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Core libraries used by microservices created from the vertx-kuickstart template

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package dev.fuelyour.vertxkuickstartcore.tools

import kotlin.reflect.KProperty1
import kotlin.reflect.full.declaredFunctions
import kotlin.reflect.full.declaredMemberProperties

/**
 * Helper function for combining an object and a patch, such that patch fields
 * override the fields in the object if they are present, otherwise the fields
 * from the object come through. Note that the object and patch remain
 * unchanged,and a new object is created and returned.
 */
@Suppress("UNCHECKED_CAST")
fun  T.applyPatch(patch: Any): T {
    if (this::class.isData) {
        val copy = this::class.declaredFunctions.first { it.name == "copy" }
        val args = patch::class.declaredMemberProperties
            .filter { copy.parameters.any { param -> param.name == it.name } }
            .map {
                copy.parameters.first { param -> param.name == it.name } to
                    (it as KProperty1).get(patch)
            }
            .filter {
                with(it.second) {
                    (this is Field<*> && present) ||
                        (this !is Field<*> && this != null)
                }
            }
            .map {
                it.first to with(it.second) {
                    if (this is Field<*>) value else this
                }
            }
            .toMap() + mapOf(copy.parameters[0] to this)
        return copy.callBy(args) as T
    } else {
        throw Exception("Must be a data class")
    }
}