// ============================================================================
// ResourcePreloader.cs — 资源预加载管理器
// Feature: 001-async-resource-loading
// ============================================================================

using System;
using System.Collections.Generic;
using UnityEngine;
using Cysharp.Threading.Tasks;

namespace ProjSG.Resource
{
    /// <summary>
    /// 资源预加载管理器。
    /// 按场景/流程组织预加载配置，通过 ResourceCacheManager 执行实际缓存。
    /// </summary>
    public class ResourcePreloader : Singleton<ResourcePreloader>, IResourcePreloader
    {
        private readonly Dictionary<string, PreloadConfig> _configs = new Dictionary<string, PreloadConfig>();
        private readonly HashSet<string> _loadedConfigs = new HashSet<string>();

        // ====================================================================
        // 预设配置
        // ====================================================================

        /// <summary>
        /// 注册默认预加载配置。应在 YooAsset 初始化后调用。
        /// </summary>
        public void RegisterDefaultConfigs()
        {
            // 启动必需资源（常驻）
            RegisterConfig(new PreloadConfig
            {
                ConfigName = "StartupEssential",
                Locations = new[]
                {
                    "Assets/ResourcesOut/Shader",                // Shader 全部
                    "Assets/ResourcesOut/Materials",             // 通用 Material
                    "Assets/ResourcesOut/BuiltIn/Font",          // 常用字体
                    "Assets/ResourcesOut/BuiltIn/UIRoot",        // UIRoot 预制体
                    "Assets/ResourcesOut/BuiltIn/SoundPlayer",   // 音频播放器
                },
                Tags = null,
                IsPermanent = true,
            });

            // 战斗场景资源（非常驻，战斗结束后可释放）
            RegisterConfig(new PreloadConfig
            {
                ConfigName = "BattleScene",
                Locations = null,
                Tags = new[] { "tag_battle_spine", "tag_battle_effect", "tag_battle_sound" },
                IsPermanent = false,
            });
        }

        // ====================================================================
        // IResourcePreloader 实现
        // ====================================================================

        /// <inheritdoc/>
        public void RegisterConfig(PreloadConfig config)
        {
            if (config == null || string.IsNullOrEmpty(config.ConfigName))
            {
                Debug.LogError("ResourcePreloader.RegisterConfig: config or ConfigName is null");
                return;
            }

            _configs[config.ConfigName] = config;
        }

        /// <inheritdoc/>
        public async UniTask PreloadAsync(string configName, IProgress<float> progress = null)
        {
            if (string.IsNullOrEmpty(configName))
            {
                Debug.LogError("ResourcePreloader.PreloadAsync: configName is null or empty");
                progress?.Report(1f);
                return;
            }

            if (!_configs.TryGetValue(configName, out var config))
            {
                Debug.LogWarning($"ResourcePreloader.PreloadAsync: config '{configName}' not found");
                progress?.Report(1f);
                return;
            }

            if (_loadedConfigs.Contains(configName))
            {
                progress?.Report(1f);
                return;
            }

            var cacheManager = ResourceCacheManager.Instance;
            int totalSteps = 0;
            int completedSteps = 0;

            // 计算总步骤
            if (config.Locations != null) totalSteps += config.Locations.Length;
            if (config.Tags != null) totalSteps += config.Tags.Length;

            if (totalSteps == 0)
            {
                progress?.Report(1f);
                _loadedConfigs.Add(configName);
                return;
            }

            // 加载 Locations
            if (config.Locations != null && config.Locations.Length > 0)
            {
                var locationProgress = new Progress<float>(p =>
                {
                    float locationWeight = (float)config.Locations.Length / totalSteps;
                    progress?.Report(p * locationWeight);
                });

                await cacheManager.PreloadAsync(config.Locations, config.IsPermanent, locationProgress);
                completedSteps += config.Locations.Length;
            }

            // 按 Tag 加载
            if (config.Tags != null)
            {
                foreach (var tag in config.Tags)
                {
                    await PreloadByTagAsync(tag);
                    completedSteps++;
                    progress?.Report((float)completedSteps / totalSteps);
                }
            }

            _loadedConfigs.Add(configName);
            progress?.Report(1f);
        }

        /// <inheritdoc/>
        public async UniTask PreloadByTagAsync(string tag, IProgress<float> progress = null)
        {
            if (string.IsNullOrEmpty(tag))
            {
                progress?.Report(1f);
                return;
            }

            try
            {
                // 使用 YooAssetService 按标签下载/缓存
                await YooAssetService.Instance.DownloadByTagsAsync(
                    new[] { tag },
                    progress: progress);

                progress?.Report(1f);
            }
            catch (Exception e)
            {
                Debug.LogError($"ResourcePreloader.PreloadByTagAsync failed for tag '{tag}': {e.Message}");
                progress?.Report(1f);
            }
        }

        /// <inheritdoc/>
        public void UnloadConfig(string configName)
        {
            if (string.IsNullOrEmpty(configName)) return;

            if (!_configs.TryGetValue(configName, out var config)) return;

            // 常驻配置不卸载
            if (config.IsPermanent)
            {
                Debug.LogWarning($"ResourcePreloader.UnloadConfig: config '{configName}' is permanent, skipping unload");
                return;
            }

            if (config.Locations != null)
            {
                var cacheManager = ResourceCacheManager.Instance;
                foreach (var loc in config.Locations)
                {
                    cacheManager.Release(loc);
                }
            }

            _loadedConfigs.Remove(configName);
        }

        /// <inheritdoc/>
        public bool IsConfigLoaded(string configName)
        {
            return _loadedConfigs.Contains(configName);
        }
    }
}