Rotate Object inside room according to wall

I have a room. I am trying to move object whenever it collides with wall. its working properly except at the edge of two meeting walls. at edge its flicking. I tried to move object when its colliding at edge. but that also not working properly.

i want to use rotation like this

here's my code

using UnityEngine; using System.Collections; using DG.Tweening;

public class DragNDropObjRotation : MonoBehaviour { string lastCol; GameObject controller;

 Vector3 rotation;

 void Start()
 {
     rotation = gameObject.transform.rotation.eulerAngles;
 }

 void OnTriggerEnter(Collider col)
 {
     if (col.gameObject.tag == AppConstants.WALL_LEFT_BACK && col.gameObject.tag != AppConstants.WALL_RIGHT_BACK && col.gameObject.tag != AppConstants.WALL_LEFT_FRONT && col.gameObject.tag != AppConstants.WALL_RIGHT_FRONT && lastCol != "" && lastCol != AppConstants.WALL_LEFT_BACK)
     {
         Debug.Log("inside wall left back");
         MoveObjectAtCollioson(col.gameObject.tag);
         lastCol = AppConstants.WALL_LEFT_BACK;
         Invoke("RotateObjAfterCollision", 0.25f);
     }
     else if (col.gameObject.tag != AppConstants.WALL_LEFT_BACK && col.gameObject.tag == AppConstants.WALL_RIGHT_BACK && col.gameObject.tag != AppConstants.WALL_LEFT_FRONT && col.gameObject.tag != AppConstants.WALL_RIGHT_FRONT && lastCol != "" && lastCol != AppConstants.WALL_RIGHT_BACK)
     {
         Debug.Log("inside wall right back");
         MoveObjectAtCollioson(col.gameObject.tag);
         lastCol = AppConstants.WALL_RIGHT_BACK; 
         Invoke("RotateObjAfterCollision", 0.25f);
     }
     else if (col.gameObject.tag != AppConstants.WALL_LEFT_BACK && col.gameObject.tag != AppConstants.WALL_RIGHT_BACK && col.gameObject.tag == AppConstants.WALL_LEFT_FRONT && col.gameObject.tag != AppConstants.WALL_RIGHT_FRONT && lastCol != "" && lastCol != AppConstants.WALL_LEFT_FRONT)
     {
         Debug.Log("inside wall left front");
         MoveObjectAtCollioson(col.gameObject.tag);
         lastCol = AppConstants.WALL_LEFT_FRONT; 
         Invoke("RotateObjAfterCollision", 0.25f);
     }
     else if (col.gameObject.tag != AppConstants.WALL_LEFT_BACK && col.gameObject.tag != AppConstants.WALL_RIGHT_BACK && col.gameObject.tag != AppConstants.WALL_LEFT_FRONT && col.gameObject.tag == AppConstants.WALL_RIGHT_FRONT && lastCol != "" && lastCol != AppConstants.WALL_RIGHT_FRONT)
     {
         Debug.Log("inside wall right front");
         MoveObjectAtCollioson(col.gameObject.tag);
         lastCol = AppConstants.WALL_RIGHT_FRONT; 
         Invoke("RotateObjAfterCollision", 0.25f);
     }
 }

 void MoveObjectAtCollioson(string currentCol)
 {
     Vector3 parentCol = gameObject.transform.parent.GetComponent<BoxCollider>().size;
     Vector3 parentPos = gameObject.transform.parent.transform.position;

     switch (currentCol)
     {
         case AppConstants.WALL_RIGHT_BACK:
             Debug.Log("case 0: moved @ right wall back");
             if (lastCol == AppConstants.WALL_LEFT_BACK)
             {
                 Debug.Log("moving on left wall back ");
                 parentPos = new Vector3(parentPos.x, parentPos.y, parentPos.z - parentCol.y);
             }
             if (lastCol == AppConstants.WALL_LEFT_FRONT)
             {
                 Debug.Log("moving on left wall front ");
                 parentPos = new Vector3(parentPos.x, parentPos.y, parentPos.z + parentCol.y);
             }
             break;

         case AppConstants.WALL_LEFT_BACK:
             Debug.Log("case 1: moved @ left wall back");
             if (lastCol == AppConstants.WALL_RIGHT_BACK)
             {
                 parentPos = new Vector3(parentPos.x - parentCol.y, parentPos.y, parentPos.z);
             }
             if (lastCol == AppConstants.WALL_RIGHT_FRONT)
             {
                 parentPos = new Vector3(parentPos.x + parentCol.y, parentPos.y, parentPos.z);
             }
             break;

         case AppConstants.WALL_LEFT_FRONT:
             Debug.Log("case 2: moved @ left wall fornt");
             if (lastCol == AppConstants.WALL_RIGHT_BACK)
             {
                 parentPos = new Vector3(parentPos.x + parentCol.y, parentPos.y, parentPos.z);
             }
             if (lastCol == AppConstants.WALL_RIGHT_FRONT)
             {
                 parentPos = new Vector3(parentPos.x - parentCol.y, parentPos.y, parentPos.z);
             }
             break;

         case AppConstants.WALL_RIGHT_FRONT:
             Debug.Log("case 3: moved @ right wall front");
             if (lastCol == AppConstants.WALL_LEFT_BACK)
             {
                 Debug.Log("moving on left wall back ");
                 parentPos = new Vector3(parentPos.x, parentPos.y, parentPos.z - parentCol.y);
             }
             if (lastCol == AppConstants.WALL_LEFT_FRONT)
             {
                 Debug.Log("moving on left wall front ");
                 parentPos = new Vector3(parentPos.x, parentPos.y, parentPos.z + parentCol.y);
             }
             break;
     }
     
 }

 void RotateObjAfterCollision()
 {
     Quaternion rotation = gameObject.transform.parent.transform.rotation;
     switch (lastCol)
     {
         case AppConstants.WALL_RIGHT_BACK:               
             rotation.eulerAngles = new Vector3(0, 0, 0);
             break;

         case AppConstants.WALL_LEFT_BACK:
             rotation.eulerAngles = new Vector3(0, 0, -90);
             break;

         case AppConstants.WALL_LEFT_FRONT:
             rotation.eulerAngles = new Vector3(0, 0, 90);
             break;

         case AppConstants.WALL_RIGHT_FRONT:
             rotation.eulerAngles = new Vector3(0, 0, 180);
             break;
     }
     gameObject.transform.parent.transform.GetComponent<Rigidbody>().MoveRotation(rotation);
 }

}