(feature) Implement registry that manages observables and property paths.

[hastebrot]

The registry orchestrates trees of observable objects (property paths) with multiple observable values (bindings).

[hastebrot]

data class TestBean(
    var string: String = "foo",
    var integer: Int = 1,
    val stringReadonly: String = "bar",
    val integerReadonly: Int = 2,
    val array: MutableList<String> = mutableListOf(),
    val bean: TestBean? = null
)

fun main(vararg args: String) {
    properties(TestBean::class).forEach {
        val propertyName = it.name
        val propertyType = it.returnType
        val propertyImpl = it::class.simpleName
        println("$propertyName: $propertyType ($propertyImpl)")
    }
}

private fun <T: Any> properties(type: KClass<T>): Collection<KProperty1<T, *>>
    = type.memberProperties

array: kotlin.collections.MutableList<kotlin.String> (KProperty1Impl)
bean: protokolax.TestBean? (KProperty1Impl)
integer: kotlin.Int (KMutableProperty1Impl)
integerReadonly: kotlin.Int (KProperty1Impl)
string: kotlin.String (KMutableProperty1Impl)
stringReadonly: kotlin.String (KProperty1Impl)

[hastebrot]

So, reflection of properties is not very nice. Let us use annotations instead and directly tell, what we want to to with the properties.

@Target(AnnotationTarget.PROPERTY)
annotation class Observe(vararg val types: ObserveType)

enum class ObserveType {
    CHANGES, SPLICES, PATHS
}

data class Person(
    @Observe(CHANGES) var firstName: String? = null,
    @Observe(CHANGES) var lastName: String? = null,
    @Observe(SPLICES) val foods: List<String> = mutableListOf(),
    @Observe(SPLICES, PATHS) val friends: List<Person> = mutableListOf()
)