AssetBundleLoader.cs

using System.IO;
using System.Linq;
using Base_Mod;
using JetBrains.Annotations;
using UnityEngine;

namespace Decal_Loader;

[UsedImplicitly]
public class AssetBundleLoader(string configPath) : BaseLoader(configPath) {
    private static readonly byte[] UNITY_FS = [0x55, 0x6E, 0x69, 0x74, 0x79, 0x46, 0x53]; // Asset bundle header: `UnityFS`

    protected override void Load() {
        var files = Directory.EnumerateFiles(configPath, "*", SearchOption.TopDirectoryOnly)
                             .Where(IsAssetBundle);

        foreach (var file in files) {
            var bundle      = AssetBundle.LoadFromFile(file);
            var allTextures = bundle.LoadAllAssets<Texture2D>().ToList();

            if (allTextures.Count == 0) return;

            var bundleName = Path.GetFileNameWithoutExtension(file);
            var category   = CreateDecalCategory(bundleName);

            var log = new LogBuffer();
            log.WriteLine($"Loading asset bundle: {bundleName}");
            foreach (var texture in allTextures) {
                CreateDecal(category, bundleName, texture, log);
            }
            log.Flush();
        }
    }

    private bool IsAssetBundle(string file) {
        try {
            using var reader = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read);
            var       buffer = new byte[7];
            return reader.Read(buffer, 0, buffer.Length) == 7 && buffer.SequenceEqual(UNITY_FS);
        } catch (IOException) {
            return false;
        }
    }

    protected static void CreateDecal(DecalCategory category, string bundleName, Texture2D texture, LogBuffer log) {
        var name = texture.name;
        var file = bundleName + "::" + name;

        var guid = Database.instance.GetGuidForUri(file);
        if (guid == null) {
            guid = GUID.Create();
            Database.instance.Add(file, (GUID) guid);
        }

        RegisterDecal(category, (GUID) guid, texture);
        log.WriteLine($"Loaded decal: {file}.");
    }
}