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>
    /// LANTERN "light is territory" relevancy prototype (Build Spec Phase 1 step 8): per connection, marks every
    /// ENEMY ghost OUTSIDE that player's lamp radius IRRELEVANT — so monsters in the dark aren't replicated (the
    /// gamma test: "nothing to see"). Players + untagged/global ghosts stay relevant for free (SetIsIrrelevant).
    /// <para>
    /// SHARED-SET DISCIPLINE: <see cref="RegionRelevancySystem"/> is the SOLE clearer of the <c>GhostRelevancy</c>
    /// set — its OnUpdate runs every tick (requires only <c>GhostRelevancy</c>), setting the mode + clearing +
    /// adding its region hides. This system runs <b>[UpdateAfter(RegionRelevancySystem)]</b> and only ADDS light
    /// hides (never clears) via <c>TryAdd</c> (defensive against a ghost hidden by BOTH region and light for one
    /// connection — a duplicate <c>Add</c> would throw). Gated on <see cref="GymTag"/> so it runs ONLY in the
    /// LANTERN gym; the legacy base/expedition game keeps region relevancy alone. Runs in
    /// <see cref="GhostSimulationSystemGroup"/> before GhostSendSystem reads the set. Per-player dim/bright (a
    /// variable radius) is the tuning follow-up; the prototype uses <see cref="LightRelevancyMath.LampRadiusDefault"/>.
    /// </para>
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(GhostSimulationSystemGroup))]
    [UpdateAfter(typeof(RegionRelevancySystem))]
    public partial struct LightRelevancySystem : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<GhostRelevancy>();
            state.RequireForUpdate<GymTag>(); // prototype: light-as-territory runs only in the LANTERN gym
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            // Each in-game connection's player position (per-player lamp radius = the dim/bright follow-up; fixed here).
            var connPos = new NativeHashMap<int, float3>(8, Allocator.Temp);
            foreach (var (owner, lt) in
                     SystemAPI.Query<RefRO<GhostOwner>, RefRO<LocalTransform>>().WithAll<PlayerTag>())
                connPos[owner.ValueRO.NetworkId] = lt.ValueRO.Position;

            if (connPos.IsEmpty) { connPos.Dispose(); return; }

            // The set is already mode=SetIsIrrelevant + cleared + region-populated THIS tick by RegionRelevancySystem.
            ref var relevancy = ref SystemAPI.GetSingletonRW<GhostRelevancy>().ValueRW;
            var set = relevancy.GhostRelevancySet;
            var conns = connPos.GetKeyValueArrays(Allocator.Temp);

            float rSq = LightRelevancyMath.LampRadiusDefault * LightRelevancyMath.LampRadiusDefault;
            foreach (var (ghost, lt) in
                     SystemAPI.Query<RefRO<GhostInstance>, RefRO<LocalTransform>>().WithAll<EnemyTag>())
            {
                int ghostId = ghost.ValueRO.ghostId;
                if (ghostId == 0) continue; // ghost id not assigned yet this tick

                float3 gp = lt.ValueRO.Position;
                for (int i = 0; i < conns.Keys.Length; i++)
                {
                    if (LightRelevancyMath.IsHidden(conns.Values[i], gp, rSq))
                        set.TryAdd(new RelevantGhostForConnection { Connection = conns.Keys[i], Ghost = ghostId }, 1);
                }
            }

            conns.Dispose();
            connPos.Dispose();
        }
    }
}