using System.IO;
using System.Security.Cryptography;
using System.Text;
using System.Text.Json;

namespace UtopiaCanteenSystem.Services;

/// <summary>
/// Simple JSON-backed configuration stored alongside the app binaries.
/// </summary>
public class ConfigService : IConfigService
{
    private readonly string _configPath;
    private AppConfig _config;

    public ConfigService()
    {
        _configPath = Path.Combine(AppContext.BaseDirectory, "appsettings.json");
        _config = LoadConfig();
    }

    public string GetSyncApiEndpoint() => _config.SyncApiEndpoint ?? string.Empty;

    public void SetSyncApiEndpoint(string endpoint)
    {
        _config.SyncApiEndpoint = endpoint ?? string.Empty;
        SaveConfig();
    }

    public bool GetScannerConnected() => _config.ScannerConnected;

    public void SetScannerConnected(bool connected)
    {
        _config.ScannerConnected = connected;
        SaveConfig();
    }

    public int GetScanTimeoutSeconds() => _config.ScanTimeoutSeconds;

    public void SetScanTimeoutSeconds(int seconds)
    {
        _config.ScanTimeoutSeconds = seconds;
        SaveConfig();
    }

    public string GetAdminCardId() => _config.AdminCardId ?? string.Empty;

    public void SetAdminCardId(string cardId)
    {
        _config.AdminCardId = cardId ?? string.Empty;
        SaveConfig();
    }

    public bool GetRememberAdminCredentials() => _config.RememberAdminCredentials;

    public void SetRememberAdminCredentials(bool remember)
    {
        _config.RememberAdminCredentials = remember;
        SaveConfig();
    }

    public string GetSavedAdminUsername() => _config.SavedAdminUsername ?? string.Empty;

    public void SetSavedAdminUsername(string username)
    {
        _config.SavedAdminUsername = username ?? string.Empty;
        SaveConfig();
    }

    public string GetSavedAdminPassword()
    {
        if (!_config.RememberAdminCredentials)
            return string.Empty;

        var protectedValue = _config.SavedAdminPasswordProtected ?? string.Empty;
        if (string.IsNullOrWhiteSpace(protectedValue))
            return string.Empty;

        try
        {
            var bytes = Convert.FromBase64String(protectedValue);
            var clear = ProtectedData.Unprotect(bytes, null, DataProtectionScope.CurrentUser);
            return Encoding.UTF8.GetString(clear);
        }
        catch
        {
            return string.Empty;
        }
    }

    public void SetSavedAdminPassword(string password)
    {
        if (!_config.RememberAdminCredentials)
        {
            _config.SavedAdminPasswordProtected = string.Empty;
            SaveConfig();
            return;
        }

        try
        {
            var clear = Encoding.UTF8.GetBytes(password ?? string.Empty);
            var protectedBytes = ProtectedData.Protect(clear, null, DataProtectionScope.CurrentUser);
            _config.SavedAdminPasswordProtected = Convert.ToBase64String(protectedBytes);
        }
        catch
        {
            _config.SavedAdminPasswordProtected = string.Empty;
        }

        SaveConfig();
    }

    private AppConfig LoadConfig()
    {
        try
        {
            if (!File.Exists(_configPath))
            {
                var defaults = new AppConfig();
                SaveConfig(defaults);
                return defaults;
            }

            var json = File.ReadAllText(_configPath);
            var config = JsonSerializer.Deserialize<AppConfig>(json);
            return config ?? new AppConfig();
        }
        catch
        {
            return new AppConfig();
        }
    }

    private void SaveConfig()
    {
        SaveConfig(_config);
    }

    private void SaveConfig(AppConfig config)
    {
        try
        {
            var json = JsonSerializer.Serialize(config, new JsonSerializerOptions
            {
                WriteIndented = true
            });
            File.WriteAllText(_configPath, json);
        }
        catch
        {
            // Ignore write failures (e.g., read-only location).
        }
    }

    private sealed class AppConfig
    {
        public string SyncApiEndpoint { get; set; } = "https://api.example.com/uind/sync";
        public bool ScannerConnected { get; set; } = false;
        public int ScanTimeoutSeconds { get; set; } = 60;
        public string AdminCardId { get; set; } = "ADMIN";

        // Admin credential persistence (optional).
        public bool RememberAdminCredentials { get; set; } = false;
        public string SavedAdminUsername { get; set; } = string.Empty;
        public string SavedAdminPasswordProtected { get; set; } = string.Empty;
    }
}