Svelto.ECS/com.sebaslab.svelto.ecs/Core/ComponentBuilder.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Threading;
using DBC.ECS;
using Svelto.Common;
using Svelto.DataStructures;
using Svelto.ECS.Hybrid;
using Svelto.ECS.Internal;
using Svelto.Utilities;

namespace Svelto.ECS
{
    struct ComponentBuilderComparer : IEqualityComparer<IComponentBuilder>
    {
        public bool Equals(IComponentBuilder x, IComponentBuilder y)
        {
            return x.GetEntityComponentType() == y.GetEntityComponentType();
        }

        public int GetHashCode(IComponentBuilder obj)
        {
            return obj.GetEntityComponentType().GetHashCode();
        }
    }

    public static class BurstCompatibleCounter
    {
        public static int counter;        
    }
    
    public class ComponentID<T> where T : struct, IEntityComponent
    {
        public static readonly SharedStaticWrapper<int, ComponentID<T>> id;

#if UNITY_BURST 
        [Unity.Burst.BurstDiscard] 
        //SharedStatic values must be initialized from not burstified code
#endif
        public static void Init()
        {
            id.Data = Interlocked.Increment(ref BurstCompatibleCounter.counter);

            DBC.ECS.Check.Ensure(id.Data < ushort.MaxValue, "too many types registered, HOW :)");
        }
    }

    public class ComponentBuilder<T> : IComponentBuilder where T : struct, IEntityComponent
    {
        internal static readonly Type ENTITY_COMPONENT_TYPE;
        internal static readonly bool IS_ENTITY_VIEW_COMPONENT;

        static readonly T      DEFAULT_IT;
        static readonly string ENTITY_COMPONENT_NAME;
        static readonly bool   IS_UNMANAGED;
#if SLOW_SVELTO_SUBMISSION            
        public static readonly bool HAS_EGID;
        public static readonly bool HAS_REFERENCE;
#endif

        static ComponentBuilder()
        {
            ENTITY_COMPONENT_TYPE = typeof(T);
            DEFAULT_IT = default;
            IS_ENTITY_VIEW_COMPONENT = typeof(IEntityViewComponent).IsAssignableFrom(ENTITY_COMPONENT_TYPE);
#if SLOW_SVELTO_SUBMISSION            
            HAS_EGID = typeof(INeedEGID).IsAssignableFrom(ENTITY_COMPONENT_TYPE);
            HAS_REFERENCE = typeof(INeedEntityReference).IsAssignableFrom(ENTITY_COMPONENT_TYPE);
            
            SetEGIDWithoutBoxing<T>.Warmup();
#endif
            ComponentID<T>.Init();
            ENTITY_COMPONENT_NAME = ENTITY_COMPONENT_TYPE.ToString();
            IS_UNMANAGED = TypeType.isUnmanaged<T>(); //attention this is important as it serves as warm up for Type<T>
#if UNITY_NATIVE
            if (IS_UNMANAGED)
                EntityComponentIDMap.Register<T>(new Filler<T>());
#endif

            ComponentBuilderUtilities.CheckFields(ENTITY_COMPONENT_TYPE, IS_ENTITY_VIEW_COMPONENT);

            if (IS_ENTITY_VIEW_COMPONENT)
            {
                EntityViewComponentCache.InitCache();
            }
            else
            {
                if (ENTITY_COMPONENT_TYPE != ComponentBuilderUtilities.ENTITY_INFO_COMPONENT &&
                    ENTITY_COMPONENT_TYPE.IsUnmanagedEx() == false)
                    throw new Exception(
                        $"Entity Component check failed, unexpected struct type (must be unmanaged) {ENTITY_COMPONENT_TYPE}");
            }
        }

        public ComponentBuilder()
        {
            _initializer = DEFAULT_IT;
        }

        public ComponentBuilder(in T initializer) : this()
        {
            _initializer = initializer;
        }

        public bool isUnmanaged => IS_UNMANAGED;

        public void BuildEntityAndAddToList(ITypeSafeDictionary dictionary, EGID egid, IEnumerable<object> implementors)
        {
            var castedDic = dictionary as ITypeSafeDictionary<T>;

            if (IS_ENTITY_VIEW_COMPONENT)
            {
                T entityComponent = default;
                
                Check.Require(castedDic.ContainsKey(egid.entityID) == false,
                    $"building an entity with already used entity id! id: '{(ulong)egid}', {ENTITY_COMPONENT_NAME}");

                this.SetEntityViewComponentImplementors(ref entityComponent, EntityViewComponentCache.cachedFields,
                    implementors, EntityViewComponentCache.implementorsByType, EntityViewComponentCache.cachedTypes);

                castedDic.Add(egid.entityID, entityComponent);
            }
            else
            {
                Check.Require(!castedDic.ContainsKey(egid.entityID),
                    $"building an entity with already used entity id! id: '{egid.entityID}'");

                castedDic.Add(egid.entityID, _initializer);
            }
        }

        void IComponentBuilder.Preallocate(ITypeSafeDictionary dictionary, uint size)
        {
            Preallocate(dictionary, size);
        }

        public ITypeSafeDictionary CreateDictionary(uint size)
        {
            return TypeSafeDictionaryFactory<T>.Create(size);
        }

        public Type GetEntityComponentType()
        {
            return ENTITY_COMPONENT_TYPE;
        }

        public override int GetHashCode()
        {
            return _initializer.GetHashCode();
        }

        static void Preallocate(ITypeSafeDictionary dictionary, uint size)
        {
            dictionary.EnsureCapacity(size);
        }

        readonly T _initializer;

        /// <summary>
        ///     Note: this static class will hold forever the references of the entities implementors. These references
        ///     are not even cleared when the engines root is destroyed, as they are static references.
        ///     It must be seen as an application-wide cache system. Honestly, I am not sure if this may cause leaking
        ///     issues in some kind of applications. To remember.
        /// </summary>
        static class EntityViewComponentCache
        {
            internal static readonly FasterList<KeyValuePair<Type, FastInvokeActionCast<T>>> cachedFields;
            internal static readonly Dictionary<Type, Type[]>                                cachedTypes;
#if DEBUG && !PROFILE_SVELTO
            internal static readonly Dictionary<Type, ECSTuple<object, int>> implementorsByType;
#else
            internal static readonly Dictionary<Type, object> implementorsByType;
#endif
            static EntityViewComponentCache()
            {
                cachedFields = new FasterList<KeyValuePair<Type, FastInvokeActionCast<T>>>();

                var type   = typeof(T);
                var fields = type.GetFields(BindingFlags.Public | BindingFlags.Instance);

                for (var i = fields.Length - 1; i >= 0; --i)
                {
                    var field = fields[i];
                    if (field.FieldType.IsInterface == true)
                    {
                        var setter = FastInvoke<T>.MakeSetter(field);

                        //for each interface, cache the setter for this type 
                        cachedFields.Add(new KeyValuePair<Type, FastInvokeActionCast<T>>(field.FieldType, setter));
                    }
                }
#if DEBUG && !PROFILE_SVELTO
                if (fields.Length == 0)
                    Console.LogWarning($"No fields found in component {type}. Are you declaring only properties?");
#endif

                cachedTypes = new Dictionary<Type, Type[]>();

#if DEBUG && !PROFILE_SVELTO
                implementorsByType = new Dictionary<Type, ECSTuple<object, int>>();
#else
                implementorsByType = new Dictionary<Type, object>();
#endif
            }

            internal static void InitCache()
            {
            }
        }
    }
}