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/*
 * Copyright (C) 2016 The Dagger Authors.
 *
 * 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 dagger.internal;

import static dagger.internal.Preconditions.checkNotNull;
import static dagger.internal.Providers.asDaggerProvider;

import dagger.Lazy;

/**
 * A {@link Provider} of {@link Lazy} instances that each delegate to a given {@link Provider}.
 */
public final class ProviderOfLazy implements Provider> {

  private final Provider provider;

  private ProviderOfLazy(Provider provider) {
    assert provider != null;
    this.provider = provider;
  }

  /**
   * Returns a new instance of {@link Lazy Lazy<T>}, which calls {@link Provider#get()} at
   * most once on the {@link Provider} held by this object.
   */
  @Override
  public Lazy get() {
    return DoubleCheck.lazy(provider);
  }

  /**
   * Creates a new {@link Provider Provider<Lazy<T>>} that decorates the given
   * {@link Provider}.
   *
   * @see #get()
   */
  public static  Provider> create(Provider provider) {
    return new ProviderOfLazy(checkNotNull(provider));
  }

  /**
   * Legacy javax version of the method to support libraries compiled with an older version of
   * Dagger. Do not use directly.
   */
  @Deprecated
  public static  Provider> create(javax.inject.Provider provider) {
    return create(asDaggerProvider(provider));
  }
}