btcpayserver/BTCPayServer/Blazor/UserLoginCode.razor

@using System.Timers
@using BTCPayServer.Data
@using BTCPayServer.Fido2
@using Microsoft.AspNetCore.Http
@using Microsoft.AspNetCore.Identity
@using Microsoft.AspNetCore.Mvc
@using Microsoft.AspNetCore.Routing
@using Microsoft.Extensions.Localization
@inject AuthenticationStateProvider AuthenticationStateProvider
@inject UserManager<ApplicationUser> UserManager
@inject UserLoginCodeService UserLoginCodeService
@inject LinkGenerator LinkGenerator
@inject IHttpContextAccessor HttpContextAccessor
@inject IStringLocalizer StringLocalizer
@implements IDisposable

@if (!string.IsNullOrEmpty(_data))
{
    <div @attributes="Attrs" class="@CssClass" style="width:@(Size)px">
        <div class="qr-container mb-2">
            <QrCode Data="@_data" Size="Size"/>
        </div>
        <p class="text-center text-muted mb-1" id="progress">@StringLocalizer["Valid for {0} seconds", _seconds]</p>
        <div class="progress only-for-js" data-bs-toggle="tooltip" data-bs-placement="top">
            <div class="progress-bar progress-bar-striped progress-bar-animated @(Percent < 15 ? "bg-warning" : null)" role="progressbar" style="width:@Percent%" id="progressbar"></div>
        </div>
    </div>
}

@code {
    [Parameter]
    public string UserId { get; set; }
    
    [Parameter]
    public string RedirectUrl { get; set; }

    [Parameter]
    public int Size { get; set; } = 256;

    [Parameter(CaptureUnmatchedValues = true)]
    public Dictionary<string, object> Attrs { get; set; }

    private static readonly double Seconds = UserLoginCodeService.ExpirationTime.TotalSeconds;
    private double _seconds = Seconds;
    private string _data;
    private ApplicationUser _user;
    private Timer _timer;

    protected override async Task OnParametersSetAsync()
    {
        UserId ??= await GetUserId();
        if (!string.IsNullOrEmpty(UserId)) _user = await UserManager.FindByIdAsync(UserId);
        if (_user == null) return;

        GenerateCodeAndStartTimer();
    }

    public void Dispose()
    {
        _timer?.Dispose();
    }

    private void GenerateCodeAndStartTimer()
    {
        var loginCode = UserLoginCodeService.GetOrGenerate(_user.Id);
        _data = GetData(loginCode);
        _seconds = Seconds;
        _timer?.Dispose();
        _timer = new Timer(1000);
        _timer.Elapsed += CountDownTimer;
        _timer.Enabled = true;
    }

    private void CountDownTimer(object source, ElapsedEventArgs e)
    {
        if (_seconds > 0)
            _seconds -= 1;
        else
            GenerateCodeAndStartTimer();
        InvokeAsync(StateHasChanged);
    }

    private async Task<string> GetUserId()
    {
        var state = await AuthenticationStateProvider.GetAuthenticationStateAsync();
        return state.User.Identity?.IsAuthenticated is true
            ? UserManager.GetUserId(state.User)
            : null;
    }

    private string GetData(string loginCode)
    {
        var req = HttpContextAccessor.HttpContext?.Request;
        if (req == null) return loginCode;
        return !string.IsNullOrEmpty(RedirectUrl)
            ? LinkGenerator.LoginCodeLink(loginCode, RedirectUrl, req.Scheme, req.Host, req.PathBase)
            : $"{loginCode};{LinkGenerator.IndexLink(req.Scheme, req.Host, req.PathBase)};{_user.Email}";
    }

    private double Percent => Math.Round(_seconds / Seconds * 100);
    private string CssClass => $"user-login-code d-inline-flex flex-column {(Attrs?.ContainsKey("class") is true ? Attrs["class"] : "")}".Trim();
}