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

namespace Elternbeirat.Web.Tests;

/// <summary>
/// Unit tests for the calendar sheet texts and the time line beside it. Pure logic,
/// no PocketBase needed. All times are Berlin wall-clock, as the contract delivers them.
/// </summary>
public class EventDateFormatTests
{
    private static Event Event(DateTime start, DateTime? end = null) =>
        new() { Id = "test", Title = "Termin", Start = start, End = end };

    [Theory]
    [InlineData(1, "Jan")]
    [InlineData(3, "März")]
    [InlineData(5, "Mai")]
    [InlineData(10, "Okt")]
    [InlineData(12, "Dez")]
    public void Sheet_month_is_the_German_short_month_without_period(int month, string expected) =>
        EventDateFormat.SheetMonth(new DateTime(2026, month, 1)).ShouldBe(expected);

    [Fact]
    public void Sheet_day_has_no_leading_zero() =>
        EventDateFormat.SheetDay(new DateTime(2026, 10, 8, 19, 30, 0)).ShouldBe("8");

    [Theory]
    [InlineData(8, "Do")]  // Thursday, 8 October 2026
    [InlineData(11, "So")] // Sunday
    public void Sheet_weekday_is_the_German_short_weekday_without_period(int day, string expected) =>
        EventDateFormat.SheetWeekday(new DateTime(2026, 10, day)).ShouldBe(expected);

    [Fact]
    public void Past_all_day_event_shows_the_day_and_no_time()
    {
        var allDay = Event(new DateTime(2026, 11, 13));

        EventDateFormat.PastDays(allDay).ShouldBe("13. November");
        EventDateFormat.PastTime(allDay).ShouldBe("");
    }

    [Fact]
    public void Past_timed_event_shows_the_day_and_its_start_time()
    {
        var timed = Event(new DateTime(2026, 9, 1, 19, 0, 0));

        EventDateFormat.PastDays(timed).ShouldBe("1. September"); // no leading zero
        EventDateFormat.PastTime(timed).ShouldBe("19:00 Uhr");
    }

    [Fact]
    public void Past_timed_event_ending_the_same_day_shows_the_time_range()
    {
        var evening = Event(new DateTime(2026, 11, 13, 19, 0, 0), new DateTime(2026, 11, 13, 21, 0, 0));

        EventDateFormat.PastDays(evening).ShouldBe("13. November");
        EventDateFormat.PastTime(evening).ShouldBe("19:00–21:00 Uhr");
    }

    [Fact]
    public void Past_multi_day_event_in_one_month_names_the_month_once() =>
        EventDateFormat.PastDays(Event(new DateTime(2026, 2, 8), new DateTime(2026, 2, 9))).ShouldBe("8.–9. Februar");

    [Fact]
    public void Past_multi_day_event_across_a_month_names_both_months() =>
        EventDateFormat.PastDays(Event(new DateTime(2026, 1, 30), new DateTime(2026, 2, 2)))
            .ShouldBe("30. Januar – 2. Februar");

    [Fact]
    public void Past_multi_day_event_across_a_year_names_the_end_year() =>
        // The list is grouped by the start year, so only the end needs its year.
        EventDateFormat.PastDays(Event(new DateTime(2026, 12, 30), new DateTime(2027, 1, 2)))
            .ShouldBe("30. Dezember – 2. Januar 2027");

    [Fact]
    public void Past_timed_multi_day_event_shows_only_the_start_time() =>
        // A range here would read as the daily hours.
        EventDateFormat.PastTime(Event(new DateTime(2026, 2, 8, 9, 0, 0), new DateTime(2026, 2, 9, 13, 0, 0)))
            .ShouldBe("09:00 Uhr");

    [Fact]
    public void Span_of_a_timed_event_without_end_is_its_start_time() =>
        EventDateFormat.Span(Event(new DateTime(2026, 10, 8, 19, 30, 0))).ShouldBe("19:30 Uhr");

    [Fact]
    public void Span_of_a_same_day_event_is_the_time_range() =>
        EventDateFormat.Span(Event(new DateTime(2026, 10, 8, 19, 30, 0), new DateTime(2026, 10, 8, 21, 0, 0)))
            .ShouldBe("19:30–21:00 Uhr");

    [Fact]
    public void Span_of_a_multi_day_event_names_the_last_day() =>
        EventDateFormat.Span(Event(new DateTime(2026, 10, 9, 9, 0, 0), new DateTime(2026, 10, 11, 13, 0, 0)))
            .ShouldBe("09:00 Uhr bis Sonntag, 11. Oktober 2026, 13:00 Uhr");

    [Fact]
    public void Span_of_a_multi_day_all_day_event_has_no_times() =>
        EventDateFormat.Span(Event(new DateTime(2026, 10, 9), new DateTime(2026, 10, 11)))
            .ShouldBe("bis Sonntag, 11. Oktober 2026");

    [Fact]
    public void Span_of_a_single_all_day_event_is_empty() =>
        // The sheet already shows the day; there is nothing left to say.
        EventDateFormat.Span(Event(new DateTime(2026, 10, 8))).ShouldBe("");
}