ConcurrentCache.java

/*
 * Copyright 2014 serso aka se.solovyev
 *
 * 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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * Contact details
 *
 * Email: se.solovyev@gmail.com
 * Site:  http://se.solovyev.org
 */

package org.solovyev.android.checkout;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;

import static java.lang.System.currentTimeMillis;

@ThreadSafe
final class ConcurrentCache implements Cache {

    @Nonnull
    private static final String TAG = "Cache";

    @GuardedBy("this")
    @Nullable
    private final Cache mCache;

    ConcurrentCache(@Nullable Cache cache) {
        mCache = cache;
    }

    public boolean hasCache() {
        return mCache != null;
    }

    @Override
    @Nullable
    public Entry get(@Nonnull Key key) {
        if (mCache == null) {
            return null;
        }
        synchronized (this) {
            final Entry entry = mCache.get(key);
            if (entry == null) {
                Billing.debug(TAG, "Key=" + key + " is not in the cache");
                return null;
            }
            final long now = currentTimeMillis();
            if (now >= entry.expiresAt) {
                Billing.debug(TAG, "Key=" + key + " is in the cache but was expired at " + entry.expiresAt + ", now is " + now);
                mCache.remove(key);
                return null;
            }
            Billing.debug(TAG, "Key=" + key + " is in the cache");
            return entry;
        }

    }

    @Override
    public void put(@Nonnull Key key, @Nonnull Entry entry) {
        if (mCache == null) {
            return;
        }
        synchronized (this) {
            Billing.debug(TAG, "Adding entry with key=" + key + " to the cache");
            mCache.put(key, entry);
        }
    }

    public void putIfNotExist(@Nonnull Key key, @Nonnull Entry entry) {
        if (mCache == null) {
            return;
        }
        synchronized (this) {
            if (mCache.get(key) == null) {
                Billing.debug(TAG, "Adding entry with key=" + key + " to the cache");
                mCache.put(key, entry);
            } else {
                Billing.debug(TAG, "Entry with key=" + key + " is already in the cache, won't add");
            }
        }
    }

    @Override
    public void init() {
        if (mCache == null) {
            return;
        }
        synchronized (this) {
            Billing.debug(TAG, "Initializing cache");
            mCache.init();
        }
    }

    @Override
    public void remove(@Nonnull Key key) {
        if (mCache == null) {
            return;
        }
        synchronized (this) {
            Billing.debug(TAG, "Removing entry with key=" + key + " from the cache");
            mCache.remove(key);
        }
    }

    @Override
    public void removeAll(int type) {
        if (mCache == null) {
            return;
        }
        synchronized (this) {
            Billing.debug(TAG, "Removing all entries with type=" + type + " from the cache");
            mCache.removeAll(type);
        }
    }

    @Override
    public void clear() {
        if (mCache == null) {
            return;
        }
        synchronized (this) {
            Billing.debug(TAG, "Clearing the cache");
            mCache.clear();
        }
    }
}