using UnityEngine;

/// <summary>
///	Example script using the Singleton<T> generic class.  This object
/// rotates a camera around an object.
/// </summary>
public class MyScript : MonoBehaviour
{
	#region Properties
	
	/// <summary>
	/// Camera being moved
	/// </summary>
	public Camera targetCamera;
	
	/// <summary>
	/// Object camera is moving around
	/// </summary>
	public Transform target;
	
	/// <summary>
	/// Number of seconds to take to revolve around the target object.
	/// </summary>
	public float duration = 5f;
	
	/// <summary>
	/// Number of units away from object to place camera.
	/// </summary>
	public float distance = 10f;
	
	#endregion
	
	#region Events
	
	/// <summary>
	/// We're assigning the singleton during awake, since its the 
	/// earliest access we have to the MonoBehaviour object instance.  
	/// Note that the .instance property is write-once, meaning that 
	/// once it has an instance additional calls will not overwrite 
	/// the original reference.
	/// </summary>
	void Awake()
	{
		Singleton<MyScript>.instance = this;
	}
	
	/// <summary>
	/// Use the active camera by default, and the game object attached to
	/// this component to look at.
	/// </summary>
	void Start()
	{
		this.targetCamera = Camera.main;
		this.target = this.transform;
	}
	
	/// <summary>
	/// Updates object position.  I'm using trig functions here, but 
	/// you could use a quaternion to achieve the same effect.
	/// </summary>
	void Update()
	{
		this.theta += Time.deltaTime / this.duration;
		
		Vector3 offset = new Vector3();
		offset.x = Mathf.Cos(this.theta) * this.distance;
		offset.y = Mathf.Sin(this.theta) * this.distance;
		offset.z = 0;
		
		Vector3 v = this.target.position + offset;
		
		this.targetCamera.transform.position = v;
		this.targetCamera.transform.LookAt(this.target);		
	}
	
	#endregion
	
	#region Private
	
	/// <summary>
	/// Current angle around target.
	/// </summary>
	private float theta = 0f;
	
	#endregion
}