using System.Text;
using System;

namespace Terminal.Gui;
/// <summary>
/// Specifies the style that a <see cref="ProgressBar"/> uses to indicate the progress of an operation.
/// </summary>
public enum ProgressBarStyle {
	/// <summary>
	/// Indicates progress by increasing the number of segmented blocks in a <see cref="ProgressBar"/>.
	/// </summary>
	Blocks,
	/// <summary>
	/// Indicates progress by increasing the size of a smooth, continuous bar in a <see cref="ProgressBar"/>.
	/// </summary>
	Continuous,
	/// <summary>
	/// Indicates progress by continuously scrolling a block across a <see cref="ProgressBar"/> in a marquee fashion.
	/// </summary>
	MarqueeBlocks,
	/// <summary>
	/// Indicates progress by continuously scrolling a block across a <see cref="ProgressBar"/> in a marquee fashion.
	/// </summary>
	MarqueeContinuous
}

/// <summary>
///Specifies the format that a <see cref="ProgressBar"/> uses to indicate the visual presentation.
/// </summary>
public enum ProgressBarFormat {
	/// <summary>
	/// A simple visual presentation showing only the progress bar.
	/// </summary>
	Simple,
	/// <summary>
	/// A simple visual presentation showing the progress bar overlaid with the percentage.
	/// </summary>
	SimplePlusPercentage,
}

/// <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;
	int _delta;

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

	void SetInitialProperties ()
	{
		Height = 1; // This will be updated when Bounds is updated in ProgressBar_LayoutStarted
		CanFocus = false;
		_fraction = 0;
		LayoutStarted += ProgressBar_LayoutStarted;
		Initialized += ProgressBar_Initialized;
	}

	void ProgressBar_Initialized (object sender, EventArgs e)
	{
		ColorScheme = new ColorScheme (ColorScheme ?? SuperView?.ColorScheme ?? Colors.ColorSchemes ["Base"]) {
			HotNormal = new Attribute (Color.BrightGreen, Color.Gray)
		};
	}

	void ProgressBar_LayoutStarted (object sender, EventArgs e)
	{
		// TODO: use Dim.Auto
		Height = 1 + GetAdornmentsThickness ().Vertical;
	}

	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 = Math.Min (value, 1);
			_isActivity = false;
			SetNeedsDisplay ();
		}
	}

	ProgressBarStyle _progressBarStyle;

	/// <summary>
	/// Gets/Sets the progress bar style based on the <see cref="Terminal.Gui.ProgressBarStyle"/>
	/// </summary>
	public ProgressBarStyle ProgressBarStyle {
		get => _progressBarStyle;
		set {
			_progressBarStyle = value;
			switch (value) {
			case ProgressBarStyle.Blocks:
				SegmentCharacter = CM.Glyphs.BlocksMeterSegment;
				break;
			case ProgressBarStyle.Continuous:
				SegmentCharacter = CM.Glyphs.ContinuousMeterSegment;
				break;
			case ProgressBarStyle.MarqueeBlocks:
				SegmentCharacter = CM.Glyphs.BlocksMeterSegment;
				break;
			case ProgressBarStyle.MarqueeContinuous:
				SegmentCharacter = CM.Glyphs.ContinuousMeterSegment;
				break;
			}
			SetNeedsDisplay ();
		}
	}

	/// <summary>
	/// Specifies the format that a <see cref="ProgressBar"/> uses to indicate the visual presentation.
	/// </summary>
	public ProgressBarFormat ProgressBarFormat { get; set; }
	private Rune _segmentCharacter = CM.Glyphs.BlocksMeterSegment;

	/// <summary>
	/// Segment indicator for meter views.
	/// </summary>
	public Rune SegmentCharacter {
		get => _segmentCharacter;
		set {
			_segmentCharacter = value;
			SetNeedsDisplay ();
		}
	}

