using GFramework.Core.logging;
using GFramework.Core.system;

namespace GFramework.Core.ioc;

/// <summary>
///     IOC容器类，用于管理对象的注册和获取
/// </summary>
public class IocContainer
{
    #region Core

    /// <summary>
    /// 存储所有已注册对象实例的集合，用于跟踪和管理容器中的所有对象
    /// 使用HashSet确保对象唯一性，避免重复注册同一实例
    /// </summary>
    private readonly HashSet<object> _objects = [];

    /// <summary>
    /// 类型索引字典，用于快速查找指定类型的所有实例
    /// 键为类型对象，值为该类型对应的所有实例集合
    /// </summary>
    private readonly Dictionary<Type, HashSet<object>> _typeIndex = new();

    #endregion

    #region Lock

    /// <summary>
    /// 读写锁对象，用于控制多线程环境下对共享资源的访问
    /// 使用ReaderWriterLockSlim提供高效的读写锁定机制
    /// 配置为不支持递归锁，避免死锁风险
    /// </summary>
    private readonly ReaderWriterLockSlim _lock = new(LockRecursionPolicy.NoRecursion);

    #endregion

    #region Flag

    /// <summary>
    /// 冻结标志位，用于标识对象是否已被冻结
    /// true表示对象已冻结，不可修改；false表示对象可正常修改
    /// </summary>
    private volatile bool _frozen;

    #endregion


    #region Register

    /// <summary>
    /// 注册单例
    /// 一个类型只允许一个实例
    /// </summary>
    /// <typeparam name="T">要注册为单例的类型</typeparam>
    /// <param name="instance">要注册的单例实例</param>
    /// <exception cref="InvalidOperationException">当该类型已经注册过单例时抛出异常</exception>
    public void RegisterSingleton<T>(T instance)
    {
        var type = typeof(T);
        var logger = Log.CreateLogger("IOC");

        _lock.EnterWriteLock();
        try
        {
            if (_frozen)
            {
                var errorMsg = "IocContainer is frozen";
                logger.Error(errorMsg);
                throw new InvalidOperationException(errorMsg);
            }

            if (_typeIndex.TryGetValue(type, out var set) && set.Count > 0)
            {
                var errorMsg = $"Singleton already registered for type: {type.Name}";
                logger.Error(errorMsg);
                throw new InvalidOperationException(errorMsg);
            }

            RegisterInternal(type, instance!);
            logger.Debug($"Singleton registered: {type.Name}");
        }
        finally
        {
            _lock.ExitWriteLock();
        }
    }


    /// <summary>
    /// 注册一个实例及其所有可赋值的接口类型到容器中
    /// </summary>
    /// <typeparam name="T">实例的类型</typeparam>
    /// <param name="instance">要注册的实例对象，不能为null</param>
    public void RegisterPlurality<T>(T instance)
    {
        var concreteType = instance!.GetType();
        var logger = Log.CreateLogger("IOC");
        
        // 获取实例类型直接实现的所有接口，并筛选出可以赋值给T类型的接口
        var interfaces = concreteType.GetInterfaces()
            .Where(typeof(T).IsAssignableFrom);

        _lock.EnterWriteLock();
        try
        {
            // 注册具体类型
            RegisterInternal(concreteType, instance);
            logger.Debug($"Registered concrete type: {concreteType.Name}");

            // 注册所有匹配的接口类型
            foreach (var itf in interfaces)
            {
                RegisterInternal(itf, instance);
                logger.Debug($"Registered interface: {itf.Name} for {concreteType.Name}");
            }
        }
        finally
        {
            _lock.ExitWriteLock();
        }
    }

    /// <summary>
    /// 在内部字典中注册指定类型和实例的映射关系
    /// </summary>
    /// <param name="type">要注册的类型</param>
    /// <param name="instance">要注册的实例</param>
    private void RegisterInternal(Type type, object instance)
    {
        if (_frozen)
        {
            var errorMsg = "IocContainer is frozen";
            Log.CreateLogger("IOC").Error(errorMsg);
            throw new InvalidOperationException(errorMsg);
        }

        _objects.Add(instance);

        if (!_typeIndex.TryGetValue(type, out var set))
        {
            set = [];
            _typeIndex[type] = set;
        }

        set.Add(instance);
    }


    /// <summary>
    /// 注册系统实例，将其绑定到其所有实现的接口上
    /// </summary>
    /// <param name="system">系统实例对象</param>
    public void RegisterSystem(ISystem system)
    {
        RegisterPlurality(system);
    }


    /// <summary>
    /// 注册指定类型的实例到容器中
    /// </summary>
    /// <typeparam name="T">要注册的实例类型</typeparam>
    /// <param name="instance">要注册的实例对象，不能为null</param>
    public void Register<T>(T instance)
    {
        // 获取写锁以确保线程安全
        _lock.EnterWriteLock();
        try
        {
            RegisterInternal(typeof(T), instance!);
        }
        finally
        {
            // 释放写锁
            _lock.ExitWriteLock();
        }
    }

