using MAX.Core.DependencyInjection;
using MAX.Core.Interfaces;
using MAX.Framework.Commons;
using MAX.Framework.Dtos;
using MAX.Framework.Interfaces;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System.Diagnostics;
using System.Reflection;

namespace MAX.Framework.DependencyInjection
{
	/// <summary>
	/// IOC 注册入口（由宿主 Program.cs 调用）
	/// </summary>
	public static class ServiceCollectionExtensions
	{
		private static readonly Type[] DependencyMarkers =
		[
			typeof(ISingletonDependency),
			typeof(IScopedDependency),
			typeof(ITransientDependency),
		];

		/// <summary>
		/// 兼容入口：只有服务集合，没有配置与环境（模块拿到的 <see cref="ModuleContext.Configuration"/> 是空配置）。
		/// 新代码请用 <c>builder.AddStoreHub()</c>。
		/// </summary>
		public static IServiceCollection AddStoreHub(this IServiceCollection services)
		{
			return services.AddStoreHub(null, null);
		}

		/// <summary>
		/// 带配置的注册入口：<c>builder.Services.AddStoreHub(builder.Configuration)</c>
		/// </summary>
		public static IServiceCollection AddStoreHub(this IServiceCollection services, IConfiguration? configuration)
		{
			return services.AddStoreHub(configuration, null);
		}

		/// <summary>
		/// 注册应用服务：
		/// <list type="number">
		/// <item>自动注册所有实现 <see cref="ISingletonDependency"/> / <see cref="IScopedDependency"/> / <see cref="ITransientDependency"/> 的类型；</item>
		/// <item>发现所有 <see cref="IStartup"/>，按 <see cref="IStartup.Priority"/> 降序执行 Initialize + Register；</item>
		/// <item>发现所有 <see cref="IModule"/>，按 <see cref="IModule.Priority"/> 降序执行 <see cref="IModule.AddModule"/>，
		/// 并把模块实例登记进容器，留给 <c>app.UseStoreHubModules()</c> 执行管道阶段。</item>
		/// </list>
		/// </summary>
		public static IServiceCollection AddStoreHub(this IServiceCollection services, IConfiguration? configuration, IHostEnvironment? environment)
		{
			IEnumerable<Assembly> assemblies = GetApplicationAssemblies();

			// 同一个类可能同时实现 IStartup 与 IModule，这里缓存实例，保证两个阶段拿到的是同一个对象
			Dictionary<Type, object> instances = [];

			RegisterDependencyMarkers(services, assemblies);
			RunStartups(services, assemblies, instances);

			ModuleContext context = new(
				services,
				new ServiceRegistrarProxy(services),
				configuration ?? new ConfigurationBuilder().Build(),
				environment);

			// 注册表必须在 Build() 之前进容器，UseStoreHubModules() 才拿得到
			services.AddSingleton(RunModules(assemblies, instances, context));


			services.AddControllers(options =>
			{
				options.Filters.Add<GlobalExceptionFilter>();
				options.Filters.Add<UnifyResultFilter>();
			}).ConfigureApiBehaviorOptions(options =>
			{
				options.InvalidModelStateResponseFactory = context =>
				{
					// 取出所有校验错误信息，拼成一个字符串（或者只取第一个）
					var errors = context.ModelState
						.Where(e => e.Value?.Errors.Count > 0)
						.SelectMany(e => e.Value!.Errors.Select(err => err.ErrorMessage))
						.ToList();

					var msg = string.Join("; ", errors);

					var result = ApiResult.Fail(msg, ResultCode.ValidationError);

					return new ObjectResult(result)
					{
						StatusCode = 200 // 和其他接口保持一致，用Code表达失败，而不是HTTP 400
					};
				};

