using System;
namespace Terminal.Gui {

	/// <summary>
	/// A Progress Bar view that can indicate progress of an activity visually.
	/// </summary>
	/// <remarks>
	///   <para>
	///     <see cref="ProgressBar"/> can operate in two modes, percentage mode, or
	///     activity mode.  The progress bar starts in percentage mode and
	///     setting the Fraction property will reflect on the UI the progress 
	///     made so far.   Activity mode is used when the application has no 
	///     way of knowing how much time is left, and is started when the <see cref="Pulse"/> method is called.  
	///     Call <see cref="Pulse"/> repeatedly as progress is made.
	///   </para>
	/// </remarks>
	public class ProgressBar : View {
		bool isActivity;
		int activityPos, delta;

		/// <summary>
		/// Initializes a new instance of the <see cref="ProgressBar"/> class, starts in percentage mode with an absolute position and size.
		/// </summary>
		/// <param name="rect">Rect.</param>
		public ProgressBar (Rect rect) : base (rect)
		{
			CanFocus = false;
			fraction = 0;
		}

		/// <summary>
		/// Initializes a new instance of the <see cref="ProgressBar"/> class, starts in percentage mode and uses relative layout.
		/// </summary>
		public ProgressBar () : base ()
		{
			CanFocus = false;
			fraction = 0;
		}

		float fraction;

		/// <summary>
		/// Gets or sets the <see cref="ProgressBar"/> fraction to display, must be a value between 0 and 1.
		/// </summary>
		/// <value>The fraction representing the progress.</value>
		public float Fraction {
			get => fraction;
			set {
				fraction = value;
				isActivity = false;
				SetNeedsDisplay ();
			}
		}

		/// <summary>
		/// Notifies the <see cref="ProgressBar"/> that some progress has taken place.
		/// </summary>
		/// <remarks>
		/// If the <see cref="ProgressBar"/> is is percentage mode, it switches to activity
		/// mode.   If is in activity mode, the marker is moved.
		/// </remarks>
		public void Pulse ()
		{
			if (!isActivity) {
				isActivity = true;
				activityPos = 0;
				delta = 1;
			} else {
				activityPos += delta;
				if (activityPos < 0) {
					activityPos = 1;
					delta = 1;
				} else if (activityPos >= Frame.Width) {
					activityPos = Frame.Width - 2;
					delta = -1;
				}
			}

			SetNeedsDisplay ();
		}

		///<inheritdoc cref="Redraw"/>
		public override void Redraw(Rect region)
		{
			Driver.SetAttribute (ColorScheme.Normal);

			int top = Frame.Width;
			if (isActivity) {
				Move (0, 0);
				for (int i = 0; i < top; i++)
					if (i == activityPos)
						Driver.AddRune (Driver.Stipple);
					else
						Driver.AddRune (' ');
			} else {
				Move (0, 0);
				int mid = (int)(fraction * top);
				int i;
				for (i = 0; i < mid; i++)
					Driver.AddRune (Driver.Stipple);
				for (; i < top; i++)
					Driver.AddRune (' ');
			}
		}
	}
}