Bundle+Resources.swift

import Foundation

public extension Bundle {

    private final class Marker {}

    // Looking for bundle involves a lot of IO
    private static let cache: NSCache<NSString, Bundle> = NSCache<NSString, Bundle>()

    public static func resourcesBundle(forModuleName moduleName: String) -> Bundle {
        if let cachedBundle = cache.object(forKey: moduleName as NSString) {
            return cachedBundle
        }
        let bundle = resolved(forModuleName: moduleName)
        cache.setObject(bundle, forKey: moduleName as NSString)
        return bundle
    }

    private static func resolved(forModuleName moduleName: String) -> Bundle {
        return Bundle.main.anyNested(forModuleName: moduleName)
            ?? Bundle.main
    }

    private func anyNested(forModuleName moduleName: String) -> Bundle? {
        if let framework = nestedFramework(name: moduleName) {
            return framework.nestedResourceBundle(moduleName: moduleName)
                ?? framework
        }
        return nestedResourceBundle(moduleName: moduleName)
    }

    private func nestedFramework(name: String) -> Bundle? {
        return path(forResource: name, ofType: "framework", inDirectory: "Frameworks")
            .flatMap(Bundle.init(path:))
    }

    private func nestedResourceBundle(moduleName: String) -> Bundle? {
        guard let resourceBundlePath =
            path(forResource: moduleName + "Resources", ofType: "bundle")
            ?? path(forResource: moduleName, ofType: "bundle")
        else { return nil }
        return Bundle(path: resourceBundlePath)
    }
}