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

namespace ProjectM.Server
{
    /// <summary>
    /// Server-authoritative per-connection ghost relevancy for the base/expedition region split. Each tick:
    /// build a connection -&gt; region map from the region-tagged player ghosts, then mark every region-tagged
    /// ghost IRRELEVANT to each connection whose player is in a DIFFERENT region. Uses
    /// <see cref="GhostRelevancyMode.SetIsIrrelevant"/> so untagged/global ghosts (e.g. the cycle director)
    /// stay relevant to everyone for free — only cross-region ghosts are hidden. Runs in the
    /// <see cref="GhostSimulationSystemGroup"/> (before GhostSendSystem reads the set). The set holds
    /// (connection, ghost) pairs for the CURRENT simulated tick only, so it is cleared and repopulated every
    /// update. A connection with no spawned player yet is absent from the map and simply sees everything.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(GhostSimulationSystemGroup))]
    public partial struct RegionRelevancySystem : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<GhostRelevancy>();
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            // Map each in-game connection (by NetworkId) to its player's region.
            var connRegion = new NativeHashMap<int, byte>(8, Allocator.Temp);
            foreach (var (owner, region) in
                     SystemAPI.Query<RefRO<GhostOwner>, RefRO<RegionTag>>().WithAll<PlayerTag>())
            {
                connRegion[owner.ValueRO.NetworkId] = region.ValueRO.Region;
            }

            ref var relevancy = ref SystemAPI.GetSingletonRW<GhostRelevancy>().ValueRW;
            relevancy.GhostRelevancyMode = GhostRelevancyMode.SetIsIrrelevant;
            var set = relevancy.GhostRelevancySet;
            set.Clear();

            if (!connRegion.IsEmpty)
            {
                var conns = connRegion.GetKeyValueArrays(Allocator.Temp);
                foreach (var (ghost, region) in
                         SystemAPI.Query<RefRO<GhostInstance>, RefRO<RegionTag>>())
                {
                    int ghostId = ghost.ValueRO.ghostId;
                    if (ghostId == 0)
                        continue; // ghost id not assigned yet this tick

                    byte ghostRegion = region.ValueRO.Region;
                    for (int i = 0; i < conns.Keys.Length; i++)
                    {
                        if (conns.Values[i] != ghostRegion)
                            set.Add(new RelevantGhostForConnection { Connection = conns.Keys[i], Ghost = ghostId }, 1);
                    }
                }
                conns.Dispose();
            }

            connRegion.Dispose();
        }
    }
}