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

namespace ProjectM.Server
{
    /// <summary>
    /// Server-only, one-shot spawner for the shared home-base storage container (mirrors
    /// UpgradePickupSpawnSystem). On its first update it reads the baked <see cref="StorageSpawner"/>
    /// singleton and the <see cref="BaseAnchor"/>, instantiates the container ghost at the cell center
    /// (<see cref="BaseGridMath.CellToWorld"/>), then destroys the spawner singleton so the system idles
    /// (spawned exactly once). Runs in the default SimulationSystemGroup (NOT the prediction loop); the
    /// container replicates to clients as an ownerless interpolated ghost. The container is intentionally
    /// NOT linked to any connection's LinkedEntityGroup, so it persists across player disconnects.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    public partial struct SharedStorageSpawnSystem : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
            state.RequireForUpdate<StorageSpawner>();
            state.RequireForUpdate<BaseAnchor>();
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            var spawnerEntity = SystemAPI.GetSingletonEntity<StorageSpawner>();
            var spawner = SystemAPI.GetComponent<StorageSpawner>(spawnerEntity);
            var anchor = SystemAPI.GetSingleton<BaseAnchor>();

            var ecb = new EntityCommandBuffer(Allocator.Temp);

            if (spawner.Prefab != Entity.Null)
            {
                var container = ecb.Instantiate(spawner.Prefab);
                var position = BaseGridMath.CellToWorld(anchor, spawner.Cell);
                // Phase 0: the grid Y (GridOrigin.y=1) is the CC capsule-CENTER plane; center-pivot structure
                // meshes look grounded there, but the crate's pivot is at its base -> it floated 1 u. Sit it on
                // the terrain surface instead.
                position.y = 0f;
                // Preserve the prefab's baked scale/rotation (FromPosition would reset Scale to 1).
                var xform = SystemAPI.GetComponent<LocalTransform>(spawner.Prefab);
                xform.Position = position;
                ecb.SetComponent(container, xform);
                // M6: scope the shared storage to the base region for ghost relevancy.
                ecb.AddComponent(container, new RegionTag { Region = RegionId.Base });
            }

            // One-shot: remove the spawner so RequireForUpdate fails and the system idles.
            ecb.DestroyEntity(spawnerEntity);

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