I need HELP ! Wall Jump in 3D Platformer CharacterController

I am working on a 3D platformer and I want to be able to wall jump, I can control my character while my player is in air, but I need wall jump using CharacterController.

Here is the movement code that I am using to move, jump and control my player while he is jumping:

 // Movement fields
     float speed = 6f;
     float jumpSpeed = 12f;
     float gravity = 20f;
     Vector3 moveDir;
 
 void Update ()
 {
     Movement ();
 }
 
 void Movement ()
 {
         if (controller.isGrounded) {
             moveDir = new Vector3 (Input.GetAxis ("Horizontal"), 0, Input.GetAxis ("Vertical"));
             moveDir = trans.TransformDirection (moveDir);
             moveDir *= speed;
             if (Input.GetButton ("Jump"))
                 moveDir.y = jumpSpeed;
         } else {
             moveDir.x = Input.GetAxis ("Horizontal") * speed;
             moveDir.z = Input.GetAxis ("Vertical") * speed;
         }
 
         moveDir.y -= gravity * Time.deltaTime;
         controller.Move (moveDir * Time.deltaTime);
 }