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>
    /// Detonates lit-fuse EXPLOSIVE barrels (Exploding_Barrels_Build_Spec, design-review wf_2cb10454-fdf):
    /// when a <see cref="BarrelFuse"/>'s ExplodeTick elapses, radius-damage LIVING enemies AND players
    /// (friendly fire = the bait mechanic), then the single DestroyEntity. Player gather mirrors the
    /// BossAISystem slam filter VERBATIM (Health &gt; 0 + RegionTag == Expedition — a dead player lying in
    /// radius gets nothing; a review-confirmed precedent). <see cref="DamageEvent.SourceTick"/> is stamped at
    /// DETONATION (the authoring moment — dash i-frames negate against it, honouring the DamageEvent
    /// authored-tick contract) and <see cref="DamageEvent.SourceNetworkId"/> = -1 (the environment
    /// convention: a player id would score+consume Charger whiff-punish windows). Plain server
    /// <see cref="SimulationSystemGroup"/>, NO ordering edges; presence-gated on BarrelFuse only — NEVER
    /// lifecycle-gated (a fuse must always drain; it rides the RoomTag'd barrel, so room teardown / the
    /// Staging sweep clean unexploded barrels for free). An invalid NetworkTime skips the tick; the fuse
    /// persists.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(SimulationSystemGroup))]
    public partial struct HazardExplosionSystem : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<BarrelFuse>();
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            if (!SystemAPI.TryGetSingleton<NetworkTime>(out var netTime) || !netTime.ServerTick.IsValid)
                return;
            var serverTick = netTime.ServerTick;

            var ecb = new EntityCommandBuffer(Allocator.Temp);
            var blasts = new NativeList<float3>(Allocator.Temp);
            foreach (var (fuse, lt, barrel) in
                     SystemAPI.Query<RefRO<BarrelFuse>, RefRO<LocalTransform>>().WithEntityAccess())
            {
                var until = new NetworkTick(fuse.ValueRO.ExplodeTick);
                if (until.IsValid && until.IsNewerThan(serverTick)) continue; // still burning
                blasts.Add(lt.ValueRO.Position);
                ecb.DestroyEntity(barrel); // the single destroy site for a popped explosive
            }

            if (blasts.Length > 0)
            {
                float radiusSq = Tuning.BarrelExplodeRadius * Tuning.BarrelExplodeRadius;
                uint stamp = TickUtil.NonZero(serverTick.TickIndexForValidTick);

                // Players: the BossAISystem slam gather verbatim — living + expedition only.
                foreach (var (hp, region, plt, player) in
                         SystemAPI.Query<RefRO<Health>, RefRO<RegionTag>, RefRO<LocalTransform>>()
                             .WithAll<PlayerTag>().WithEntityAccess())
                {
                    if (hp.ValueRO.Current <= 0f || region.ValueRO.Region != RegionId.Expedition) continue;
                    for (int i = 0; i < blasts.Length; i++)
                        if (math.distancesq(plt.ValueRO.Position.xz, blasts[i].xz) <= radiusSq)
                            ecb.AppendToBuffer(player, new DamageEvent
                            {
                                Amount = Tuning.BarrelExplodeDamage,
                                SourceNetworkId = -1,
                                SourceTick = stamp,
                            });
                }

                // Enemies: living only (Health > 0 also excludes Dying corpses, the established convention).
                foreach (var (hp, elt, enemy) in
                         SystemAPI.Query<RefRO<Health>, RefRO<LocalTransform>>()
                             .WithAll<EnemyTag>().WithEntityAccess())
                {
                    if (hp.ValueRO.Current <= 0f) continue;
                    for (int i = 0; i < blasts.Length; i++)
                        if (math.distancesq(elt.ValueRO.Position.xz, blasts[i].xz) <= radiusSq)
                            ecb.AppendToBuffer(enemy, new DamageEvent
                            {
                                Amount = Tuning.BarrelExplodeDamage,
                                SourceNetworkId = -1,
                                SourceTick = stamp,
                            });
                }
            }

            ecb.Playback(state.EntityManager);
            ecb.Dispose();
            blasts.Dispose();
        }
    }
}