using System.Reflection;
using System.Runtime.Loader;
using IdentityShroud.PluginSupport;

namespace IdentityShroud.Core.Plugins;

public static class PluginLoader
{
    public static IEnumerable<IPlugin> LoadPlugins(string pluginsFolder)
    {
        if (!Directory.Exists(pluginsFolder))
            yield break;

        foreach (var dll in Directory.EnumerateFiles(pluginsFolder, "*.dll"))
        {
            foreach (var plugin in LoadPluginDll(dll)) yield return plugin;
        }
    }

    private static IEnumerable<IPlugin> LoadPluginDll(string dll)
    {
        Assembly asm;
        try
        {
            asm = AssemblyLoadContext.Default.LoadFromAssemblyPath(Path.GetFullPath(dll));
        }
        catch
        {
            yield break;
        }

        IEnumerable<Type> pluginTypes;
        try
        {
            pluginTypes = asm.GetTypes()
                .Where(t => typeof(IPlugin).IsAssignableFrom(t) && t is { IsInterface: false, IsAbstract: false });
        }
        catch
        {
            yield break;
        }

        foreach (var t in pluginTypes)
        {
            IPlugin? instance = null;
            try
            {
                instance = (IPlugin?)Activator.CreateInstance(t);
            }
            catch
            {
                // ignore bad plugin types
            }

            if (instance != null)
                yield return instance;
        }
    }
}