//----------------------------------------------
//            NGUI: Next-Gen UI kit
// Copyright © 2011-2012 Tasharen Entertainment
//----------------------------------------------

using UnityEngine;

/// <summary>
/// Tween the audio source's volume.
/// </summary>

[AddComponentMenu("NGUI/Tween/Volume")]
public class TweenVolume : UITweener
{
	public float from = 0f;
	public float to = 1f;

	AudioSource mSource;

	/// <summary>
	/// Cached version of 'audio', as it's always faster to cache.
	/// </summary>

	public AudioSource audioSource
	{
		get
		{
			if (mSource == null)
			{
				mSource = audio;
				
				if (mSource == null)
				{
					mSource = GetComponentInChildren<AudioSource>();

					if (mSource == null)
					{
						Debug.LogError("TweenVolume needs an AudioSource to work with", this);
						enabled = false;
					}
				}
			}
			return mSource;
		}
	}

	/// <summary>
	/// Audio source's current volume.
	/// </summary>

	public float volume { get { return audioSource.volume; } set { audioSource.volume = value; } }

	/// <summary>
	/// Tween update function.
	/// </summary>

	override protected void OnUpdate (float factor, bool isFinished)
	{
		volume = from * (1f - factor) + to * factor;
		mSource.enabled = (mSource.volume > 0.01f);
	}

	/// <summary>
	/// Start the tweening operation.
	/// </summary>

	static public TweenVolume Begin (GameObject go, float duration, float targetVolume)
	{
		TweenVolume comp = UITweener.Begin<TweenVolume>(go, duration);
		comp.from = comp.volume;
		comp.to = targetVolume;

		if (duration <= 0f)
		{
			comp.Sample(1f, true);
			comp.enabled = false;
		}
		return comp;
	}
}