using Elternbeirat.Contracts;
using Elternbeirat.Web.Features.Events;
using Elternbeirat.Web.Shared;

namespace Elternbeirat.Web.Tests;

/// <summary>
/// Unit tests for the "what is coming up?" rule and the Berlin day behind it. Pure
/// logic, no PocketBase needed.
/// </summary>
public class UpcomingEventsTests
{
    private static Event Event(string title, DateTime start) =>
        new() { Id = "test", Title = title, Start = start };

    [Fact]
    public void Keeps_today_and_later_ordered_by_start()
    {
        var events = new[]
        {
            Event("Basar", new DateTime(2026, 11, 22, 9, 0, 0)),
            Event("Gestern", new DateTime(2026, 9, 30, 19, 30, 0)),
            Event("Heute früh", new DateTime(2026, 10, 1, 7, 0, 0)), // already begun, still today
            Event("Sitzung", new DateTime(2026, 10, 8, 19, 30, 0)),
        };

        var upcoming = UpcomingEvents.From(events, new DateOnly(2026, 10, 1));

        upcoming.Select(@event => @event.Title).ShouldBe(["Heute früh", "Sitzung", "Basar"]);
    }

    [Fact]
    public void Nothing_upcoming_gives_an_empty_list() =>
        UpcomingEvents.From([Event("Vorbei", new DateTime(2026, 1, 1))], new DateOnly(2026, 10, 1))
            .ShouldBeEmpty();

    [Fact]
    public void Berlin_day_starts_before_the_UTC_day()
    {
        // 22:30 UTC on 30 September is 00:30 on 1 October in Berlin (summer time).
        var time = new FixedTimeProvider(new DateTimeOffset(2026, 9, 30, 22, 30, 0, TimeSpan.Zero));

        BerlinClock.Today(time).ShouldBe(new DateOnly(2026, 10, 1));
    }
}