Project-M/Assets/_Project/Tests/EditMode/KnockbackTests.cs

using NUnit.Framework;
using ProjectM.Server;
using ProjectM.Simulation;
using Unity.Core;
using Unity.Entities;
using Unity.Mathematics;
using Unity.NetCode;
using Unity.Transforms;

namespace ProjectM.Tests
{
    /// <summary>
    /// Plain-Entities EditMode tests for enemy KNOCKBACK (server-only, no re-bake). Two halves:
    /// ProjectileDamageSystem STAMPS a <see cref="KnockbackState"/> on a hit Husk (Dir = the projectile heading,
    /// UntilTick = now + Tuning.KnockbackDurationTicks); EnemyAISystem APPLIES it — moving the Husk along the
    /// knockback heading (overriding seek) and suppressing its strike for the window, then resuming seek. Both
    /// systems are server-only Burst ISystems; a NetworkTime singleton is seeded (TurretFireSystems pattern).
    /// Knockback is gated by Tuning.KnockbackSpeed (0 disables) — so ProjectileDamageSystem only stamps when &gt; 0.
    /// </summary>
    public class KnockbackTests
    {
        static void SetServerTick(World world, uint tick)
        {
            var em = world.EntityManager;
            using var q = em.CreateEntityQuery(typeof(NetworkTime));
            Entity e = q.IsEmpty ? em.CreateEntity(typeof(NetworkTime)) : q.GetSingletonEntity();
            em.SetComponentData(e, new NetworkTime { ServerTick = new NetworkTick(tick) });
        }

        [Test]
        public void ProjectileDamage_Stamps_Knockback_On_Hit_Husk()
        {
            var world = new World("KnockbackStampWorld");
            var group = world.GetOrCreateSystemManaged<SimulationSystemGroup>();
            group.AddSystemToUpdateList(world.GetOrCreateSystem<ProjectileDamageSystem>());
            group.SortSystems();
            using (world)
            {
                var em = world.EntityManager;
                SetServerTick(world, 200);

                var husk = em.CreateEntity();
                em.AddComponentData(husk, LocalTransform.FromPosition(new float3(0, 0, 5)));
                em.AddComponentData(husk, new HitRadius { Value = 0.8f });
                em.AddComponentData(husk, new Health { Current = 50f, Max = 50f });
                em.AddBuffer<DamageEvent>(husk);
                em.AddComponentData(husk, new KnockbackState()); // baked on real Husks

                var proj = em.CreateEntity();
                em.AddComponentData(proj, LocalTransform.FromPosition(new float3(0, 0, 5)));
                em.AddComponentData(proj, new Projectile { Direction = new float2(0, 1), Speed = 10f, Damage = 20f, Range = 20f, DistanceTravelled = 5f });
                em.AddComponentData(proj, new GhostOwner { NetworkId = 1 });

                world.SetTime(new TimeData(elapsedTime: 0.1f, deltaTime: 0.1f));
                group.Update();

                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(husk).Length, "The hit still deals damage.");
                Assert.IsFalse(em.Exists(proj), "The projectile is consumed on hit.");
                var kb = em.GetComponentData<KnockbackState>(husk);
                Assert.AreEqual(TickUtil.NonZero(200 + (uint)Tuning.KnockbackDurationTicks), kb.UntilTick,
                    "Knockback is scheduled until now + KnockbackDurationTicks.");
                Assert.AreEqual(0f, kb.Dir.x, 1e-4f);
                Assert.AreEqual(1f, kb.Dir.y, 1e-4f, "Knockback heading matches the projectile direction.");
                Assert.AreEqual(Tuning.KnockbackSpeed, kb.Speed, 1e-4f);
            }
        }

        static (World world, SimulationSystemGroup group) MakeAiWorld(string name, uint serverTick)
        {
            var world = new World(name);
            var group = world.GetOrCreateSystemManaged<SimulationSystemGroup>();
            group.AddSystemToUpdateList(world.GetOrCreateSystem<EnemyAISystem>());
            group.SortSystems();
            world.SetTime(new TimeData(elapsedTime: 0f, deltaTime: 1f / 60f));
            SetServerTick(world, serverTick);
            return (world, group);
        }

        static Entity MakePlayer(EntityManager em, float3 pos)
        {
            var e = em.CreateEntity();
            em.AddComponentData(e, LocalTransform.FromPosition(pos));
            em.AddComponentData(e, new Health { Current = 100f, Max = 100f });
            em.AddComponent<PlayerTag>(e);
            em.AddBuffer<DamageEvent>(e);
            em.AddComponentData(e, new RegionTag { Region = RegionId.Base });
            return e;
        }

        static Entity MakeHusk(EntityManager em, float3 pos, KnockbackState kb)
        {
            var e = em.CreateEntity();
            em.AddComponentData(e, LocalTransform.FromPosition(pos));
            em.AddComponentData(e, new EnemyStats { MoveSpeed = 3f, AttackRange = 1.6f, AttackDamage = 8f, AttackCooldownTicks = 36 });
            em.AddComponentData(e, new EnemyAttackCooldown { NextAttackTick = 0 });
            em.AddComponentData(e, kb);
            em.AddComponentData(e, new AttackWindup());
            em.AddComponent<EnemyTag>(e);
            em.AddComponentData(e, new RegionTag { Region = RegionId.Base });
            return e;
        }

        [Test]
        public void Knockback_Overrides_Seek_Then_Resumes()
        {
            var (world, group) = MakeAiWorld("KnockbackAiWorld", 200);
            using (world)
            {
                var em = world.EntityManager;
                MakePlayer(em, new float3(10, 1, 0)); // player at +X
                var husk = MakeHusk(em, new float3(5, 1, 0),
                    new KnockbackState { Dir = new float2(-1, 0), Speed = Tuning.KnockbackSpeed, UntilTick = TickUtil.NonZero(208) });

                group.Update(); // tick 200: knocked -> moves -X (against the seek toward +X)
                float xKnocked = em.GetComponentData<LocalTransform>(husk).Position.x;
                Assert.Less(xKnocked, 5f, "While knocked the Husk moves along the knockback heading (-X), not toward the player (+X).");

                SetServerTick(world, 208);
                group.Update(); // window elapsed -> seek resumes toward the player at +X
                float xResumed = em.GetComponentData<LocalTransform>(husk).Position.x;
                Assert.Greater(xResumed, xKnocked, "Once the knockback window elapses the Husk seeks back toward the player.");
                Assert.AreEqual(0u, em.GetComponentData<KnockbackState>(husk).UntilTick, "Knockback state is cleared after the window.");
            }
        }

        [Test]
        public void Knocked_Husk_Does_Not_Strike()
        {
            var (world, group) = MakeAiWorld("KnockbackNoStrikeWorld", 200);
            using (world)
            {
                var em = world.EntityManager;
                var player = MakePlayer(em, new float3(10, 1, 0));
                // Husk inside AttackRange of the player, but knocked.
                MakeHusk(em, new float3(9, 1, 0),
                    new KnockbackState { Dir = new float2(-1, 0), Speed = Tuning.KnockbackSpeed, UntilTick = TickUtil.NonZero(208) });

                group.Update();

                Assert.AreEqual(0, em.GetBuffer<DamageEvent>(player).Length,
                    "A recoiling Husk does not strike even when inside AttackRange.");
            }
        }
    }
}