Rename Style and Appearance

* Renames Style -> Decoration
* Renames Appearance -> Style
* Adds Style.Parse and Style.TryParse

src/Spectre.Console/Style.cs

@@ -0,0 +1,134 @@
+using System;
+using Spectre.Console.Internal;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// Represents color and text decoration.
+    /// </summary>
+    public sealed class Style : IEquatable<Style>
+    {
+        /// <summary>
+        /// Gets the foreground color.
+        /// </summary>
+        public Color Foreground { get; }
+
+        /// <summary>
+        /// Gets the background color.
+        /// </summary>
+        public Color Background { get; }
+
+        /// <summary>
+        /// Gets the text decoration.
+        /// </summary>
+        public Decoration Decoration { get; }
+
+        /// <summary>
+        /// Gets an <see cref="Style"/> with the
+        /// default colors and without text decoration.
+        /// </summary>
+        public static Style Plain { get; } = new Style();
+
+        private Style()
+            : this(null, null, null)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Style"/> class.
+        /// </summary>
+        /// <param name="foreground">The foreground color.</param>
+        /// <param name="background">The background color.</param>
+        /// <param name="decoration">The text decoration.</param>
+        public Style(Color? foreground = null, Color? background = null, Decoration? decoration = null)
+        {
+            Foreground = foreground ?? Color.Default;
+            Background = background ?? Color.Default;
+            Decoration = decoration ?? Decoration.None;
+        }
+
+        /// <summary>
+        /// Converts the string representation of a style to its <see cref="Style"/> equivalent.
+        /// </summary>
+        /// <param name="text">A string containing a style to parse.</param>
+        /// <returns>A <see cref="Style"/> equivalent of the text contained in <paramref name="text"/>.</returns>
+        public static Style Parse(string text)
+        {
+            return StyleParser.Parse(text);
+        }
+
+        /// <summary>
+        /// Converts the string representation of a style to its <see cref="Style"/> equivalent.
+        /// A return value indicates whether the operation succeeded.
+        /// </summary>
+        /// <param name="text">A string containing a style to parse.</param>
+        /// <param name="result">
+        /// When this method returns, contains the <see cref="Style"/> equivalent of the text contained in <paramref name="text"/>,
+        /// if the conversion succeeded, or <c>null</c> if the conversion failed.
+        /// </param>
+        /// <returns><c>true</c> if s was converted successfully; otherwise, <c>false</c>.</returns>
+        public static bool TryParse(string text, out Style result)
+        {
+            return StyleParser.TryParse(text, out result);
+        }
+
+        /// <summary>
+        /// Combines this style with another one.
+        /// </summary>
+        /// <param name="other">The item to combine with this.</param>
+        /// <returns>A new style representing a combination of this and the other one.</returns>
+        public Style Combine(Style other)
+        {
+            if (other is null)
+            {
+                throw new ArgumentNullException(nameof(other));
+            }
+
+            var foreground = Foreground;
+            if (!other.Foreground.IsDefault)
+            {
+                foreground = other.Foreground;
+            }
+
+            var background = Background;
+            if (!other.Background.IsDefault)
+            {
+                background = other.Background;
+            }
+
+            return new Style(foreground, background, Decoration | other.Decoration);
+        }
+
+        /// <inheritdoc/>
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                var hash = (int)2166136261;
+                hash = (hash * 16777619) ^ Foreground.GetHashCode();
+                hash = (hash * 16777619) ^ Background.GetHashCode();
+                hash = (hash * 16777619) ^ Decoration.GetHashCode();
+                return hash;
+            }
+        }
+
+        /// <inheritdoc/>
+        public override bool Equals(object obj)
+        {
+            return Equals(obj as Style);
+        }
+
+        /// <inheritdoc/>
+        public bool Equals(Style other)
+        {
+            if (other == null)
+            {
+                return false;
+            }
+
+            return Foreground.Equals(other.Foreground) &&
+                Background.Equals(other.Background) &&
+                Decoration == other.Decoration;
+        }
+    }
+}