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
        {
            var sourcePath = File.Exists(_filePath) ? _filePath : FindLegacyPackagedState();
            if (sourcePath is null) return new TerminalState();
            var encrypted = await File.ReadAllBytesAsync(sourcePath);
            var clear = ProtectedData.Unprotect(encrypted, Entropy, DataProtectionScope.CurrentUser);
            var state = JsonSerializer.Deserialize<TerminalState>(clear, JsonOptions) ?? new TerminalState();
            if (!string.Equals(sourcePath, _filePath, StringComparison.OrdinalIgnoreCase))
            {
                await SaveAsync(state);
            }
            return state;
        }
        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);
    }

    private static string? FindLegacyPackagedState()
    {
        var packagesPath = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
            "Packages");
        if (!Directory.Exists(packagesPath)) return null;
        return Directory.EnumerateDirectories(packagesPath, "223A9635-262B-4298-9F19-1D2FE0A6B5F7_*")
            .Select(directory => Path.Combine(directory, "LocalCache", "Local", "Krona", "StaffTerminal", "terminal-state.dat"))
            .FirstOrDefault(File.Exists);
    }
}