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 the server-only <see cref="TurretFireSystem"/> (hitscan defense turret).
    /// A bare world is seeded with a <c>NetworkTime</c> singleton, a <see cref="ResourceLedger"/> Charge pool (the
    /// turret's EB-2 ammo), a turret (PlacedStructure + Turret + RegionTag + LocalTransform) and Husks (Health +
    /// EnemyTag + RegionTag + LocalTransform + a DamageEvent buffer). The system snapshots living Husks, fires at
    /// the nearest in-range one in its OWN region on the <c>PlacedStructure.NextTick</c> cooldown — but ONLY when
    /// it can withdraw <see cref="Tuning.TurretChargeCostPerShot"/> Charge from the ledger; out of Charge =
    /// soft-fail (no shot, no cooldown burn, so it fires the instant Charge returns). These tests pin range
    /// filtering, region gating, the wrap-safe cooldown, and the EB-2 Charge spend / soft-fail.
    /// </summary>
    public class TurretFireSystemTests
    {
        // Range/region/cooldown tests never need to run dry; the spend tests pass an explicit small pool.
        const int AmpleCharge = 1_000_000;

        static (World world, SimulationSystemGroup group, Entity ledger) MakeWorld(
            string name, uint serverTick, int charge = AmpleCharge)
        {
            var world = new World(name);
            var group = world.GetOrCreateSystemManaged<SimulationSystemGroup>();
            group.AddSystemToUpdateList(world.GetOrCreateSystem<TurretFireSystem>());
            group.SortSystems();
            world.SetTime(new TimeData(elapsedTime: 0f, deltaTime: 1f / 60f));
            SetServerTick(world, serverTick);
            var em = world.EntityManager;
            var ledger = em.CreateEntity(typeof(ResourceLedger));
            var buf = em.AddBuffer<StorageEntry>(ledger);
            if (charge > 0)
                buf.Add(new StorageEntry { ItemId = ResourceId.Charge, Count = charge });
            return (world, group, ledger);
        }

        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) });
        }

        static Entity MakeTurret(EntityManager em, float3 pos, byte region, float range, int cooldown, float damage)
        {
            var e = em.CreateEntity();
            em.AddComponentData(e, LocalTransform.FromPosition(pos));
            em.AddComponentData(e, new RegionTag { Region = region });
            em.AddComponentData(e, new PlacedStructure { Type = StructureType.Turret, NextTick = 0 });
            em.AddComponentData(e, new Turret { Range = range, CooldownTicks = cooldown, Damage = damage });
            return e;
        }

        static Entity MakeHusk(EntityManager em, float3 pos, byte region, float health)
        {
            var e = em.CreateEntity();
            em.AddComponentData(e, LocalTransform.FromPosition(pos));
            em.AddComponentData(e, new RegionTag { Region = region });
            em.AddComponentData(e, new Health { Current = health, Max = health });
            em.AddComponent<EnemyTag>(e);
            em.AddBuffer<DamageEvent>(e);
            return e;
        }

        static int LedgerCharge(EntityManager em, Entity ledger)
        {
            var buf = em.GetBuffer<StorageEntry>(ledger);
            for (int i = 0; i < buf.Length; i++)
                if (buf[i].ItemId == ResourceId.Charge) return buf[i].Count;
            return 0;
        }

        [Test]
        public void Turret_Fires_At_InRange_Husk_In_Its_Region()
        {
            var (world, group, _) = MakeWorld("TurretFireWorld", serverTick: 200);
            using (world)
            {
                var em = world.EntityManager;
                var turret = MakeTurret(em, new float3(5, 1, 5), RegionId.Base, range: 20f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(10, 1, 10), RegionId.Base, health: 50f);

                group.Update();

                var dmg = em.GetBuffer<DamageEvent>(husk);
                Assert.AreEqual(1, dmg.Length, "An in-range, same-region Husk takes exactly one turret hit.");
                Assert.AreEqual(10f, dmg[0].Amount, 1e-4f, "DamageEvent carries the turret's damage.");
                Assert.AreEqual(-1, dmg[0].SourceNetworkId, "Turret damage uses the -1 (world) source id.");
                Assert.AreNotEqual(0u, em.GetComponentData<PlacedStructure>(turret).NextTick,
                    "The cooldown tick is stamped after firing.");
            }
        }

        [Test]
        public void Turret_Ignores_Husk_Out_Of_Range()
        {
            var (world, group, _) = MakeWorld("TurretRangeWorld", serverTick: 200);
            using (world)
            {
                var em = world.EntityManager;
                MakeTurret(em, new float3(0, 1, 0), RegionId.Base, range: 5f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(100, 1, 0), RegionId.Base, health: 50f);

                group.Update();

