/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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.neo4j.time;

import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

/**
 * A {@link java.time.Clock} that is manually controlled.
 * The implementation is thread safe.
 */
public class FakeClock extends SystemNanoClock {
    private final AtomicLong nanoTime = new AtomicLong();

    public FakeClock() {}

    public FakeClock(long initialTime, TimeUnit unit) {
        forward(initialTime, unit);
    }

    @Override
    public ZoneId getZone() {
        return ZoneOffset.UTC;
    }

    @Override
    public Clock withZone(ZoneId zone) {
        return new WithZone(zone);
    }

    @Override
    public Instant instant() {
        return Instant.ofEpochMilli(millis());
    }

    @Override
    public long millis() {
        return TimeUnit.NANOSECONDS.toMillis(nanos());
    }

    @Override
    public long nanos() {
        return nanoTime.get();
    }

    @Override
    public Stopwatch startStopWatch() {
        return new Stopwatch(this::nanos);
    }

    public FakeClock forward(Duration delta) {
        return forward(delta.toNanos(), TimeUnit.NANOSECONDS);
    }

    public FakeClock forward(long delta, TimeUnit unit) {
        nanoTime.addAndGet(unit.toNanos(delta));
        return this;
    }

    private class WithZone extends Clock {
        private final ZoneId zone;

        WithZone(ZoneId zone) {
            this.zone = zone;
        }

        @Override
        public ZoneId getZone() {
            return zone;
        }

        @Override
        public Clock withZone(ZoneId zone) {
            return new WithZone(zone);
        }

        @Override
        public long millis() {
            return FakeClock.this.millis();
        }

        @Override
        public Instant instant() {
            return FakeClock.this.instant();
        }
    }
}
