using Friflo.Engine.ECS;
using Friflo.Engine.ECS.Systems;
using MrGameEng.Core;
using Xunit;

namespace MrGameEng.Core.Tests;

public class SceneSystemsTests
{
    private struct Velocity : IComponent
    {
        public float X;
    }

    private struct Translation : IComponent
    {
        public float X;
    }

    private sealed class MoveSystem : QuerySystem<Translation, Velocity>
    {
        protected override void OnUpdate()
        {
            foreach (var (translations, velocities, _) in Query.Chunks)
            {
                var t = translations.Span;
                var v = velocities.Span;
                for (var i = 0; i < t.Length; i++)
                {
                    t[i].X += v[i].X * Tick.deltaTime;
                }
            }
        }
    }

    private sealed class MovingScene : Scene
    {
        public Entity Mover;

        protected override void OnLoad()
        {
            Mover = Store.CreateEntity(new Translation { X = 0f }, new Velocity { X = 10f });
            UpdateSystems.Add(new MoveSystem());
        }
    }

    [Fact]
    public void Update_RunsRegisteredQuerySystem_WithClockDelta()
    {
        var context = new EngineContext();
        var scene = new MovingScene();
        context.Scenes.Switch(scene);

        context.Clock.Advance(0.5f);
        context.Scenes.Update(context.Clock);

        Assert.Equal(5f, scene.Mover.GetComponent<Translation>().X, 3);
    }

    [Fact]
    public void TimeScale_AffectsSystemDelta()
    {
        var context = new EngineContext();
        var scene = new MovingScene();
        context.Scenes.Switch(scene);
        context.Clock.TimeScale = 0f;

        context.Clock.Advance(0.5f);
        context.Scenes.Update(context.Clock);

        Assert.Equal(0f, scene.Mover.GetComponent<Translation>().X);
    }
}