gui-cs.Terminal.Gui/Terminal.Gui/Drawing/Color.cs

global using Attribute = Terminal.Gui.Attribute;
using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Text.Json.Serialization;
using System.Text.RegularExpressions;

namespace Terminal.Gui;

/// <summary>
/// Defines the 16 legacy color names and values that can be used to set the
/// foreground and background colors in Terminal.Gui apps. Used with <see cref="Color"/>.
/// </summary>
/// <remarks>
///         <para>
///         These colors match the 16 colors defined for ANSI escape sequences for 4-bit (16) colors.
///         </para>
///         <para>
///         For terminals that support 24-bit color (TrueColor), the RGB values for each of these colors can be configured
///         using the
///         <see cref="Color.Colors"/> property.
///         </para>
/// </remarks>
public enum ColorName {
	/// <summary>
	/// The black color. ANSI escape sequence: <c>\u001b[30m</c>.
	/// </summary>
	Black,

	/// <summary>
	/// The blue color. ANSI escape sequence: <c>\u001b[34m</c>.
	/// </summary>
	Blue,

	/// <summary>
	/// The green color. ANSI escape sequence: <c>\u001b[32m</c>.
	/// </summary>
	Green,

	/// <summary>
	/// The cyan color. ANSI escape sequence: <c>\u001b[36m</c>.
	/// </summary>
	Cyan,

	/// <summary>
	/// The red color. ANSI escape sequence: <c>\u001b[31m</c>.
	/// </summary>
	Red,

	/// <summary>
	/// The magenta color. ANSI escape sequence: <c>\u001b[35m</c>.
	/// </summary>
	Magenta,

	/// <summary>
	/// The yellow color (also known as Brown). ANSI escape sequence: <c>\u001b[33m</c>.
	/// </summary>
	Yellow,

	/// <summary>
	/// The gray color (also known as White). ANSI escape sequence: <c>\u001b[37m</c>.
	/// </summary>
	Gray,

	/// <summary>
	/// The dark gray color (also known as Bright Black). ANSI escape sequence: <c>\u001b[30;1m</c>.
	/// </summary>
	DarkGray,

	/// <summary>
	/// The bright blue color. ANSI escape sequence: <c>\u001b[34;1m</c>.
	/// </summary>
	BrightBlue,

	/// <summary>
	/// The bright green color. ANSI escape sequence: <c>\u001b[32;1m</c>.
	/// </summary>
	BrightGreen,

	/// <summary>
	/// The bright cyan color. ANSI escape sequence: <c>\u001b[36;1m</c>.
	/// </summary>
	BrightCyan,

	/// <summary>
	/// The bright red color. ANSI escape sequence: <c>\u001b[31;1m</c>.
	/// </summary>
	BrightRed,

	/// <summary>
	/// The bright magenta color. ANSI escape sequence: <c>\u001b[35;1m</c>.
	/// </summary>
	BrightMagenta,

	/// <summary>
	/// The bright yellow color. ANSI escape sequence: <c>\u001b[33;1m</c>.
	/// </summary>
	BrightYellow,

	/// <summary>
	/// The White color (also known as Bright White). ANSI escape sequence: <c>\u001b[37;1m</c>.
	/// </summary>
	White
}

/// <summary>
/// The 16 foreground color codes used by ANSI Esc sequences for 256 color terminals. Add 10 to these values for background
/// color.
/// </summary>
public enum AnsiColorCode {
	/// <summary>
	/// The ANSI color code for Black.
	/// </summary>
	BLACK = 30,

	/// <summary>
	/// The ANSI color code for Red.
	/// </summary>
	RED = 31,

	/// <summary>
	/// The ANSI color code for Green.
	/// </summary>
	GREEN = 32,

	/// <summary>
	/// The ANSI color code for Yellow.
	/// </summary>
	YELLOW = 33,

	/// <summary>
	/// The ANSI color code for Blue.
	/// </summary>
	BLUE = 34,

	/// <summary>
	/// The ANSI color code for Magenta.
	/// </summary>
	MAGENTA = 35,

	/// <summary>
	/// The ANSI color code for Cyan.
	/// </summary>
	CYAN = 36,

	/// <summary>
	/// The ANSI color code for White.
	/// </summary>
	WHITE = 37,

	/// <summary>
	/// The ANSI color code for Bright Black.
	/// </summary>
	BRIGHT_BLACK = 90,

