using UnityEngine;

namespace AppUI
{
    /// <summary>
    /// 将「设计稿坐标系」下的像素尺寸/位置换算为 Unity UI CanvasScaler 的 referenceResolution 空间下的数值（与 Inspector 中 RectTransform 一致）。
    /// </summary>
    public static class DesignResolutionConverter
    {
        public const float DefaultDesignWidth = 402f;
        public const float DefaultDesignHeight = 874f;

        /// <summary>
        /// 各轴缩放：canvasRef / designArtboard。
        /// </summary>
        public static Vector2 GetScaleFactors(Vector2 designArtboardPx, Vector2 canvasReferenceResolution)
        {
            if (designArtboardPx.x <= 0f || designArtboardPx.y <= 0f)
            {
                Debug.LogWarning("[DesignResolutionConverter] 设计稿宽高必须大于 0。");
                return Vector2.one;
            }

            return new Vector2(
                canvasReferenceResolution.x / designArtboardPx.x,
                canvasReferenceResolution.y / designArtboardPx.y);
        }

        /// <summary>
        /// 设计稿中的宽、高（像素）→ Canvas 参考分辨率空间下的 SizeDelta / 尺寸。
        /// </summary>
        public static Vector2 DesignSizeToCanvasUnits(Vector2 designSizePx, Vector2 designArtboardPx, Vector2 canvasReferenceResolution)
        {
            Vector2 s = GetScaleFactors(designArtboardPx, canvasReferenceResolution);
            return new Vector2(designSizePx.x * s.x, designSizePx.y * s.y);
        }

        /// <summary>
        /// 单轴长度：设计稿 px → Canvas 参考分辨率空间（按宽度用 scaleX，按高度用 scaleY）。
        /// </summary>
        public static float DesignLengthToCanvas(float designPx, bool useWidthAxis, Vector2 designArtboardPx, Vector2 canvasReferenceResolution)
        {
            Vector2 s = GetScaleFactors(designArtboardPx, canvasReferenceResolution);
            return designPx * (useWidthAxis ? s.x : s.y);
        }

        /// <summary>
        /// 单轴长度：Canvas 参考分辨率空间 → 设计稿 px。
        /// </summary>
        public static float CanvasLengthToDesign(float canvasUnits, bool useWidthAxis, Vector2 designArtboardPx, Vector2 canvasReferenceResolution)
        {
            Vector2 s = GetScaleFactors(designArtboardPx, canvasReferenceResolution);
            float factor = useWidthAxis ? s.x : s.y;
            if (factor == 0f)
                return canvasUnits;
            return canvasUnits / factor;
        }

        /// <summary>
        /// Canvas 参考分辨率空间 → 设计稿像素（逆换算）。
        /// </summary>
        public static Vector2 CanvasUnitsToDesignSize(Vector2 canvasUnits, Vector2 designArtboardPx, Vector2 canvasReferenceResolution)
        {
            Vector2 s = GetScaleFactors(designArtboardPx, canvasReferenceResolution);
            if (s.x == 0f || s.y == 0f)
                return canvasUnits;
            return new Vector2(canvasUnits.x / s.x, canvasUnits.y / s.y);
        }

        /// <summary>
        /// 设计稿中的点 (px)，原点在左上角、X 向右、Y 向下（与常见 UI 设计工具一致）→
        /// Unity UI 以左下角为原点、Y 向上时，在参考分辨率空间中的 anchored 局部坐标（需结合锚点理解）。
        /// </summary>
        /// <param name="designPointTopLeftOriginPx">设计坐标，左上角为 (0,0)，Y 向下增长。</param>
        public static Vector2 DesignPointToCanvasSpaceBottomLeftOrigin(
            Vector2 designPointTopLeftOriginPx,
            Vector2 designArtboardPx,
            Vector2 canvasReferenceResolution)
        {
            Vector2 s = GetScaleFactors(designArtboardPx, canvasReferenceResolution);
            float x = designPointTopLeftOriginPx.x * s.x;
            float yCanvas = (designArtboardPx.y - designPointTopLeftOriginPx.y) * s.y;
            return new Vector2(x, yCanvas);
        }
    }
}