using UnityEngine;
using UnityEngine.UI;

namespace MeowmentDebugTool
{
    /// <summary>
    /// 简单的自动换行布局，用于运行时 Tab 栏。
    /// </summary>
    public class WrapLayoutGroup : LayoutGroup
    {
        [SerializeField] private float spacing = 8f;
        [SerializeField] private float lineSpacing = 8f;
        [SerializeField] private bool childControlWidth = false;
        [SerializeField] private bool childControlHeight = false;

        public float Spacing
        {
            get => spacing;
            set => spacing = value;
        }

        public float LineSpacing
        {
            get => lineSpacing;
            set => lineSpacing = value;
        }

        public override void CalculateLayoutInputHorizontal()
        {
            base.CalculateLayoutInputHorizontal();

            float totalMinWidth = padding.horizontal;
            float totalPreferredWidth = padding.horizontal;

            for (int i = 0; i < rectChildren.Count; i++)
            {
                RectTransform child = rectChildren[i];
                totalMinWidth += GetChildWidth(child);
                totalPreferredWidth += GetChildWidth(child);

                if (i < rectChildren.Count - 1)
                {
                    totalMinWidth += spacing;
                    totalPreferredWidth += spacing;
                }
            }

            SetLayoutInputForAxis(totalMinWidth, totalPreferredWidth, -1f, 0);
        }

        public override void CalculateLayoutInputVertical()
        {
            float requiredHeight = CalculateRequiredHeight(GetUsableWidth());
            SetLayoutInputForAxis(requiredHeight, requiredHeight, -1f, 1);
        }

        public override void SetLayoutHorizontal()
        {
            SetChildrenAlongBothAxis();
        }

        public override void SetLayoutVertical()
        {
            SetChildrenAlongBothAxis();
        }

        private float GetContainerWidth()
        {
            float selfWidth = rectTransform.rect.width;
            float parentWidth = 0f;

            if (rectTransform.parent is RectTransform parentRect)
            {
                parentWidth = parentRect.rect.width;
                if (parentWidth > 0f)
                {
                    if (selfWidth > 0f)
                    {
                        return Mathf.Min(selfWidth, parentWidth);
                    }

                    return parentWidth;
                }
            }

            if (selfWidth > 0f)
            {
                return selfWidth;
            }

            return float.MaxValue;
        }

        private float GetUsableWidth()
        {
            float width = GetContainerWidth() - padding.horizontal;
            return width > 0f ? width : float.MaxValue;
        }

        private float CalculateRequiredHeight(float usableWidth)
        {
            if (rectChildren.Count == 0)
            {
                return padding.vertical;
            }

            float currentLineWidth = 0f;
            float currentLineHeight = 0f;
            float totalHeight = padding.vertical;

            for (int i = 0; i < rectChildren.Count; i++)
            {
                RectTransform child = rectChildren[i];
                float childWidth = GetChildWidth(child);
                float childHeight = GetChildHeight(child);

                bool needWrap = currentLineWidth > 0f && currentLineWidth + spacing + childWidth > usableWidth;
                if (needWrap)
                {
                    totalHeight += currentLineHeight + lineSpacing;
                    currentLineWidth = 0f;
                    currentLineHeight = 0f;
                }

                if (currentLineWidth > 0f)
                {
                    currentLineWidth += spacing;
                }

                currentLineWidth += childWidth;
                currentLineHeight = Mathf.Max(currentLineHeight, childHeight);
            }

            totalHeight += currentLineHeight;
            return totalHeight;
        }

        private void SetChildrenAlongBothAxis()
        {
            float usableWidth = GetUsableWidth();
            float containerRight = padding.left + usableWidth;
            float x = padding.left;
            float y = padding.top;
            float currentLineHeight = 0f;

            for (int i = 0; i < rectChildren.Count; i++)
            {
                RectTransform child = rectChildren[i];
                float childWidth = GetChildWidth(child);
                float childHeight = GetChildHeight(child);

                bool needWrap = x > padding.left && x + childWidth > containerRight;
                if (needWrap)
                {
                    x = padding.left;
                    y += currentLineHeight + lineSpacing;
                    currentLineHeight = 0f;
                }

                SetChildAlongAxis(child, 0, x, childWidth);
                SetChildAlongAxis(child, 1, y, childHeight);

                x += childWidth + spacing;
                currentLineHeight = Mathf.Max(currentLineHeight, childHeight);
            }
        }

        private float GetChildWidth(RectTransform child)
        {
            return childControlWidth ? LayoutUtility.GetPreferredWidth(child) : GetPreferredOrRectWidth(child);
        }

        private float GetChildHeight(RectTransform child)
        {
            return childControlHeight ? LayoutUtility.GetPreferredHeight(child) : GetPreferredOrRectHeight(child);
        }

        private static float GetPreferredOrRectWidth(RectTransform child)
        {
            float preferredWidth = LayoutUtility.GetPreferredWidth(child);
            return preferredWidth > 0f ? preferredWidth : child.rect.width;
        }

        private static float GetPreferredOrRectHeight(RectTransform child)
        {
            float preferredHeight = LayoutUtility.GetPreferredHeight(child);
            return preferredHeight > 0f ? preferredHeight : child.rect.height;
        }
    }
}