AssetBundleAssetPostProcessor.cs

using UnityEngine;
using System.IO;
using System.Text.RegularExpressions;
using UnityEditor;

/// <summary>
/// This post processor will detect when assets move in and out of a specified bundles directory
/// and assign the correct Asset Bundle name to it.
/// Current design is to create an asset bundle for each 2-folder deep combination.
/// For example /Assets/Bundles/Tilesets/Spacestation/* will set any folders and assets under it
/// to a bundle called 'tilesets-spacestation'.
/// </summary>
public class AssetBundleAssetPostProcessor : AssetPostprocessor
{
    private const string BundlesLocation = "Assets/Bundles";

    static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths) {
        foreach (var path in importedAssets)
        {
            if(IsValidBundlePath(path)) UpdateBundleInformation(path);
        }

        for (var i = 0; i < movedAssets.Length; i++)
        {
            if (IsValidBundlePath(movedAssets[i]))
            {
                UpdateBundleInformation(movedAssets[i]);
            } else if (IsValidBundlePath(movedFromAssetPaths[i]))
            {
                var assetImporter = AssetImporter.GetAtPath(movedAssets[i]);
                assetImporter.SetAssetBundleNameAndVariant("", "");
            }
        }
    }

    private static void UpdateBundleInformation(string assetPath) {
        var assetImporter = AssetImporter.GetAtPath(assetPath);
        
        //var assetBundleName = GetParentAssetBundleName(assetPath);

        SetParentFolderBundleNames(assetPath);

        var assetBundleName = GetAssetBundleName(assetPath);

        Debug.Log("Setting bundle for asset " + assetPath + " to " + assetBundleName);

        assetImporter.SetAssetBundleNameAndVariant(assetBundleName, "");
    }

    private static string GetAssetBundleName(string assetPath) {
        var regex = new Regex(BundlesLocation + "/(.*?/.*?)/.*");
        var isFolder = !Path.HasExtension(assetPath);

        var path = isFolder ? assetPath + "/" : Path.GetDirectoryName(assetPath) + "/";

        var match = regex.Match(path);

        var assetBundleName = match.Groups[1].Value.Replace("/", "-").ToLower();

        return assetBundleName;
    }

    private static bool IsValidBundlePath(string path)
    {
        if (!new Regex(BundlesLocation + "/.*").IsMatch(path)) return false;

        var bundlesFolder = new Regex(BundlesLocation + "/.*?/.*?/");

        var isFolder = !Path.HasExtension(path);

        var dir = isFolder ? path + "/" : Path.GetDirectoryName(path) + "/";

        var isMatch = bundlesFolder.IsMatch(dir);

        if(!isMatch) Debug.LogError("File or folder " + path + " is not in a valid location in the Asset Bundle path!");

        return isMatch;
    }

    private static string GetParentAssetBundleName(string path) {
        var regex = new Regex("(.*)/");
        var isFolder = !Path.HasExtension(path);

        path = isFolder ? path : Path.GetDirectoryName(path);

        var assetImporter = AssetImporter.GetAtPath(path);

        if (string.IsNullOrEmpty(assetImporter.assetBundleName))
        {
            if (!regex.IsMatch(path))
            {
                Debug.LogError("There was no valid parent asset bundle set for some asset recently added!");
                return null;
            }

            path = GetParentAssetBundleName(regex.Split(path)[0]);
        }

        return assetImporter.assetBundleName;
    }

    private static void SetParentFolderBundleNames(string path)
    {
        var bundleName = GetAssetBundleName(path);

        var folder2 = new Regex("(" + BundlesLocation + "/.*?/.*?)/");
        if (folder2.IsMatch(path))
        {
            var assetImporter = AssetImporter.GetAtPath(folder2.Split(path)[1]);
            assetImporter.SetAssetBundleNameAndVariant(bundleName, "");
        }
    }
}