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>
    /// MC-2 tests for the hostile Spitter projectile systems (server-only, plain SimulationSystemGroup):
    /// EnemyProjectileMoveSystem integrates + writes LastStep; EnemyProjectileDamageSystem swept-hit-tests players +
    /// structures, REGION-FILTERED, appending a DamageEvent + destroying the spit at-most-once. Covers the two
    /// review-mandated regressions: swept anti-TUNNELLING (a per-tick step bigger than the target radius still
    /// registers) and the cross-region damage guard (an Expedition spit must not damage a Base target on its path).
    /// </summary>
    public class EnemyProjectileTests
    {
        static void SetTick(World w, uint tick)
        {
            var em = w.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) });
        }

        static (World, SimulationSystemGroup) MoveWorld()
        {
            var w = new World("EnemyProjMove");
            var g = w.GetOrCreateSystemManaged<SimulationSystemGroup>();
            g.AddSystemToUpdateList(w.GetOrCreateSystem<EnemyProjectileMoveSystem>());
            g.SortSystems();
            w.SetTime(new TimeData(elapsedTime: 0f, deltaTime: 0.1f));
            return (w, g);
        }

        static (World, SimulationSystemGroup) DamageWorld()
        {
            var w = new World("EnemyProjDmg");
            var g = w.GetOrCreateSystemManaged<SimulationSystemGroup>();
            g.AddSystemToUpdateList(w.GetOrCreateSystem<EnemyProjectileDamageSystem>());
            g.SortSystems();
            w.SetTime(new TimeData(elapsedTime: 0f, deltaTime: 0.1f));
            SetTick(w, 200);
            return (w, g);
        }

        static Entity MakeSpit(EntityManager em, float3 pos, float2 dir, float speed, float range, byte region, float lastStep = 0f, float damage = 10f)
        {
            var e = em.CreateEntity();
            em.AddComponentData(e, LocalTransform.FromPosition(pos));
            em.AddComponentData(e, new EnemyProjectile { Direction = dir, Speed = speed, Damage = damage, Range = range, DistanceTravelled = 0f, LastStep = lastStep, Region = region });
            return e;
        }

        static Entity MakePlayerTarget(EntityManager em, float3 pos, byte region, float radius = 0.6f)
        {
            var e = em.CreateEntity();
            em.AddComponentData(e, LocalTransform.FromPosition(pos));
            em.AddComponentData(e, new Health { Current = 100f, Max = 100f });
            em.AddComponentData(e, new HitRadius { Value = radius });
            em.AddComponentData(e, new RegionTag { Region = region });
            em.AddBuffer<DamageEvent>(e);
            em.AddComponent<PlayerTag>(e);
            return e;
        }

        [Test]
        public void Move_IntegratesAndStoresLastStep()
        {
            var (w, g) = MoveWorld();
            using (w)
            {
                var em = w.EntityManager;
                var spit = MakeSpit(em, new float3(0, 1, 0), new float2(1, 0), 10f, 5f, RegionId.Base);
                g.Update(); // dt 0.1 * speed 10 = step 1
                var p = em.GetComponentData<EnemyProjectile>(spit);
                Assert.AreEqual(1f, p.LastStep, 1e-4f, "LastStep = Speed*dt (for the swept segment)");
                Assert.AreEqual(1f, p.DistanceTravelled, 1e-4f);
                Assert.AreEqual(1f, em.GetComponentData<LocalTransform>(spit).Position.x, 1e-4f, "moved along +X");
            }
        }

        [Test]
        public void Damage_HitsSameRegionPlayer_DestroysAtMostOnce()
        {
            var (w, g) = DamageWorld();
            using (w)
            {
                var em = w.EntityManager;
                var player = MakePlayerTarget(em, new float3(5, 1, 0), RegionId.Base);
                var spit = MakeSpit(em, new float3(5, 1, 0), new float2(1, 0), 10f, 20f, RegionId.Base, lastStep: 1f);
                g.Update();
                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(player).Length, "same-region player takes the hit");
                Assert.IsFalse(em.Exists(spit), "the spit is consumed on hit");
            }
        }

        [Test]
        public void Damage_RegionFilter_ExpeditionSpitSparesBasePlayer()
        {
            var (w, g) = DamageWorld();
            using (w)
            {
                var em = w.EntityManager;
                var basePlayer = MakePlayerTarget(em, new float3(5, 1, 0), RegionId.Base);
                var spit = MakeSpit(em, new float3(5, 1, 0), new float2(1, 0), 10f, 20f, RegionId.Expedition, lastStep: 1f);
                g.Update();
                Assert.AreEqual(0, em.GetBuffer<DamageEvent>(basePlayer).Length, "cross-region spit must NOT damage an off-region player");
                Assert.IsTrue(em.Exists(spit), "and it is not consumed by an off-region target");
            }
        }

        [Test]
        public void Damage_SweptSegment_NoTunnelThroughSmallTarget()
        {
            var (w, g) = DamageWorld();
            using (w)
            {
                var em = w.EntityManager;
                // target radius 0.5 at x=5; spit now at x=10 but stepped 8 this tick (start x=2) -> segment [2..10] crosses x=5.
                var player = MakePlayerTarget(em, new float3(5, 1, 0), RegionId.Base, radius: 0.5f);
                var spit = MakeSpit(em, new float3(10, 1, 0), new float2(1, 0), 80f, 50f, RegionId.Base, lastStep: 8f);
                g.Update();
                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(player).Length,
                    "swept segment hits even when the per-tick step exceeds the target radius (no tunnelling)");
            }
        }
    }
}