class PropertiesComparePlugin : Plugin<Project> {
    override fun apply(p0: Project?) {
        p0?.let { it.extensions.create("path", Holder::class.java) }

        p0?.let {
            p0.tasks.getByName("build").dependsOn(it.task("compareProps").doLast {
                val fp = Properties()
                val sp = Properties()
                val path = p0.extensions.getByType(Holder::class.java)
                fp.load(p0.file(path.firstPropFile).run { inputStream() })
                sp.load(p0.file(path.secondPropFile).run { inputStream() })
                when (compareKeysSet(fp, sp)) {
                    true -> print("key sets are equals")
                    false -> throw GradleException("different keys set in properties files")
                }
            })
        }

    }

    private fun compareKeysSet(prop1: Properties, prop2: Properties): Boolean
            = prop1.keys.containsAll(prop2.keys) && prop1.keys.size == prop2.keys.size
}