using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using Voile.Common.Reflection;
using Voile.Patchouli.Data;

namespace Voile.Patchouli.Reflection
{
	public class VoilePluginManager
	{
		private VoilePluginManager() { }

		public static VoilePluginManager _instance;
		private static Type _dataStorageFactoryType = typeof(IVoileDataStorageFactory);
		private static Type _objectStorageFactoryType = typeof(IVoileObjectStorageFactory);

		public static VoilePluginManager GetInstance()
		{
			if (_instance == null)
			{
				_instance = new VoilePluginManager();
			}
			return _instance;
		}

		private List<Assembly> _loadedAssemblies;
		private List<VoilePluginInfo> _knownDataStorages;
		private List<VoilePluginInfo> _knownObjectStorages;

		public bool ScanAssembly(Assembly assembly)
		{
			if (_loadedAssemblies == null)
				_loadedAssemblies = new List<Assembly>();
			if (_loadedAssemblies.Contains(assembly))
				return false;

			bool result = false;

			Type[] types = assembly.GetTypes();
			foreach (Type t in types)
			{
				if (ScanType(t))
					result = true;
			}
			return result;
		}

		public bool ScanType(Type t)
		{

			VoilePluginAttribute? voilePluginAttribute = t.GetCustomAttribute<VoilePluginAttribute>();
			if (voilePluginAttribute == null)
				return false;

			VoilePluginIdAttribute? voilePluginIdAttribute = t.GetCustomAttribute<VoilePluginIdAttribute>();
			if (voilePluginIdAttribute == null)
				return false;

			VoilePluginInfo child = new VoilePluginInfo(t);
			child.Id = voilePluginIdAttribute.Id;

			if (t.IsAssignableTo(_dataStorageFactoryType))
			{
				if (_knownDataStorages == null)
					_knownDataStorages = new List<VoilePluginInfo>();
				child.Subsystem = VoileSubsystemType.DataStorage;
				_knownDataStorages.Add(child);
				return true;
			}
			else if (t.IsAssignableTo(_objectStorageFactoryType))
			{
				if (_knownObjectStorages == null)
					_knownObjectStorages = new List<VoilePluginInfo>();
				child.Subsystem = VoileSubsystemType.ObjectStorage;
				_knownObjectStorages.Add(child);
				return true;
			}
			else
			{
				throw new VoileReflectionException(String.Format("Could not figure out plugin type of {0}", t.Name));
			}
		}
	}
}