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

namespace AibisDream.SaveSystem.CloudSave
{
    /// <summary>
    /// 云存档协调器：负责选择当前平台的 backend，并在槽位写入/读取后触发同步钩子。
    /// <para>
    /// P2 不实现真实云同步逻辑，仅保留扩展点。
    /// </para>
    /// </summary>
    public static class CloudSaveManager
    {
        private static readonly List<ICloudSaveBackend> Backends = new();

        /// <summary>注册一个云存档后端。应在游戏启动时调用一次。</summary>
        public static void RegisterBackend(ICloudSaveBackend backend)
        {
            if (backend == null)
            {
                return;
            }

            Backends.Add(backend);
        }

        /// <summary>清空已注册后端（主要用于测试）。</summary>
        public static void ClearBackends()
        {
            Backends.Clear();
        }

        /// <summary>槽位写入后调用：触发所有可用后端的异步上传。</summary>
        public static void OnSlotWritten(int slotIndex)
        {
            _ = UploadSlotAsync(slotIndex);
        }

        /// <summary>槽位读取前调用：可触发下载（P2 默认不自动下载，避免覆盖本地进度）。</summary>
        public static void OnSlotRestored(int slotIndex)
        {
            // P2 占位：未来可在此触发冲突检测与下载。
        }

        /// <summary>手动触发指定槽位的云同步上传。</summary>
        public static async Task UploadSlotAsync(int slotIndex)
        {
            var filePaths = CollectSlotFilePaths(slotIndex);
            if (filePaths.Count == 0)
            {
                return;
            }

            foreach (var backend in Backends)
            {
                if (!backend.IsAvailable)
                {
                    continue;
                }

                try
                {
                    await backend.UploadSlotAsync(slotIndex, filePaths.ToArray());
                    Debug.Log($"[CloudSaveManager] {backend.PlatformName} 上传槽位 {slotIndex} 完成。");
                }
                catch (Exception ex)
                {
                    Debug.LogWarning($"[CloudSaveManager] {backend.PlatformName} 上传槽位 {slotIndex} 失败: {ex.Message}");
                }
            }
        }

        /// <summary>收集槽位下需要同步的文件路径。</summary>
        private static List<string> CollectSlotFilePaths(int slotIndex)
        {
            var paths = new List<string>();

            var snapshotPath = SlotDirectory.GetSnapshotPath(slotIndex);
            if (File.Exists(snapshotPath))
            {
                paths.Add(snapshotPath);
            }

            var metaPath = SlotDirectory.GetMetaPath(slotIndex);
            if (File.Exists(metaPath))
            {
                paths.Add(metaPath);
            }

            var thumbnailPath = SlotDirectory.GetThumbnailPath(slotIndex);
            if (File.Exists(thumbnailPath))
            {
                paths.Add(thumbnailPath);
            }

            return paths;
        }
    }
}