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/*
 * Copyright 2014-2015 Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags.
 *
 * 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.
 */
package org.hawkular.metrics.tasks.impl;

import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;

import org.hawkular.metrics.tasks.log.TaskQueueLogger;
import org.hawkular.metrics.tasks.log.TaskQueueLogging;
import org.hawkular.rx.cassandra.driver.RxSession;
import org.joda.time.DateTime;

import rx.Observable;

/**
 * @author jsanda
 */
public class LeaseService {
    private static final TaskQueueLogger log = TaskQueueLogging.getTaskQueueLogger(LeaseService.class);

    public static final int DEFAULT_LEASE_TTL = 180;

    public static final int DEFAULT_RENEWAL_RATE = 60;

    @SuppressWarnings("unused")
    private RxSession session;

    @SuppressWarnings("unused")
    private Queries queries;

    private ScheduledExecutorService renewals = Executors.newScheduledThreadPool(1);

    @SuppressWarnings("unused")
    private int ttl = DEFAULT_LEASE_TTL;

    @SuppressWarnings("unused")
    private int renewalRate = DEFAULT_RENEWAL_RATE;

    public LeaseService(RxSession session, Queries queries) {
        this.session = session;
        this.queries = queries;
    }

    public void shutdown() {
        log.infoShutdown();
        renewals.shutdownNow();
    }

    void setTTL(int ttl) {
        this.ttl = ttl;
    }

    void setRenewalRate(int renewalRate) {
        this.renewalRate = renewalRate;
    }

    public Observable> loadLeases(DateTime timeSlice) {
//        return session.execute(queries.findLeases.bind(timeSlice.toDate()))
//                .flatMap(Observable::from)
//                .map(row -> new Lease(timeSlice, row.getString(0), row.getInt(1), row.getString(2), row.getBool(3)))
//                .filter(lease -> !lease.isFinished())
//                .collect(ArrayList::new, ArrayList::add);
        return null;
    }

    public Observable findUnfinishedLeases(DateTime timeSlice) {
        // TODO Add logic to "refresh" the leases
        // We need to keep polling for leases until either we get back an empty result set
        // or all leases are marked finished. And to make things more interesting, we do
        // not want to poll again until there is at least one worker thread (i.e., one of
        // the threads executing tasks) free.
//        return Observable.create(subscriber ->
//                        loadLeases(timeSlice)
//                                .flatMap(Observable::from)
//                                .filter(lease -> lease.getOwner() == null)
//                                .flatMap(lease ->
//                                        acquire(lease).map(acquired ->
//                                                acquired ? lease : null))
//                                .subscribe(subscriber::onNext, subscriber::onError, subscriber::onCompleted)
//        );
        return null;
    }


//    public Observable acquire(Lease lease) {
//        return session.execute(queries.acquireLease.bind(ttl, lease.getOwner(), lease.getTimeSlice().toDate(),
//                lease.getTaskType(), lease.getSegmentOffset())).map(ResultSet::wasApplied);
//    }
//
//    public Observable acquire(Lease lease, int ttl) {
//        return session.execute(queries.acquireLease.bind(ttl, lease.getOwner(), lease.getTimeSlice().toDate(),
//                lease.getTaskType(), lease.getSegmentOffset())).map(ResultSet::wasApplied);
//    }
//
//    public Observable renew(Lease lease) {
//        return session.execute(queries.renewLease.bind(ttl, lease.getOwner(), lease.getTimeSlice().toDate(),
//                lease.getTaskType(), lease.getSegmentOffset(), lease.getOwner())).map(ResultSet::wasApplied);
//    }

    /**
     * Schedules the lease to be automatically renewed every {@link #DEFAULT_RENEWAL_RATE} seconds in a background
     * thread. Renewals will stop once the lease is set to finished. If the lease cannot be renewed, then the lease
     * owner, i.e., the calling thread, will be interrupted. It therefore important for lease owners to handle
     * InterruptedExceptions appropriately.
     */
//    public void autoRenew(Lease lease) {
//        autoRenew(lease, Thread.currentThread());
//    }

//    private void autoRenew(Lease lease, Thread leaseOwner) {
//        renewals.schedule(createRenewRunnable(lease, leaseOwner), renewalRate, TimeUnit.SECONDS);
//    }

//    private Runnable createRenewRunnable(Lease lease, Thread leaseOwner) {
//        return () -> {
//            if (lease.isFinished()) {
//                return;
//            }
//            renew(lease).subscribe(
//                    renewed -> {
//                        if (renewed) {
//                            autoRenew(lease, leaseOwner);
//                        } else {
//                            logger.info("Failed to renew " + lease + " for " + leaseOwner);
//                            leaseOwner.interrupt();
//                        }
//                    },
//                    t -> {
//                        logger.warn("Failed to renew " + lease + " for " + leaseOwner);
//                        // TODO figure out what to do in this scenario
//                    });
//        };
//    }
//
//    public Observable finish(Lease lease) {
//        return session.execute(queries.finishLease.bind(lease.getTimeSlice().toDate(), lease.getTaskType(),
//                lease.getSegmentOffset(), lease.getOwner())).map(ResultSet::wasApplied);
//    }
//
//    public Observable deleteLeases(DateTime timeSlice) {
//        return session.execute(queries.deleteLeases.bind(timeSlice.toDate())).flatMap(resultSet -> null);
//    }

}