/*******************************************************************************
* This file is part of RedReader.
*
* RedReader is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* RedReader is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with RedReader. If not, see <http://www.gnu.org/licenses/>.
******************************************************************************/
package org.quantumbadger.redreader.io;
import org.quantumbadger.redreader.common.TimestampBound;
import org.quantumbadger.redreader.common.collections.WeakReferenceListManager;
import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
public final class WeakCache<K, V extends WritableObject<K>, F> implements CacheDataSource<K, V, F> {
private final HashMap<K, CacheEntry> cached = new HashMap<>();
private final CacheDataSource<K, V, F> cacheDataSource;
private final UpdatedVersionListenerNotifier<K, V> updatedVersionListenerNotifier = new UpdatedVersionListenerNotifier<>();
public WeakCache(CacheDataSource<K, V, F> cacheDataSource) {
this.cacheDataSource = cacheDataSource;
}
public void performRequest(K key, TimestampBound timestampBound, RequestResponseHandler<V, F> handler) {
performRequest(key, timestampBound, handler, null);
}
public synchronized void performRequest(final Collection<K> keys, final TimestampBound timestampBound,
final RequestResponseHandler<HashMap<K, V>, F> handler) {
final HashSet<K> keysRemaining = new HashSet<>(keys);
final HashMap<K, V> cacheResult = new HashMap<>(keys.size());
long oldestTimestamp = Long.MAX_VALUE;
for(final K key : keys) {
final CacheEntry entry = cached.get(key);
if(entry != null) {
final V value = entry.data.get();
if(value != null && timestampBound.verifyTimestamp(value.getTimestamp())) {
keysRemaining.remove(key);
cacheResult.put(key, value);
oldestTimestamp = Math.min(oldestTimestamp, value.getTimestamp());
}
}
}
if(keysRemaining.size() > 0) {
final long outerOldestTimestamp = oldestTimestamp;
cacheDataSource.performRequest(keysRemaining, timestampBound, new RequestResponseHandler<HashMap<K, V>, F>() {
public void onRequestFailed(F failureReason) {
handler.onRequestFailed(failureReason);
}
public void onRequestSuccess(HashMap<K, V> result, long timeCached) {
cacheResult.putAll(result);
handler.onRequestSuccess(cacheResult, Math.min(timeCached, outerOldestTimestamp));
}
});
} else {
handler.onRequestSuccess(cacheResult, oldestTimestamp);
}
}
public synchronized void performWrite(V value) {
put(value, true);
}
public void performWrite(Collection<V> values) {
put(values, true);
}
public synchronized void performRequest(final K key, final TimestampBound timestampBound,
final RequestResponseHandler<V, F> handler,
final UpdatedVersionListener<K, V> updatedVersionListener) {
if(timestampBound != null) {
final CacheEntry existingEntry = cached.get(key);
if(existingEntry != null) {
final V existing = existingEntry.data.get();
if(existing != null && timestampBound.verifyTimestamp(existing.getTimestamp())) {
handler.onRequestSuccess(existing, existing.getTimestamp());
return;
}
}
}
cacheDataSource.performRequest(key, timestampBound, new RequestResponseHandler<V, F>() {
public void onRequestFailed(F failureReason) {
handler.onRequestFailed(failureReason);
}
public void onRequestSuccess(V result, long timeCached) {
synchronized(WeakCache.this) {
put(result, false);
if(updatedVersionListener != null) cached.get(key).listeners.add(updatedVersionListener);
handler.onRequestSuccess(result, timeCached);
}
}
});
}
public synchronized void forceUpdate(final K key) {
cacheDataSource.performRequest(key, null, new RequestResponseHandler<V, F>() {
public void onRequestFailed(F failureReason) {}
public void onRequestSuccess(V result, long timeCached) {
put(result, false);
}
});
}
private synchronized void put(final V value, boolean writeDown) {
final CacheEntry oldEntry = cached.get(value.getKey());
if(oldEntry != null) {
cached.put(value.getKey(), new CacheEntry(new WeakReference<>(value), oldEntry.listeners));
oldEntry.listeners.map(updatedVersionListenerNotifier, value);
} else {
cached.put(value.getKey(), new CacheEntry(new WeakReference<>(value)));
}
if(writeDown) cacheDataSource.performWrite(value);
}
private synchronized void put(final Collection<V> values, boolean writeDown) {
for(final V value : values) {
final CacheEntry oldEntry = cached.get(value.getKey());
if(oldEntry != null) {
cached.put(value.getKey(), new CacheEntry(new WeakReference<>(value), oldEntry.listeners));
oldEntry.listeners.map(updatedVersionListenerNotifier, value);
} else {
cached.put(value.getKey(), new CacheEntry(new WeakReference<>(value)));
}
}
if(writeDown) cacheDataSource.performWrite(values);
}
private final class CacheEntry {
public final WeakReference<V> data;
public final WeakReferenceListManager<UpdatedVersionListener<K, V>> listeners;
private CacheEntry(WeakReference<V> data,
WeakReferenceListManager<UpdatedVersionListener<K, V>> listeners) {
this.data = data;
this.listeners = listeners;
}
private CacheEntry(WeakReference<V> data) {
this(data, new WeakReferenceListManager<UpdatedVersionListener<K, V>>());
}
}
}