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Bucket4j core library
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/*-
 * ========================LICENSE_START=================================
 * Bucket4j
 * %%
 * Copyright (C) 2015 - 2020 Vladimir Bukhtoyarov
 * %%
 * 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.
 * =========================LICENSE_END==================================
 */

package io.github.bucket4j.grid;

import io.github.bucket4j.Bucket;
import io.github.bucket4j.BucketConfiguration;

import java.io.Serializable;
import java.util.Optional;
import java.util.function.Supplier;

/**
 * Provides interface to instantiate an light-weight proxy to bucket which state actually stored in any external storage outside current JVM,
 * like in-memory grid or relational database.
 *
 * The proxies instantiated by ProxyManager is very cheap, you are free to instantiate as many proxies as you wish,
 * there are no any hard work performed inside {@link #getProxy(Serializable, Supplier) getProxy} method,
 * so it is not necessary to cache results of its invocation.
 * 
 * @param  type of key
 */
public interface ProxyManager {

    /**
     * Provides light-weight proxy to bucket which actually stored outside current JVM.
     * This method do not perform any hard work or network calls, it is not necessary to cache results of its invocation.
     *
     * Use this method if you use same configuration for all buckets(it can be easy stored as constant),
     * or configuration is very cheap to create.
     * 
     *
     * @param key the unique identifier used to point to the bucket in external storage.
     * @param configuration this configuration will be used to initialize bucket if it is not initialized before
     *
     * @return proxy to bucket that can be actually stored outside current JVM.
     */
    default Bucket getProxy(K key, BucketConfiguration configuration) {
        return getProxy(key, () -> configuration);
    }

    /**
     * Provides light-weight proxy to bucket which actually stored outside current JVM.
     * This method do not perform any hard work or network calls, it is not necessary to cache results of its invocation.
     *
     * Use this method in case of different configurations for each bucket and configuration is very expensive to create.
     * 
     *
     * @param key the unique identifier used to point to the bucket in external storage.
     * @param configurationLazySupplier supplier for configuration which can be called to build bucket configuration,
     *                                  if and only if first invocation of any method on proxy detects that bucket absents in remote storage,
     *                                  in this case provide configuration will be used to instantiate and persist the missed bucket.
     *
     * @return proxy to bucket that can be actually stored outside current JVM.
     */
    Bucket getProxy(K key, Supplier configurationLazySupplier);

    /**
     * Locates proxy to bucket which actually stored outside current JVM.
     *
     * @param key the unique identifier used to point to the bucket in external storage.
     *
     * @return Optional surround the proxy to bucket or empty optional if bucket with specified key are not stored.
     */
    Optional getProxy(K key);

    /**
     * Locates configuration of bucket which actually stored outside current JVM.
     *
     * @param key the unique identifier used to point to the bucket in external storage.
     *
     * @return Optional surround the configuration or empty optional if bucket with specified key are not stored.
     */
    Optional getProxyConfiguration(K key);

}