Add post and event cards, shared calendar sheet and per-event ICS; rework past events and next-event card

Elternbeirat.Web/Features/Events/EventCard.razor.cs

@@ -0,0 +1,55 @@
+using Elternbeirat.Contracts;
+using Microsoft.AspNetCore.Components;
+
+namespace Elternbeirat.Web.Features.Events;
+
+/// <summary>
+///     Renders one event as a card with a calendar sheet, time, place and note.
+/// </summary>
+/// <remarks>
+///     Shared by the events page and the home-page events embed, so both show events
+///     the same way. They differ only in what the card leads to:
+///     <list type="bullet">
+///         <item>
+///             <description>
+///                 In the embed the whole card links to the events page
+///                 (<see cref="Href"/> set).
+///             </description>
+///         </item>
+///         <item>
+///             <description>
+///                 On the events page itself a link back to the same page would lead
+///                 nowhere, so the card is no link (<see cref="Href"/> is
+///                 <see langword="null"/>) and offers "In Kalender übernehmen" instead.
+///             </description>
+///         </item>
+///     </list>
+/// </remarks>
+/// <seealso cref="CalendarSheet"/>
+/// <seealso cref="IcsCalendar"/>
+public partial class EventCard
+{
+    /// <summary>
+    ///     The event to show.
+    /// </summary>
+    [Parameter]
+    [EditorRequired]
+    public Event Value { get; set; } = null!;
+
+    /// <summary>
+    ///     Where the card links to, or <see langword="null"/> for a card that is no link
+    ///     and offers the event as a calendar file instead.
+    /// </summary>
+    [Parameter]
+    public string? Href { get; set; }
+
+    /// <summary>
+    ///     The time line beside the sheet; empty for a single all-day event.
+    /// </summary>
+    private string Span => EventDateFormat.Span(Value);
+
+    /// <summary>
+    ///     The address of this one event as a calendar file.
+    /// </summary>
+    private string IcsHref => $"/events/{Uri.EscapeDataString(Value.Id)}.ics";
+}