Unity groundedness detection with collision normals

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

enum Groundedness {
    AIRBORNE,
    SLIPPING,
    GROUNDED
}
//because of how Enums work, these 3 states correspond to the numbers 0, 1, & 2 respectively
//so it's true that AIRBORNE < SLIPPING < GROUNDED
public class GroundedExample : MonoBehaviour
{
    Groundedness groundState = Groundedness.AIRBORNE;
    public float groundedThresholdAngle = 45; //maximum slope angle that's still considered grounded (in degrees)
    float groundedThresholdCosine; //cosine of above value
    public float slippingThresholdAngle = 80; //maximum slope angle that's not considered just a wall (in degrees)
    float slippingThresholdCosine; //cosine of above value
    Vector3 upwards = new Vector3(0,1,0); //this can be changed if wanted

    void Start()
    {
        float groundedThresholdCosine = Mathf.Cos(groundedThresholdAngle * Mathf.Deg2Rad);
        float slippingThresholdCosine = Mathf.Cos(slippingThresholdAngle * Mathf.Deg2Rad);
    }

    void FixedUpdate() {
        //FixedUpdate happens before the OnCollision functions
        //put this at the end of FixedUpdate
        //or, if you're manually calling Physics.Simulate, put this right before that
        groundState = Groundedness.AIRBORNE;
    }

    void Update()
    {
        //Update happens after the OnCollision functions
    }
    void OnCollisionStay(Collision collisionInfo) {
        foreach (ContactPoint contact in collisionInfo.contacts) {
            float slopeCosine = Vector3.Dot(contact.normal, upwards);
            //this value is 1 if this collision is with flat ground, 0 if it's with a wall, and -1 if it's with a ceiling
            if (slopeCosine >= groundedThresholdCosine) {
                if (groundState < Groundedness.GROUNDED) {
                    groundState = Groundedness.GROUNDED;
                }
            }
            else if (slopeCosine >= slippingThresholdCosine) {
                if (groundState < Groundedness.SLIPPING) {
                    groundState = Groundedness.SLIPPING;
                }
            }
        }
    }
}