Splitting each element(s) in nested array field into 2 respectively

[dx123]

I've found a few threads online discussing this but what my situation requires is more complex. Basically I have a array data field called target, where in most of the cases in my feeds it just consists of 1 element but the rest are nested ( > 2 elements).

An example of its nested syntax: "target": ["A - B", "P - Q", "X - Y"]

What I would like to achieve is to split each element by the dash (-) and thereafter push each first half into a new field called "main" and and the second half into another new field called "sub".

Final desired output:
The field "main" should consist of A, P and X and the field "sub" should consist of B, Q and Y.

My code right now that doesn't completely work:

	if [target] {
	mutate {
		split => {
			"target" => "-"
		}
	}

	mutate {
		add_field => {
			"main" => "%{[target][0]}"
			"sub" => "%{[target][1]}"	
		}
	}
}

Anyone knows how to accomplish this? I know ruby filters are definitely required as well but I do not know how to write them.