mycroforge/MycroForge.CLI/Commands/Plugins.cs

using System.Reflection;
using MycroForge.Core.Contract;

namespace MycroForge.CLI.Commands;

public static class Plugins
{
    public static readonly string RootDirectory = Path.Join(
        Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".m4g", "plugins"
    );

    private static readonly List<ICommandPlugin> _loaded = [];
    public static IReadOnlyList<ICommandPlugin> Loaded => _loaded;

    static Plugins()
    {
        if (!Directory.Exists(RootDirectory))
        {
            Directory.CreateDirectory(RootDirectory);
        }
    }

    public static List<ICommandPlugin> Load()
    {
        if (_loaded.Count > 0) return _loaded;

        var pluginDirectories = Directory
            .GetDirectories(RootDirectory)
            .ToArray();

        foreach (var directory in pluginDirectories)
        {
            var dlls = Directory.GetFiles(directory)
                .Where(file => file.EndsWith(".dll"))
                .ToArray();

            foreach (var dll in dlls)
            {
                var assembly = Assembly.LoadFrom(dll);

                var plugin = assembly.GetTypes()
                    .Where(IsPluginType)
                    .Select(Activator.CreateInstance)
                    .Cast<ICommandPlugin>()
                    .FirstOrDefault();

                if (plugin is not null) 
                    _loaded.Add(plugin);
            }
        }

        return _loaded;
    }

    private static bool IsPluginType(Type type) =>
        type is { IsClass: true, IsAbstract: false } &&
        typeof(ICommandPlugin).IsAssignableFrom(type);
}