org.eclipse.jgit/src/org/eclipse/jgit/transport/ProgressSpinner.java

/*
 * Copyright (C) 2015, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.transport;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.IOException;
import java.io.OutputStream;
import java.util.concurrent.TimeUnit;

/**
 * A simple spinner connected to an {@code OutputStream}.
 * <p>
 * This is class is not thread-safe. The update method may only be used from a
 * single thread. Updates are sent only as frequently as {@link #update()} is
 * invoked by the caller, and are capped at no more than 2 times per second by
 * requiring at least 500 milliseconds between updates.
 *
 * @since 4.2
 */
public class ProgressSpinner {
	private static final long MIN_REFRESH_MILLIS = 500;
	private static final char[] STATES = new char[] { '-', '\\', '|', '/' };

	private final OutputStream out;
	private String msg;
	private int state;
	private boolean write;
	private boolean shown;
	private long nextUpdateMillis;

	/**
	 * Initialize a new spinner.
	 *
	 * @param out
	 *            where to send output to.
	 */
	public ProgressSpinner(OutputStream out) {
		this.out = out;
		this.write = true;
	}

	/**
	 * Begin a time consuming task.
	 *
	 * @param title
	 *            description of the task, suitable for human viewing.
	 * @param delay
	 *            delay to wait before displaying anything at all.
	 * @param delayUnits
	 *            unit for {@code delay}.
	 */
	public void beginTask(String title, long delay, TimeUnit delayUnits) {
		msg = title;
		state = 0;
		shown = false;

		long now = System.currentTimeMillis();
		if (delay > 0) {
			nextUpdateMillis = now + delayUnits.toMillis(delay);
		} else {
			send(now);
		}
	}

	/** Update the spinner if it is showing. */
	public void update() {
		long now = System.currentTimeMillis();
		if (now >= nextUpdateMillis) {
			send(now);
			state = (state + 1) % STATES.length;
		}
	}

	private void send(long now) {
		StringBuilder buf = new StringBuilder(msg.length() + 16);
		buf.append('\r').append(msg).append("... ("); //$NON-NLS-1$
		buf.append(STATES[state]);
		buf.append(")  "); //$NON-NLS-1$
		shown = true;
		write(buf.toString());
		nextUpdateMillis = now + MIN_REFRESH_MILLIS;
	}

	/**
	 * Denote the current task completed.
	 *
	 * @param result
	 *            text to print after the task's title
	 *            {@code "$title ... $result"}.
	 */
	public void endTask(String result) {
		if (shown) {
			write('\r' + msg + "... " + result + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
		}
	}

	private void write(String s) {
		if (write) {
			try {
				out.write(s.getBytes(UTF_8));
				out.flush();
			} catch (IOException e) {
				write = false;
			}
		}
	}
}