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

#nullable enable
using System.Globalization;
using System.Numerics;
using System.Text.Json.Serialization;

namespace Terminal.Gui;

/// <summary>Defines a standard set of <see cref="Attribute"/>s for common visible elements in a <see cref="View"/>.</summary>
/// <remarks>
///     <para>
///         ColorScheme objects are immutable. Once constructed, the properties cannot be changed. To change a
///         ColorScheme, create a new one with the desired values, using the <see cref="ColorScheme(ColorScheme)"/>
///         constructor.
///     </para>
/// </remarks>
[JsonConverter (typeof (ColorSchemeJsonConverter))]
public class ColorScheme : IEquatable<ColorScheme>, IEqualityOperators<ColorScheme, ColorScheme, bool>
{
    private readonly Attribute _disabled;
    private readonly Attribute _focus;
    private readonly Attribute _hotFocus;
    private readonly Attribute _hotNormal;
    private readonly Attribute _normal;

    /// <summary>Creates a new instance set to the default colors (see <see cref="Attribute.Default"/>).</summary>
    public ColorScheme () : this (Attribute.Default) { }

    /// <summary>Creates a new instance, initialized with the values from <paramref name="scheme"/>.</summary>
    /// <param name="scheme">The scheme to initialize the new instance with.</param>
    public ColorScheme (ColorScheme scheme)
    {
        if (scheme is null)
        {
            throw new ArgumentNullException (nameof (scheme));
        }

        _normal = scheme.Normal;
        _focus = scheme.Focus;
        _hotNormal = scheme.HotNormal;
        _disabled = scheme.Disabled;
        _hotFocus = scheme.HotFocus;
    }

    /// <summary>Creates a new instance, initialized with the values from <paramref name="attribute"/>.</summary>
    /// <param name="attribute">The attribute to initialize the new instance with.</param>
    public ColorScheme (Attribute attribute)
    {
        _normal = attribute;
        _focus = attribute;
        _hotNormal = attribute;
        _disabled = attribute;
        _hotFocus = attribute;
    }

    /// <summary>The default foreground and background color for text when the view is disabled.</summary>
    public Attribute Disabled
    {
        get => _disabled;
        init => _disabled = value;
    }

    /// <summary>The foreground and background color for text when the view has the focus.</summary>
    public Attribute Focus
    {
        get => _focus;
        init => _focus = value;
    }

    /// <summary>The foreground and background color for for text in a focused view that indicates a <see cref="View.HotKey"/>.</summary>
    public Attribute HotFocus
    {
        get => _hotFocus;
        init => _hotFocus = value;
    }

    /// <summary>The foreground and background color for text in a non-focused view that indicates a <see cref="View.HotKey"/>.</summary>
    public Attribute HotNormal
    {
        get => _hotNormal;
        init => _hotNormal = value;
    }

    /// <summary>The foreground and background color for text when the view is not focused, hot, or disabled.</summary>
    public Attribute Normal
    {
        get => _normal;
        init => _normal = value;
    }

    /// <summary>Compares two <see cref="ColorScheme"/> objects for equality.</summary>
    /// <param name="other"></param>
    /// <returns>true if the two objects are equal</returns>
    public bool Equals (ColorScheme? other)
    {
        return other is { }
               && EqualityComparer<Attribute>.Default.Equals (_normal, other._normal)
               && EqualityComparer<Attribute>.Default.Equals (_focus, other._focus)
               && EqualityComparer<Attribute>.Default.Equals (_hotNormal, other._hotNormal)
               && EqualityComparer<Attribute>.Default.Equals (_hotFocus, other._hotFocus)
               && EqualityComparer<Attribute>.Default.Equals (_disabled, other._disabled);
    }

    /// <summary>Compares two <see cref="ColorScheme"/> objects for equality.</summary>
    /// <param name="obj"></param>
    /// <returns>true if the two objects are equal</returns>
    public override bool Equals (object? obj) { return Equals (obj as ColorScheme); }

    /// <summary>Returns a hashcode for this instance.</summary>
    /// <returns>hashcode for this instance</returns>
    public override int GetHashCode ()
    {
        int hashCode = -1242460230;
        hashCode = hashCode * -1521134295 + _normal.GetHashCode ();
        hashCode = hashCode * -1521134295 + _focus.GetHashCode ();
        hashCode = hashCode * -1521134295 + _hotNormal.GetHashCode ();
        hashCode = hashCode * -1521134295 + _hotFocus.GetHashCode ();
        hashCode = hashCode * -1521134295 + _disabled.GetHashCode ();

        return hashCode;
    }

    /// <summary>Compares two <see cref="ColorScheme"/> objects for equality.</summary>
    /// <param name="left"></param>
    /// <param name="right"></param>
    /// <returns><c>true</c> if the two objects are equivalent</returns>
    public static bool operator == (ColorScheme left, ColorScheme right) { return EqualityComparer<ColorScheme>.Default.Equals (left, right); }

