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;
  
  import static java.util.Collections.singletonList;
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
  import static org.openqa.selenium.remote.ErrorCodes.SUCCESS_STRING;
  
  import com.google.common.collect.ImmutableMap;
  import java.util.Arrays;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.UUID;
  import java.util.concurrent.atomic.AtomicReference;
  import java.util.function.Function;
  import org.junit.jupiter.api.Test;
  import org.openqa.selenium.By;
  import org.openqa.selenium.Capabilities;
  import org.openqa.selenium.ImmutableCapabilities;
  import org.openqa.selenium.InvalidArgumentException;
  import org.openqa.selenium.SearchContext;
  import org.openqa.selenium.WebDriver;
  import org.openqa.selenium.WebElement;
  
  class RemotableByTest {
  
    private final SessionId id = new SessionId(UUID.randomUUID());
    private final ErrorCodes errorCodes = new ErrorCodes();
  
    @Test
    void shouldCallW3CLocatorWithW3CParameters() {
      AtomicReference<Map<?, ?>> parameters = new AtomicReference<>();
  
      WebDriver driver =
          createDriver(
              cmd -> {
                parameters.set(cmd.getParameters());
                return createResponse(new RemoteWebElement());
              });
      driver.findElement(By.cssSelector("#foo"));
  
      assertThat(parameters.get())
          .isEqualTo(ImmutableMap.of("using", "css selector", "value", "#foo"));
    }
  
    @Test
    void shouldCallDownToSearchContextForNonRemotableLocators() {
      AtomicReference<Map<?, ?>> parameters = new AtomicReference<>();
  
      WebDriver driver =
          createDriver(
              cmd -> {
                parameters.set(cmd.getParameters());
                return createResponse(singletonList(new RemoteWebElement()));
              });
  
      driver.findElement(
          new By() {
            @Override
            public List<WebElement> findElements(SearchContext context) {
              return context.findElements(By.cssSelector("#foo"));
            }
          });
  
      assertThat(parameters.get())
          .isEqualTo(ImmutableMap.of("using", "css selector", "value", "#foo"));
    }
  
    @Test
    void shouldAttemptToUseRemotableParametersIfPresent() {
      AtomicReference<Map<?, ?>> parameters = new AtomicReference<>();
  
      WebDriver driver =
          createDriver(
              cmd -> {
                parameters.set(cmd.getParameters());
                return createResponse(new RemoteWebElement());
              });
  
      class CustomBy extends By implements By.Remotable {
        @Override
        public Parameters getRemoteParameters() {
          return new Parameters("magic", "abracadabra");
        }
  
        @Override
        public List<WebElement> findElements(SearchContext context) {
          throw new UnsupportedOperationException("findElements");
        }
      }
  
      driver.findElement(new CustomBy());
  
      assertThat(parameters.get())
          .isEqualTo(ImmutableMap.of("using", "magic", "value", "abracadabra"));
    }
  
    @Test
    void shouldFallBackToCallingSearchContextIfRemotableSearchReturnsInvalidArgument() {
      AtomicReference<Map<?, ?>> parameters = new AtomicReference<>();
  
      WebDriver driver =
          createDriver(
              cmd -> createError(new InvalidArgumentException("Nope")),
              cmd -> {
                parameters.set(cmd.getParameters());
                return createResponse(singletonList(new RemoteWebElement()));
              });
  
      class CustomBy extends By implements By.Remotable {
        @Override
        public Parameters getRemoteParameters() {
          return new Parameters("magic", "abracadabra");
        }
  
        @Override
        public List<WebElement> findElements(SearchContext context) {
          return context.findElements(By.cssSelector("not-magic"));
        }
      }
  
      driver.findElement(new CustomBy());
  
      assertThat(parameters.get())
          .isEqualTo(ImmutableMap.of("using", "css selector", "value", "not-magic"));
    }
  
    @Test
    void shouldUseMechanismUsedForFirstSuccessfulSearchInLaterCalls() {
      AtomicReference<Map<?, ?>> parameters = new AtomicReference<>();
  
      // The remote driver attempts to find remotable elements by going straight
      // to the remotable version first. The spec says that may return an
      // "invalid argument" error, so the remote webdriver then falls back to
      // calling `findElement(SearchContext)`. As such, we build up the requests
      // in pairs, until we reach the final call, where we expect the remotable
      // path to be skipped.
      WebDriver driver =
          createDriver(
              // First search fails because the argument actually _is_ invalid.
              cmd -> createError(new InvalidArgumentException("remoting fail")),
              cmd -> createError(new InvalidArgumentException("context fail")),
  
              // Second search tries both mechanisms, and succeeds because fallback to search context
              // works
              cmd -> createError(new InvalidArgumentException("remoting fail")),
              cmd -> createResponse(singletonList(new RemoteWebElement())),
  
              // Third search goes straight to using the fallback
              cmd -> {
                parameters.set(cmd.getParameters());
                return createResponse(singletonList(new RemoteWebElement()));
              });
  
      class CustomBy extends By implements By.Remotable {
        private final String arg;
  
        public CustomBy(String arg) {
          this.arg = arg;
        }
  
        @Override
        public List<WebElement> findElements(SearchContext context) {
          return context.findElements(By.cssSelector(arg));
        }
  
        @Override
        public Parameters getRemoteParameters() {
          return new Parameters("custom", arg);
        }
      }
  
      assertThatExceptionOfType(InvalidArgumentException.class)
          .isThrownBy(() -> driver.findElement(new CustomBy("one")));
      driver.findElement(new CustomBy("two"));
      driver.findElement(new CustomBy("three"));
  
      assertThat(parameters.get())
          .isEqualTo(ImmutableMap.of("using", "css selector", "value", "three"));
    }
  
    private Response createResponse(Object value) {
      Response res = new Response();
      res.setState(SUCCESS_STRING);
      res.setSessionId(id.toString());
      res.setValue(value);
      return res;
    }
  
    private Response createError(Exception e) {
      Response res = new Response();
      res.setStatus(errorCodes.toStatusCode(e));
      res.setState(errorCodes.toState(res.getStatus()));
      res.setValue(ErrorCodec.createDefault().encode(e));
      return res;
    }
  
    @SafeVarargs
    private WebDriver createDriver(Function<Command, Response>... responses) {
      Iterator<Function<Command, Response>> iterator = Arrays.stream(responses).iterator();
      CommandExecutor executor = cmd -> iterator.next().apply(cmd);
  
      return new RemoteWebDriver(executor, new ImmutableCapabilities()) {
        @Override
        protected void startSession(Capabilities capabilities) {
          // no-op
        }
      };
    }
  }
  