	/// <summary>
	/// The ANSI color code for Bright Red.
	/// </summary>
	BRIGHT_RED = 91,

	/// <summary>
	/// The ANSI color code for Bright Green.
	/// </summary>
	BRIGHT_GREEN = 92,

	/// <summary>
	/// The ANSI color code for Bright Yellow.
	/// </summary>
	BRIGHT_YELLOW = 93,

	/// <summary>
	/// The ANSI color code for Bright Blue.
	/// </summary>
	BRIGHT_BLUE = 94,

	/// <summary>
	/// The ANSI color code for Bright Magenta.
	/// </summary>
	BRIGHT_MAGENTA = 95,

	/// <summary>
	/// The ANSI color code for Bright Cyan.
	/// </summary>
	BRIGHT_CYAN = 96,

	/// <summary>
	/// The ANSI color code for Bright White.
	/// </summary>
	BRIGHT_WHITE = 97
}

/// <summary>
/// Represents a 24-bit color. Provides automatic mapping between the legacy 4-bit (16 color) system and 24-bit colors (see
/// <see cref="ColorName"/>). Used with <see cref="Attribute"/>.
/// </summary>
[JsonConverter (typeof (ColorJsonConverter))]
public readonly struct Color : IEquatable<Color> {

	// TODO: Make this map configurable via ConfigurationManager
	// TODO: This does not need to be a Dictionary, but can be an 16 element array.
	/// <summary>
	/// Maps legacy 16-color values to the corresponding 24-bit RGB value.
	/// </summary>
	internal static ImmutableDictionary<Color, ColorName> _colorToNameMap = new Dictionary<Color, ColorName> {
		// using "Windows 10 Console/PowerShell 6" here: https://i.stack.imgur.com/9UVnC.png
		// See also: https://en.wikipedia.org/wiki/ANSI_escape_code
		{ new Color (12, 12, 12), ColorName.Black },
		{ new Color (0, 55, 218), ColorName.Blue },
		{ new Color (19, 161, 14), ColorName.Green },
		{ new Color (58, 150, 221), ColorName.Cyan },
		{ new Color (197, 15, 31), ColorName.Red },
		{ new Color (136, 23, 152), ColorName.Magenta },
		{ new Color (128, 64, 32), ColorName.Yellow },
		{ new Color (204, 204, 204), ColorName.Gray },
		{ new Color (118, 118, 118), ColorName.DarkGray },
		{ new Color (59, 120, 255), ColorName.BrightBlue },
		{ new Color (22, 198, 12), ColorName.BrightGreen },
		{ new Color (97, 214, 214), ColorName.BrightCyan },
		{ new Color (231, 72, 86), ColorName.BrightRed },
		{ new Color (180, 0, 158), ColorName.BrightMagenta },
		{ new Color (249, 241, 165), ColorName.BrightYellow },
		{ new Color (242, 242, 242), ColorName.White }
	}.ToImmutableDictionary ();


	/// <summary>
	/// Defines the 16 legacy color names and values that can be used to set the
	/// </summary>
	internal static ImmutableDictionary<ColorName, AnsiColorCode> _colorNameToAnsiColorMap = new Dictionary<ColorName, AnsiColorCode> {
		{ ColorName.Black, AnsiColorCode.BLACK },
		{ ColorName.Blue, AnsiColorCode.BLUE },
		{ ColorName.Green, AnsiColorCode.GREEN },
		{ ColorName.Cyan, AnsiColorCode.CYAN },
		{ ColorName.Red, AnsiColorCode.RED },
		{ ColorName.Magenta, AnsiColorCode.MAGENTA },
		{ ColorName.Yellow, AnsiColorCode.YELLOW },
		{ ColorName.Gray, AnsiColorCode.WHITE },
		{ ColorName.DarkGray, AnsiColorCode.BRIGHT_BLACK },
		{ ColorName.BrightBlue, AnsiColorCode.BRIGHT_BLUE },
		{ ColorName.BrightGreen, AnsiColorCode.BRIGHT_GREEN },
		{ ColorName.BrightCyan, AnsiColorCode.BRIGHT_CYAN },
		{ ColorName.BrightRed, AnsiColorCode.BRIGHT_RED },
		{ ColorName.BrightMagenta, AnsiColorCode.BRIGHT_MAGENTA },
		{ ColorName.BrightYellow, AnsiColorCode.BRIGHT_YELLOW },
		{ ColorName.White, AnsiColorCode.BRIGHT_WHITE }
	}.ToImmutableDictionary ();