    /// <summary>Compares two <see cref="ColorScheme"/> objects for inequality.</summary>
    /// <param name="left"></param>
    /// <param name="right"></param>
    /// <returns><c>true</c> if the two objects are not equivalent</returns>
    public static bool operator != (ColorScheme left, ColorScheme right) { return !(left == right); }

    /// <inheritdoc/>
    public override string ToString () { return $"Normal: {Normal}; Focus: {Focus}; HotNormal: {HotNormal}; HotFocus: {HotFocus}; Disabled: {Disabled}"; }
}

/// <summary>
///     Holds the <see cref="ColorScheme"/>s that define the <see cref="Attribute"/>s that are used by views to render
///     themselves.
/// </summary>
public static class Colors
{
    static Colors () { Reset (); }

    /// <summary>Gets a dictionary of defined <see cref="ColorScheme"/> objects.</summary>
    /// <remarks>
    ///     <para>
    ///         The <see cref="ColorSchemes"/> dictionary includes the following keys, by default:
    ///         <list type="table">
    ///             <listheader>
    ///                 <term>Built-in Color Scheme</term> <description>Description</description>
    ///             </listheader>
    ///             <item>
    ///                 <term>Base</term> <description>The base color scheme used for most Views.</description>
    ///             </item>
    ///             <item>
    ///                 <term>TopLevel</term>
    ///                 <description>The application Toplevel color scheme; used for the <see cref="Toplevel"/> View.</description>
    ///             </item>
    ///             <item>
    ///                 <term>Dialog</term>
    ///                 <description>
    ///                     The dialog color scheme; used for <see cref="Dialog"/>, <see cref="MessageBox"/>, and
    ///                     other views dialog-like views.
    ///                 </description>
    ///             </item>
    ///             <item>
    ///                 <term>Menu</term>
    ///                 <description>
    ///                     The menu color scheme; used for <see cref="MenuBar"/>, <see cref="ContextMenu"/>, and
    ///                     <see cref="StatusBar"/>.
    ///                 </description>
    ///             </item>
    ///             <item>
    ///                 <term>Error</term>
    ///                 <description>
    ///                     The color scheme for showing errors, such as in
    ///                     <see cref="MessageBox.ErrorQuery(string, string, string[])"/>.
    ///                 </description>
    ///             </item>
    ///         </list>
    ///     </para>
    ///     <para>Changing the values of an entry in this dictionary will affect all views that use the scheme.</para>
    ///     <para>
    ///         <see cref="ConfigurationManager"/> can be used to override the default values for these schemes and add
    ///         additional schemes. See <see cref="ConfigurationManager.Themes"/>.
    ///     </para>
    /// </remarks>
    [SerializableConfigurationProperty (Scope = typeof (ThemeScope), OmitClassName = true)]
    [JsonConverter (typeof (DictionaryJsonConverter<ColorScheme>))]
    public static Dictionary<string, ColorScheme>
        ColorSchemes { get; private set; } // Serialization requires this to have a setter (private set;)

    /// <summary>Resets the <see cref="ColorSchemes"/> dictionary to the default values.</summary>
    public static Dictionary<string, ColorScheme> Reset ()
    {
        ColorSchemes ??= new Dictionary<string, ColorScheme> (
                                                              5,
                                                              CultureInfo.InvariantCulture.CompareInfo
                                                                         .GetStringComparer (
                                                                                             CompareOptions.IgnoreCase
                                                                                            )
                                                             );
        ColorSchemes.Clear ();
        ColorSchemes.Add ("TopLevel", new ColorScheme ());
        ColorSchemes.Add ("Base", new ColorScheme ());
        ColorSchemes.Add ("Dialog", new ColorScheme ());
        ColorSchemes.Add ("Menu", new ColorScheme ());
        ColorSchemes.Add ("Error", new ColorScheme ());

        return ColorSchemes;
    }

    private class SchemeNameComparerIgnoreCase : IEqualityComparer<string>
    {
        public bool Equals (string x, string y)
        {
            if (x is { } && y is { })
            {
                return string.Equals (x, y, StringComparison.InvariantCultureIgnoreCase);
            }

            return false;
        }

        public int GetHashCode (string obj) { return obj.ToLowerInvariant ().GetHashCode (); }
    }
}