TreeTraversal.kt

data class Property(val name: String, val objectRef: String? = null)

data class Model(val name: String, val properties: List<Property>)


val m1 = Model(
    "m1", listOf(
        Property("p11"),
        Property("p12", "m2"),
    )
)
val m2 = Model(
    "m2", listOf(
        Property("p21"),
        Property("p22", "m3"),
        Property("p23", "m3"),
        Property("p24", "m5"),
    )
)
val m3 = Model(
    "m3", listOf(
        Property("p31"),
        Property("p32", "m4"),
        // Property("p33", "m2"),
    )
)
val m4 = Model(
    "m4", listOf(
        Property("p41"),
    )
)
val m5 = Model(
    "m5", listOf(
        Property("p51"),
    )
)

val models = listOf(m1, m2, m3, m4, m5)

// -----

fun List<Model>.findRefs(model: Model): List<Model> {
    val models = this

    fun String.toModel() = models.firstOrNull { it.name == this }

    fun Model.children() =
        properties.mapNotNull { it.objectRef }.toSet().mapNotNull { modelname -> modelname.toModel() }

    // TODO detect cycles
    fun Model.collectRefs(acc: List<Model>): List<Model> =
        children().flatMap { it.collectRefs(acc) } + this

    return model.collectRefs(emptyList())
}

fun main() {
    println(models.findRefs(m1).map { it.name })
    println(models.findRefs(m2).map { it.name })
    println(models.findRefs(m3).map { it.name })
    println(models.findRefs(m4).map { it.name })
}