using ProjectM.Simulation;
using Unity.Burst;
using Unity.Collections;
using Unity.Entities;
using Unity.Mathematics;
using Unity.NetCode;
using Unity.Transforms;

namespace ProjectM.Server
{
    /// <summary>
    /// Server-only per-ROOM enemy director — the Step-6 successor of the presence-keyed <c>ZoneEnemyDirectorSystem</c>.
    /// While the run FSM has a room active (<see cref="RunInfo.Lifecycle"/> == InRoom) it seeds ONE wave per
    /// <see cref="RunRuntime.RoomEpoch"/> (int-equality reseed) sized by <see cref="ZoneEnemyMath.WaveSlots"/> indexed
    /// on the room's <see cref="RoomPlan.DifficultyEpoch"/> (deeper rooms + Elite/Boss types skew heavier — the
    /// grounded MC-2 mix bands are reused verbatim), drip-spawned one SLOT per cadence at the deterministic ring
    /// around <see cref="RegionMath.ExpeditionRoomOrigin"/>(base, ActiveSubSlot), under the same
    /// <see cref="ZoneEnemyDirector.MaxAlive"/> "spawn-the-pack-only-if-it-fits-else-wait" relevancy guard. A
    /// <see cref="RoomTypeId.Boss"/> room spawns ONE beefed boss instead (health × <see cref="Tuning.BossHealthMultiplier"/>,
    /// scale × <see cref="Tuning.BossScaleMultiplier"/> — v1's boss is a scaled Charger). Every spawn keeps the full
    /// stack — EnemyTag + RegionTag{Expedition} + <see cref="ZoneEnemyTag"/> — PLUS <see cref="RoomTag"/>{room} (the
    /// teardown contract). Scale preserved via <c>baked.WithPosition</c>.
    ///
    /// The room CLEAR edge surfaces ONLY through the replicated <see cref="ExpeditionObjective"/>.State == Cleared
    /// (wave fully spawned AND zero alive, latched per seeded epoch) — written FIRST, ABOVE every early-return
    /// (snapshot-above-early-return) so the HUD never freezes; RunDirectorSystem consumes it one-tick-late (Step 7).
    /// The old CycleRuntime.ClearedThisEpoch write is gone (the C4 collapse), and the old base-siege Calm gate is
    /// deliberately DROPPED — a home retaliation siege no longer freezes a live sortie (the DR-042 latent gap).
    ///
    /// Ordering: <c>[UpdateAfter(RunDirectorSystem)]</c> ONLY — reads the freshly-advanced room state same-tick.
    /// NO CyclePhase edge may ever return to the room chain (Play-only sort-cycle, invisible to EditMode).
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(SimulationSystemGroup))]
    [UpdateAfter(typeof(RunDirectorSystem))]
    public partial struct RoomEnemyDirectorSystem : ISystem
    {
        EntityQuery m_ZoneEnemies;

        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<NetworkTime>();
            state.RequireForUpdate<RunInfo>();
            state.RequireForUpdate<RunRuntime>();
            state.RequireForUpdate<ZoneEnemyDirector>();
            m_ZoneEnemies = state.GetEntityQuery(ComponentType.ReadOnly<ZoneEnemyTag>(), ComponentType.Exclude<Dying>()); // room clear + MaxAlive fit count LIVING only (B3) - corpses neither hold the room open nor crowd out spawns
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            var serverTick = SystemAPI.GetSingleton<NetworkTime>().ServerTick;
            if (!serverTick.IsValid)
                return;
            uint now = serverTick.TickIndexForValidTick;

            var runEntity = SystemAPI.GetSingletonEntity<RunInfo>();
            var info = SystemAPI.GetComponent<RunInfo>(runEntity);
            var run = SystemAPI.GetComponent<RunRuntime>(runEntity);
            bool roomActive = info.Lifecycle == RunLifecycle.InRoom;

            var directorEntity = SystemAPI.GetSingletonEntity<ZoneEnemyDirector>();
            var dir = SystemAPI.GetComponent<ZoneEnemyDirector>(directorEntity);
            var zs = SystemAPI.GetComponent<ZoneEnemyState>(directorEntity);

            int aliveZone = m_ZoneEnemies.CalculateEntityCount();

