GhostEngine/Ghost.Entities/Templates/EntityQuery.EntityComponentIterator.tt

<#@ template language="C#" #>
<#@ output extension="gen.cs" #>
<#@ assembly name="System.Core" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Text" #>
<#@ include file="Helpers.ttinclude" #>
using Ghost.Core;
using Misaki.HighPerformance.LowLevel;
using Misaki.HighPerformance.LowLevel.Buffer;
using Misaki.HighPerformance.LowLevel.Collections;
using System.Runtime.CompilerServices;

namespace Ghost.Entities;

public unsafe partial struct EntityQuery
{
<# for (var i = 1; i <= Amount; i++)
{
    var generics = AppendParameters(i, "T{0}");
    var compGenerics = AppendParameters(i, "ref T{0} component{0}");
    var deconstrictOutPrams = AppendParameters(i, "out Ref<T{0}> component{0}");
    var restrictions = AppendGenericRestrictionsMultiline(i, "unmanaged, IComponent", 2);
#>
    public readonly ref struct EntityComponentIterator<<#= generics #>>
<#= restrictions #>
    {
        public ref struct QueryItem
        {
            public Entity entity;

<# for (var j = 0; j < i; j++) { #>
            public ref T<#= j #> component<#= j #>;
<# } #>
            internal QueryItem(Entity entity, <#= compGenerics #>)
            {
                this.entity = entity;

<# for (var j = 0; j < i; j++) { #>
                this.component<#= j #> = ref component<#= j #>;
<# } #>
            }

            public void Deconstruct(out Entity entity, <#= deconstrictOutPrams #>)
            {
                entity = this.entity;

<# for (var j = 0; j < i; j++) { #>
                component<#= j #> = new Ref<T<#= j #>>(ref this.component<#= j #>);
<# } #>
            }
        }

        public ref struct Enumerator : IDisposable
        {
            private fixed int _compTypeIDs[<#= i #>];
            private fixed int _offsets[<#= i #>];
            private fixed long _compBasePtrs[<#= i #>];

            private readonly ReadOnlyUnsafeCollection<Identifier<Archetype>> _matchingArchetypes;
            private readonly EntityQueryMask _mask;
            private readonly World _world;

            private readonly Stack.Scope _scope;
            private UnsafeList<int> _changedComponentIDs;

            private ref Archetype _currentArchetype;
            private ref Chunk _currentChunk;
            private byte* _chunkBasePtr;

            private int _currentChunkEntityCount;
            private int _currentArchetypeIndex;
            private int _currentChunkIndex;
            private int _currentEntityIndex;

            internal Enumerator(ReadOnlyUnsafeCollection<Identifier<Archetype>> matchingArchetypes, EntityQueryMask mask, World world)
            {
<# for (var j = 0; j < i; j++) { #>
                _compTypeIDs[<#= j #>] = ComponentTypeID<T<#= j #>>.Value;
                _offsets[<#= j #>] = 0;
                _compBasePtrs[<#= j #>] = 0;

<# } #>
                _matchingArchetypes = matchingArchetypes;
                _mask = mask;
                _world = world;

                _scope = AllocationManager.CreateStackScope();
                _changedComponentIDs = new UnsafeList<int>(<#= i #>, _scope.AllocationHandle);

                var it = _mask.writeAccess.GetIterator();
                while (it.Next(out var id))
                {
                    for (var i = 0; i < <#= i #>; i++)
                    {
                        if (id == _compTypeIDs[i])
                        {
                            _changedComponentIDs.Add(id);
                            break;
                        }
                    }
                }

                Reset();
            }

            public QueryItem Current => new(
                *(Entity*)(_chunkBasePtr + _currentArchetype.EntityIDsOffset + _currentEntityIndex * sizeof(Entity)),
<# for (var j = 0; j < i; j++) { #>
                ref *(T<#= j #>*)(_compBasePtrs[<#= j #>] + _currentEntityIndex * sizeof(T<#= j #>))<#= j < i - 1 ? "," : "" #>
<# } #>
            );