	/// <summary>
	/// Initializes a new instance of the <see cref="Color"/> class.
	/// </summary>
	/// <param name="red">The red 8-bits.</param>
	/// <param name="green">The green 8-bits.</param>
	/// <param name="blue">The blue 8-bits.</param>
	/// <param name="alpha">Optional; defaults to 0xFF. The Alpha channel is not supported by Terminal.Gui.</param>
	public Color (int red, int green, int blue, int alpha = 0xFF)
	{
		R = red;
		G = green;
		B = blue;
		A = alpha;
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="Color"/> class with an encoded 24-bit color value.
	/// </summary>
	/// <param name="rgba">The encoded 24-bit color value (see <see cref="Rgba"/>).</param>
	public Color (int rgba)
	{
		A = (byte)(rgba >> 24 & 0xFF);
		R = (byte)(rgba >> 16 & 0xFF);
		G = (byte)(rgba >> 8 & 0xFF);
		B = (byte)(rgba & 0xFF);
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="Color"/> color from a legacy 16-color value.
	/// </summary>
	/// <param name="colorName">The 16-color value.</param>
	public Color (ColorName colorName)
	{
		var c = FromColorName (colorName);
		R = c.R;
		G = c.G;
		B = c.B;
		A = c.A;
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="Color"/> color from string. See <see cref="TryParse(string, out Color)"/>
	/// for details.
	/// </summary>
	/// <param name="colorString"></param>
	/// <exception cref="Exception"></exception>
	public Color (string colorString)
	{
		if (!TryParse (colorString, out var c)) {
			throw new ArgumentOutOfRangeException (nameof (colorString));
		}
		R = c.R;
		G = c.G;
		B = c.B;
		A = c.A;
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="Color"/>.
	/// </summary>
	public Color ()
	{
		R = 0;
		G = 0;
		B = 0;
		A = 0xFF;
	}

	/// <summary>
	/// Red color component.
	/// </summary>
	public int R { get; }

	/// <summary>
	/// Green color component.
	/// </summary>
	public int G { get; }

	/// <summary>
	/// Blue color component.
	/// </summary>
	public int B { get; }

	/// <summary>
	/// Alpha color component.
	/// </summary>
	/// <remarks>
	/// The Alpha channel is not supported by Terminal.Gui.
	/// </remarks>
	public int A { get; } // Not currently supported; here for completeness.

	/// <summary>
	/// Gets or sets the color value encoded as ARGB32.
	/// <code>
	/// (&lt;see cref="A"/&gt; &lt;&lt; 24) | (&lt;see cref="R"/&gt; &lt;&lt; 16) | (&lt;see cref="G"/&gt; &lt;&lt; 8) | &lt;see cref="B"/&gt;
	/// </code>
	/// </summary>
	[JsonIgnore]
	public int Rgba => A << 24 | R << 16 | G << 8 | B;

	/// <summary>
	/// Gets or sets the 24-bit color value for each of the legacy 16-color values.
	/// </summary>
	[SerializableConfigurationProperty (Scope = typeof (SettingsScope), OmitClassName = true)]
	public static Dictionary<ColorName, string> Colors {
		get =>
			// Transform _colorToNameMap into a Dictionary<ColorNames,string>
			_colorToNameMap.ToDictionary (kvp => kvp.Value, kvp => $"#{kvp.Key.R:X2}{kvp.Key.G:X2}{kvp.Key.B:X2}");
		set {
			// Transform Dictionary<ColorNames,string> into _colorToNameMap
			var newMap = value.ToDictionary (kvp => new Color (kvp.Value), kvp => {
				if (Enum.TryParse<ColorName> (kvp.Key.ToString (), true, out var colorName)) {
					return colorName;
				}
				throw new ArgumentException ($"Invalid color name: {kvp.Key}");
			});
			_colorToNameMap = newMap.ToImmutableDictionary ();
		}
	}

