using System.Text.Json;
using LehrerApp.Sync.Crypto;

namespace LehrerApp.Desktop.Services;

internal sealed class AnnualPlanSettingsConfig
{
    public bool Enabled { get; set; }
    public string? EncryptedIcalUrl { get; set; }
    public DateTime? LastSyncAt { get; set; }
    public string LastSyncStatus { get; set; } = "";
}

/// <summary>
/// Gerätebezogene Einstellungen für den externen Schuljahresplan. Der eingebettete Feed-Schlüssel
/// wird wie die WebUntis-URL verschlüsselt in einer separaten Datei gespeichert.
/// </summary>
public sealed class AnnualPlanSettingsService
{
    private readonly string _configPath;
    private readonly byte[] _urlKey;
    private AnnualPlanSettingsConfig _config;

    public bool Enabled => _config.Enabled;
    public bool IsConfigured => _config.EncryptedIcalUrl is not null;
    public DateTime? LastSyncAt => _config.LastSyncAt;
    public string LastSyncStatus => _config.LastSyncStatus;

    public AnnualPlanSettingsService(string appDataPath)
    {
        _configPath = Path.Combine(appDataPath, "annual-plan-settings.json");
        var keyPath = Path.Combine(appDataPath, "annual-plan-url.key");
        _urlKey = SyncCrypto.LoadKey(keyPath) ?? GenerateAndSaveKey(keyPath);
        _config = Load();
    }

    public void SetIcalUrl(string url)
    {
        _config.EncryptedIcalUrl = SyncCrypto.EncryptObject(url, _urlKey);
        Save();
    }

    public string? GetIcalUrl() => _config.EncryptedIcalUrl is null
        ? null
        : SyncCrypto.DecryptObject<string>(_config.EncryptedIcalUrl, _urlKey);

    public void SetEnabled(bool enabled)
    {
        _config.Enabled = enabled;
        Save();
    }

    public void ClearIcalUrl()
    {
        _config.EncryptedIcalUrl = null;
        _config.Enabled = false;
        Save();
    }

    public void SetLastSync(DateTime at, string status)
    {
        _config.LastSyncAt = at;
        _config.LastSyncStatus = status;
        Save();
    }

    private byte[] GenerateAndSaveKey(string keyPath)
    {
        var key = SyncCrypto.GenerateKey();
        SyncCrypto.SaveKey(key, keyPath);
        return key;
    }

    private AnnualPlanSettingsConfig Load()
    {
        try
        {
            if (File.Exists(_configPath))
                return JsonSerializer.Deserialize<AnnualPlanSettingsConfig>(File.ReadAllText(_configPath))
                       ?? new AnnualPlanSettingsConfig();
        }
        catch { /* beschädigte lokale Konfiguration -> Standardwerte */ }
        return new AnnualPlanSettingsConfig();
    }

    private void Save() => File.WriteAllText(_configPath, JsonSerializer.Serialize(_config));
}