/**
 * ============LICENSE_START=======================================================
 * org.onap.aaf
 * ================================================================================
 * Copyright © 2018 European Software Marketing Ltd.
 * ================================================================================
 * 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 org.onap.aaf.fproxy.cache;

import java.lang.ref.SoftReference;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;
import org.onap.aaf.fproxy.data.CredentialCacheData;

public class InMemoryCredentialCache implements CredentialCache {

    private final ConcurrentHashMap<String, SoftReference<CredentialCacheData>> cache = new ConcurrentHashMap<>();
    private final DelayQueue<DelayedCacheObject> cleaningUpQueue = new DelayQueue<>();

    public InMemoryCredentialCache() {
        Thread cleanerThread = new Thread(() -> {
            while (!Thread.currentThread().isInterrupted()) {
                try {
                    DelayedCacheObject delayedCacheObject = cleaningUpQueue.take();
                    cache.remove(delayedCacheObject.getKey(), delayedCacheObject.getReference());
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
        });
        cleanerThread.setDaemon(true);
        cleanerThread.start();
    }

    @Override
    public void add(String key, CredentialCacheData value, long periodInMillis) {
        if (key == null) {
            return;
        }
        if (value == null) {
            cache.remove(key);
        } else {
            long expiryTime = System.currentTimeMillis() + periodInMillis;
            SoftReference<CredentialCacheData> reference = new SoftReference<>(value);
            cache.put(key, reference);
            cleaningUpQueue.put(new DelayedCacheObject(key, reference, expiryTime));
        }
    }

    @Override
    public void remove(String key) {
        cache.remove(key);
    }

    @Override
    public CredentialCacheData get(String key) {
        return Optional.ofNullable(cache.get(key)).map(SoftReference::get).orElse(null);
    }

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

    @Override
    public long size() {
        return cache.size();
    }

    private static class DelayedCacheObject implements Delayed {

        private final String key;
        private final SoftReference<CredentialCacheData> reference;
        private final long expiryTime;

        public DelayedCacheObject(String key, SoftReference<CredentialCacheData> reference, long expiryTime) {
            super();
            this.key = key;
            this.reference = reference;
            this.expiryTime = expiryTime;
        }

        @Override
        public long getDelay(TimeUnit unit) {
            return unit.convert(expiryTime - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
        }

        @Override
        public int compareTo(Delayed o) {
            return Long.compare(expiryTime, ((DelayedCacheObject) o).expiryTime);
        }

        public String getKey() {
            return key;
        }

        public SoftReference<CredentialCacheData> getReference() {
            return reference;
        }
    }
}