Construct Binary Search Tree from Preorder Traversal (wrong solution))

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {

    fun bstFromPreorder(preorder: IntArray): TreeNode? {
        if(preorder.size == 0) return null

        val root = TreeNode(preorder[0], null, null)
        buildBst(root, min = Int.MIN_VALUE, max = Int.MAX_VALUE, preorder = preorder, nodeIdx = 1)

        return root
    }

    private fun buildBst(root: TreeNode, min: Int, max: Int, preorder: IntArray, nodeIdx: Int) {
        println("root=${root.`val`}/${root.left}/${root.right}, min=$min, max=$max, node=${preorder[nodeIdx]}")
        if(nodeIdx >= preorder.size) return

        val nodeVal = preorder[nodeIdx]//5
        val node = TreeNode(nodeVal, null, null)

        if(nodeVal > min && nodeVal < root.`val`) {
            root.left = node
            buildBst(root = node, min = min, max = root.`val`, preorder = preorder, nodeIdx = nodeIdx + 1)
        } else if(nodeVal > root.`val` && nodeVal < max) {
            root.right = node
            buildBst(root = node, min = root.`val`, max = max, preorder = preorder, nodeIdx = nodeIdx + 1)
        } else {

/*error is here. I cannot return to parent boundaries
input: [8,5,1,7,10,12]

stdout:
root=8/null/null, min=-2147483648, max=2147483647, node=5
root=5/null/null, min=-2147483648, max=8, node=1
root=1/null/null, min=-2147483648, max=5, node=7

actual output: [8,5,null,1]
expected output: [8,5,10,1,7,null,12]
*/
        }
    }
}