/*
    * Copyright (C) 2015, 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.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;
 			}
 		}
 	}
 }