LANCommander/LANCommander.Launcher/UI/Pages/Authenticate/Components/ServerSelector.razor

@using LANCommander.Launcher.Models
@using LANCommander.SDK.Models
@using ListItem = AntDesign.ListItem
@namespace LANCommander.Launcher.UI
@implements IDisposable
@inject IConnectionClient ConnectionClient
@inject BeaconClient BeaconClient
@inject NavigationManager NavigationManager
@inject AuthenticationService AuthenticationService
@inject LocalizationService LocalizationService

<PageHeader>
    <TitleTemplate>
        @LocalizationService.GetString("Connect")
    </TitleTemplate>
</PageHeader>

<Form Model="Model" OnFinish="() => SelectServer(ServerAddress)">

    @if (OfflineModeAvailable)
    {
        <Alert Message="@LocalizationService.GetString("ServerOfflineMessage")" Type="AlertType.Warning" ShowIcon="true" Style="margin-bottom: 16px;" />
    }

    <FormItem>
        <Flex Gap="FlexGap.Small">
            <Input @bind-Value="ServerAddress" Placeholder="@LocalizationService.GetString("ServerAddressPlaceholder")" AutoFocus Disabled="Connecting" />
            <Button Type="ButtonType.Primary" HtmlType="submit" Disabled="Connecting" Loading="Connecting">@LocalizationService.GetString("Connect")</Button>

            @if (OfflineModeAvailable)
            {
                <Button OnClick="() => OfflineMode()">@LocalizationService.GetString("Offline")</Button>
            }
        </Flex>
    </FormItem>
</Form>

<Divider Text="@LocalizationService.GetString("Discovered")" Orientation="DividerOrientation.Center" />

<AntList DataSource="DiscoveredServers">
    <ChildContent>
        <ListItem OnClick="() => SelectServer(context.Address)">
            <ListItemMeta Title="@context.Name" Description="@context.Address.ToString()"/>
        </ListItem>
    </ChildContent>

    <LoadMore>
        <Flex Justify="FlexJustify.Center" Class="load-more">
            @if (BeaconActive)
            {
                <Dropdown Trigger="@(new [] { Trigger.Hover })">
                    <Overlay>
                        <Menu>
                            <MenuItem Key="Cancel" OnClick="CancelBeacon">@LocalizationService.GetString("Cancel")</MenuItem>
                        </Menu>
                    </Overlay>
                    <ChildContent>
                        <Button Type="ButtonType.Primary" Loading="true" Disabled>@LocalizationService.GetString("Scanning")</Button>
                    </ChildContent>
                </Dropdown>
            }
            else
            {
                <Button Type="ButtonType.Primary" OnClick="() => ActivateBeacon()">@LocalizationService.GetString("Rescan")</Button>
            }
        </Flex>
    </LoadMore>
</AntList>

@code {
    [Parameter] public EventCallback<Uri> OnSelected { get; set; }
    [Parameter] public bool Connecting { get; set; } = false;
    bool IsInitializing = false;

    bool BeaconActive = false;
    bool OfflineModeAvailable = false;

    Uri ServerAddress;

    AuthRequest Model = new();
    List<DiscoveredServer> DiscoveredServers = new();
    private CancellationTokenSource DiscoveryToken = new CancellationTokenSource();

    protected override async Task OnInitializedAsync()
    {
        IsInitializing = true;

        ServerAddress = ConnectionClient.GetServerAddress();

        Connecting = true;
        OfflineModeAvailable = await AuthenticationService.OfflineModeAvailableAsync();

        BeaconClient.OnBeaconResponse += OnBeaconResponse;

        if (!OfflineModeAvailable)
        {
            ActivateBeacon();
        }

        Connecting = false;
        IsInitializing = false;
    }

    private void OnBeaconResponse(object sender, BeaconResponseArgs e)
    {
        var discoveredServer = new DiscoveredServer(e.Message, e.EndPoint);

        if (DiscoveredServers.All(s => s.Address != discoveredServer.Address))
        {
            DiscoveredServers.Add(discoveredServer);
            InvokeAsync(StateHasChanged);
        }
    }

    async Task SelectServer(Uri serverAddress)
    {
        await BeaconClient.StopProbeAsync();

        BeaconActive = false;

        if (OnSelected.HasDelegate)
            await OnSelected.InvokeAsync(serverAddress);
    }

    void OfflineMode()
    {
        AuthenticationService.LoginOffline();
        NavigationManager.NavigateTo("/", forceLoad: true);
    }

    void CancelBeacon()
    {
        DiscoveryToken?.Cancel();
    }

    async Task ActivateBeacon()
    {
        try
        {
            BeaconActive = true;
            await InvokeAsync(StateHasChanged);

            // give the UI a chance to render:
            await Task.Yield();

            if ((DiscoveryToken?.TryReset() ?? false) == false)
            {
                DiscoveryToken = new();
            }

            await BeaconClient.StartProbeAsync(cancellationToken: DiscoveryToken.Token);
            await Task.Delay(10000, DiscoveryToken.Token);
            await BeaconClient.StopProbeAsync();
        }
        catch (OperationCanceledException)
        {
            // ignore, handled in finally
        }
        finally
        {
            BeaconClient.CleanupProbe();
            BeaconActive = false;
            await InvokeAsync(StateHasChanged);
        }
    }

    public void Dispose()
    {
        BeaconClient.OnBeaconResponse -= OnBeaconResponse;
        DiscoveryToken?.Cancel();
        DiscoveryToken?.Dispose();
    }
}