object ClassCollector {

    private val KINDS = setOf(JavaFileObject.Kind.CLASS)

    private val fileManager: JavaFileManager

    init {
        val compiler = ToolProvider.getSystemJavaCompiler()
        fileManager = compiler.getStandardFileManager(DiagnosticCollector<JavaFileObject>(), null, null)
    }

    fun collect(vararg pkgs: String): Collection<Class<*>> {
        return pkgs.map { collect(it) }.flatten()
    }

    fun collect(pkg: String): Collection<Class<*>> {
        return fileManager.list(StandardLocation.CLASS_PATH, pkg, KINDS, true).map {
            val path = it.toUri().path.replace(".class", "").replace("/", ".")
            val p = path.lastIndexOf(pkg)
            Class.forName(if (p > 0) path.substring(p, path.length) else path)
        }
    }

}