using System.IO;
using AibisDream.Utility;
using Newtonsoft.Json;
using UnityEngine;

namespace AibisDream.SaveSystem
{
    /// <summary>
    /// 快照与磁盘的边界：序列化和读写 JSON 文件。
    /// <para>
    /// P2 起，业务存档统一通过 <see cref="SlotManager"/> 写入槽位目录；
    /// 本类保留按路径读写的低级接口，供迁移和外部调试使用。
    /// </para>
    /// </summary>
    public static class SnapshotPersistence
    {
        private static readonly JsonSerializerSettings Settings = new()
        {
            TypeNameHandling = TypeNameHandling.None,
            ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
            NullValueHandling = NullValueHandling.Ignore
        };

        /// <summary>P1 自测落盘：<c>SnapshotTestPath/latest_snapshot.json</c>（P2 迁移源）。</summary>
        public static string GetTestFilePath()
        {
            return Path.Combine(ConstRef.SnapshotTestPath, ConstRef.SnapshotTestFileName);
        }

        /// <summary>将快照序列化并写入指定槽位。</summary>
        public static void SaveToSlot(int slotIndex, SaveSnapshot snapshot)
        {
            SlotManager.SaveToSlot(slotIndex, snapshot, null);
        }

        /// <summary>从指定槽位读取快照。</summary>
        public static SaveSnapshot LoadFromSlot(int slotIndex)
        {
            return SlotManager.LoadSnapshot(slotIndex);
        }

        /// <summary>将快照序列化为 JSON 字符串（紧凑格式）。</summary>
        public static string Serialize(SaveSnapshot snapshot)
        {
            return JsonConvert.SerializeObject(snapshot, Formatting.None, Settings);
        }

        /// <summary>从 JSON 字符串反序列化为快照。</summary>
        public static SaveSnapshot Deserialize(string json)
        {
            var snapshot = JsonConvert.DeserializeObject<SaveSnapshot>(json, Settings);
            if (snapshot != null && snapshot.schemaVersion != SaveSnapshotSchema.CurrentVersion)
            {
                Debug.LogWarning(
                    $"[SnapshotPersistence] schemaVersion {snapshot.schemaVersion} != {SaveSnapshotSchema.CurrentVersion}，按当前结构读取。");
            }

            return snapshot;
        }

        /// <summary>将快照序列化并写入 path（自动补 .json 后缀）。</summary>
        public static void Save(SaveSnapshot snapshot, string pathWithoutExtension)
        {
            var json = Serialize(snapshot);
            var path = JsonUtil.FormatAsJsonPath(pathWithoutExtension);
            var dir = Path.GetDirectoryName(path);
            if (!string.IsNullOrEmpty(dir))
            {
                Directory.CreateDirectory(dir);
            }

            File.WriteAllText(path, json);
        }

        /// <summary>从 path 读取并反序列化为 <see cref="SaveSnapshot"/>。</summary>
        public static SaveSnapshot Load(string pathWithoutExtension)
        {
            var json = File.ReadAllText(JsonUtil.FormatAsJsonPath(pathWithoutExtension));
            return Deserialize(json);
        }

    }
}