			});
			return services;
		}

		/// <summary>
		/// 自动注册标记接口（ISingletonDependency / IScopedDependency / ITransientDependency）的实现类型
		/// </summary>
		private static void RegisterDependencyMarkers(IServiceCollection services, IEnumerable<Assembly> assemblies)
		{
			foreach (Type type in GetConcreteTypes(assemblies))
			{
				Debug.WriteLine(type.Namespace);
				Type? marker = DependencyMarkers.FirstOrDefault(m => m.IsAssignableFrom(type));
				if (marker is null)
				{
					continue;
				}

				ServiceLifetime lifetime = marker == typeof(ISingletonDependency) ? ServiceLifetime.Singleton
					: marker == typeof(IScopedDependency) ? ServiceLifetime.Scoped
					: ServiceLifetime.Transient;

				// 注册为自身
				services.Add(new ServiceDescriptor(type, type, lifetime));

				// 注册为实现的接口（排除标记接口与系统接口）
				foreach (Type iface in type.GetInterfaces())
				{
					if (DependencyMarkers.Contains(iface) || IsSystemInterface(iface))
					{
						continue;
					}

					services.Add(new ServiceDescriptor(iface, type, lifetime));
				}
			}
		}

		/// <summary>
		/// 发现所有 <see cref="IStartup"/> 实现，按 <see cref="IStartup.Priority"/> 降序执行
		/// </summary>
		private static void RunStartups(IServiceCollection services, IEnumerable<Assembly> assemblies, IDictionary<Type, object> instances)
		{
			IServiceRegistrar registrar = new ServiceRegistrarProxy(services);

			foreach (IStartup startup in CreateInstances<IStartup>(assemblies, instances).OrderByDescending(s => s.Priority))
			{
				startup.Initialize();
				startup.Register(registrar);
			}
		}

		/// <summary>
		/// 发现所有 <see cref="IModule"/> 实现，按 <see cref="IModule.Priority"/> 降序执行服务注册阶段
		/// </summary>
		private static ModuleRegistry RunModules(IEnumerable<Assembly> assemblies, IDictionary<Type, object> instances, ModuleContext context)
		{
			List<IModule> modules = [.. CreateInstances<IModule>(assemblies, instances).OrderByDescending(m => m.Priority)];

			foreach (IModule module in modules)
			{
				try
				{
					module.AddModule(context);
				}
				catch (Exception ex)
				{
					// 带上模块名，避免只看到一个没有上下文的异常
					throw new InvalidOperationException($"模块 {module.GetType().FullName} 的 AddModule 执行失败。", ex);
				}
			}

			return new ModuleRegistry(modules);
		}

		/// <summary>
		/// 反射创建（或复用）所有实现 <typeparamref name="T"/> 的具体类型实例
		/// </summary>
		private static IEnumerable<T> CreateInstances<T>(IEnumerable<Assembly> assemblies, IDictionary<Type, object> instances) where T : class
		{
			foreach (Type type in GetConcreteTypes(assemblies).Where(t => typeof(T).IsAssignableFrom(t)))
			{
				if (!instances.TryGetValue(type, out object? instance))
				{
					instance = Activator.CreateInstance(type, true)
						?? throw new InvalidOperationException($"无法创建 {type.FullName} 的实例（需要有参数量为 0 的构造函数）。");
					instances[type] = instance;
				}

				yield return (T)instance;
			}
		}

		private static IEnumerable<Type> GetConcreteTypes(IEnumerable<Assembly> assemblies)
		{
			return assemblies
				.SelectMany(SafeGetTypes)
				.Where(t => t.IsClass && !t.IsAbstract && !t.IsGenericTypeDefinition);
		}

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

		private static IEnumerable<Assembly> GetApplicationAssemblies()
		{
			// 使用 AppTypeFinder：扫描应用输出目录 + 已加载程序集，
			return StoreHubAppTypeFinder.Current.GetAssemblies();
		}

		private static bool IsSystemInterface(Type type)
		{
			return type.Namespace is null
				|| type.Namespace.StartsWith("System", StringComparison.Ordinal)
				|| type.Namespace.StartsWith("Microsoft", StringComparison.Ordinal);
		}

	}
}