    /// <summary>
    /// 注册指定类型的实例到容器中
    /// </summary>
    /// <param name="type">要注册的实例类型</param>
    /// <param name="instance">要注册的实例对象</param>
    public void Register(Type type, object instance)
    {
        // 获取写锁以确保线程安全
        _lock.EnterWriteLock();
        try
        {
            RegisterInternal(type, instance);
        }
        finally
        {
            // 释放写锁
            _lock.ExitWriteLock();
        }
    }

    #endregion

    #region Get

    /// <summary>
    /// 获取单个实例（通常用于具体类型）
    /// 如果存在多个，只返回第一个
    /// </summary>
    /// <typeparam name="T">期望获取的实例类型</typeparam>
    /// <returns>找到的第一个实例；如果未找到则返回 null</returns>
    public T? Get<T>() where T : class
    {
        var logger = Log.CreateLogger("IOC");
        
        _lock.EnterReadLock();
        try
        {
            if (_typeIndex.TryGetValue(typeof(T), out var set) && set.Count > 0)
            {
                var result = set.First() as T;
                logger.Debug($"Retrieved instance: {typeof(T).Name}");
                return result;
            }

            logger.Debug($"No instance found for type: {typeof(T).Name}");
            return null;
        }
        finally
        {
            _lock.ExitReadLock();
        }
    }


    /// <summary>
    /// 获取指定类型的必需实例
    /// </summary>
    /// <typeparam name="T">期望获取的实例类型</typeparam>
    /// <returns>找到的唯一实例</returns>
    /// <exception cref="InvalidOperationException">当没有注册实例或注册了多个实例时抛出</exception>
    public T GetRequired<T>() where T : class
    {
        var logger = Log.CreateLogger("IOC");
        var list = GetAll<T>();

        switch (list.Count)
        {
            case 0:
                var notFoundMsg = $"No instance registered for {typeof(T).Name}";
                logger.Error(notFoundMsg);
                throw new InvalidOperationException(notFoundMsg);

            case 1:
                logger.Debug($"Retrieved required instance: {typeof(T).Name}");
                return list[0];

            default:
                var multipleMsg = $"Multiple instances registered for {typeof(T).Name}";
                logger.Error(multipleMsg);
                throw new InvalidOperationException(multipleMsg);
        }
    }

    /// <summary>
    /// 获取指定类型的所有实例（接口 / 抽象类推荐使用）
    /// </summary>
    /// <typeparam name="T">期望获取的实例类型</typeparam>
    /// <returns>所有符合条件的实例列表；如果没有则返回空数组</returns>
    public IReadOnlyList<T> GetAll<T>() where T : class
    {
        _lock.EnterReadLock();
        try
        {
            return _typeIndex.TryGetValue(typeof(T), out var set)
                ? set.Cast<T>().ToList() // 快照
                : Array.Empty<T>();
        }
        finally
        {
            _lock.ExitReadLock();
        }
    }


    /// <summary>
    /// 获取并排序（系统调度专用）
    /// </summary>
    /// <typeparam name="T">期望获取的实例类型</typeparam>
    /// <param name="comparison">比较器委托，定义排序规则</param>
    /// <returns>按指定方式排序后的实例列表</returns>
    public IReadOnlyList<T> GetAllSorted<T>(Comparison<T> comparison)
        where T : class
    {
        var list = GetAll<T>().ToList();
        list.Sort(comparison);
        return list;
    }

    #endregion

    #region Utility

    /// <summary>
    /// 检查容器中是否包含指定类型的实例
    /// </summary>
    /// <typeparam name="T">要检查的类型</typeparam>
    /// <returns>如果容器中包含指定类型的实例则返回true，否则返回false</returns>
    public bool Contains<T>()
    {
        _lock.EnterReadLock();
        try
        {
            return _typeIndex.TryGetValue(typeof(T), out var set) && set.Count > 0;
        }
        finally
        {
            _lock.ExitReadLock();
        }
    }

    /// <summary>
    /// 清空容器中的所有实例
    /// </summary>
    public void Clear()
    {
        _lock.EnterWriteLock();
        try
        {
            _objects.Clear();
            _typeIndex.Clear();
        }
        finally
        {
            _lock.ExitWriteLock();
        }
    }

    /// <summary>
    /// 判断容器中是否包含某个具体的实例对象
    /// </summary>
    /// <param name="instance">待查询的实例对象</param>
    /// <returns>若容器中包含该实例则返回true，否则返回false</returns>
    public bool ContainsInstance(object instance)
    {
        _lock.EnterReadLock();
        try
        {
            return _objects.Contains(instance);
        }
        finally
        {
            _lock.ExitReadLock();
        }
    }


    /// <summary>
    /// 冻结容器，防止后续修改
    /// </summary>
    public void Freeze()
    {
        var logger = Log.CreateLogger("IOC");
        
        // 获取写锁以确保线程安全的状态修改
        _lock.EnterWriteLock();
        try
        {
            _frozen = true;
            logger.Info("IOC Container frozen - no further registrations allowed");
        }
        finally
        {
            _lock.ExitWriteLock();
        }
    }

    #endregion
}