using UnityEngine;
using System.Collections.Generic;

public static class CuttingUtils
{
    public static int FindNearestEdgePointIndex(Vector2 pos, List<Vector2> edgePoints, out float minDist)
    {
        int nearestIndex = 0;
        minDist = float.MaxValue;

        for (int i = 0; i < edgePoints.Count; i++)
        {
            float dist = Vector2.Distance(pos, edgePoints[i]);
            if (dist < minDist)
            {
                minDist = dist;
                nearestIndex = i;
            }
        }
        return nearestIndex;
    }

    public static Vector2 GetClosestPointOnSegment(Vector2 a, Vector2 b, Vector2 p)
    {
        Vector2 ab = b - a;
        float t = Vector2.Dot(p - a, ab) / ab.sqrMagnitude;
        t = Mathf.Clamp01(t);
        return a + ab * t;
    }

    public static int WrapIndex(int index, int count)
    {
        if (index < 0) return count - 2;
        if (index >= count - 1) return 0;
        return index;
    }

    public static List<Vector2> GetSpritePhysicsShapePoints(SpriteRenderer spriteRenderer)
    {
        List<Vector2> shapePoints = new List<Vector2>();
        spriteRenderer.sprite.GetPhysicsShape(0, shapePoints);

        if (shapePoints.Count == 0)
        {
            Debug.LogError("目标Sprite没有物理形状点");
            return null;
        }

        return shapePoints;
    }

    public static (List<Vector2> scaledPoints, List<Vector2> originalPoints) ProcessEdgePoints(
        List<Vector2> shapePoints, 
        SpriteRenderer spriteRenderer, 
        float edgePointsScale = 1.2f, 
        float desiredSegmentLength = 0.1f)
    {
        if (shapePoints == null || shapePoints.Count == 0) return (null, null);

        List<Vector2> scaledPoints = new List<Vector2>();
        List<Vector2> originalPoints = new List<Vector2>();

        // 计算中心点
        Vector2 center = Vector2.zero;
        foreach (Vector2 point in shapePoints)
        {
            center += point;
        }
        center /= shapePoints.Count;

        // 处理每个线段
        for (int i = 0; i < shapePoints.Count; i++)
        {
            Vector2 p1 = spriteRenderer.transform.TransformPoint(shapePoints[i]);
            Vector2 p2 = spriteRenderer.transform.TransformPoint(shapePoints[(i + 1) % shapePoints.Count]);

            Vector2 scaledP1 = center + (p1 - center) * edgePointsScale;
            Vector2 scaledP2 = center + (p2 - center) * edgePointsScale;

            float segmentLength = Vector2.Distance(scaledP1, scaledP2);
            int steps = Mathf.Max(1, Mathf.CeilToInt(segmentLength / desiredSegmentLength));

            for (int s = 0; s < steps; s++)
            {
                float t = (float)s / steps;
                Vector2 interpolated = Vector2.Lerp(scaledP1, scaledP2, t);
                Vector2 originalInterpolated = Vector2.Lerp(p1, p2, t);
                scaledPoints.Add(interpolated);
                originalPoints.Add(originalInterpolated);
            }
        }

        // 确保首尾相连
        if ((scaledPoints[0] - scaledPoints[scaledPoints.Count - 1]).sqrMagnitude > 0.0001f)
        {
            scaledPoints.Add(scaledPoints[0]);
            originalPoints.Add(originalPoints[0]);
        }

        return (scaledPoints, originalPoints);
    }
}