ProgressBar.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Confirmator
{
	public class ProgressBar : IDisposable, IProgress<double>
	{
		private const int blockCount = 10;
		private readonly TimeSpan animationInterval = TimeSpan.FromSeconds(1.0 / 8);
		private const string animation = @"┐┘└┌";

		private readonly Timer timer;

		private double currentProgress = 0;
		private string currentText = string.Empty;
		private bool disposed = false;
		private int animationIndex = 0;

		private string customLabel = null;

		public ProgressBar() {
			timer = new Timer( TimerHandler );

			// A progress bar is only for temporary display in a console window.
			// If the console output is redirected to a file, draw nothing.
			// Otherwise, we'll end up with a lot of garbage in the target file.
			if ( !Console.IsOutputRedirected ) {
				ResetTimer();
			}
		}

		public void Report( double value ) {
			// Make sure value is in [0..1] range
			value = Math.Max( 0, Math.Min( 1, value ) );
			Interlocked.Exchange( ref currentProgress, value );
		}

		private void TimerHandler( object state ) {
			lock ( timer ) {
				if ( disposed ) return;

				int progressBlockCount = (int) (currentProgress * blockCount);
				int percent = (int) (currentProgress * 100);
				string text = string.Format("[{0}{1}] "+(customLabel == null ?"{2,3}%":"{3}")+" {4}",
				new string('▓', progressBlockCount), new string('░', blockCount - progressBlockCount),
				percent,
				customLabel,
				animation[animationIndex++ % animation.Length]);
				UpdateText( text );

				ResetTimer();
			}
		}
		public void setCustomLabel(string text) {
			customLabel = text;
		}
		private void UpdateText( string text ) {
			// Get length of common portion
			int commonPrefixLength = 0;
			int commonLength = Math.Min(currentText.Length, text.Length);
			while ( commonPrefixLength < commonLength && text[commonPrefixLength] == currentText[commonPrefixLength] ) {
				commonPrefixLength++;
			}

			// Backtrack to the first differing character
			StringBuilder outputBuilder = new StringBuilder();
			outputBuilder.Append( '\b', currentText.Length - commonPrefixLength );

			// Output new suffix
			outputBuilder.Append( text.Substring( commonPrefixLength ) );

			// If the new text is shorter than the old one: delete overlapping characters
			int overlapCount = currentText.Length - text.Length;
			if ( overlapCount > 0 ) {
				outputBuilder.Append( ' ', overlapCount );
				outputBuilder.Append( '\b', overlapCount );
			}

			Console.Write( outputBuilder );
			currentText = text;
		}

		private void ResetTimer() {
			timer.Change( animationInterval, TimeSpan.FromMilliseconds( -1 ) );
		}

		public void Dispose() {
			lock ( timer ) {
				disposed = true;
				UpdateText( string.Empty );
			}
		}

	}
}