TechbloxModdingAPI/TechbloxModdingAPI/Utility/ECS/NativeApiExtensions.EntitiesDBHelper.cs

using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Reflection;
using HarmonyLib;
using Svelto.DataStructures;
using Svelto.ECS;

namespace TechbloxModdingAPI.Utility.ECS
{
    public static partial class NativeApiExtensions
    {
        [SuppressMessage("ReSharper", "StaticMemberInGenericType")]
        private static class EntitiesDBHelper<T> where T : unmanaged, IEntityComponent
        { // Each type gets a new set of fields here (that's what the ReSharper warning is about too)
            public static readonly Lazy<MethodInfo> EntityStream =
                new(() => AccessTools.PropertyGetter(typeof(EntitiesDB), "_entityStream"));

            public static readonly Lazy<FieldInfo> Streams = new(() =>
                AccessTools.Field(EntityStream.Value.ReturnType, "_streams"));

            public static readonly Lazy<FieldInfo> Consumers = new(() =>
                AccessTools.Field(typeof(EntityStream<T>), "_consumers"));

            public static readonly Lazy<MethodInfo> TryGetValue =
                new(AccessTools.Method(Streams.Value.FieldType, "TryGetValue"));

            public static readonly Lazy<FieldInfo> RingBuffer =
                new(() => AccessTools.Field(typeof(Consumer<T>), "_ringBuffer"));
        }

        private static EntityStream<T> GetEntityStream<T>(this EntitiesDB entitiesDB) where T : unmanaged, IEntityComponent
        {
            // EntitiesStreams (internal)
            var entitiesStreams = EntitiesDBHelper<T>.EntityStream.Value.Invoke(entitiesDB, Array.Empty<object>());
            // FasterDictionary<RefWrapperType, ITypeSafeStream> (interface is internal)
            var streams = EntitiesDBHelper<T>.Streams.Value.GetValue(entitiesStreams);
            
            var parameters = new object[] { TypeRefWrapper<T>.wrapper, null };
            var success = EntitiesDBHelper<T>.TryGetValue.Value.Invoke(streams, parameters);
            if (!(bool)success)
                return null; // There is no entity stream for this type
            return (EntityStream<T>)parameters[1];
        }
        
        private static ThreadSafeFasterList<Consumer<T>> GetConsumers<T>(this EntityStream<T> stream) where T : unmanaged, IEntityComponent
        {
            return (ThreadSafeFasterList<Consumer<T>>)EntitiesDBHelper<T>.Consumers.Value.GetValue(stream);
        }

        private static RingBuffer<(T, EGID)> GetRingBuffer<T>(this Consumer<T> consumer) where T : unmanaged, IEntityComponent
        {
            return (RingBuffer<(T, EGID)>)EntitiesDBHelper<T>.RingBuffer.Value.GetValue(consumer);
        }
    }
}