MutateThenThenThen.kt

data class AA(
    val a1: String,
    val a2: BB,
    val a3: Int,
)

data class BB(
    val b1: CC,
    val b2: Int,
)

data class CC(
    val c1: String,
    val c2: String
)

fun main() {
    val foo = AA(
        a1 = "A here",
        a2 = BB(
            b1 = CC(
                c1 = "C here",
                c2 = "Hello!"
            ),
            b2 = 2
        ),
        a3 = 1
    )

    val bar = foo.copy(a2 = foo.a2.copy(b1 = foo.a2.b1.copy(c2 = "Hello world!")))
    val bar2 = foo.mutate { ::a2 }.then { ::b1 }.then { ::c2 }.replace("Hello world!")

    println("foo=$foo")
    println("bar=$bar")
    println("bar=$bar2")


    //val bar2 = foo.mutate { it.a2.b1.c2 }.with("Hello world!")
}

fun <T : Any, A : Any> T.mutate(fieldToMutate: T.() -> KProperty0<A>): Then<T, A> {
    return Then(this, fieldToMutate.invoke(this))
}

class Then<T, A>(val origin: T, val acc: KProperty0<A>)
class Then2<T, A, B>(val origin: T, val acc: KProperty0<A>, val acc2: KProperty0<B>)
class Then3<T, A, B, C>(val origin: T, val acc: KProperty0<A>, val acc2: KProperty0<B>, val acc3: KProperty0<C>)
class Then4<T, A, B, C, D>(val origin: T, val acc: KProperty0<A>, val acc2: KProperty0<B>, val acc3: KProperty0<C>, val acc4: KProperty0<D>)
class Then5<T, A, B, C, D, E>(val origin: T, val acc: KProperty0<A>, val acc2: KProperty0<B>, val acc3: KProperty0<C>, val acc4: KProperty0<D>, val acc5: KProperty0<E>)
class Then6<T, A, B, C, D, E, F>(val origin: T, val acc: KProperty0<A>, val acc2: KProperty0<B>, val acc3: KProperty0<C>, val acc4: KProperty0<D>, val acc5: KProperty0<E>, val acc6: KProperty0<F>)

inline fun<reified T: Any, reified A: Any> Then<T, A>.replace(with: A): T {
    val originCopy = T::class.memberFunctions.first { it.name == "copy" }
    return originCopy.callBy(mapOf(
        originCopy.instanceParameter!! to this.origin,
        originCopy.parameters.first { it.name == acc.name } to with
    )) as T
}

inline fun<reified T: Any, reified A: Any, reified B: Any> Then2<T, A, B>.replace(with: B): T {
    val originCopy = T::class.memberFunctions.first { it.name == "copy" }
    return originCopy.callBy(mapOf(
        originCopy.instanceParameter!! to this.origin,
        originCopy.parameters.first { it.name == acc.name } to acc.invoke().mutate { acc2 }.replace(with)
    )) as T
}

inline fun<reified T: Any, reified A: Any, reified B: Any, reified C: Any> Then3<T, A, B, C>.replace(with: C): T {
    val originCopy = T::class.memberFunctions.first { it.name == "copy" }
    return originCopy.callBy(mapOf(
        originCopy.instanceParameter!! to this.origin,
        originCopy.parameters.first { it.name == acc.name } to acc.invoke().mutate { acc2 }.then { acc3 }.replace(with)
    )) as T
}

inline fun<reified T: Any, reified A: Any, reified B: Any, reified C: Any, reified D: Any> Then4<T, A, B, C, D>.replace(with: D): T {
    val originCopy = T::class.memberFunctions.first { it.name == "copy" }
    return originCopy.callBy(mapOf(
        originCopy.instanceParameter!! to this.origin,
        originCopy.parameters.first { it.name == acc.name } to acc.invoke().mutate { acc2 }.then { acc3 }.then { acc4 }.replace(with)
    )) as T
}

inline fun<reified T: Any, reified A: Any, reified B: Any, reified C: Any, reified D: Any, reified E: Any> Then5<T, A, B, C, D, E>.replace(with: E): T {
    val originCopy = T::class.memberFunctions.first { it.name == "copy" }
    return originCopy.callBy(mapOf(
        originCopy.instanceParameter!! to this.origin,
        originCopy.parameters.first { it.name == acc.name } to acc.invoke().mutate { acc2 }.then { acc3 }.then { acc4 }.then { acc5 }.replace(with)
    )) as T
}

inline fun<reified T: Any, reified A: Any, reified B: Any, reified C: Any, reified D: Any, reified E: Any, reified F: Any> Then6<T, A, B, C, D, E, F>.replace(with: F): T {
    val originCopy = T::class.memberFunctions.first { it.name == "copy" }
    return originCopy.callBy(mapOf(
        originCopy.instanceParameter!! to this.origin,
        originCopy.parameters.first { it.name == acc.name } to acc.invoke().mutate { acc2 }.then { acc3 }.then { acc4 }.then { acc5 }.then { acc6 }.replace(with)
    )) as T
}

fun <T : Any, N : Any, O : Any> Then<T, N>.then(fieldToMutate: N.() -> KProperty0<O>): Then2<T, N, O> {
    return Then2(origin, acc, fieldToMutate.invoke(acc.invoke()))
}

fun <T : Any, N : Any, O : Any, P : Any> Then2<T, N, O>.then(fieldToMutate: O.() -> KProperty0<P>): Then3<T, N, O, P> {
    return Then3(origin, acc, acc2, fieldToMutate.invoke(acc2.invoke()))
}

fun <T : Any, N : Any, O : Any, P : Any, Q: Any> Then3<T, N, O, P>.then(fieldToMutate: P.() -> KProperty0<Q>): Then4<T, N, O, P, Q> {
    return Then4(origin, acc, acc2, acc3, fieldToMutate.invoke(acc3.invoke()))
}

fun <T : Any, N : Any, O : Any, P : Any, Q: Any, R: Any> Then4<T, N, O, P, Q>.then(fieldToMutate: Q.() -> KProperty0<R>): Then5<T, N, O, P, Q, R> {
    return Then5(origin, acc, acc2, acc3, acc4, fieldToMutate.invoke(acc4.invoke()))
}

fun <T : Any, N : Any, O : Any, P : Any, Q: Any, R: Any, S: Any> Then5<T, N, O, P, Q, R>.then(fieldToMutate: R.() -> KProperty0<S>): Then6<T, N, O, P, Q, R, S> {
    return Then6(origin, acc, acc2, acc3, acc4, acc5, fieldToMutate.invoke(acc5.invoke()))
}