route.post;
  
  import java.net.URI;
  import java.util.Map;
  import org.openqa.selenium.NoSuchSessionException;
  import org.openqa.selenium.grid.data.Session;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.json.Json;
  import org.openqa.selenium.remote.SessionId;
  import org.openqa.selenium.remote.http.HttpRequest;
  import org.openqa.selenium.remote.http.HttpResponse;
  import org.openqa.selenium.remote.http.Routable;
  import org.openqa.selenium.remote.http.Route;
  import org.openqa.selenium.remote.tracing.Tracer;
  import org.openqa.selenium.status.HasReadyState;
  
  /**
   * Provides a stable API for looking up where on the Grid a particular webdriver instance is
   * running.
   *
   * <p>This class responds to the following URLs:
   *
   * <table summary="HTTP commands the SessionMap understands">
   * <tr>
   *   <th>Verb</th>
   *   <th>URL Template</th>
   *   <th>Meaning</th>
   * </tr>
   * <tr>
   *   <td>DELETE</td>
   *   <td>/se/grid/session/{sessionId}</td>
   *   <td>Removes a {@link URI} from the session map. Calling this method more than once for the same
   *     {@link SessionId} will not throw an error.</td>
   * </tr>
   * <tr>
   *   <td>GET</td>
   *   <td>/se/grid/session/{sessionId}</td>
   *   <td>Retrieves the {@link URI} associated the {@link SessionId}, or throws a
   *     {@link org.openqa.selenium.NoSuchSessionException} should the session not be present.</td>
   * </tr>
   * <tr>
   *   <td>POST</td>
   *   <td>/se/grid/session/{sessionId}</td>
   *   <td>Registers the session with session map. In theory, the session map never expires a session
   *     from its mappings, but realistically, sessions may end up being removed for many reasons.
   *     </td>
   * </tr>
   * </table>
   */
  public abstract class SessionMap implements HasReadyState, Routable {
  
    protected final Tracer tracer;
  
    private final Route routes;
  
    public abstract boolean add(Session session);
  
    public abstract Session get(SessionId id) throws NoSuchSessionException;
  
    public abstract void remove(SessionId id);
  
    public URI getUri(SessionId id) throws NoSuchSessionException {
      return get(id).getUri();
    }
  
    public SessionMap(Tracer tracer) {
      this.tracer = Require.nonNull("Tracer", tracer);
  
      Json json = new Json();
      routes =
          combine(
              Route.get("/se/grid/session/{sessionId}/uri")
                  .to(params -> new GetSessionUri(this, sessionIdFrom(params))),
              post("/se/grid/session").to(() -> new AddToSessionMap(tracer, json, this)),
              Route.get("/se/grid/session/{sessionId}")
                  .to(params -> new GetFromSessionMap(tracer, this, sessionIdFrom(params))),
              delete("/se/grid/session/{sessionId}")
                  .to(params -> new RemoveFromSession(tracer, this, sessionIdFrom(params))));
    }
  
    private SessionId sessionIdFrom(Map<String, String> params) {
      return new SessionId(params.get("sessionId"));
    }
  
    @Override
    public boolean matches(HttpRequest req) {
      return routes.matches(req);
    }
  
    @Override
    public HttpResponse execute(HttpRequest req) {
      return routes.execute(req);
    }
  }
  