using System.Text.Json;

namespace MSCO.Server;

/// <summary>
/// Prüft Steam-Anmeldetickets der Spieler über die Steam Web API
/// (ISteamUserAuth/AuthenticateUserTicket), sofern in server.json ein Key eingetragen ist.
/// Ohne Key wird nur geprüft, dass der Client eine Steam-ID und ein Ticket mitschickt.
/// </summary>
public sealed class SteamVerifier
{
    const int MySummerCarAppId = 516750;

    readonly HttpClient http = new() { Timeout = TimeSpan.FromSeconds(10) };
    readonly string apiKey;

    public bool Enabled => !string.IsNullOrWhiteSpace(apiKey);

    public SteamVerifier(string apiKey)
    {
        this.apiKey = apiKey;
    }

    /// <summary>Gibt null zurück, wenn alles passt, sonst den Ablehnungsgrund.</summary>
    public async Task<string> VerifyAsync(ulong claimedSteamId, byte[] ticket, bool requireSteam)
    {
        bool hasSteam = claimedSteamId != 0 && ticket != null && ticket.Length > 0;
        if (!hasSteam) return requireSteam ? "Steam is required to join this server" : null; // Non-Steam-Server
        if (!Enabled) return null;

        string url = "https://api.steampowered.com/ISteamUserAuth/AuthenticateUserTicket/v1/?key=" + apiKey +
                     "&appid=" + MySummerCarAppId + "&ticket=" + Convert.ToHexString(ticket);
        try
        {
            // Frisch erzeugte Tickets sind manchmal erst nach einem Moment gültig
            for (int attempt = 0; attempt < 3; attempt++)
            {
                using var doc = JsonDocument.Parse(await http.GetStringAsync(url));
                var response = doc.RootElement.GetProperty("response");
                if (response.TryGetProperty("params", out var p))
                {
                    string steamId = p.GetProperty("steamid").GetString();
                    if (steamId != claimedSteamId.ToString()) return "Steam ticket does not match your account";
                    if (p.TryGetProperty("vacbanned", out var vac) && vac.GetBoolean()) return "VAC banned";
                    return null;
                }
                await Task.Delay(1000);
            }
            return "Steam could not verify your ticket";
        }
        catch (Exception e)
        {
            Console.WriteLine("[steam] verification failed: " + e.Message);
            return "Steam verification failed, try again";
        }
    }
}