/*
 * 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 flowless;

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(key, baseContext);
    }

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