using System.Collections.Generic;
using HexagonSurvive.Environment.Components;
using HexagonSurvive.Environment.Settings;
using HexagonSurvive.Game.Managers;
using HexagonSurvive.Map.Components;
using Unity.Collections;
using Unity.Entities;
using UnityEngine;

namespace HexagonSurvive.Containers.ECS
{
    public class EntityContainerBaker : Baker<EntityContainerMono>
    {
        public override void Bake(EntityContainerMono authoring)
        {
            var builder = new BlobBuilder(Allocator.Temp);
            ref BlobArray<Entity> trees = ref builder.ConstructRoot<BlobArray<Entity>>();
            List<GameObject> treePrefabs = PrefabsContainer.Instance.treePrefabs;
            BlobBuilderArray<Entity> arrayBuilder = builder.Allocate(ref trees, treePrefabs.Count);

            for (int i = 0; i < treePrefabs.Count; i++)
                arrayBuilder[i] = GetEntity(treePrefabs[i], TransformUsageFlags.Renderable);

            Entity e = GetEntity(authoring, TransformUsageFlags.None);
            GlobalEnvironment gEnv = EnvironmentManager.Instance.globalEnvironment;
            AddComponent(e, new GlobalEnvironmentData
            {
                planeMeshRes = gEnv.planeMeshRes,
                planeMeshSize = gEnv.planeMeshSize
            });
            AddComponent(e, new HexMapPrefabsData
            {
                hexUnit = GetEntity(authoring.hexUnit, TransformUsageFlags.NonUniformScale),
                trees = builder.CreateBlobAssetReference<BlobArray<Entity>>(Allocator.Persistent),
                waterSurface = GetEntity(PrefabsContainer.Instance.waterSurface, TransformUsageFlags.Renderable)
            });
            builder.Dispose();
        }
    }
}

-------------------------------------

[UpdateInGroup(typeof(InitializationSystemGroup))]
public partial struct HexMapInitSystem : ISystem
{
...
// there's too much code in this class, so I picked the related code only
private void InstantiateUnit(ref SystemState state, float2 pos)
{
    Entity hexUnit = state.EntityManager.Instantiate(_prefabs.hexUnit);
    HexUnitAspect unitAspect = SystemAPI.GetAspect<HexUnitAspect>(hexUnit);
    float height = GetUnitHeight(pos);
    int altitude = StepAltitude(height);
    TerrainNoiseProperties settings = _map.Data.tnProp;
    float unitHeight = altitude * settings.stepHeight + settings.baseHeight;
    Biome biome = height > settings.seaLevel
        ? GetBiomeLand(unitAspect, pos, unitHeight)
        : GetBiomeWater(unitAspect, pos, unitHeight);
    unitAspect.AdjustData
    (
        altitude,
        unitHeight / 2,
        unitHeight > _map.Data.tnProp.seaLevel,
        biome
    );
    unitAspect.Transform
    (
        new float3(pos.x, unitHeight / 4, pos.y),
        float3.zero,
        new float3(1, unitHeight / 2, 1)
    );
    // GenerateVegetation(ref state, unitAspect);
}
...
}

------------------------------------

using UnityEngine;

namespace HexagonSurvive.Containers.ECS
{
    public class EntityContainerMono : MonoBehaviour
    {
        public PrefabsContainer prefabs;
        public GameObject hexUnit;
    }
}