using System.Reflection;
using System.Runtime.Loader;
using ZymonicGateway.Contracts;
using ZymonicGateway.Options;

namespace ZymonicGateway.Services;

public class ZymonicGatewayPluginCatalog
{
    private readonly List<IZymonicGatewayPlugin> _plugins = new();

    public IReadOnlyList<IZymonicGatewayPlugin> Plugins => _plugins;

    public void Register(IZymonicGatewayPlugin plugin)
    {
        _plugins.Add(plugin);
    }

    public void LoadFromOptions(ZymonicGatewayOptions options, ILogger logger)
    {
        foreach (var assemblyPath in GetAssemblyPaths(options).Distinct(StringComparer.OrdinalIgnoreCase))
        {
            try
            {
                var assembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(assemblyPath);
                RegisterPluginsFromAssembly(assembly, logger);
            }
            catch (Exception ex)
            {
                logger.LogError(ex, "Failed to load ZymonicGateway plugin assembly {AssemblyPath}", assemblyPath);
            }
        }
    }

    private void RegisterPluginsFromAssembly(Assembly assembly, ILogger logger)
    {
        foreach (var pluginType in GetLoadableTypes(assembly)
            .Where(type => !type.IsAbstract && typeof(IZymonicGatewayPlugin).IsAssignableFrom(type)))
        {
            if (Activator.CreateInstance(pluginType) is IZymonicGatewayPlugin plugin)
            {
                Register(plugin);
                logger.LogInformation("Loaded ZymonicGateway plugin {PluginName} from {AssemblyName}", plugin.Name, assembly.GetName().Name);
            }
        }
    }

    private static IEnumerable<Type> GetLoadableTypes(Assembly assembly)
    {
        try
        {
            return assembly.GetTypes();
        }
        catch (ReflectionTypeLoadException ex)
        {
            return ex.Types.OfType<Type>();
        }
    }

    private static IEnumerable<string> GetAssemblyPaths(ZymonicGatewayOptions options)
    {
        foreach (var assemblyPath in options.PluginAssemblies.Where(path => !string.IsNullOrWhiteSpace(path)))
        {
            yield return Path.GetFullPath(assemblyPath);
        }

        var pluginDirectory = Path.GetFullPath(options.PluginDirectory);
        if (!Directory.Exists(pluginDirectory))
        {
            yield break;
        }

        foreach (var assemblyPath in Directory.EnumerateFiles(pluginDirectory, "*.dll", SearchOption.TopDirectoryOnly))
        {
            yield return assemblyPath;
        }
    }
}