Inbox with undo

@inject ToastService Toasts
@inject NavigationManager Navigation

<ToastRegion />

<Card Title="Inbox" Description="@($"{Shown.Count} conversations")" Grow MaxWidth="40.Rem">
    <CardBody Flush>
        @if (Shown.Count == 0)
        {
            <EmptyState Icon="Lucide.Inbox" Title="All caught up" Description="Archived conversations stay in Archive for 30 days." Size="ControlSize.Sm" />
        }
        else
        {
            <form method="post" @formname="inbox" @onsubmit="Archive" data-enhance>
                <AntiforgeryToken />
                @foreach (var message in Shown)
                {
                    <Row Gap="3" Align="Align.Center" PaddingX="4" PaddingY="3" BorderTop="1">
                        <Avatar Name="@message.From" Decorative />
                        <Stack Gap="0" Grow MinWidth="0.Rem">
                            <TextBlock Weight="FontWeight.Medium" Truncate>@message.From</TextBlock>
                            <TextBlock Size="TextSize.Sm" Color="Color.Muted" Truncate>@message.Subject</TextBlock>
                        </Stack>
                        @* On phones the button is the icon alone, which keeps "Archive" as its name. *@
                        <Button Submit Name="archive" Value="@message.Id" OnClick="() => _clicked = message.Id" VisibleFrom="Breakpoint.Sm"
                                Size="ControlSize.Sm" Variant="ButtonVariant.Ghost" Accent="Accent.Neutral" StartIcon="Lucide.Archive">Archive</Button>
                        <IconButton Submit Name="archive" Value="@message.Id" OnClick="() => _clicked = message.Id" HiddenFrom="Breakpoint.Sm" Shrink="false"
                                    Size="ControlSize.Sm" Variant="ButtonVariant.Ghost" Accent="Accent.Neutral" Icon="Lucide.Archive" Label="Archive" />
                    </Row>
                }
            </form>
        }
    </CardBody>
</Card>

@code {
    // Static pages: the archived ids live in the address (?archived=…), so each page load knows them.
    [SupplyParameterFromQuery(Name = "archived")]
    private string[]? ArchivedQuery { get; set; }

    // The pressed button's Name=Value posts with the form.
    [SupplyParameterFromForm(FormName = "inbox", Name = "archive")]
    private string? Posted { get; set; }

    // Interactive pages post nothing, so OnClick says which button it was.
    private string? _clicked;
    private HashSet<string> _archived = [];

    private List<Conversation> Shown => Conversations.Where(c => !_archived.Contains(c.Id)).ToList();

    protected override void OnParametersSet() => _archived = [.. ArchivedQuery ?? []];

    private void Archive()
    {
        var conversation = Conversations.FirstOrDefault(c => c.Id == (Posted ?? _clicked));
        if (conversation is null)
        {
            return;
        }

        var undo = UrlWith(_archived.Where(id => id != conversation.Id));
        _archived.Add(conversation.Id);
        Toasts.Info($"Archived \"{conversation.Subject}\".", action: new("Undo", Href: undo)
        {
            OnClick = () =>
            {
                _archived.Remove(conversation.Id);
                StateHasChanged();
                return Task.CompletedTask;
            },
        });

        // A static post redirects to the new address, and the toast follows it.
        if (!RendererInfo.IsInteractive)
        {
            Navigation.NavigateTo(UrlWith(_archived));
        }
    }

    private string UrlWith(IEnumerable<string> archived) =>
        Navigation.GetUriWithQueryParameters(new Dictionary<string, object?> { ["archived"] = archived.ToArray() });

}