/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * All rights reserved.
 *
 * Licensed under the Oculus SDK License Agreement (the "License");
 * you may not use the Oculus SDK except in compliance with the License,
 * which is provided at the time of installation or download, or which
 * otherwise accompanies this software in either electronic or hard copy form.
 *
 * You may obtain a copy of the License at
 *
 * https://developer.oculus.com/licenses/oculussdk/
 *
 * Unless required by applicable law or agreed to in writing, the Oculus SDK
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using UnityEngine;
using UnityEngine.UI;

[RequireComponent(typeof(RectTransform), typeof(GridLayoutGroup))]
public class GridSpacingScaler : MonoBehaviour
{
    public enum Axis
    {
        Horizontal = 0,
        Vertical = 1
    }

    public Axis scaleAxis;
    public Vector2 minSpacing;

    private GridLayoutGroup _gridLayoutGroup;
    private RectTransform _rectTransform;

    void Start()
    {
        _rectTransform = transform as RectTransform;
        if (_rectTransform == null) Debug.LogError("GameObject Transform is not a Rect Transform");
        _gridLayoutGroup = gameObject.GetComponent<GridLayoutGroup>();
        if (_gridLayoutGroup == null) Debug.LogError("GameObject does not include a GridLayoutGroup");
    }

    void LateUpdate()
    {
        var contianerSize = Mathf.Floor(_rectTransform.rect.size[(int)scaleAxis]);
        var spacing = minSpacing[(int)scaleAxis];
        var elementSize = _gridLayoutGroup.cellSize[(int)scaleAxis];
        var padding = scaleAxis == Axis.Horizontal ? _gridLayoutGroup.padding.horizontal : _gridLayoutGroup.padding.vertical;

        if (elementSize + spacing <= 0)
        {
            return;
        }

        var cellCount = Mathf.Max(1, Mathf.FloorToInt((contianerSize - padding + spacing + 0.001f) / (elementSize + spacing)));
        var availableSpace = contianerSize - (cellCount * elementSize);

        _gridLayoutGroup.constraint = scaleAxis == Axis.Horizontal ? GridLayoutGroup.Constraint.FixedColumnCount : GridLayoutGroup.Constraint.FixedRowCount;
        _gridLayoutGroup.constraintCount = cellCount;
        if (cellCount > 1)
        {
            var scaledSpacing = availableSpace / ((float)(cellCount - 1));
            var layoutSpacing = _gridLayoutGroup.spacing;
            layoutSpacing[(int)scaleAxis] = Mathf.Floor(scaledSpacing);
            _gridLayoutGroup.spacing = layoutSpacing;
            return;
        }
    }
}