NewPipe/app/src/main/java/org/schabi/newpipe/util/InfoCache.java

/*
 * Copyright 2017 Mauricio Colli <mauriciocolli@outlook.com>
 * InfoCache.java is part of NewPipe
 *
 * License: GPL-3.0+
 * This program 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.
 *
 * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
 */

package org.schabi.newpipe.util;

import android.util.Log;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.collection.LruCache;

import org.schabi.newpipe.MainActivity;
import org.schabi.newpipe.extractor.Info;

import java.util.Map;

public final class InfoCache {
    private final String TAG = getClass().getSimpleName();
    private static final boolean DEBUG = MainActivity.DEBUG;

    private static final InfoCache INSTANCE = new InfoCache();
    private static final int MAX_ITEMS_ON_CACHE = 60;
    /**
     * Trim the cache to this size.
     */
    private static final int TRIM_CACHE_TO = 30;

    private static final LruCache<String, CacheData> LRU_CACHE = new LruCache<>(MAX_ITEMS_ON_CACHE);

    private InfoCache() {
        // no instance
    }

    /**
     * Identifies the type of {@link Info} to put into the cache.
     */
    public enum Type {
        STREAM,
        CHANNEL,
        CHANNEL_TAB,
        COMMENTS,
        PLAYLIST,
        KIOSK,
    }

    public static InfoCache getInstance() {
        return INSTANCE;
    }

    @NonNull
    private static String keyOf(final int serviceId,
                                @NonNull final String url,
                                @NonNull final Type cacheType) {
        return serviceId + ":" + cacheType.ordinal() + ":" + url;
    }

    private static void removeStaleCache() {
        for (final Map.Entry<String, CacheData> entry : InfoCache.LRU_CACHE.snapshot().entrySet()) {
            final CacheData data = entry.getValue();
            if (data != null && data.isExpired()) {
                InfoCache.LRU_CACHE.remove(entry.getKey());
            }
        }
    }

    @Nullable
    private static Info getInfo(@NonNull final String key) {
        final CacheData data = InfoCache.LRU_CACHE.get(key);
        if (data == null) {
            return null;
        }

        if (data.isExpired()) {
            InfoCache.LRU_CACHE.remove(key);
            return null;
        }

        return data.info;
    }

    @Nullable
    public Info getFromKey(final int serviceId,
                           @NonNull final String url,
                           @NonNull final Type cacheType) {
        if (DEBUG) {
            Log.d(TAG, "getFromKey() called with: "
                    + "serviceId = [" + serviceId + "], url = [" + url + "]");
        }
        synchronized (LRU_CACHE) {
            return getInfo(keyOf(serviceId, url, cacheType));
        }
    }

    public void putInfo(final int serviceId,
                        @NonNull final String url,
                        @NonNull final Info info,
                        @NonNull final Type cacheType) {
        if (DEBUG) {
            Log.d(TAG, "putInfo() called with: info = [" + info + "]");
        }

        final long expirationMillis = ServiceHelper.getCacheExpirationMillis(info.getServiceId());
        synchronized (LRU_CACHE) {
            final CacheData data = new CacheData(info, expirationMillis);
            LRU_CACHE.put(keyOf(serviceId, url, cacheType), data);
        }
    }

    public void removeInfo(final int serviceId,
                           @NonNull final String url,
                           @NonNull final Type cacheType) {
        if (DEBUG) {
            Log.d(TAG, "removeInfo() called with: "
                    + "serviceId = [" + serviceId + "], url = [" + url + "]");
        }
        synchronized (LRU_CACHE) {
            LRU_CACHE.remove(keyOf(serviceId, url, cacheType));
        }
    }

    public void clearCache() {
        if (DEBUG) {
            Log.d(TAG, "clearCache() called");
        }
        synchronized (LRU_CACHE) {
            LRU_CACHE.evictAll();
        }
    }

    public void trimCache() {
        if (DEBUG) {
            Log.d(TAG, "trimCache() called");
        }
        synchronized (LRU_CACHE) {
            removeStaleCache();
            LRU_CACHE.trimToSize(TRIM_CACHE_TO);
        }
    }

    public long getSize() {
        synchronized (LRU_CACHE) {
            return LRU_CACHE.size();
        }
    }

    private static final class CacheData {
        private final long expireTimestamp;
        private final Info info;

        private CacheData(@NonNull final Info info, final long timeoutMillis) {
            this.expireTimestamp = System.currentTimeMillis() + timeoutMillis;
            this.info = info;
        }

        private boolean isExpired() {
            return System.currentTimeMillis() > expireTimestamp;
        }
    }
}