using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using UnityEngine;

public static class LocalRecoveryMirror
{
    private const string RecoveryDirectoryName = ".save_recovery";

    public static void SaveJson<T>(string slotKey, T data)
    {
        if (string.IsNullOrWhiteSpace(slotKey) || (!typeof(T).IsValueType && (object)data == null))
        {
            return;
        }

        try
        {
            string json = JsonUtility.ToJson(data, false);
            SaveRaw(slotKey, json);
        }
        catch (Exception ex)
        {
            Debug.LogWarning($"[LocalRecoveryMirror] SaveJson failed ({slotKey}): {ex.Message}");
        }
    }

    public static bool TryLoadJson<T>(string slotKey, out T data)
    {
        data = default(T);
        if (string.IsNullOrWhiteSpace(slotKey))
        {
            return false;
        }

        string json;
        if (!TryLoadRaw(slotKey, out json) || string.IsNullOrWhiteSpace(json))
        {
            return false;
        }

        try
        {
            data = JsonUtility.FromJson<T>(json);
            if (typeof(T).IsValueType)
            {
                return true;
            }

            return (object)data != null;
        }
        catch (Exception ex)
        {
            Debug.LogWarning($"[LocalRecoveryMirror] TryLoadJson failed ({slotKey}): {ex.Message}");
            data = default(T);
            return false;
        }
    }

    public static void SaveRaw(string slotKey, string json)
    {
        if (string.IsNullOrWhiteSpace(slotKey) || json == null)
        {
            return;
        }

        try
        {
            string path = GetCanonicalPath(slotKey);
            string directory = Path.GetDirectoryName(path);
            if (!string.IsNullOrWhiteSpace(directory))
            {
                Directory.CreateDirectory(directory);
            }

            string backupPath = path + ".bak";
            string tempPath = path + ".tmp";
            File.WriteAllText(tempPath, json, Encoding.UTF8);
            if (File.Exists(path))
            {
                File.Copy(path, backupPath, true);
            }

            File.Copy(tempPath, path, true);
            File.Delete(tempPath);
        }
        catch (Exception ex)
        {
            Debug.LogWarning($"[LocalRecoveryMirror] SaveRaw failed ({slotKey}): {ex.Message}");
        }
    }

    public static bool TryLoadRaw(string slotKey, out string json)
    {
        json = null;
        if (string.IsNullOrWhiteSpace(slotKey))
        {
            return false;
        }

        IReadOnlyList<string> candidates = GetVariantPaths(slotKey);
        for (int i = 0; i < candidates.Count; i++)
        {
            string path = candidates[i];
            if (string.IsNullOrWhiteSpace(path) || !File.Exists(path))
            {
                continue;
            }

            try
            {
                string loaded = File.ReadAllText(path, Encoding.UTF8);
                if (string.IsNullOrWhiteSpace(loaded))
                {
                    continue;
                }

                json = loaded;
                return true;
            }
            catch (Exception ex)
            {
                Debug.LogWarning($"[LocalRecoveryMirror] TryLoadRaw failed ({path}): {ex.Message}");
            }
        }

        return false;
    }

    public static bool HasSlotData(string slotKey)
    {
        if (string.IsNullOrWhiteSpace(slotKey))
        {
            return false;
        }

        IReadOnlyList<string> candidates = GetVariantPaths(slotKey);
        for (int i = 0; i < candidates.Count; i++)
        {
            string path = candidates[i];
            if (!string.IsNullOrWhiteSpace(path) && File.Exists(path))
            {
                return true;
            }
        }

        return false;
    }

    public static void DeleteSlot(string slotKey)
    {
        if (string.IsNullOrWhiteSpace(slotKey))
        {
            return;
        }

        IReadOnlyList<string> candidates = GetVariantPaths(slotKey);
        for (int i = 0; i < candidates.Count; i++)
        {
            string path = candidates[i];
            if (string.IsNullOrWhiteSpace(path) || !File.Exists(path))
            {
                continue;
            }

            try
            {
                File.Delete(path);
            }
            catch (Exception ex)
            {
                Debug.LogWarning($"[LocalRecoveryMirror] DeleteSlot failed ({path}): {ex.Message}");
            }
        }
    }

    private static string GetCanonicalPath(string slotKey)
    {
        string fileName = BuildFileName(slotKey);
        return Path.Combine(SaveIdentityUtility.GetCanonicalPersistentRoot(), RecoveryDirectoryName, fileName);
    }

    private static IReadOnlyList<string> GetVariantPaths(string slotKey)
    {
        var result = new List<string>();
        string fileName = BuildFileName(slotKey);
        string backupFileName = fileName + ".bak";
        IReadOnlyList<string> roots = SaveIdentityUtility.GetPersistentRootVariants();
        for (int i = 0; i < roots.Count; i++)
        {
            string root = roots[i];
            if (string.IsNullOrWhiteSpace(root))
            {
                continue;
            }

            AddDistinct(result, Path.Combine(root, RecoveryDirectoryName, fileName));
            AddDistinct(result, Path.Combine(root, RecoveryDirectoryName, backupFileName));
        }

        return result;
    }

    private static string BuildFileName(string slotKey)
    {
        return slotKey.Trim().Replace('/', '_').Replace('\\', '_').Replace(':', '_') + ".json";
    }

    private static void AddDistinct(List<string> target, string value)
    {
        if (target == null || string.IsNullOrWhiteSpace(value))
        {
            return;
        }

        for (int i = 0; i < target.Count; i++)
        {
            if (string.Equals(target[i], value, StringComparison.OrdinalIgnoreCase))
            {
                return;
            }
        }

        target.Add(value);
    }
}