SwatchesProvider.cs

using System.Collections;
using System.Globalization;
using System.Reflection;
using System.Resources;
using System.Text.RegularExpressions;
using System.Windows.Media;

namespace MaterialDesignColors;

/// <summary>
/// Provides access to all colour swatches.  For information regarding Material Design colours see https://www.google.com/design/spec/style/color.html
/// </summary>
public class SwatchesProvider
{
    private static readonly object _syncLock = new();
    /// <summary>
    /// Generates an instance reading swatches from the provided assembly, allowing 
    /// colours outside of the standard material palette to be loaded provided the are stored in the expected XAML format.
    /// </summary>
    /// <param name="assembly"></param>
    public SwatchesProvider(Assembly assembly)
    {
        string resourcesName = assembly.GetName().Name + ".g";
        var manager = new ResourceManager(resourcesName, assembly);
        var resourceSet = manager.GetResourceSet(CultureInfo.CurrentUICulture, true, true);
        var dictionaryEntries = resourceSet?.OfType<DictionaryEntry>().ToList();
        string? assemblyName = assembly.GetName().Name;

        var regex = new Regex(@"^themes\/materialdesigncolor\.(?<name>[a-z]+)\.(?<type>primary|secondary)\.baml$");

        Swatches =
            dictionaryEntries?
            .Select(x => new { key = x.Key.ToString(), match = regex.Match(x.Key.ToString() ?? "") })
            .Where(x => x.match.Success && x.match.Groups["name"].Value != "black")
            .GroupBy(x => x.match.Groups["name"].Value)
            .Select(x =>
            CreateSwatch
            (
                x.Key,
                Read(assemblyName, x.SingleOrDefault(y => y.match.Groups["type"].Value == "primary")?.key),
                Read(assemblyName, x.SingleOrDefault(y => y.match.Groups["type"].Value == "secondary")?.key)
            ))
            .ToList() ?? [];
    }

    /// <summary>
    /// Creates a new swatch provider based on standard Material Design colors.
    /// </summary>
    public SwatchesProvider() : this(Assembly.GetExecutingAssembly())
    { }

    public IEnumerable<Swatch> Swatches { get; }

    private static Swatch CreateSwatch(string name, ResourceDictionary? primaryDictionary, ResourceDictionary? secondaryDictionary)
    {
        return new Swatch(name, GetHues(primaryDictionary), GetHues(secondaryDictionary));

        static List<Hue> GetHues(ResourceDictionary? resourceDictionary)
        {
            var hues = new List<Hue>();
            if (resourceDictionary != null)
            {
                foreach (var entry in resourceDictionary.OfType<DictionaryEntry>()
                    .OrderBy(de => de.Key)
                    .Where(de => !(de.Key.ToString() ?? "").EndsWith("Foreground", StringComparison.Ordinal)))
                {

                    hues.Add(GetHue(resourceDictionary, entry));
                }
            }
            return hues;
        }

        static Hue GetHue(ResourceDictionary dictionary, DictionaryEntry entry)
        {
            if (entry.Value is not Color colour)
            {
                throw new InvalidOperationException($"Entry {entry.Key} was not of type {nameof(Color)}");
            }
            string foregroundKey = entry.Key?.ToString() + "Foreground";
            if (dictionary.OfType<DictionaryEntry>()
                    .Single(de => string.Equals(de.Key.ToString(), foregroundKey, StringComparison.Ordinal))
                    .Value is not Color foregroundColour)
            {
                throw new InvalidOperationException($"Entry {foregroundKey} was not of type {nameof(Color)}");
            }

            return new Hue(entry.Key?.ToString() ?? "", colour, foregroundColour);
        }
    }

    private static ResourceDictionary? Read(string? assemblyName, string? path)
    {
        if (assemblyName is null || path is null)
            return null;

        lock (_syncLock)
        {
            //NB: Application.LoadComponent is not thread safe
            return (ResourceDictionary)Application.LoadComponent(new Uri(
                $"/{assemblyName};component/{path.Replace(".baml", ".xaml")}",
                UriKind.RelativeOrAbsolute));
        }
    }
}