#region USING

using UnityEngine;
using UnityEngine.UI;

#endregion

[RequireComponent(typeof (ScrollRect))]
public class ScrollRectEnsureVisible : MonoBehaviour
{
    public float AnimTime = 0.15f;
    public bool Log = true;
    public RectTransform MaskTransform;

    private RectTransform _content;
    private ScrollRect _sr;

    private void Awake()
    {
        _sr = GetComponent<ScrollRect>();
        _content = _sr.content;
    }

    public void CenterOnItem(RectTransform target)
    {
        if (Log) Debug.Log("Updating scrollrect for item: " + target);

        //this is the center point of the visible area
        var maskHalfSize = MaskTransform.rect.size*0.5f;
        var contentSize = _content.rect.size;
        //get object position inside content
        var targetRelativePosition =
            _content.InverseTransformPoint(target.parent.TransformPoint(target.anchoredPosition));
        //adjust for item size
        targetRelativePosition += new Vector3(target.rect.size.x, target.rect.size.y, 0f)*0.25f;
        //get the normalized position inside content
        var normalizedPosition = new Vector2(
            Mathf.Clamp01(targetRelativePosition.x/(contentSize.x - maskHalfSize.x)),
            1f - Mathf.Clamp01(targetRelativePosition.y/-(contentSize.y - maskHalfSize.y))
            );
        //we want the position to be at the middle of the visible area
        //so get the normalized center offset based on the visible area width and height
        var normalizedOffsetPosition = new Vector2(maskHalfSize.x / contentSize.x, maskHalfSize.y / contentSize.y);
        //and apply it
        normalizedPosition.x -= (1f -normalizedPosition.x)*normalizedOffsetPosition.x;
        normalizedPosition.y += normalizedPosition.y*normalizedOffsetPosition.y;

        normalizedPosition.x = Mathf.Clamp01(normalizedPosition.x);
        normalizedPosition.y = Mathf.Clamp01(normalizedPosition.y);

        if (Log)
            Debug.Log(string.Format(
                @"Target normalized position [{3}]
Mask half size [{0}]
Content size: [{1}]
Target relative position [{2}]",
                maskHalfSize,
                contentSize,
                targetRelativePosition,
                normalizedPosition
                ));

        //_sr.normalizedPosition = normalizedPosition;
        Go.to(_sr, AnimTime, new GoTweenConfig().vector2Prop("normalizedPosition", normalizedPosition));
    }

    /// <summary>
    /// Takes a float value from a [0f,1f] range and translates it to a [-1f,1f] range
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    float Transtale01RangeToMinus11Range(float value)
    {
        return (value + ((1f - value)*-1f));
    }
}