            // REPLICATED objective summary FIRST, above every early-return (snapshot-above-early-return): the HUD
            // readout must never freeze stale. Cleared latches only for a wave seeded FOR THIS RoomEpoch.
            if (SystemAPI.HasComponent<ExpeditionObjective>(runEntity))
            {
                byte objState;
                short objRemaining;
                if (roomActive && (aliveZone > 0 || zs.RemainingToSpawn > 0))
                {
                    objState = ExpeditionObjectiveState.Active;
                    objRemaining = (short)math.min(aliveZone + zs.RemainingToSpawn, short.MaxValue);
                }
                else if (roomActive && zs.SeededEpoch == run.RoomEpoch && zs.RemainingToSpawn == 0 && aliveZone == 0)
                {
                    objState = ExpeditionObjectiveState.Cleared; // fully spawned + fully dead -> advance-ready
                    objRemaining = 0;
                }
                else
                {
                    objState = ExpeditionObjectiveState.Idle;
                    objRemaining = 0;
                }
                SystemAPI.SetComponent(runEntity, new ExpeditionObjective { State = objState, Remaining = objRemaining });
            }

            if (!roomActive)
                return;

            var prefabs = SystemAPI.GetBuffer<ZoneEnemyPrefab>(directorEntity);
            if (prefabs.Length == 0)
                return;

            // Single plan authority: the node RunDirector published — never re-derived here.
            var map = RunMapMath.Generate(run.RunSeed);
            var node = map.NodeAt(run.CurrentNodeId);
            var plan = RoomLayoutMath.Plan(node, info.CurrentRoom, info.RoomCount);
            byte room = (byte)(info.CurrentRoom & 0xFF);
            bool bossRoom = plan.RoomType == RoomTypeId.Boss;

            var bands = new MixBands
            {
                GruntBase = dir.GruntsPerWave,
                ChargerBase = dir.ChargersPerWave,
                SpitterBase = dir.SpitterBase,
                SwarmerSlotBase = dir.SwarmerSlotBase,
                ChargerPerEpoch = dir.ChargerPerEpoch,
                SpitterPerEpoch = dir.SpitterPerEpoch,
                SwarmerSlotPerEpoch = dir.SwarmerSlotPerEpoch,
                SwarmerPackPerEpoch = dir.SwarmerPackPerEpoch,
            };

            // (Re)seed once per ROOM (its OWN counter, in SLOTS; a swarmer slot is one pack; a boss room is 1 slot).
            if (zs.SeededEpoch != run.RoomEpoch)
            {
                zs.SeededEpoch = run.RoomEpoch;
                zs.SpawnCounter = 0;
                zs.RemainingToSpawn = bossRoom ? 1 : ZoneEnemyMath.WaveSlots(plan.DifficultyEpoch, bands);
                zs.NextSpawnTick = TickUtil.NonZero(now + Tuning.RoomEntryGraceTicks); // landing grace — let the party orient
            }

            if (zs.RemainingToSpawn > 0)
            {
                bool dueNow = zs.NextSpawnTick == 0 || !new NetworkTick(zs.NextSpawnTick).IsNewerThan(serverTick);
                if (dueNow)
                {
                    int slot = (int)zs.SpawnCounter;
                    byte kind = bossRoom ? ZoneEnemyMath.KindCharger
                        : ZoneEnemyMath.KindForSlot(plan.DifficultyEpoch, slot, bands);
                    int packSize = !bossRoom && kind == ZoneEnemyMath.KindSwarmer
                        ? ZoneEnemyMath.PackSizeForSlot(plan.DifficultyEpoch, slot, bands, dir.SwarmerPackSize) : 1;

