using System.Security.Cryptography;
using System.Text.Json;
using KronaStaffTerminal.Models;

namespace KronaStaffTerminal.Services;

public sealed class TerminalStore
{
    private static readonly byte[] Entropy = "Krona.Staff.Terminal.v1"u8.ToArray();
    private static readonly JsonSerializerOptions JsonOptions = new() { WriteIndented = true };
    private readonly string _filePath = Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
        "Krona",
        "StaffTerminal",
        "terminal-state.dat");

    public async Task<TerminalState> LoadAsync()
    {
        try
        {
            if (!File.Exists(_filePath)) return new TerminalState();
            var encrypted = await File.ReadAllBytesAsync(_filePath);
            var clear = ProtectedData.Unprotect(encrypted, Entropy, DataProtectionScope.CurrentUser);
            return JsonSerializer.Deserialize<TerminalState>(clear, JsonOptions) ?? new TerminalState();
        }
        catch
        {
            return new TerminalState();
        }
    }

    public async Task SaveAsync(TerminalState state)
    {
        var directory = Path.GetDirectoryName(_filePath)!;
        Directory.CreateDirectory(directory);
        var clear = JsonSerializer.SerializeToUtf8Bytes(state, JsonOptions);
        var encrypted = ProtectedData.Protect(clear, Entropy, DataProtectionScope.CurrentUser);
        var temporaryPath = _filePath + ".tmp";
        await File.WriteAllBytesAsync(temporaryPath, encrypted);
        File.Move(temporaryPath, _filePath, true);
    }
}