using UnityEngine;
using UnityEngine.UI;

/// <summary>
/// Tween the object's alpha.
/// </summary>
[RequireComponent(typeof(Image))]
public class TweenFillAmount : Tweener
{
    [Range(0f, 1f)]
    public float from = 1f;
    [Range(0f, 1f)]
    public float to = 1f;

    public bool resetOnEnable = false;

    Image mGraphic;
    /// <summary>
    /// Tween's current value.
    /// </summary>

    public float value {
        get {
            if (mGraphic == null)
                mGraphic = GetComponent<Image>();
            return mGraphic.fillAmount;
        }
        set {
            if (mGraphic == null)
                mGraphic = GetComponent<Image>();
            mGraphic.fillAmount = value;
        }
    }

    protected override void Awake()
    {
        base.Awake();
        mGraphic = GetComponent<Image>();
    }

    void OnEnable()
    {
        if (resetOnEnable)
        {
            tweenFactor = 0;
            Sample(0, false);
        }
    }

    /// <summary>
    /// Tween the value.
    /// </summary>

    protected override void OnUpdate(float factor, bool isFinished)
    {
        value = Mathf.Lerp(from, to, factor);
    }

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

    static public TweenFillAmount Begin(GameObject go, float duration, float alpha)
    {
        TweenFillAmount comp = Tweener.Begin<TweenFillAmount>(go, duration);
        comp.from = comp.value;
        comp.to = alpha;

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

    public override void SetStartToCurrentValue()
    {
        from = value;
    }
    public override void SetEndToCurrentValue()
    {
        to = value;
    }
}