Project-M/Assets/_Project/Scripts/Simulation/Persistence/SaveStructureScan.cs

using System.Collections.Generic;
using Unity.Collections;
using Unity.Entities;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Scans a server world for PLAYER-built structures (<see cref="PlacedStructure"/> + <see cref="RuntimePlacedTag"/>)
    /// into the flat SaveData arrays — the SINGLE shared scan used by BOTH the autosave (SaveWriteSystem) and the
    /// quit-to-menu save (WorldLauncher), so the two paths can never drift (only RuntimePlacedTag structures are saved;
    /// anything baked into the subscene is the subscene's source of truth, not the save's). Managed (List/array) —
    /// runs only on a save, never in the hot loop.
    /// </summary>
    public static class SaveStructureScan
    {
        public static void Collect(EntityManager em, uint nowTick, out StructureSave[] structures, out StructureIoRow[] io)
        {
            var structs = new List<StructureSave>();

            using var q = em.CreateEntityQuery(
                ComponentType.ReadOnly<PlacedStructure>(),
                ComponentType.ReadOnly<RuntimePlacedTag>());
            using var entities = q.ToEntityArray(Allocator.Temp);

            for (int k = 0; k < entities.Length; k++)
            {
                var e = entities[k];
                var ps = em.GetComponentData<PlacedStructure>(e);

                structs.Add(new StructureSave
                {
                    Type = ps.Type,
                    CellX = ps.Cell.x,
                    CellZ = ps.Cell.y,
                    // EB-1: guarded so structures without Health don't crash the autosave path (no try/catch).
                    HP = em.HasComponent<Health>(e) ? em.GetComponentData<Health>(e).Current : 0f,
                });
            }

            structures = structs.ToArray();
            io = System.Array.Empty<StructureIoRow>(); // machine I/O retired with the automation chain (row type dies at save v7)
        }
    }
}