geometry-tower-defense-base/src-ref/CustomComponent/InventoryGeneration/InventoryGenerationRandomContext.cs

using System;
using Random = System.Random;

namespace GeometryTD.Definition
{
    public readonly struct InventoryGenerationRandomContext
    {
        public InventoryGenerationRandomContext(
            int runSeed,
            int nodeSequenceIndex,
            InventoryTagSourceType sourceType,
            int localOrdinal)
        {
            RunSeed = runSeed;
            NodeSequenceIndex = nodeSequenceIndex;
            SourceType = sourceType;
            LocalOrdinal = localOrdinal;
        }

        public int RunSeed { get; }

        public int NodeSequenceIndex { get; }

        public InventoryTagSourceType SourceType { get; }

        public int LocalOrdinal { get; }

        public Random CreateRandom()
        {
            return new Random(BuildSeed());
        }

        public long CreateStableItemInstanceId()
        {
            long normalizedSource = ((long)Math.Max(0, (int)SourceType) + 1L) << 48;
            long normalizedSequence = ((long)Math.Max(0, NodeSequenceIndex) + 1L) << 24;
            long normalizedOrdinal = (uint)(Math.Max(0, LocalOrdinal) + 1);
            return normalizedSource | normalizedSequence | normalizedOrdinal;
        }

        public InventoryTagRandomContext CreateTagRandomContext(int configId)
        {
            return SourceType switch
            {
                InventoryTagSourceType.Shop => InventoryTagRandomContext.CreateShop(RunSeed, NodeSequenceIndex, LocalOrdinal, configId),
                InventoryTagSourceType.Reward => InventoryTagRandomContext.CreateReward(RunSeed, NodeSequenceIndex, LocalOrdinal, configId),
                InventoryTagSourceType.Event => InventoryTagRandomContext.CreateEvent(RunSeed, NodeSequenceIndex, LocalOrdinal, configId),
                _ => InventoryTagRandomContext.CreateDrop(RunSeed, NodeSequenceIndex, LocalOrdinal, configId)
            };
        }

        private int BuildSeed()
        {
            unchecked
            {
                int seed = 17;
                seed = seed * 31 + RunSeed;
                seed = seed * 31 + NodeSequenceIndex;
                seed = seed * 31 + (int)SourceType;
                seed = seed * 31 + LocalOrdinal;
                return seed;
            }
        }
    }
}