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private void SetChunk(int chunkIndex)
            {
                _currentChunk = ref _currentArchetype.GetChunkReference(chunkIndex);
                _chunkBasePtr = _currentChunk.GetUnsafePtr();
                _currentChunkEntityCount = _currentChunk._count;

                for (var index = 0; index < <#= i #>; index++)
                {
                    var layout = _currentArchetype.GetLayout(_compTypeIDs[index])
                        .GetValueOrThrow();
                    _offsets[index] = layout.offset;
                    _compBasePtrs[index] = (long)(_chunkBasePtr + _offsets[index]);
                }

                for (var i = 0; i < _changedComponentIDs.Count; i++)
                {
                    _currentArchetype.MarkChanged(_currentChunkIndex, _changedComponentIDs[i], _world.Version);
                }
            }

            public bool MoveNext()
            {
                while (true)
                {
                    _currentEntityIndex++;
                    if (_currentEntityIndex < _currentChunk._count)
                    {
                        var pChunkData = _currentChunk.GetUnsafePtr();
                        if (IsEntityValid(pChunkData, _currentEntityIndex, in _currentArchetype, in _mask))
                        {
                            return true;
                        }

                        continue;
                    }

                    _currentChunkIndex++;
                    if (!Unsafe.IsNullRef(ref _currentArchetype) && _currentChunkIndex < _currentArchetype.ChunkCount)
                    {
                        SetChunk(_currentChunkIndex);
                        _currentEntityIndex = -1; // Reset for new chunk

                        continue;
                    }

                    _currentArchetypeIndex++;
                    if (_currentArchetypeIndex < _matchingArchetypes.Count)
                    {
                        _currentArchetype = ref _world.ComponentManager.GetArchetypeReference(_matchingArchetypes[_currentArchetypeIndex]);

                        _currentChunkIndex = 0;
                        if (_currentArchetype.ChunkCount > 0)
                        {
                            SetChunk(0);
                            _currentEntityIndex = -1;
                            continue;
                        }

                        // If archetype has no chunks, loop will try next archetype
                    }
                    else
                    {
                        return false; // End of all data
                    }
                }
            }

            public void Reset()
            {
                _currentArchetype = ref Unsafe.NullRef<Archetype>();
                _currentChunk = ref Unsafe.NullRef<Chunk>();
                _currentArchetypeIndex = 0;
                _currentChunkIndex = 0;
                _currentEntityIndex = -1;

                if (_matchingArchetypes.Count > 0)
                {
                    _currentArchetype = ref _world.ComponentManager.GetArchetypeReference(_matchingArchetypes[0]);
                    if (_currentArchetype.ChunkCount > 0)
                    {
                        SetChunk(0);
                    }
                }
            }

            public readonly void Dispose()
            {
                _scope.Dispose();
            }
        }

        private readonly ReadOnlyUnsafeCollection<Identifier<Archetype>> _matchingArchetypes;
        private readonly EntityQueryMask _mask;
        private readonly World _world;

        internal EntityComponentIterator(ReadOnlyUnsafeCollection<Identifier<Archetype>> matchingArchetypes, EntityQueryMask mask, World world)
        {
            _matchingArchetypes = matchingArchetypes;
            _mask = mask;
            _world = world;
        }

        public Enumerator GetEnumerator()
        {
            return new Enumerator(_matchingArchetypes, _mask, _world);
        }
    }

    public readonly EntityComponentIterator<<#= generics#>> GetEntityComponentIterator<<#= generics#>>()
<#= restrictions #>
    {
        var world = World.GetWorld(_worldID);
        if (world is null)
        {
            return default;
        }

        return new EntityComponentIterator<<#= generics#>>(_matchingArchetypes.AsReadOnly(), _mask, world);
    }

<# } #>
}