/*
 * Copyright (C) 2016, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.util.time;

import static java.util.concurrent.TimeUnit.MICROSECONDS;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

import java.sql.Timestamp;
import java.time.Duration;
import java.time.Instant;
import java.util.Date;
import java.util.Iterator;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

A timestamp generated by MonotonicClock.propose(). 
 ProposedTimestamp implements AutoCloseable so that implementations can release resources associated with obtaining certainty about time elapsing. For example the constructing MonotonicClock may start network IO with peers when creating the ProposedTimestamp, and close() can ensure those network resources are released in a timely fashion. 
Since:
4.6/**
 * A timestamp generated by
 * {@link org.eclipse.jgit.util.time.MonotonicClock#propose()}.
 * <p>
 * ProposedTimestamp implements AutoCloseable so that implementations can
 * release resources associated with obtaining certainty about time elapsing.
 * For example the constructing MonotonicClock may start network IO with peers
 * when creating the ProposedTimestamp, and {@link #close()} can ensure those
 * network resources are released in a timely fashion.
 *
 * @since 4.6
 */
public abstract class ProposedTimestamp implements AutoCloseable {
	
Wait for several timestamps.
Params:
times – 
           timestamps to wait on.
maxWait – 
           how long to wait for the timestamps.
Throws:
InterruptedException – 
            current thread was interrupted before the waiting process
            completed normally.
TimeoutException – 
            the timeout was reached without the proposed timestamp become
            certainly in the past./**
	 * Wait for several timestamps.
	 *
	 * @param times
	 *            timestamps to wait on.
	 * @param maxWait
	 *            how long to wait for the timestamps.
	 * @throws java.lang.InterruptedException
	 *             current thread was interrupted before the waiting process
	 *             completed normally.
	 * @throws java.util.concurrent.TimeoutException
	 *             the timeout was reached without the proposed timestamp become
	 *             certainly in the past.
	 */
	public static void blockUntil(Iterable<ProposedTimestamp> times,
			Duration maxWait) throws TimeoutException, InterruptedException {
		Iterator<ProposedTimestamp> itr = times.iterator();
		if (!itr.hasNext()) {
			return;
		}

		long now = System.currentTimeMillis();
		long deadline = now + maxWait.toMillis();
		for (;;) {
			long w = deadline - now;
			if (w < 0) {
				throw new TimeoutException();
			}
			itr.next().blockUntil(Duration.ofMillis(w));
			if (itr.hasNext()) {
				now = System.currentTimeMillis();
			} else {
				break;
			}
		}
	}

	
Read the timestamp as unit since the epoch. 
 The timestamp value for a specific ProposedTimestamp object never changes, and can be read before blockUntil(Duration). 
Params:
unit – 
           what unit to return the timestamp in. The timestamp will be
           rounded if the unit is bigger than the clock's granularity.
Returns:
unit since the epoch./**
	 * Read the timestamp as {@code unit} since the epoch.
	 * <p>
	 * The timestamp value for a specific {@code ProposedTimestamp} object never
	 * changes, and can be read before {@link #blockUntil(Duration)}.
	 *
	 * @param unit
	 *            what unit to return the timestamp in. The timestamp will be
	 *            rounded if the unit is bigger than the clock's granularity.
	 * @return {@code unit} since the epoch.
	 */
	public abstract long read(TimeUnit unit);

	
Wait for this proposed timestamp to be certainly in the recent past.
 This method forces the caller to wait up to timeout for this to pass sufficiently into the past such that the creating MonotonicClock instance will not create an earlier timestamp. 
Params:
maxWait – 
           how long the implementation may block the caller.
Throws:
InterruptedException – 
            current thread was interrupted before the waiting process
            completed normally.
TimeoutException – 
            the timeout was reached without the proposed timestamp
            becoming certainly in the past./**
	 * Wait for this proposed timestamp to be certainly in the recent past.
	 * <p>
	 * This method forces the caller to wait up to {@code timeout} for
	 * {@code this} to pass sufficiently into the past such that the creating
	 * {@link org.eclipse.jgit.util.time.MonotonicClock} instance will not
	 * create an earlier timestamp.
	 *
	 * @param maxWait
	 *            how long the implementation may block the caller.
	 * @throws java.lang.InterruptedException
	 *             current thread was interrupted before the waiting process
	 *             completed normally.
	 * @throws java.util.concurrent.TimeoutException
	 *             the timeout was reached without the proposed timestamp
	 *             becoming certainly in the past.
	 */
	public abstract void blockUntil(Duration maxWait)
			throws InterruptedException, TimeoutException;

	
Get milliseconds since epoch; read(MILLISECONDS). 
Returns:
milliseconds since epoch; read(MILLISECONDS)./**
	 * Get milliseconds since epoch; {@code read(MILLISECONDS}).
	 *
	 * @return milliseconds since epoch; {@code read(MILLISECONDS}).
	 */
	public long millis() {
		return read(MILLISECONDS);
	}

	
Get microseconds since epoch; read(MICROSECONDS). 
Returns:
microseconds since epoch; read(MICROSECONDS)./**
	 * Get microseconds since epoch; {@code read(MICROSECONDS}).
	 *
	 * @return microseconds since epoch; {@code read(MICROSECONDS}).
	 */
	public long micros() {
		return read(MICROSECONDS);
	}

	
Get time since epoch, with up to microsecond resolution.
Returns:
time since epoch, with up to microsecond resolution./**
	 * Get time since epoch, with up to microsecond resolution.
	 *
	 * @return time since epoch, with up to microsecond resolution.
	 */
	public Instant instant() {
		long usec = micros();
		long secs = usec / 1000000L;
		long nanos = (usec % 1000000L) * 1000L;
		return Instant.ofEpochSecond(secs, nanos);
	}

	
Get time since epoch, with up to microsecond resolution.
Returns:
time since epoch, with up to microsecond resolution./**
	 * Get time since epoch, with up to microsecond resolution.
	 *
	 * @return time since epoch, with up to microsecond resolution.
	 */
	public Timestamp timestamp() {
		return Timestamp.from(instant());
	}

	
Get time since epoch, with up to millisecond resolution.
Returns:
time since epoch, with up to millisecond resolution./**
	 * Get time since epoch, with up to millisecond resolution.
	 *
	 * @return time since epoch, with up to millisecond resolution.
	 */
	public Date date() {
		return new Date(millis());
	}

	
{@inheritDoc}

Release resources allocated by this timestamp.
/**
	 * {@inheritDoc}
	 * <p>
	 * Release resources allocated by this timestamp.
	 */
	@Override
	public void close() {
		// Do nothing by default.
	}

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public String toString() {
		return instant().toString();
	}
}