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

namespace ProjectM.Server
{
    /// <summary>
    /// Server-only walk-in gate transit: a player who walks within a gate's radius (and whose region matches the
    /// gate's <see cref="ExpeditionGate.FromRegion"/>) is transited to the gate's ToRegion at its ArrivalPos
    /// (RegionTag flipped + LocalTransform teleported — GhostRelevancy re-scopes their ghosts, as in
    /// <c>RegionTransitSystem</c>). Returning to the BASE during the Expedition phase expires the Expedition
    /// timer so Defend starts early ("timer cap + early return"). Plain server SimulationSystemGroup
    /// <c>[UpdateAfter(CyclePhaseSystem)]</c>. Arrival points are offset from the destination gate so a transited
    /// player does not immediately re-trigger.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateInGroup(typeof(SimulationSystemGroup))]
    [UpdateAfter(typeof(CyclePhaseSystem))]
    public partial struct ExpeditionGateSystem : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<ExpeditionGate>();
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            // Snapshot gates once.
            var gateFrom = new NativeList<byte>(Allocator.Temp);
            var gateTo = new NativeList<byte>(Allocator.Temp);
            var gateRadiusSq = new NativeList<float>(Allocator.Temp);
            var gatePos = new NativeList<float2>(Allocator.Temp);
            var gateArrival = new NativeList<float3>(Allocator.Temp);
            foreach (var (gate, xform) in SystemAPI.Query<RefRO<ExpeditionGate>, RefRO<LocalTransform>>())
            {
                gateFrom.Add(gate.ValueRO.FromRegion);
                gateTo.Add(gate.ValueRO.ToRegion);
                gateRadiusSq.Add(gate.ValueRO.Radius * gate.ValueRO.Radius);
                gatePos.Add(xform.ValueRO.Position.xz);
                gateArrival.Add(gate.ValueRO.ArrivalPos);
            }

            bool returnedToBase = false;
            foreach (var (region, xform) in
                     SystemAPI.Query<RefRW<RegionTag>, RefRW<LocalTransform>>().WithAll<PlayerTag>())
            {
                byte r = region.ValueRO.Region;
                float2 pp = xform.ValueRO.Position.xz;
                for (int i = 0; i < gateFrom.Length; i++)
                {
                    if (gateFrom[i] != r) continue;
                    if (math.distancesq(pp, gatePos[i]) > gateRadiusSq[i]) continue;
                    region.ValueRW.Region = gateTo[i];
                    xform.ValueRW.Position = gateArrival[i];
                    if (gateTo[i] == RegionId.Base)
                        returnedToBase = true;
                    break;
                }
            }

            gateFrom.Dispose();
            gateTo.Dispose();
            gateRadiusSq.Dispose();
            gatePos.Dispose();
            gateArrival.Dispose();

            // Early return: a player came back to base mid-Expedition -> expire the Expedition timer (-> Defend).
            if (returnedToBase && SystemAPI.TryGetSingletonEntity<CycleState>(out var cycleEntity))
            {
                var cs = SystemAPI.GetComponent<CycleState>(cycleEntity);
                if (cs.Phase == CyclePhase.Expedition)
                {
                    cs.PhaseEndTick = 1; // CyclePhaseSystem sees timedPhaseDue next tick -> Defend
                    SystemAPI.SetComponent(cycleEntity, cs);
                }
            }
        }
    }
}