using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using UnityEditor;
using UnityEngine;
using Object = UnityEngine.Object;

namespace LanLib.Singleton.EditorUtilities
{
    static class SingletonManager
    {
        private static Dictionary<Type, SingletonCreateCondition> _lutSingletonCreation = null;

        static void DestroyGameObject(GameObject go)
        {
            if (Application.isPlaying)
            {
                Object.Destroy(go);
            }
            else
            {
                Object.DestroyImmediate(go);
            }
        }

        static void RemoveAllSingletons(Func<SingletonBase, bool> predicate)
        {
            if (Selection.activeGameObject?.GetComponent<SingletonBase>())
            {
                Selection.activeGameObject = null;
            }

            var instances = Resources
                .FindObjectsOfTypeAll<SingletonBase>()
                .Where(predicate)
                .ToArray();
            foreach (var inst in instances)
            {
                DestroyGameObject(inst.gameObject);
            }
        }

        static Dictionary<Type, SingletonCreateCondition> GetSingletonTypes()
        {
            if (_lutSingletonCreation != null) return _lutSingletonCreation;
            var baseType = typeof(SingletonAutoLoadAttribute);
            var thisAssemblyName = baseType.Assembly.GetName().ToString();
            return _lutSingletonCreation = AppDomain.CurrentDomain.GetAssemblies()
                .Where(assembly
                    => assembly.GetReferencedAssemblies().Any(r => r.ToString() == thisAssemblyName)
                       && assembly.GetName().ToString() != thisAssemblyName)
                .SelectMany(assembly
                    => assembly.GetCustomAttributes(false).OfType<SingletonAutoLoadAttribute>())
                .Select(att => (att.type, att.createCondition))
                .ToDictionary(d => d.type, d => d.createCondition);
        }

        [InitializeOnLoadMethod]
#if !UNITY_EDITOR
        [RuntimeInitializeOnLoadMethod]
#endif
        static void AutoCreateOnDomainReload()
        {
            foreach (var (t, con) in GetSingletonTypes())
            {
                if (con.Contains(SingletonCreateCondition.ReloadDomain))
                {
                    t.BaseType.GetProperty("Instance", bindingFlags).GetValue(null);
                }
            }
        }

        [InitializeOnLoadMethod]
        static void AutoCreateOnEnterPlayMode()
        {
            EditorApplication.playModeStateChanged += e =>
            {
                if (e == PlayModeStateChange.EnteredPlayMode)
                {
                    foreach (var (t, con) in GetSingletonTypes())
                    {
                        if (con.Contains(SingletonCreateCondition.EnterPlay))
                        {
                            t.BaseType.GetProperty("Instance", bindingFlags).GetValue(null);
                        }
                    }
                }
            };
        }

        [InitializeOnLoadMethod]
        static void CleanOnRecompileIfNeeded()
        {
            RemoveAllSingletons(inst => inst.shouldDestroyOnReloadDomain());
        }

        [InitializeOnLoadMethod]
        static void CleanOnPlayModeChangeIfNeeded()
        {
            EditorApplication.playModeStateChanged += e =>
            {
                if (e == PlayModeStateChange.ExitingPlayMode)
                {
                    RemoveAllSingletons(inst => inst.shouldDestroyOnExitPlayMode());
                }
                else if (e == PlayModeStateChange.ExitingEditMode)
                {
                    RemoveAllSingletons(inst => inst.shouldDestroyOnExitEditMode());
                }
                else if (e == PlayModeStateChange.EnteredPlayMode)
                {
                    var instances = Resources
                        .FindObjectsOfTypeAll<SingletonBase>()
                        .ToArray();
                    foreach (var inst in instances)
                    {
                        inst.DestroyOnSceneUnload = inst.DestroyOnSceneUnload;
                    }
                }
            };
        }


        static bool shouldDestroyOnReloadDomain(this SingletonBase singleton)
        {
            var t = singleton.GetType();
            var isAutoCreate = GetSingletonTypes().ContainsKey(t)
                               && GetSingletonTypes()[t].Contains(SingletonCreateCondition.ReloadDomain);
            return singleton.DestroyCondition.Contains(SingletonDestroyCondition.ReloadDomain)
                   && !isAutoCreate;
        }

        static bool shouldDestroyOnExitPlayMode(this SingletonBase singleton)
            => singleton.DestroyCondition.Contains(SingletonDestroyCondition.ExitPlay);

        static bool shouldDestroyOnExitEditMode(this SingletonBase singleton)
            => singleton.DestroyCondition.Contains(SingletonDestroyCondition.ExitEdit);

        static BindingFlags bindingFlags = 0
                                           | BindingFlags.Static
                                           // | BindingFlags.Instance
                                           | BindingFlags.Public
            // | BindingFlags.NonPublic
            ;
    }
}