Highlight text within square bracket (regex ?) Android kotlin

Question

I would like to highlight all of the substring which are inside square brackets, ex: "[Toto] is [doing a lot of] stuff at the same time."
I know how to extract it.
I know how to highlight:

val str = SpannableString("Toto is doing a lot of stuff at the same time.")
str.setSpan(BackgroundColorSpan(Color.YELLOW), 0, 4, 0)
str.setSpan(BackgroundColorSpan(Color.YELLOW), 8, 22 , 0)
textView.text = str

But the problem is I don't know how to achieve both together.

I obviously want to remove the square bracket after have applied the highlight effect but when I do a toString() then a replace() the highlight is removed.

Also, the highlight is made with index, and I don't want to extract the substring but let it in the original string, I don't know by which optimized way I should achieve that.

There is the result:

Answer 1

Maybe it's better not to use regex in order to extract the texts between close brackets. I think it increases the complexity of this job. Using a simple iteration over the text, we can achieve the result in linear complexity.

val text = "[Toto] is [doing a lot of] stuff at the same time."

val spanStack = Stack<Pair<Int, Int>>()
var index = 0

text.forEach {
    when (it) {
        '[' -> spanStack.push(index to index)
        ']' -> spanStack.push(spanStack.pop().first to index)
        else -> index++
    }
}

val spannableString = text
    .replace("[\\[\\]]".toRegex(), "")
    .let { SpannableString(it) }
    .apply {
        spanStack.forEach {
            setSpan(
                BackgroundColorSpan(Color.YELLOW),
                it.first,
                it.second,
                SpannableString.SPAN_INCLUSIVE_INCLUSIVE
            )
        }
    }

textView.text = spannableString

Result: