Android RecyclerView Item Decoration : Equal Margin + Auto Span Count + Auto Orientation

MarginItemDecoration.kt

import android.graphics.Rect
import android.view.View
import androidx.annotation.Px
import androidx.recyclerview.widget.GridLayoutManager
import androidx.recyclerview.widget.RecyclerView

class MarginItemDecoration(
    @Px private val marginInPixels: Int
) : RecyclerView.ItemDecoration() {
    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
        val spanCount = getSpanCount(parent)
        val orientation = getOrientation(parent)

        val position = parent.getChildAdapterPosition(view)
        val isFirstRow = position < spanCount
        val isStartOfRow = position % spanCount == 0

        with(outRect) {
            if (orientation == RecyclerView.VERTICAL) {
                top = if (isFirstRow) marginInPixels else 0
                left = if (isStartOfRow) marginInPixels else 0
            } else if (orientation == RecyclerView.HORIZONTAL) {
                left = if (isFirstRow) marginInPixels else 0
                top = if (isStartOfRow) marginInPixels else 0
            }
            right = marginInPixels
            bottom = marginInPixels
        }
    }

    private fun getSpanCount(recyclerView: RecyclerView): Int {
        return (recyclerView.layoutManager as? GridLayoutManager)?.spanCount ?: 1
    }

    @RecyclerView.Orientation
    private fun getOrientation(recyclerView: RecyclerView): Int {
        return (recyclerView.layoutManager as? GridLayoutManager)?.orientation ?: RecyclerView.VERTICAL
    }
}