	/// <summary>
	/// Gets the <see cref="Color"/> using a legacy 16-color <see cref="Gui.ColorName"/> value.
	/// <see langword="get"/> will return the closest 16 color match to the true color when no exact value is found.
	/// </summary>
	/// <remarks>
	/// Get returns the <see cref="ColorName"/> of the closest 24-bit color value. Set sets the RGB value using a hard-coded
	/// map.
	/// </remarks>
	[JsonIgnore]
	public ColorName ColorName => FindClosestColor (this);

	/// <summary>
	/// Gets the <see cref="Color"/> using a legacy 16-color <see cref="Gui.ColorName"/> value.
	/// <see langword="get"/> will return the closest 16 color match to the true color when no exact value is found.
	/// </summary>
	/// <remarks>
	/// Get returns the <see cref="ColorName"/> of the closest 24-bit color value. Set sets the RGB value using a hard-coded
	/// map.
	/// </remarks>
	[JsonIgnore]
	public AnsiColorCode AnsiColorCode => _colorNameToAnsiColorMap [ColorName];

	/// <summary>
	/// Converts a legacy <see cref="Gui.ColorName"/> to a 24-bit <see cref="Color"/>.
	/// </summary>
	/// <param name="colorName">The <see cref="Color"/> to convert.</param>
	/// <returns></returns>
	static Color FromColorName (ColorName colorName) => _colorToNameMap.FirstOrDefault (x => x.Value == colorName).Key;

	// Iterates through the entries in the _colorNames dictionary, calculates the
	// Euclidean distance between the input color and each dictionary color in RGB space,
	// and keeps track of the closest entry found so far. The function returns a KeyValuePair
	// representing the closest color entry and its associated color name.
	internal static ColorName FindClosestColor (Color inputColor)
	{
		var closestColor = ColorName.Black; // Default to Black
		var closestDistance = double.MaxValue;

		foreach (var colorEntry in _colorToNameMap) {
			var distance = CalculateColorDistance (inputColor, colorEntry.Key);
			if (distance < closestDistance) {
				closestDistance = distance;
				closestColor = colorEntry.Value;
			}
		}

		return closestColor;
	}

	static double CalculateColorDistance (Color color1, Color color2)
	{
		// Calculate the Euclidean distance between two colors
		var deltaR = color1.R - (double)color2.R;
		var deltaG = color1.G - (double)color2.G;
		var deltaB = color1.B - (double)color2.B;

		return Math.Sqrt (deltaR * deltaR + deltaG * deltaG + deltaB * deltaB);
	}

	/// <summary>
	/// Converts the provided string to a new <see cref="Color"/> instance.
	/// </summary>
	/// <param name="text">
	/// The text to analyze. Formats supported are
	/// "#RGB", "#RRGGBB", "#RGBA", "#RRGGBBAA", "rgb(r,g,b)", "rgb(r,g,b,a)", and any of the
	/// <see cref="Gui.ColorName"/>.
	/// </param>
	/// <param name="color">The parsed value.</param>
	/// <returns>A boolean value indicating whether parsing was successful.</returns>
	/// <remarks>
	/// While <see cref="Color"/> supports the alpha channel <see cref="A"/>, Terminal.Gui does not.
	/// </remarks>
	public static bool TryParse (string text, [NotNullWhen (true)] out Color color)
	{
		// empty color
		if (string.IsNullOrEmpty (text)) {
			color = new Color ();
			return false;
		}

		// #RRGGBB, #RGB
		if (text [0] == '#' && text.Length is 7 or 4) {
			if (text.Length == 7) {
				var r = Convert.ToInt32 (text.Substring (1, 2), 16);
				var g = Convert.ToInt32 (text.Substring (3, 2), 16);
				var b = Convert.ToInt32 (text.Substring (5, 2), 16);
				color = new Color (r, g, b);
			} else {
				var rText = char.ToString (text [1]);
				var gText = char.ToString (text [2]);
				var bText = char.ToString (text [3]);

				var r = Convert.ToInt32 (rText + rText, 16);
				var g = Convert.ToInt32 (gText + gText, 16);
				var b = Convert.ToInt32 (bText + bText, 16);
				color = new Color (r, g, b);
			}
			return true;
		}

