using System;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.CompilerServices;
using Cysharp.Threading.Tasks;
using UnityEngine;

namespace ShrinkEventBus
{
    public static class EventBus
    {
        public static event Action<EventBase, Type> OnEventTriggered;

#if UNITY_EDITOR
        public static bool EnableDebugRecord { get; set; }
        public static event Action<EventBase, string, string> OnEventTriggeredForEditor;
#endif

        private static readonly Dictionary<Type, ListenerList> EventHandlers = new();
        private static readonly HashSet<object> RegisteredInstances = new();
        private static readonly object InstanceLock = new();

        static EventBus()
        {
            EventBusRegHelper.RegStaticEventHandler();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static void EnsureAutoManagerInitialized() => EventAutoRegHelper.EnsureInitialized();

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void RegisterEvent<TEvent>(Func<TEvent, UniTask> handler, int priority = 0)
            where TEvent : EventBase
        {
            var eventPriority = PriorityHelper.ConvertToEventPriority(priority);
            RegisterEventInternal(typeof(TEvent), handler, eventPriority, priority, false,
                $"Manual Async Handler (Priority: {priority})");
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void RegisterEvent<TEvent>(Action<TEvent> handler, EventPriority priority = EventPriority.NORMAL,
            bool receiveCanceled = false) where TEvent : EventBase
        {
            RegisterEventInternal(typeof(TEvent), handler, priority, 0, receiveCanceled,
                $"Manual Sync Handler (Priority: {priority})", handler.Method);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void RegisterEvent<TEvent>(Action<TEvent> handler, int priority = 0) where TEvent : EventBase
        {
            var eventPriority = PriorityHelper.ConvertToEventPriority(priority);
            RegisterEventInternal(typeof(TEvent), handler, eventPriority, priority, false,
                $"Manual Sync Handler (Priority: {priority})", handler.Method);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void RegisterEvent<TEvent>(Func<TEvent, UniTask> handler,
            EventPriority priority = EventPriority.NORMAL, bool receiveCanceled = false) where TEvent : EventBase
        {
            RegisterEventInternal(typeof(TEvent), handler, priority, 0, receiveCanceled,
                $"Manual Async Handler (Priority: {priority})");
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static void RegisterEventInternal(Type eventType, Delegate handler, EventPriority priority,
            int numericPriority, bool receiveCanceled, string debugInfo = "", MethodInfo originalMethod = null)
        {
            lock (EventHandlers)
            {
                if (!EventHandlers.TryGetValue(eventType, out var collection))
                {
                    collection = new ListenerList();
                    EventHandlers[eventType] = collection;
                    var cacheType = typeof(EventCache<>).MakeGenericType(eventType);
                    cacheType.GetField("List", BindingFlags.Static | BindingFlags.Public)?.SetValue(null, collection);
                }

                collection.Add(handler, priority, numericPriority, receiveCanceled, debugInfo, originalMethod);
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UnregisterEvent<TEvent>(Func<TEvent, UniTask> handler) where TEvent : EventBase
        {
            var eventType = typeof(TEvent);
            lock (EventHandlers)
            {
                if (!EventHandlers.TryGetValue(eventType, out var collection)) return;
                collection.Remove(handler);
                if (collection.Count == 0)
                {
                    EventHandlers.Remove(eventType);
                    EventCache<TEvent>.List = null;
                }
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UnregisterEvent<TEvent>(Action<TEvent> handler) where TEvent : EventBase
        {
            var eventType = typeof(TEvent);
            lock (EventHandlers)
            {
                if (!EventHandlers.TryGetValue(eventType, out var collection)) return;
                collection.Remove(handler);
                if (collection.Count == 0)
                {
                    EventHandlers.Remove(eventType);
                    EventCache<TEvent>.List = null;
                }
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void ClearAllSubscribersForEvent<TEvent>() where TEvent : EventBase
        {
            var eventType = typeof(TEvent);
            lock (EventHandlers)
            {
                if (EventHandlers.Remove(eventType))
                    EventCache<TEvent>.List = null;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UnregisterAllEventsForObject(object targetObject)
        {
            if (targetObject is null) return;
            lock (EventHandlers)
            {
                var eventTypesToRemove = new List<Type>();
                foreach (var kvp in EventHandlers)
                {
                    kvp.Value.RemoveTarget(targetObject);
                    if (kvp.Value.Count == 0) eventTypesToRemove.Add(kvp.Key);
                }

