using TheLivingWorld.Core.Simulation;

namespace TheLivingWorld.Tests;

public sealed class GameTimeTests
{
    [Fact]
    public void Advance_at_x1_adds_five_game_minutes_per_real_second()
    {
        var start = GameTime.DefaultStart;
        var next = GameTime.Advance(start, TimeSpan.FromSeconds(1), timeScale: 1, paused: false);

        Assert.Equal(start.AddMinutes(5), next);
    }

    [Fact]
    public void Advance_scales_with_time_scale()
    {
        var start = GameTime.DefaultStart;

        Assert.Equal(start.AddMinutes(10), GameTime.Advance(start, TimeSpan.FromSeconds(1), 2, false));
        Assert.Equal(start.AddMinutes(20), GameTime.Advance(start, TimeSpan.FromSeconds(1), 4, false));
    }

    [Fact]
    public void Advance_does_nothing_when_paused_or_non_positive()
    {
        var start = GameTime.DefaultStart;

        Assert.Equal(start, GameTime.Advance(start, TimeSpan.FromSeconds(10), 4, paused: true));
        Assert.Equal(start, GameTime.Advance(start, TimeSpan.Zero, 1, paused: false));
        Assert.Equal(start, GameTime.Advance(start, TimeSpan.FromSeconds(-1), 1, paused: false));
    }

    [Fact]
    public void Advance_handles_a_large_wall_clock_gap()
    {
        var start = GameTime.DefaultStart;
        // One real hour at x1 → 5 * 3600 = 18_000 game minutes = 12.5 game days.
        var next = GameTime.Advance(start, TimeSpan.FromHours(1), timeScale: 1, paused: false);

        Assert.Equal(start.AddMinutes(5 * 3600), next);
        Assert.Equal(new DateTime(2012, 4, 24, 18, 0, 0, DateTimeKind.Unspecified), next);
    }

    [Fact]
    public void DefaultStart_is_morning_of_12_April_2012()
    {
        Assert.Equal(new DateTime(2012, 4, 12, 6, 0, 0, DateTimeKind.Unspecified), GameTime.DefaultStart);
    }

    [Theory]
    [InlineData(1, true)]
    [InlineData(4, true)]
    [InlineData(0, false)]
    [InlineData(5, false)]
    public void IsValidTimeScale_accepts_1_through_4(int scale, bool expected)
    {
        Assert.Equal(expected, GameTime.IsValidTimeScale(scale));
    }

    [Fact]
    public void ResolveStart_defaults_and_normalises()
    {
        Assert.Equal(GameTime.DefaultStart, GameTime.ResolveStart(null));
        Assert.Equal(
            new DateTime(1999, 12, 31, 23, 45, 0, DateTimeKind.Unspecified),
            GameTime.ResolveStart(new DateTime(1999, 12, 31, 23, 45, 59, DateTimeKind.Utc)));
    }

    [Fact]
    public void ResolveStart_rejects_out_of_range_years()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() =>
            GameTime.ResolveStart(new DateTime(10000, 1, 1)));
    }
}