Unity camera collision

using UnityEngine;
using System.Collections;

public class ThirdPersonController : MonoBehaviour {

	public GameObject player;
	public GameObject mainCamera;
	public GameObject cameraCollisionBox;
	public CollisionCounter cameraProbe;

	public float Maxdistance;
	public float moveSpeed;
	public float verticalRatio;

	void CalculateHeight(){
		Vector3 originVector = mainCamera.transform.position;
		Vector3 localVector = mainCamera.transform.localPosition;
		
		// REMOVE Y to caculate XZ magnitude
		originVector.y = player.transform.position.y;
		
		float y = Maxdistance - (originVector - player.transform.position).magnitude;
		localVector.y=y;
		mainCamera.transform.localPosition = localVector*verticalRatio;
	}

	// Update is called once per frame
	void Update () {
		// GET INPUT AXIS
		float vertical = Input.GetAxis ("Vertical");
		float horizontal = Input.GetAxis ("Horizontal");
		// GET DIRECTION
		Vector3 forward = mainCamera.transform.forward;
		//Calibrate Y AXIS 
		forward.y = 0;
		// GET DIRECTION UNIT VECTOR
		forward.Normalize ();

		Vector3 distance = (mainCamera.transform.position - player.transform.position);
		distance.y = 0;
		
		if (vertical > 0) {
			player.rigidbody.velocity = forward * moveSpeed;
			//Camera chases the player
			if (distance.magnitude > Maxdistance) {
					float originY = cameraCollisionBox.transform.position.y;
					Vector3 newPosition = player.transform.position + distance.normalized * Maxdistance;
					newPosition.y = originY;
					cameraCollisionBox.transform.position = newPosition;
			}
			CalculateHeight();
				
		} else if (vertical < 0) {
			player.rigidbody.velocity = -forward * moveSpeed;
			if( cameraProbe.counter == 0 ){
				//Camera chases the player
				float originY = cameraCollisionBox.transform.position.y;
				Vector3 newPosition = player.transform.position + distance.normalized * Maxdistance;
				newPosition.y = originY;
				cameraCollisionBox.transform.position = newPosition;
			}else{
				CalculateHeight();
			}
		}else{
			player.rigidbody.velocity = Vector3.zero;
		}
	}
}