                foreach (var eventType in eventTypesToRemove)
                {
                    EventHandlers.Remove(eventType);
                    var cacheType = typeof(EventCache<>).MakeGenericType(eventType);
                    cacheType.GetField("List", BindingFlags.Static | BindingFlags.Public)?.SetValue(null, null);
                }
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UnregisterInstance(object targetObject)
        {
            if (targetObject is null) return;
            lock (InstanceLock)
            {
                RegisteredInstances.Remove(targetObject);
            }

            UnregisterAllEventsForObject(targetObject);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void UnregisterAllEvents()
        {
            lock (EventHandlers)
            {
                foreach (var type in EventHandlers.Keys)
                {
                    var cacheType = typeof(EventCache<>).MakeGenericType(type);
                    cacheType.GetField("List", BindingFlags.Static | BindingFlags.Public).SetValue(null, null);
                }

                EventHandlers.Clear();
            }

            lock (InstanceLock)
            {
                RegisteredInstances.Clear();
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static bool TryPrepareHandler<TEvent>(TEvent eventArgs, EventHandlerInfo handlerInfo)
            where TEvent : EventBase
        {
            eventArgs.CurrentHandler = handlerInfo;
            eventArgs.SetPhase(handlerInfo.Priority);
            if (eventArgs.IsCancelable && eventArgs.IsCanceled && !handlerInfo.ReceiveCanceled)
                return false;
            return true;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static async UniTask<bool> TriggerEventAsync<TEvent>(TEvent eventArgs) where TEvent : EventBase
        {
            EnsureAutoManagerInitialized();
            eventArgs.PrepareForDispatch();
            var collection = EventCache<TEvent>.List;
            var handlers = collection?.GetHandlers() ?? Array.Empty<EventHandlerInfo>();
            var wasHandled = false;

            for (var i = 0; i < handlers.Length; i++)
            {
                var handlerInfo = handlers[i];
                if (!TryPrepareHandler(eventArgs, handlerInfo)) continue;

                try
                {
                    if (handlerInfo.Handler is Action<TEvent> syncHandler)
                    {
                        syncHandler(eventArgs);
                        wasHandled = true;
                    }
                    else if (handlerInfo.Handler is Func<TEvent, UniTask> asyncHandler)
                    {
                        await asyncHandler(eventArgs);
                        wasHandled = true;
                    }
                }
                catch (Exception ex)
                {
                    Debug.LogException(ex);
                    Debug.LogError($"[EventBus] Async Handler Exception: {ex.Message}");
                }
            }

            eventArgs.CurrentHandler = null;
            CompleteEventDispatch(eventArgs, typeof(TEvent), handlers);
            return wasHandled;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool TriggerEvent<TEvent>(TEvent eventArgs) where TEvent : EventBase
        {
            EnsureAutoManagerInitialized();
            eventArgs.PrepareForDispatch();
            var collection = EventCache<TEvent>.List;
            var handlers = collection?.GetHandlers() ?? Array.Empty<EventHandlerInfo>();
            var wasHandled = false;

            for (var i = 0; i < handlers.Length; i++)
            {
                var handlerInfo = handlers[i];
                if (!TryPrepareHandler(eventArgs, handlerInfo)) continue;

                try
                {
                    if (handlerInfo.Handler is Action<TEvent> syncHandler)
                    {
                        syncHandler(eventArgs);
                        wasHandled = true;
                    }
                    else if (handlerInfo.Handler is Func<TEvent, UniTask> asyncHandler)
                    {
                        var detachedEvent = EventCloneUtility.CloneForDetachedDispatch(eventArgs);
                        FireAndForgetSafe(() => asyncHandler(detachedEvent),
                            $"{handlerInfo.DisplayDeclaringType.Name}.{handlerInfo.DisplayMethodName}");
                        wasHandled = true;
                    }
                }
                catch (Exception ex)
                {
                    Debug.LogException(ex);
                    Debug.LogError($"[EventBus] Sync Handler Exception: {ex.Message}");
                }
            }

