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package org.dataloader.impl;


import org.dataloader.ValueCache;
import org.dataloader.annotations.Internal;

import java.util.concurrent.CompletableFuture;

/**
 * Implementation of {@link ValueCache} that does nothing.
 * 
 * We don't want to store values in memory twice, so when using the default store we just
 * say we never have the key and complete the other methods by doing nothing.
 *
 * @param  the type of cache keys
 * @param  the type of cache values
 *
 * @author Craig Day
 */
@Internal
public class NoOpValueCache implements ValueCache {

    public static NoOpValueCache NOOP = new NoOpValueCache<>();

    /**
     * {@inheritDoc}
     */
    @Override
    public CompletableFuture get(K key) {
        return CompletableFutureKit.failedFuture(new UnsupportedOperationException());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public CompletableFuture set(K key, V value) {
        return CompletableFuture.completedFuture(value);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public CompletableFuture delete(K key) {
        return CompletableFuture.completedFuture(null);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public CompletableFuture clear() {
        return CompletableFuture.completedFuture(null);
    }
}