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.interactions;
  
  import java.time.Duration;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  
  /**
   * A sequence of action objects for a given {@link InputSource} for use with the W3C <a
   * href="https://www.w3.org/TR/webdriver/#actions">Action commands</a>. In the spec, an action is
   * composed of a list of sequences, one per {@link InputSource}. Each of these is composed of {@link
   * Interaction}s, with the first item in each sequence being executed at the same time, then the
   * second, and so on, until all interactions in all sequences have been executed.
   */
  public class Sequence implements Encodable {
  
    private final List<Encodable> actions = new LinkedList<>();
    private final InputSource device;
  
    public Sequence(InputSource device, int initialLength) {
      if (!(device instanceof Encodable)) {
        throw new IllegalArgumentException("Input device must implement Encodable: " + device);
      }
  
      this.device = device;
  
      for (int i = 0; i < initialLength; i++) {
        addAction(new Pause(device, Duration.ZERO));
      }
    }
  
    public Sequence addAction(Interaction action) {
      if (!action.isValidFor(device.getInputType())) {
        throw new IllegalArgumentException(
            String.format(
                "Interaction (%s) is for wrong kind of input device: %s ",
                action.getClass(), device));
      }
      if (!(action instanceof Encodable)) {
        throw new IllegalArgumentException("Interaction must implement Encodable: " + action);
      }
  
      actions.add((Encodable) action);
  
      return this;
    }
  
    @Override
    public Map<String, Object> encode() {
      Map<String, Object> toReturn = new HashMap<>(((Encodable) device).encode());
  
      List<Map<String, Object>> encodedActions = new LinkedList<>();
      for (Encodable action : actions) {
        Map<String, Object> encodedAction = new HashMap<>(action.encode());
        encodedActions.add(encodedAction);
      }
      toReturn.put("actions", encodedActions);
  
      return toReturn;
    }
  
    public Map<String, Object> toJson() {
      return encode();
    }
  
    int size() {
      return actions.size();
    }
  }
  