                    // MaxAlive counts ENTITIES; spawn the whole pack only if it fits (else WAIT — keep the slot).
                    if (aliveZone + packSize <= math.max(1, dir.MaxAlive))
                    {
                        float3 baseCenter = new float3(0f, 1f, 0f);
                        if (SystemAPI.TryGetSingleton<BaseAnchor>(out var anchor))
                            baseCenter = BaseGridMath.PlotCenter(anchor);
                        float3 origin = RegionMath.ExpeditionRoomOrigin(baseCenter, run.ActiveSubSlot);
                        float3 center = bossRoom
                            ? origin + new float3(0f, 0f, 12f) // the boss anchors the room center
                            : EnemyAIMath.RingPosition(origin, slot, math.max(1, dir.RingSlots), dir.RingRadius);
                        center.y = origin.y;

                        int prefabIdx = kind;
                        if (prefabIdx >= prefabs.Length) prefabIdx = 0; // 4-entry buffer expected; clamp defensively
                        var prefab = prefabs[prefabIdx].Prefab;
                        var baked = state.EntityManager.GetComponentData<LocalTransform>(prefab);

                        var ecb = new EntityCommandBuffer(Allocator.Temp);
                        for (int k = 0; k < packSize; k++)
                        {
                            float3 pos = packSize > 1
                                ? EnemyAIMath.ClusterOffset(center, k, packSize, dir.ClusterTightRadius) : center;
                            pos.y = origin.y;
                            var enemy = ZoneEnemySpawnUtil.Spawn(ecb, prefab, in baked, pos, RegionId.Expedition, room);
                            if (bossRoom)
                            {
                                // Boss = a scaled Charger given a real kit by BossAISystem. Scale the visual AND the
                                // hitbox/reach (so hits register on the big model + its reach matches), multiply Health,
                                // and tag BossState (server-only discriminator) so BossAISystem alone drives it.
                                var bxform = baked.WithPosition(pos);
                                bxform.Scale = baked.Scale * Tuning.BossScaleMultiplier;
                                ecb.SetComponent(enemy, bxform);
                                if (SystemAPI.HasComponent<Health>(prefab))
                                {
                                    // B5: party-size HP scaling by LIVING EXPEDITION players at spawn (NOT the
                                    // RunParticipant count - dead-respawned members keep the tag while parked at
                                    // base). Health.Max is a [GhostField] since DR-046, so the scaled max replicates.
                                    int livingParty = 0;
                                    foreach (var (pHealth, pRegion) in SystemAPI.Query<RefRO<Health>, RefRO<RegionTag>>().WithAll<PlayerTag>())
                                        if (pHealth.ValueRO.Current > 0f && pRegion.ValueRO.Region == RegionId.Expedition) livingParty++;
                                    float partyScale = 1f + Tuning.BossHealthPerExtraPlayer * math.max(0, livingParty - 1);
                                    var hp = SystemAPI.GetComponent<Health>(prefab);
                                    hp.Current *= Tuning.BossHealthMultiplier * partyScale;
                                    hp.Max *= Tuning.BossHealthMultiplier * partyScale;
                                    ecb.SetComponent(enemy, hp);
                                }
                                if (SystemAPI.HasComponent<HitRadius>(prefab))
                                {
                                    var hr = SystemAPI.GetComponent<HitRadius>(prefab);
                                    hr.Value *= Tuning.BossScaleMultiplier;
                                    ecb.SetComponent(enemy, hr);
                                }
                                if (SystemAPI.HasComponent<EnemyStats>(prefab))
                                {
                                    var es = SystemAPI.GetComponent<EnemyStats>(prefab);
                                    es.AttackRange *= Tuning.BossScaleMultiplier;
                                    ecb.SetComponent(enemy, es);
                                }
                                ecb.AddComponent(enemy, new BossState { Phase = 1 });
                            }
                        }
                        ecb.Playback(state.EntityManager);
                        ecb.Dispose();

                        zs.SpawnCounter += 1;   // ONE slot consumed even for a pack
                        zs.RemainingToSpawn -= 1;
                        zs.NextSpawnTick = TickUtil.NonZero(now + (uint)math.max(1, dir.SpawnIntervalTicks));
                    }
                }
            }

            SystemAPI.SetComponent(directorEntity, zs);
        }
    }
}