/*

 * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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package jdk.incubator.http;

import java.time.Duration;

import java.time.Instant;

import java.util.concurrent.atomic.AtomicLong;

/**

 * Timeout event notified by selector thread. Executes the given handler if

 * the timer not canceled first.

 *

 * Register with {@link HttpClientImpl#registerTimer(TimeoutEvent)}.

 *

 * Cancel with {@link HttpClientImpl#cancelTimer(TimeoutEvent)}.

 */

abstract class TimeoutEvent implements Comparable<TimeoutEvent> {

    private static final AtomicLong COUNTER = new AtomicLong();

    // we use id in compareTo to make compareTo consistent with equals

    // see TimeoutEvent::compareTo below;

    private final long id = COUNTER.incrementAndGet();

    private final Instant deadline;

    TimeoutEvent(Duration duration) {

        deadline = Instant.now().plus(duration);

    }

    public abstract void handle();

    public Instant deadline() {

        return deadline;

    }

    @Override

    public int compareTo(TimeoutEvent other) {

        if (other == this) return 0;

        // if two events have the same deadline, but are not equals, then the

        // smaller is the one that was created before (has the smaller id).

        // This is arbitrary and we don't really care which is smaller or

        // greater, but we need a total order, so two events with the

        // same deadline cannot compare == 0 if they are not equals.

        final int compareDeadline = this.deadline.compareTo(other.deadline);

        if (compareDeadline == 0 && !this.equals(other)) {

            long diff = this.id - other.id; // should take care of wrap around

            if (diff < 0) return -1;

            else if (diff > 0) return 1;

            else assert false : "Different events with same id and deadline";

        }

        return compareDeadline;

    }

    @Override

    public String toString() {

        return "TimeoutEvent[id=" + id + ", deadline=" + deadline + "]";

    }

}