ppc_amnet/AMNet.Server/DllMain.cs

using System;
using System.Globalization;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text.Json;
using System.Threading;
using Windows.Win32;
using Windows.Win32.Foundation;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

namespace AMNet.Server;

public static class DllMain
{
    private const int ApiVersion = 1;
    private const string WebAddress = "http://card.ppc.moe";

    private static ILogger _serverLogger;

    private static string[] _serverAddresses;
    private static string _serverName;
    private static string _gameId;

    private static (byte[] IdBytes, string OriginalId, long Expires)? _currentCard;

    private static readonly object _cardLock = new();

    static DllMain()
    {
        PInvoke.AllocConsole();
    }

    [UnmanagedCallersOnly(EntryPoint = "aime_io_get_api_version")]
    public static ushort GetApiVersion() => 0x0100;

    [UnmanagedCallersOnly(EntryPoint = "aime_io_init")]
    public static int Init()
    {
        LoadConfiguration();

        var builder = WebServer.BuildServer();
        builder.WebHost.UseUrls(_serverAddresses);

        var app = builder.Build();

        _serverLogger = app.Logger;

        app.UseCors();
        app.MapGet("/amnet/info", () => Results.Ok(new SystemState(ApiVersion, _gameId, _serverName)));
        app.MapPost("/amnet/signin", async ctx =>
        {
            CardReadRequest request;

            try
            {
                request = await ctx.Request.ReadFromJsonAsync<CardReadRequest>();
            }
            catch (JsonException e)
            {
                ctx.Response.StatusCode = 400;
                await ctx.Response.WriteAsync(e.Message);

                return;
            }

            if (string.IsNullOrEmpty(request?.MatrixCode))
            {
                ctx.Response.StatusCode = 400;
                await ctx.Response.WriteAsync("Card id not provided.");
                return;
            }

            if (request.MatrixCode.Length is 0 or < 20)
            {
                ctx.Response.StatusCode = 422;
                await ctx.Response.WriteAsync("Invalid card id length.");
                return;
            }

            if (request.MatrixCode.Any(x => !char.IsNumber(x)))
            {
                ctx.Response.StatusCode = 422;
                await ctx.Response.WriteAsync("Invalid card id format.");
                return;
            }

            lock (_cardLock)
            {
                // ratelimit check
                if (_currentCard?.Expires > Environment.TickCount64)
                {
                    ctx.Response.StatusCode = 429;
                    ctx.Response.Headers.RetryAfter = ((int)TimeSpan.FromMilliseconds(_currentCard.Value.Expires - Environment.TickCount64).TotalSeconds).ToString();
                    return;
                }

                // ensure the matrix code is 20-digits long, otherwise pad with zeros
                var matrixCode = request.MatrixCode.PadLeft(20, '0');
                var bytes = new byte[10];

                for (var i = 0; i < 10; i++)
                {
                    var value = matrixCode.Substring(i * 2, 2);
                    bytes[i] = byte.Parse(value, NumberStyles.HexNumber);
                }

                // it's called a tick count, but it uses milliseconds despite having a unit of time called a tick???
                _currentCard = (bytes, matrixCode, Environment.TickCount64 + 5000);
            }

            ctx.Response.StatusCode = 202;
        });

        CancellationTokenRegistration cancellationRegistration = default;
        cancellationRegistration = app.Lifetime.ApplicationStarted.Register(() =>
        {
            _serverLogger.LogInformation("AMNet Server ({gameId}) started successfully.", _gameId);
            _serverLogger.LogInformation("Visit {addr} from a mobile device on the same network to get started.", WebAddress);

            cancellationRegistration.Dispose();
        });

        app.RunAsync();
        return 0;
    }

    [UnmanagedCallersOnly(EntryPoint = "aime_io_nfc_poll")]
    public static int NfcPoll(byte unitNo)
    {
        if (_currentCard.HasValue && _currentCard.Value.Expires < Environment.TickCount64)
        {
            lock (_cardLock)
            {
                _currentCard = null;
            }
        }

        // there's no polling here (handled by the webserver)
        return 0;
    }

    [UnmanagedCallersOnly(EntryPoint = "aime_io_nfc_get_aime_id")]
    public static int GetAimeId(byte unitNo, nint luid, nint luidSize)
    {
        lock (_cardLock)
        {
            if (unitNo != 0 || _currentCard == null)
            {
                return 1;
            }

            if (_currentCard.Value.Expires < Environment.TickCount64)
            {
                _serverLogger.LogWarning("Submitted card id expired before it could be read.");
                _currentCard = null;

                return 1;
            }

            Marshal.Copy(_currentCard.Value.IdBytes, 0, luid, (int)luidSize);

            _serverLogger.LogInformation("Card read in: {0}", string.Join(" ", Enumerable.Range(0, 5).Select(x => _currentCard.Value.OriginalId.Substring(x * 4, 4))));
            _currentCard = null;
        }

        return 0;
    }

    [UnmanagedCallersOnly(EntryPoint = "aime_io_nfc_get_felica_id")]
    public static unsafe int GetFelicaId(byte unitNo, ulong* idm)
    {
        // felica not supported
        return 1;
    }

    [UnmanagedCallersOnly(EntryPoint = "aime_io_led_set_color")]
    public static void SetLedColour(byte unitNo, byte r, byte g, byte b)
    {
        // do nothing
    }

    private static unsafe void LoadConfiguration()
    {
        const string configFileName = @".\segatools.ini";

        var gameId = stackalloc char[5];
        var gameIdStr = new PWSTR(gameId);

        var serverName = stackalloc char[64];
        var serverNameStr = new PWSTR(serverName);

        var serverAddress = stackalloc char[1024];
        var serverAddressStr = new PWSTR(serverAddress);

        PInvoke.GetPrivateProfileString("aimeio", "gameId", string.Empty, gameIdStr, 5, configFileName);
        PInvoke.GetPrivateProfileString("aimeio", "serverName", Environment.MachineName, serverNameStr, 64, configFileName);
        PInvoke.GetPrivateProfileString("aimeio", "serverAddress", "http://+:6070", serverAddressStr, 1024, configFileName);

        _gameId = gameIdStr.ToString();
        _serverName = serverNameStr.ToString();
        _serverAddresses = serverAddressStr.ToString().Split(';');
    }
}