using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.AddressableAssets.ResourceLocators;
using UnityEngine.ResourceManagement.AsyncOperations;

namespace BrewMonster.Scripts
{
    public class AddressableManager : MonoSingleton<AddressableManager>
    {
        private bool _isInitialized = false;

        private Dictionary<string, AsyncOperationHandle<GameObject>> _loadedAssets = new();
        private Dictionary<string, AsyncOperationHandle<TextAsset>> _loadedTextAssets = new();
        public event Action OnDispose;

        protected override void Initialize()
        {
            base.Initialize();
            _isInitialized = false;
            Addressables.InitializeAsync().Completed += OnInitializeComplete;
        }   

        public bool IsInitialized()
        {
            return _isInitialized;
        }

        void OnInitializeComplete(AsyncOperationHandle<IResourceLocator> handle)
        {
            if (handle.Status == AsyncOperationStatus.Succeeded)
            {
                _isInitialized = true;
                BMLogger.Log($"AddressableManager: Initialized");
            }
            else
            {
                // print out the error
                BMLogger.LogError($"AddressableManager: Failed to initialize: {handle.OperationException?.Message} {handle.OperationException?.StackTrace}");
            }
        }

        /// <summary>
        /// Load a text asset asynchronously.
        /// NOTE: The key must match the Addressables "Address" (or another valid key like a label/GUID).
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="assetPath"></param>
        /// <returns></returns>
        public async Task<TextAsset> LoadTextAssetAsync(string assetPath)
        {
            if (_loadedTextAssets.ContainsKey(assetPath))
            {
                return _loadedTextAssets[assetPath].Result;
            }
            try
            {
                var handle = Addressables.LoadAssetAsync<TextAsset>(assetPath);
                await handle.Task;
                _loadedTextAssets[assetPath] = handle;
                return handle.Result;
            }
            catch (Exception e)
            {
                BMLogger.LogError($"AddressableManager: Failed to load TextAsset '{assetPath}': {e}");
                return null;
            }
        }

        private static IEnumerable<string> GetCandidateKeys(string assetPath)
        {
            if (string.IsNullOrWhiteSpace(assetPath))
            {
                yield break;
            }

            // Exact key (what caller asked for)
            yield return assetPath;

            // Common fallback used by this repo's Addressables settings: full asset path address.
            // Example in `Assets/AddressableAssetsData/AssetGroups/configuration.asset`:
            //   m_Address: Assets/Addressable/elements.txt
            if (!assetPath.Contains("/") && !assetPath.Contains("\\"))
            {
                yield return $"Assets/Addressable/{assetPath}";
            }
        }

        private static void LogSimilarKeys(string needle)
        {
            // Helpful diagnostics in dev builds: show a few keys containing the substring.
            try
            {
                var lower = needle?.ToLowerInvariant();
                if (string.IsNullOrEmpty(lower))
                {
                    return;
                }

                const int max = 20;
                var matches = new List<string>(max);

                foreach (var locator in Addressables.ResourceLocators)
                {
                    foreach (var keyObj in locator.Keys)
                    {
                        if (keyObj is not string keyStr)
                        {
                            continue;
                        }

                        if (!keyStr.ToLowerInvariant().Contains(lower))
                        {
                            continue;
                        }

                        matches.Add(keyStr);
                        if (matches.Count >= max)
                        {
                            goto Done;
                        }
                    }
                }

            Done:
                if (matches.Count > 0)
                {
                    BMLogger.LogWarning($"AddressableManager: Similar Addressables keys for '{needle}': {string.Join(", ", matches)}");
                }
            }
            catch
            {
                // ignore diagnostics failures
            }
        }

        /// <summary>
        /// Load an asset asynchronously. The address should look like this: "models/npcs/npc/魅灵首领/魅灵首领/魅灵首领.prefab"
        /// </summary>
        /// <returns></returns>
        public async Task<GameObject> LoadPrefabAsync(string assetPath)
        {
            if (_loadedAssets.ContainsKey(assetPath))
            {
                return _loadedAssets[assetPath].Result;
            }

            try
            {
                var handle = Addressables.LoadAssetAsync<GameObject>(assetPath);
                await handle.Task;
                _loadedAssets[assetPath] = handle;
                return handle.Result;
            }
            catch (System.Exception e)
            {
                BMLogger.LogError(e.StackTrace);
                return null;
            }
        }

        /// <summary>
        /// When the asset is no longer needed, call this method to unload it.
        /// </summary>
        /// <param name="assetPath">The asset path used when loading the asset</param>
        public void ReleaseAsset(string assetPath)
        {
            if (_loadedAssets.TryGetValue(assetPath, out var handle))
            {
                if (handle.IsValid())
                {
                    Addressables.Release(handle);
                }
                _loadedAssets.Remove(assetPath);
                BMLogger.Log($"AddressableManager: Released asset: {assetPath}");
            }
            else
            {
                BMLogger.LogWarning($"AddressableManager: Asset not found in cache: {assetPath}");
            }
        }

        /// <summary>
        /// Release a specific asset by its handle directly.
        /// </summary>
        /// <param name="handle">The async operation handle to release</param>
        public void ReleaseAsset(AsyncOperationHandle<GameObject> handle)
        {
            if (handle.IsValid())
            {
                Addressables.Release(handle);
            }
        }

        /// <summary>
        /// Release all loaded assets from the cache.
        /// </summary>
        public void ReleaseAllAssets()
        {
            foreach (var kvp in _loadedAssets)
            {
                if (kvp.Value.IsValid())
                {
                    Addressables.Release(kvp.Value);
                }
            }
            _loadedAssets.Clear();
            BMLogger.Log("AddressableManager: Released all assets");
        }

        /// <summary>
        /// Check if an asset is currently loaded in the cache.
        /// </summary>
        /// <param name="assetPath">The asset path to check</param>
        /// <returns>True if the asset is loaded</returns>
        public bool IsAssetLoaded(string assetPath)
        {
            return _loadedAssets.ContainsKey(assetPath) && _loadedAssets[assetPath].IsValid();
        }

        /// <summary>
        /// Get the count of currently loaded assets.
        /// </summary>
        public int LoadedAssetCount => _loadedAssets.Count;

        private void OnDestroy()
        {
            OnDispose?.Invoke();
            ReleaseAllAssets();
        }
    }
}