                Assert.AreEqual(0, em.GetBuffer<DamageEvent>(husk).Length, "A Husk beyond Range takes no hit.");
            }
        }

        [Test]
        public void Turret_Ignores_Husk_In_A_Different_Region()
        {
            var (world, group, _) = MakeWorld("TurretRegionWorld", serverTick: 200);
            using (world)
            {
                var em = world.EntityManager;
                MakeTurret(em, new float3(0, 1, 0), RegionId.Base, range: 50f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(2, 1, 2), RegionId.Expedition, health: 50f);

                group.Update();

                Assert.AreEqual(0, em.GetBuffer<DamageEvent>(husk).Length,
                    "A Husk in a different region is never targeted (region gating).");
            }
        }

        [Test]
        public void Turret_Respects_Cooldown_Then_Fires_Again()
        {
            var (world, group, _) = MakeWorld("TurretCooldownWorld", serverTick: 200);
            using (world)
            {
                var em = world.EntityManager;
                MakeTurret(em, new float3(0, 1, 0), RegionId.Base, range: 50f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(3, 1, 0), RegionId.Base, health: 5000f);

                group.Update(); // fires at tick 200, NextTick -> 230
                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(husk).Length, "Fires on the first ready tick.");

                SetServerTick(world, 210);
                group.Update(); // 210 < 230 -> still cooling down
                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(husk).Length, "No second shot while cooling down.");

                SetServerTick(world, 240);
                group.Update(); // 240 >= 230 -> ready again
                Assert.AreEqual(2, em.GetBuffer<DamageEvent>(husk).Length, "Fires again once the cooldown elapses.");
            }
        }

        // ---- EB-2: turret ammo (Charge) spend + soft-fail ----

        [Test]
        public void Turret_Out_Of_Charge_Soft_Fails_No_Shot_No_Cooldown_Burn()
        {
            var (world, group, ledger) = MakeWorld("TurretNoChargeWorld", serverTick: 200, charge: 0);
            using (world)
            {
                var em = world.EntityManager;
                var turret = MakeTurret(em, new float3(0, 1, 0), RegionId.Base, range: 50f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(3, 1, 0), RegionId.Base, health: 50f);

                group.Update();

                Assert.AreEqual(0, em.GetBuffer<DamageEvent>(husk).Length,
                    "With an empty Charge pool the turret cannot fire (soft-fail).");
                Assert.AreEqual(0u, em.GetComponentData<PlacedStructure>(turret).NextTick,
                    "A soft-failed shot burns no cooldown — the turret stays ready for the instant Charge returns.");
                Assert.AreEqual(0, LedgerCharge(em, ledger), "No Charge is consumed when no shot is fired.");
            }
        }

        [Test]
        public void Turret_Consumes_One_Charge_Per_Shot()
        {
            var (world, group, ledger) = MakeWorld("TurretSpendWorld", serverTick: 200, charge: 5);
            using (world)
            {
                var em = world.EntityManager;
                MakeTurret(em, new float3(0, 1, 0), RegionId.Base, range: 50f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(3, 1, 0), RegionId.Base, health: 50f);

                group.Update();

                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(husk).Length, "A funded turret fires.");
                Assert.AreEqual(5 - Tuning.TurretChargeCostPerShot, LedgerCharge(em, ledger),
                    "Exactly TurretChargeCostPerShot Charge is withdrawn for the shot.");
            }
        }

        [Test]
        public void Two_Turrets_Share_A_Finite_Charge_Pool_Second_Soft_Fails()
        {
            // One Charge, two turrets, one Husk: the first turret (query/creation order) spends the last Charge and
            // fires; the second withdraws 0 and soft-fails. The Husk takes exactly one hit and the pool empties.
            var (world, group, ledger) = MakeWorld("TurretSharedPoolWorld", serverTick: 200, charge: 1);
            using (world)
            {
                var em = world.EntityManager;
                MakeTurret(em, new float3(-2, 1, 0), RegionId.Base, range: 50f, cooldown: 30, damage: 10f);
                MakeTurret(em, new float3(2, 1, 0), RegionId.Base, range: 50f, cooldown: 30, damage: 10f);
                var husk = MakeHusk(em, new float3(0, 1, 0), RegionId.Base, health: 500f);

                group.Update();

                Assert.AreEqual(1, em.GetBuffer<DamageEvent>(husk).Length,
                    "A single Charge funds exactly one of the two turrets this tick.");
                Assert.AreEqual(0, LedgerCharge(em, ledger), "The shared Charge pool is drained to zero.");
            }
        }
    }
}