/*
 * Copyright 2002-2020 the original author or 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
 *
 *      https://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 org.springframework.cache.caffeine;

import java.util.concurrent.Callable;
import java.util.function.Function;

import com.github.benmanes.caffeine.cache.LoadingCache;

import org.springframework.cache.support.AbstractValueAdaptingCache;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

/**
 * Spring {@link org.springframework.cache.Cache} adapter implementation
 * on top of a Caffeine {@link com.github.benmanes.caffeine.cache.Cache} instance.
 *
 * <p>Requires Caffeine 2.1 or higher.
 *
 * @author Ben Manes
 * @author Juergen Hoeller
 * @author Stephane Nicoll
 * @since 4.3
 * @see CaffeineCacheManager
 */
public class CaffeineCache extends AbstractValueAdaptingCache {

        private final String name;

        private final com.github.benmanes.caffeine.cache.Cache<Object, Object> cache;


        /**
         * Create a {@link CaffeineCache} instance with the specified name and the
         * given internal {@link com.github.benmanes.caffeine.cache.Cache} to use.
         * @param name the name of the cache
         * @param cache the backing Caffeine Cache instance
         */
        public CaffeineCache(String name, com.github.benmanes.caffeine.cache.Cache<Object, Object> cache) {
                this(name, cache, true);
        }

        /**
         * Create a {@link CaffeineCache} instance with the specified name and the
         * given internal {@link com.github.benmanes.caffeine.cache.Cache} to use.
         * @param name the name of the cache
         * @param cache the backing Caffeine Cache instance
         * @param allowNullValues whether to accept and convert {@code null}
         * values for this cache
         */
        public CaffeineCache(String name, com.github.benmanes.caffeine.cache.Cache<Object, Object> cache,
                        boolean allowNullValues) {

                super(allowNullValues);
                Assert.notNull(name, "Name must not be null");
                Assert.notNull(cache, "Cache must not be null");
                this.name = name;
                this.cache = cache;
        }


        @Override
        public final String getName() {
                return this.name;
        }

        @Override
        public final com.github.benmanes.caffeine.cache.Cache<Object, Object> getNativeCache() {
                return this.cache;
        }

        @Override
        @Nullable
        public ValueWrapper get(Object key) {
                if (this.cache instanceof LoadingCache) {
                        Object value = ((LoadingCache<Object, Object>) this.cache).get(key);
                        return toValueWrapper(value);
                }
                return super.get(key);
        }

        @SuppressWarnings("unchecked")
        @Override
        @Nullable
        public <T> T get(Object key, final Callable<T> valueLoader) {
                return (T) fromStoreValue(this.cache.get(key, new LoadFunction(valueLoader)));
        }

        @Override
        @Nullable
        protected Object lookup(Object key) {
                return this.cache.getIfPresent(key);
        }

        @Override
        public void put(Object key, @Nullable Object value) {
                this.cache.put(key, toStoreValue(value));
        }

        @Override
        @Nullable
        public ValueWrapper putIfAbsent(Object key, @Nullable final Object value) {
                PutIfAbsentFunction callable = new PutIfAbsentFunction(value);
                Object result = this.cache.get(key, callable);
                return (callable.called ? null : toValueWrapper(result));
        }

        @Override
        public void evict(Object key) {
                this.cache.invalidate(key);
        }

        @Override
        public boolean evictIfPresent(Object key) {
                return (this.cache.asMap().remove(key) != null);
        }

        @Override
        public void clear() {
                this.cache.invalidateAll();
        }

        @Override
        public boolean invalidate() {
                boolean notEmpty = !this.cache.asMap().isEmpty();
                this.cache.invalidateAll();
                return notEmpty;
        }


        private class PutIfAbsentFunction implements Function<Object, Object> {

                @Nullable
                private final Object value;

                private boolean called;

                public PutIfAbsentFunction(@Nullable Object value) {
                        this.value = value;
                }

                @Override
                public Object apply(Object key) {
                        this.called = true;
                        return toStoreValue(this.value);
                }
        }


        private class LoadFunction implements Function<Object, Object> {

                private final Callable<?> valueLoader;

                public LoadFunction(Callable<?> valueLoader) {
                        this.valueLoader = valueLoader;
                }

                @Override
                public Object apply(Object o) {
                        try {
                                return toStoreValue(this.valueLoader.call());
                        }
                        catch (Exception ex) {
                                throw new ValueRetrievalException(o, this.valueLoader, ex);
                        }
                }
        }

}