using UnityEngine;

public static class RectTransformExtensions
{
    /// <summary>
    /// 座標を保ったままPivotを変更する
    /// </summary>
    /// <param name="rectTransform">自身の参照</param>
    /// <param name="targetPivot">変更先のPivot座標</param>
    public static void SetPivotWithKeepingPosition(this RectTransform rectTransform, Vector2 targetPivot)
    {
        var diffPivot = targetPivot - rectTransform.pivot;
        rectTransform.pivot = targetPivot;
        var diffPos = new Vector2(rectTransform.sizeDelta.x * diffPivot.x, rectTransform.sizeDelta.y * diffPivot.y);
        rectTransform.anchoredPosition += diffPos;
    }
    /// <summary>
    /// 座標を保ったままPivotを変更する
    /// </summary>
    /// <param name="rectTransform">自身の参照</param>
    /// <param name="x">変更先のPivotのx座標</param>
    /// <param name="y">変更先のPivotのy座標</param>
    public static void SetPivotWithKeepingPosition(this RectTransform rectTransform, int x, int y)
    {
        rectTransform.SetPivotWithKeepingPosition(new Vector2(x, y));
    }
    /// <summary>
    /// 座標を保ったままAnchorを変更する
    /// </summary>
    /// <param name="rectTransform">自身の参照</param>
    /// <param name="targetAnchor">変更先のAnchor座標 (min,maxが共通の場合)</param>
    public static void SetAnchorWithKeepingPosition(this RectTransform rectTransform, Vector2 targetAnchor)
    {
        rectTransform.SetAnchorWithKeepingPosition(targetAnchor, targetAnchor);
    }
    /// <summary>
    /// 座標を保ったままAnchorを変更する
    /// </summary>
    /// <param name="rectTransform">自身の参照</param>
    /// <param name="x">変更先のAnchorのx座標 (min,maxが共通の場合)</param>
    /// <param name="y">変更先のAnchorのy座標 (min,maxが共通の場合)</param>
    public static void SetAnchorWithKeepingPosition(this RectTransform rectTransform, int x, int y)
    {
        rectTransform.SetAnchorWithKeepingPosition(new Vector2(x, y));
    }
    /// <summary>
    /// 座標を保ったままAnchorを変更する
    /// </summary>
    /// <param name="rectTransform">自身の参照</param>
    /// <param name="targetMinAnchor">変更先のAnchorMin座標</param>
    /// <param name="targetMaxAnchor">変更先のAnchorMax座標</param>
    public static void SetAnchorWithKeepingPosition(this RectTransform rectTransform, Vector2 targetMinAnchor, Vector2 targetMaxAnchor)
    {
        var parent = rectTransform.parent as RectTransform;
        if (parent == null)
        {
            Debug.LogError("nullreferenceexception: Parent cannot find.");
        }
        var diffMin = targetMinAnchor - rectTransform.anchorMin;
        var diffMax = targetMaxAnchor - rectTransform.anchorMax;
        // anchorの更新
        rectTransform.anchorMin = targetMinAnchor;
        rectTransform.anchorMax = targetMaxAnchor;
        // 上下左右の距離の差分を計算
        var diffLeft = parent.rect.width * diffMin.x;
        var diffRight = parent.rect.width * diffMax.x;
        var diffBottom = parent.rect.height * diffMin.y;
        var diffTop = parent.rect.height * diffMax.y;
        // サイズと座標の修正
        rectTransform.sizeDelta += new Vector2(diffLeft - diffRight, diffBottom - diffTop);
        var pivot = rectTransform.pivot;
        rectTransform.anchoredPosition -= new Vector2(
             (diffLeft * (1 - pivot.x)) + (diffRight * pivot.x),
             (diffBottom * (1 - pivot.y)) + (diffTop * pivot.y)
        );
    }
    /// <summary>
    /// 座標を保ったままAnchorを変更する
    /// </summary>
    /// <param name="rectTransform">自身の参照</param>
    /// <param name="minX">変更先のAnchorMinのx座標</param>
    /// <param name="minY">変更先のAnchorMinのy座標</param>
    /// <param name="maxX">変更先のAnchorMaxのx座標</param>
    /// <param name="maxY">変更先のAnchorMaxのy座標</param>
    public static void SetAnchorWithKeepingPosition(this RectTransform rectTransform, int minX, int minY, int maxX, int maxY)
    {
        rectTransform.SetAnchorWithKeepingPosition(new Vector2(minX, minY), new Vector2(maxX, maxY));
    }
}