using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.U2D;
using UnityEngine.UI;
using YooAsset;

namespace HotUpdate.UI
{
    /// <summary>移植 AtlasManager 的延迟绑定；所有平台异步加载，句柄随 UI 生命周期释放。</summary>
    public sealed class UiAtlasLoader : MonoBehaviour
    {
        private sealed class Entry
        {
            public bool Loading = true;
            public SpriteAtlas Atlas;
            public AssetHandle Handle;
        }

        private readonly Dictionary<string, Entry> _atlases = new Dictionary<string, Entry>(StringComparer.Ordinal);
        private readonly Dictionary<string, Sprite> _sprites = new Dictionary<string, Sprite>(StringComparer.Ordinal);
        private readonly Dictionary<Image, object> _imageRequests = new Dictionary<Image, object>();
        private ResourcePackage _preferredPackage;
        private bool _allowEditorFallback = true;
        private bool _disposed;

        public void Init(ResourcePackage preferredPackage = null, bool allowEditorFallback = true)
        {
            _preferredPackage = preferredPackage;
            _allowEditorFallback = allowEditorFallback;
        }

        private void Awake() { SpriteAtlasManager.atlasRequested += RequestAtlas; }

        private void RequestAtlas(string atlasName, Action<SpriteAtlas> callback)
        {
            // 只接管本项目的 UI 图集，不拦截字体或第三方图集。
            if (string.IsNullOrEmpty(atlasName) || !atlasName.StartsWith(UiAtlasPaths.AtlasNamePrefix, StringComparison.Ordinal)
                || !atlasName.EndsWith("Atlas", StringComparison.Ordinal)
                || atlasName.IndexOfAny(new[] { '/', '\\' }) >= 0) return;
            StartCoroutine(LoadAtPathAsync(UiAtlasPaths.AtlasRoot + "/" + atlasName + ".spriteatlas", callback));
        }

        public IEnumerator LoadAtlasAsync(string relativeFolder, Action<SpriteAtlas> onLoaded)
        {
            return LoadAtPathAsync(UiAtlasPaths.GetAtlasPath(relativeFolder), onLoaded);
        }

        private IEnumerator LoadAtPathAsync(string path, Action<SpriteAtlas> onLoaded)
        {
            if (_disposed) { onLoaded?.Invoke(null); yield break; }
            if (_atlases.TryGetValue(path, out var cached))
            {
                while (cached.Loading && !_disposed) yield return null;
                if (!_disposed) onLoaded?.Invoke(cached.Atlas);
                yield break;
            }
            var entry = new Entry();
            _atlases.Add(path, entry);
            var packages = new List<ResourcePackage>();
            if (_preferredPackage != null) packages.Add(_preferredPackage);
            if (YooAssets.IsInitialized)
                foreach (string name in new[] { "Art", "DefaultPackage" })
                    if (YooAssets.TryGetPackage(name, out var package) && !packages.Contains(package)) packages.Add(package);
            try
            {
                foreach (var package in packages)
                {
                    if (package.InitializeStatus != EOperationStatus.Succeeded || !package.IsLocationValid(path)) continue;
                    entry.Handle = package.LoadAssetAsync<SpriteAtlas>(path);
                    yield return entry.Handle;
                    if (_disposed) yield break;
                    if (entry.Handle.Status == EOperationStatus.Succeeded)
                    {
                        entry.Atlas = entry.Handle.GetAssetObject<SpriteAtlas>();
                        if (entry.Atlas != null) break;
                    }
                    entry.Handle.Release();
                    entry.Handle = null;
                }
#if UNITY_EDITOR
                if (entry.Atlas == null && _allowEditorFallback)
                    entry.Atlas = UnityEditor.AssetDatabase.LoadAssetAtPath<SpriteAtlas>(path);
#endif
            }
            finally
            {
                entry.Loading = false;
                // 失败不留缓存，允许资源包就绪后重试。
                if (entry.Atlas == null && !_disposed)
                {
                    entry.Handle?.Release();
                    entry.Handle = null;
                    _atlases.Remove(path);
                }
            }
            if (_disposed) yield break;
            if (entry.Atlas == null) Debug.LogWarning("[UIAtlas] Atlas unavailable: " + path);
            onLoaded?.Invoke(entry.Atlas);
        }

        public IEnumerator WaitForPending()
        {
            while (!_disposed)
            {
                bool pending = false;
                foreach (var entry in _atlases.Values) pending |= entry.Loading;
                if (!pending) yield break;
                yield return null;
            }
        }

        public IEnumerator LoadSpriteAsync(string relativeFolder, string spriteName, Action<Sprite> onLoaded)
        {
            if (string.IsNullOrEmpty(spriteName) || _disposed) { onLoaded?.Invoke(null); yield break; }
            string key = UiAtlasPaths.GetAtlasPath(relativeFolder) + "|" + spriteName;
            if (_sprites.TryGetValue(key, out var sprite) && sprite != null)
            {
                onLoaded?.Invoke(sprite);
                yield break;
            }
            SpriteAtlas atlas = null;
            yield return LoadAtlasAsync(relativeFolder, loaded => atlas = loaded);
            if (_disposed) yield break;
            if (atlas != null)
            {
                // GetSprite 创建的克隆需缓存并在销毁时释放。
                if (!_sprites.TryGetValue(key, out sprite) || sprite == null)
                {
                    sprite = atlas.GetSprite(spriteName);
                    if (sprite != null) _sprites[key] = sprite;
                }
            }
            if (sprite == null) Debug.LogWarning($"[UIAtlas] Sprite unavailable: {relativeFolder}/{spriteName}");
            onLoaded?.Invoke(sprite);
        }

        public IEnumerator SetSpriteAsync(Image image, string relativeFolder, string spriteName, Action<Sprite> onLoaded = null)
        {
            if (image == null || _disposed) yield break;
            var request = new object();
            _imageRequests[image] = request;
            Sprite sprite = null;
            yield return LoadSpriteAsync(relativeFolder, spriteName, loaded => sprite = loaded);
            // 同一个 Image 后来的请求优先，旧请求不能覆盖新图片。
            if (_disposed || !_imageRequests.TryGetValue(image, out var current) || current != request) yield break;
            _imageRequests.Remove(image);
            if (image == null) yield break;
            image.sprite = sprite;
            onLoaded?.Invoke(sprite);
        }

        private void OnDestroy()
        {
            _disposed = true;
            SpriteAtlasManager.atlasRequested -= RequestAtlas;
            StopAllCoroutines();
            foreach (var sprite in _sprites.Values) if (sprite != null) Destroy(sprite);
            _sprites.Clear();
            foreach (var entry in _atlases.Values) entry.Handle?.Release();
            _atlases.Clear();
            _imageRequests.Clear();
        }
    }
}