            eventArgs.CurrentHandler = null;
            CompleteEventDispatch(eventArgs, typeof(TEvent), handlers);
            return wasHandled;
        }

        private static void FireAndForgetSafe(Func<UniTask> action, string handlerName)
        {
            action().Forget(e =>
            {
                Debug.LogException(e);
                Debug.LogError($"[EventBus] Async Handler {handlerName} threw exception: {e.Message}");
            });
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static void CompleteEventDispatch(EventBase eventArgs, Type eventType, EventHandlerInfo[] handlers)
        {
            OnEventTriggered?.Invoke(eventArgs, eventType);

#if UNITY_EDITOR
            if (!EnableDebugRecord) return;
            PrepareEditorTrace(handlers, eventArgs);
            OnEventTriggeredForEditor?.Invoke(eventArgs, eventType.Name, GetSenderInfo());
#endif
        }

#if UNITY_EDITOR
        private static void PrepareEditorTrace(EventHandlerInfo[] handlers, EventBase eventArgs)
        {
            if (!EnableDebugRecord) return;
            var listenerList = eventArgs.GetListenerList();
            listenerList.Clear();
            for (var i = 0; i < handlers.Length; i++)
                listenerList.Add(handlers[i]);
        }

        private static string GetSenderInfo()
        {
            var senderInfo = "Unknown";
            try
            {
                var trace = new System.Diagnostics.StackTrace(0, false);
                for (var i = 0; i < trace.FrameCount; i++)
                {
                    var method = trace.GetFrame(i)?.GetMethod();
                    var declaringType = method?.DeclaringType;
                    if (declaringType == null) continue;
                    if (declaringType == typeof(EventBus) || declaringType.DeclaringType == typeof(EventBus)) continue;
                    var ns = declaringType.Namespace ?? "";
                    if (ns.StartsWith("System") || ns.StartsWith("Cysharp") || ns.StartsWith("UnityEngine")) continue;
                    var className = declaringType.Name;
                    var methodName = method.Name;
                    if (declaringType.DeclaringType != null && className.StartsWith("<") && className.Contains(">"))
                    {
                        className = declaringType.DeclaringType.Name;
                        var startIndex = declaringType.Name.IndexOf('<') + 1;
                        var endIndex = declaringType.Name.IndexOf('>');
                        if (startIndex > 0 && endIndex > startIndex)
                            methodName = declaringType.Name.Substring(startIndex, endIndex - startIndex);
                    }

                    return $"{className}.{methodName}()";
                }
            }
            catch
            {
            }

            return senderInfo;
        }
#endif

        public static EventHandlerInfo[] GetEventSubscribers<TEvent>() where TEvent : EventBase
        {
            var eventType = typeof(TEvent);
            lock (EventHandlers)
            {
                return EventHandlers.TryGetValue(eventType, out var collection)
                    ? collection.GetHandlers()
                    : Array.Empty<EventHandlerInfo>();
            }
        }

        public static ListenerList GetListenerList<TEvent>() where TEvent : EventBase
        {
            var eventType = typeof(TEvent);
            lock (EventHandlers)
            {
                EventHandlers.TryGetValue(eventType, out var collection);
                return collection;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void AutoRegister(object target)
        {
            if (target == null) return;
            if (IsInstanceRegistered(target)) return;
            EventBusRegHelper.RegisterEventHandlers(target);
            lock (InstanceLock)
            {
                if (!RegisteredInstances.Add(target)) return;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static bool IsInstanceRegistered(object target)
        {
            if (target == null) return false;
            lock (InstanceLock)
            {
                return RegisteredInstances.Contains(target);
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int GetRegisteredInstanceCount()
        {
            lock (InstanceLock)
            {
                return RegisteredInstances.Count;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static int GetRegisteredEventTypeCount()
        {
            lock (EventHandlers)
            {
                return EventHandlers.Count;
            }
        }
    }
}