Groovy groupBy on multiple properties and extracting only value - groovy

Question

Having a list of elements:
List list = [
[category: 'A', name: 'a' value: 10],
[category: 'A', name: 'b' value: 20],
[category: 'B', name: 'a' value: 30],
[category: 'B', name: 'c' value: 40],
[category: 'B', name: 'd' value: 50],
]
I want to transform it into a nested map:
Map map = [
A: [a: 10, b: 20],
B: [a: 30, c: 40, d: 50],
]
The only solution I have come up with is to do something like this:
list.groupBy(
{ it.category }, { it.name }
).collectEntries { category, names ->
[(category): names.collectEntries { name, values ->
[(name): values.value[0]]
}]
}
However, I will have to deal with more than 2 levels of nesting in the future, and this approach will be unfeasible.
Is there any neat way to obtain the proper result in Groovy that will be more flexible?
EDIT:
By more than 2 levels of nesting I mean converting structure like:
List list = [
[category: 'A', subcategory: 'I', group: 'x', name: 'a', value: 10],
[category: 'A', subcategory: 'I', group: 'y', name: 'b', value: 20],
]
Into:
Map map = [
A: [I: [
x: [a: 10],
y: [b: 20],
]],
]
By adding nesting (depth) it would require more nested collectEntries calls, which will become unreadable.

Answer 1

I have found a neat solution to the problem by using Map's withDefault method and recursive Closure calls:
Map map = { [:].withDefault { owner.call() } }.call()
list.each {
map[it.category][it.name] = it.value
}
Or for the second case:
Map map = { [:].withDefault { owner.call() } }.call()
list.each {
map[it.category][it.subcategory][it.group][it.name] = it.value
}