/*
 * Licensed to Crate under one or more contributor license agreements.
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.  Crate licenses this file
 * to you 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.
 *
 * However, if you have executed another commercial license agreement
 * with Crate these terms will supersede the license and you may use the
 * software solely pursuant to the terms of the relevant commercial
 * agreement.
 */

package io.crate.operation.collect.stats;

import com.google.common.annotations.VisibleForTesting;
import io.crate.operation.reference.sys.job.ContextLog;
import org.elasticsearch.common.unit.TimeValue;

import java.util.Queue;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

class TimeExpiring {

    /**
     * clean interval in milliseconds
     */
    private static final long DEFAULT_QUEUE_CLEAN_INTERVAL = 5000L;

    private static TimeExpiring INSTANCE = new TimeExpiring(DEFAULT_QUEUE_CLEAN_INTERVAL, 0L);
    private final long interval;
    private final long delay;

    TimeExpiring(long interval, long delay) {
        this.interval = interval;
        this.delay = delay;
    }

    public TimeExpiring(long interval) {
        this(interval, 0L);
    }

    public static TimeExpiring instance() {
        return INSTANCE;
    }

    public ScheduledFuture<?> registerTruncateTask(Queue<? extends ContextLog> q,
                                                   ScheduledExecutorService scheduler,
                                                   TimeValue expiration) {
        return scheduler.scheduleWithFixedDelay(
            () -> removeExpiredLogs(q, System.currentTimeMillis(), expiration.getMillis()),
            delay, interval, TimeUnit.MILLISECONDS);
    }

    @VisibleForTesting
    static <T extends ContextLog> void removeExpiredLogs(Queue<T> q, long currentTimeMillis, long expirationTime) {
        long expired = currentTimeMillis - expirationTime;
        for (T t : q) {
            if (t.ended() < expired) {
                q.remove();
            } else {
                break;
            }
        }
    }
}