		// #RRGGBB, #RGBA
		if (text [0] == '#' && text.Length is 8 or 5) {
			if (text.Length == 7) {
				var r = Convert.ToInt32 (text.Substring (1, 2), 16);
				var g = Convert.ToInt32 (text.Substring (3, 2), 16);
				var b = Convert.ToInt32 (text.Substring (5, 2), 16);
				var a = Convert.ToInt32 (text.Substring (7, 2), 16);
				color = new Color (a, r, g, b);
			} else {
				var rText = char.ToString (text [1]);
				var gText = char.ToString (text [2]);
				var bText = char.ToString (text [3]);
				var aText = char.ToString (text [4]);

				var r = Convert.ToInt32 (aText + aText, 16);
				var g = Convert.ToInt32 (rText + rText, 16);
				var b = Convert.ToInt32 (gText + gText, 16);
				var a = Convert.ToInt32 (bText + bText, 16);
				color = new Color (r, g, b, a);
			}
			return true;
		}

		// rgb(r,g,b)
		var match = Regex.Match (text, @"rgb\((\d+),(\d+),(\d+)\)");
		if (match.Success) {
			var r = int.Parse (match.Groups [1].Value);
			var g = int.Parse (match.Groups [2].Value);
			var b = int.Parse (match.Groups [3].Value);
			color = new Color (r, g, b);
			return true;
		}

		// rgb(r,g,b,a)
		match = Regex.Match (text, @"rgb\((\d+),(\d+),(\d+),(\d+)\)");
		if (match.Success) {
			var r = int.Parse (match.Groups [1].Value);
			var g = int.Parse (match.Groups [2].Value);
			var b = int.Parse (match.Groups [3].Value);
			var a = int.Parse (match.Groups [4].Value);
			color = new Color (r, g, b, a);
			return true;
		}

		if (Enum.TryParse<ColorName> (text, true, out var colorName)) {
			color = new Color (colorName);
			return true;
		}

		color = new Color ();
		return false;
	}

	/// <summary>
	/// Converts the color to a string representation.
	/// </summary>
	/// <remarks>
	///         <para>
	///         If the color is a named color, the name is returned. Otherwise, the color is returned as a hex string.
	///         </para>
	///         <para>
	///         <see cref="A"/> (Alpha channel) is ignored and the returned string will not include it.
	///         </para>
	/// </remarks>
	/// <returns></returns>
	public override string ToString ()
	{
		// If Values has an exact match with a named color (in _colorNames), use that.
		if (_colorToNameMap.TryGetValue (this, out var colorName)) {
			return Enum.GetName (typeof (ColorName), colorName);
		}
		// Otherwise return as an RGB hex value.
		return $"#{R:X2}{G:X2}{B:X2}";
	}

	#region Legacy Color Names
	/// <summary>
	/// The black color.
	/// </summary>
	public const ColorName Black = ColorName.Black;

	/// <summary>
	/// The blue color.
	/// </summary>
	public const ColorName Blue = ColorName.Blue;

	/// <summary>
	/// The green color.
	/// </summary>
	public const ColorName Green = ColorName.Green;

	/// <summary>
	/// The cyan color.
	/// </summary>
	public const ColorName Cyan = ColorName.Cyan;

	/// <summary>
	/// The red color.
	/// </summary>
	public const ColorName Red = ColorName.Red;

	/// <summary>
	/// The magenta color.
	/// </summary>
	public const ColorName Magenta = ColorName.Magenta;

	/// <summary>
	/// The yellow color.
	/// </summary>
	public const ColorName Yellow = ColorName.Yellow;

	/// <summary>
	/// The gray color.
	/// </summary>
	public const ColorName Gray = ColorName.Gray;

	/// <summary>
	/// The dark gray color.
	/// </summary>
	public const ColorName DarkGray = ColorName.DarkGray;

	/// <summary>
	/// The bright bBlue color.
	/// </summary>
	public const ColorName BrightBlue = ColorName.BrightBlue;

	/// <summary>
	/// The bright green color.
	/// </summary>
	public const ColorName BrightGreen = ColorName.BrightGreen;

