Traversal.java

/*
 * Copyright 2016 Square Inc.
 *
 * Licensed 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 flow;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

public final class Traversal {
  /** May be null if this is a traversal into the start state. */
  @Nullable public final History origin;
  @NonNull public final History destination;
  @NonNull public final Direction direction;
  private final KeyManager keyManager;

  Traversal(@Nullable History from, @NonNull History to, @NonNull Direction direction,
      KeyManager keyManager) {
    this.origin = from;
    this.destination = to;
    this.direction = direction;
    this.keyManager = keyManager;
  }

  /**
   * Creates a Context for the given key.
   *
   * Contexts can be created only for keys at the top of the origin and destination Histories.
   */
  @NonNull public Context createContext(@NonNull Object key, @NonNull Context baseContext) {
    return new FlowContextWrapper(keyManager.findServices(key), baseContext);
  }

  @NonNull public State getState(@NonNull Object key) {
    return keyManager.getState(key);
  }
}