	/// <summary>
	/// Gets or sets the text displayed on the progress bar. If set to an empty string and <see cref="ProgressBarFormat"/> is
	/// <see cref="ProgressBarFormat.SimplePlusPercentage"/> the percentage will be displayed.
	/// If <see cref="ProgressBarStyle"/> is a marquee style, the text will be displayed.
	/// </summary>
	public override string Text {
		get => string.IsNullOrEmpty (base.Text) ? $"{_fraction * 100:F0}%" : base.Text;
		set {
			if (ProgressBarStyle == ProgressBarStyle.MarqueeBlocks || ProgressBarStyle == ProgressBarStyle.MarqueeContinuous) {
				base.Text = value;
			}
		}
	}

	bool _bidirectionalMarquee = true;

	/// <summary>
	/// Specifies if the <see cref="ProgressBarStyle.MarqueeBlocks"/> or the
	///  <see cref="ProgressBarStyle.MarqueeContinuous"/> styles is unidirectional
	///  or bidirectional.
	/// </summary>
	public bool BidirectionalMarquee {
		get => _bidirectionalMarquee;
		set {
			_bidirectionalMarquee = value;
			SetNeedsDisplay ();
		}
	}

	/// <summary>
	/// Notifies the <see cref="ProgressBar"/> that some progress has taken place.
	/// </summary>
	/// <remarks>
	/// If the <see cref="ProgressBar"/> is percentage mode, it switches to activity
	/// mode. If is in activity mode, the marker is moved.
	/// </remarks>
	public void Pulse ()
	{
		if (_activityPos == null || _activityPos.Length == 0) {
			PopulateActivityPos ();
		}

		if (_activityPos!.Length == 0) {
			return;
		}

		if (!_isActivity) {
			_isActivity = true;
			_delta = 1;
		} else {
			for (var i = 0; i < _activityPos.Length; i++) {
				_activityPos [i] += _delta;
			}

			if (_activityPos [^1] < 0) {
				for (var i = 0; i < _activityPos.Length; i++) {
					_activityPos [i] = i - _activityPos.Length + 2;
				}
				_delta = 1;
			} else if (_activityPos [0] >= Bounds.Width) {
				if (_bidirectionalMarquee) {
					for (var i = 0; i < _activityPos.Length; i++) {
						_activityPos [i] = Bounds.Width + i - 2;
					}
					_delta = -1;
				} else {
					PopulateActivityPos ();
				}
			}
		}

		SetNeedsDisplay ();
	}

	///<inheritdoc/>
	public override void OnDrawContent (Rect contentArea)
	{
		Driver.SetAttribute (GetHotNormalColor ());

		Move (0, 0);
		if (_isActivity) {
			for (int i = 0; i < Bounds.Width; i++)
				if (Array.IndexOf (_activityPos, i) != -1) {
					Driver.AddRune (SegmentCharacter);
				} else {
					Driver.AddRune ((Rune)' ');
				}
		} else {
			int mid = (int)(_fraction * Bounds.Width);
			int i;
			for (i = 0; i < mid & i < Bounds.Width; i++) {
				Driver.AddRune (SegmentCharacter);
			}
			for (; i < Bounds.Width; i++) {
				Driver.AddRune ((Rune)' ');
			}
		}


		if (ProgressBarFormat != ProgressBarFormat.Simple && !_isActivity) {
			var tf = new TextFormatter () {
				Alignment = TextAlignment.Centered,
				Text = Text
			};
			Attribute attr = new Attribute (ColorScheme.HotNormal.Foreground, ColorScheme.HotNormal.Background);
			if (_fraction > .5) {
				attr = new Attribute (ColorScheme.HotNormal.Background, ColorScheme.HotNormal.Foreground);
			}
			tf?.Draw (BoundsToScreen (Bounds),
				attr,
				ColorScheme.Normal,
				SuperView?.BoundsToScreen (SuperView.Bounds) ?? default,
				fillRemaining: false);


		}
	}

	void PopulateActivityPos ()
	{
		_activityPos = new int [Math.Min (Frame.Width / 3, 5)];
		for (var i = 0; i < _activityPos.Length; i++) {
			_activityPos [i] = i - _activityPos.Length + 1;
		}
	}

	///<inheritdoc/>
	public override bool OnEnter (View view)
	{
		Application.Driver.SetCursorVisibility (CursorVisibility.Invisible);
		return base.OnEnter (view);
	}
}