	/// <summary>
	/// The bright cyan color.
	/// </summary>
	public const ColorName BrightCyan = ColorName.BrightCyan;

	/// <summary>
	/// The bright red color.
	/// </summary>
	public const ColorName BrightRed = ColorName.BrightRed;

	/// <summary>
	/// The bright magenta color.
	/// </summary>
	public const ColorName BrightMagenta = ColorName.BrightMagenta;

	/// <summary>
	/// The bright yellow color.
	/// </summary>
	public const ColorName BrightYellow = ColorName.BrightYellow;

	/// <summary>
	/// The White color.
	/// </summary>
	public const ColorName White = ColorName.White;
	#endregion

	// TODO: Verify implict/explicit are correct for below
	#region Operators
	/// <summary>
	/// Cast from int.
	/// </summary>
	/// <param name="rgba"></param>
	public static implicit operator Color (int rgba) => new (rgba);

	/// <summary>
	/// Cast to int. 
	/// </summary>
	/// <param name="color"></param>
	public static implicit operator int (Color color) => color.Rgba;

	/// <summary>
	/// Cast from <see cref="Gui.ColorName"/>. May fail if the color is not a named color.
	/// </summary>
	/// <param name="colorName"></param>
	public static explicit operator Color (ColorName colorName) => new (colorName);

	/// <summary>
	/// Cast to <see cref="Gui.ColorName"/>. May fail if the color is not a named color.
	/// </summary>
	/// <param name="color"></param>
	public static explicit operator ColorName (Color color) => color.ColorName;

	/// <summary>
	/// Equality operator for two <see cref="Color"/> objects..
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator == (Color left, Color right) => left.Equals (right);

	/// <summary>
	/// Inequality operator for two <see cref="Color"/> objects.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator != (Color left, Color right) => !left.Equals (right);

	/// <summary>
	/// Equality operator for <see cref="Color"/> and <see cref="Gui.ColorName"/> objects.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator == (ColorName left, Color right) => left == right.ColorName;

	/// <summary>
	/// Inequality operator for <see cref="Color"/> and <see cref="Gui.ColorName"/> objects.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator != (ColorName left, Color right) => left != right.ColorName;

	/// <summary>
	/// Equality operator for <see cref="Color"/> and <see cref="Gui.ColorName"/> objects.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator == (Color left, ColorName right) => left.ColorName == right;

	/// <summary>
	/// Inequality operator for <see cref="Color"/> and <see cref="Gui.ColorName"/> objects.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator != (Color left, ColorName right) => left.ColorName != right;


	/// <inheritdoc/>
	public override bool Equals (object obj) => obj is Color other && Equals (other);

	/// <inheritdoc/>
	public bool Equals (Color other) => R == other.R &&
	                                    G == other.G &&
	                                    B == other.B &&
	                                    A == other.A;

	/// <inheritdoc/>
	public override int GetHashCode () => HashCode.Combine (R, G, B, A);
	#endregion
}

/// <summary>
/// Attributes represent how text is styled when displayed in the terminal.
/// </summary>
/// <remarks>
/// <see cref="Attribute"/> provides a platform independent representation of colors (and someday other forms of text
/// styling).
/// They encode both the foreground and the background color and are used in the <see cref="ColorScheme"/>
/// class to define color schemes that can be used in an application.
/// </remarks>
[JsonConverter (typeof (AttributeJsonConverter))]
public readonly struct Attribute : IEquatable<Attribute> {
	/// <summary>
	/// Default empty attribute.
	/// </summary>
	public static readonly Attribute Default = new (Color.White, Color.Black);

	/// <summary>
	/// The <see cref="ConsoleDriver"/>-specific color value.
	/// </summary>
	[JsonIgnore (Condition = JsonIgnoreCondition.Always)]
	internal int PlatformColor { get; }

	/// <summary>
	/// The foreground color.
	/// </summary>
	[JsonConverter (typeof (ColorJsonConverter))]
	public Color Foreground { get; }

	/// <summary>
	/// The background color.
	/// </summary>
	[JsonConverter (typeof (ColorJsonConverter))]
	public Color Background { get; }

	/// <summary>
	/// Initializes a new instance with default values.
	/// </summary>
	public Attribute ()
	{
		PlatformColor = -1;
		Foreground = new Color (Default.Foreground.ColorName);
		Background = new Color (Default.Background.ColorName);
	}

	/// <summary>
	/// Initializes a new instance from an existing instance.
	/// </summary>
	public Attribute (Attribute attr)
	{
		PlatformColor = -1;
		Foreground = new Color (attr.Foreground.ColorName);
		Background = new Color (attr.Background.ColorName);
	}

	/// <summary>
	/// Initializes a new instance with platform specific color value.
	/// </summary>
	/// <param name="platformColor">Value.</param>
	internal Attribute (int platformColor)
	{
		PlatformColor = platformColor;
		Foreground = new Color (Default.Foreground.ColorName);
		Background = new Color (Default.Background.ColorName);
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct.
	/// </summary>
	/// <param name="platformColor">platform-dependent color value.</param>
	/// <param name="foreground">Foreground</param>
	/// <param name="background">Background</param>
	internal Attribute (int platformColor, Color foreground, Color background)
	{
		Foreground = foreground;
		Background = background;
		PlatformColor = platformColor;
	}

	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct.
	/// </summary>
	/// <param name="platformColor">platform-dependent color value.</param>
	/// <param name="foreground">Foreground</param>
	/// <param name="background">Background</param>
	internal Attribute (int platformColor, ColorName foreground, ColorName background) : this (platformColor, new Color (foreground), new Color (background)) { }

	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct.
	/// </summary>
	/// <param name="foreground">Foreground</param>
	/// <param name="background">Background</param>
	public Attribute (Color foreground, Color background)
	{
		Foreground = foreground;
		Background = background;

		// TODO: Once CursesDriver supports truecolor all the PlatformColor stuff goes away
		if (Application.Driver == null) {
			PlatformColor = -1;
			return;
		}

		var make = Application.Driver.MakeColor (foreground, background);
		PlatformColor = make.PlatformColor;
	}

	/// <summary>
	/// Initializes a new instance with a <see cref="ColorName"/> value. Both <see cref="Foreground"/> and
	/// <see cref="Background"/> will be set to the specified color.
	/// </summary>
	/// <param name="colorName">Value.</param>
	internal Attribute (ColorName colorName) : this (colorName, colorName) { }

	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct.
	/// </summary>
	/// <param name="foregroundName">Foreground</param>
	/// <param name="backgroundName">Background</param>
	public Attribute (ColorName foregroundName, ColorName backgroundName) : this (new Color (foregroundName), new Color (backgroundName)) { }


	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct.
	/// </summary>
	/// <param name="foregroundName">Foreground</param>
	/// <param name="background">Background</param>
	public Attribute (ColorName foregroundName, Color background) : this (new Color (foregroundName), background) { }

	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct.
	/// </summary>
	/// <param name="foreground">Foreground</param>
	/// <param name="backgroundName">Background</param>
	public Attribute (Color foreground, ColorName backgroundName) : this (foreground, new Color (backgroundName)) { }

	/// <summary>
	/// Initializes a new instance of the <see cref="Attribute"/> struct
	/// with the same colors for the foreground and background.
	/// </summary>
	/// <param name="color">The color.</param>
	public Attribute (Color color) : this (color, color) { }


	/// <summary>
	/// Compares two attributes for equality.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator == (Attribute left, Attribute right) => left.Equals (right);

	/// <summary>
	/// Compares two attributes for inequality.
	/// </summary>
	/// <param name="left"></param>
	/// <param name="right"></param>
	/// <returns></returns>
	public static bool operator != (Attribute left, Attribute right) => !(left == right);

	/// <inheritdoc/>
	public override bool Equals (object obj) => obj is Attribute other && Equals (other);

	/// <inheritdoc/>
	public bool Equals (Attribute other) => PlatformColor == other.PlatformColor &&
	                                        Foreground == other.Foreground &&
	                                        Background == other.Background;

	/// <inheritdoc/>
	public override int GetHashCode () => HashCode.Combine (PlatformColor, Foreground, Background);

	/// <inheritdoc/>
	public override string ToString () =>
		// Note: Unit tests are dependent on this format
		$"[{Foreground},{Background}]";
}