using System.Collections.Generic;
using UnityEngine;

namespace IndianOceanAssets.Engine2_5D
{
    /// <summary>
    /// 空气墙自动生成器 —— 从 Sprite Physics Shape 或 PolygonCollider2D 提取边界，
    /// 沿边界路径生成 3D 碰撞墙，阻止玩家 / 敌人走出地图。
    ///
    /// 使用方式：
    /// 1. 场景中挂有此脚本的 GameObject（与 GroundBuilder 放在同一位置即可）
    /// 2. 指定 groundSprite 或 polygonCollider 作为数据源
    /// 3. Inspector 点 "Build Walls" 按钮生成碰撞墙
    /// 4. 点 "Clear Walls" 可清除已生成的碰撞墙
    /// </summary>
    public class BoundaryWallGenerator : MonoBehaviour
    {
        // ============================================================
        // 数据源
        // ============================================================

        [Header("数据源")]
        [Tooltip("地面精灵渲染器。从此 Sprite 的 Physics Shape 自动提取边界轮廓。\n" +
                 "需要在 Sprite Editor 里 Generate Physics Shape（默认自动生成）。")]
        [SerializeField] SpriteRenderer groundSprite;

        [Tooltip("可选：直接用 PolygonCollider2D 的路径作为边界。\n" +
                 "留空则用 Sprite Physics Shape。")]
        [SerializeField] PolygonCollider2D polygonCollider;

        // ============================================================
        // 碰撞设置
        // ============================================================

        [Header("碰撞设置")]
        [Tooltip("碰撞墙高度（Y 轴方向延伸）")]
        [SerializeField] float wallHeight = 3f;

        [Tooltip("碰撞墙厚度（XZ 平面法线方向）。BoxCollider 模式下建议 ≥ 0.3，太薄容易穿透。")]
        [SerializeField] float wallThickness = 0.5f;

        [Tooltip("碰撞墙所在的 Layer")]
        [SerializeField] int wallLayer = 0;

        [Tooltip("碰撞模式：BoxCollider 阵列（推荐，有厚度，碰撞可靠）；MeshCollider（零厚度，可能穿透）。")]
        [SerializeField] ColliderMode colliderMode = ColliderMode.BoxColliderArray;

        [Header("调试")]
        [Tooltip("勾选后为每段墙体添加可见 Cube，方便在 Scene 中查看位置和大小")]
        [SerializeField] bool showDebugVisuals = true;

        [Header("优化")]
        [Tooltip("Douglas-Peucker 简化容差（世界单位）。0 = 不简化。\n" +
                 "建议 0.05~0.2，减少顶点数同时保持轮廓形状。")]
        [SerializeField] float simplifyTolerance = 0.1f;

        public enum ColliderMode
        {
            MeshCollider,
            BoxColliderArray
        }

        private const string GENERATED = "Generated_BoundaryWalls";

        // ============================================================
        // 公开 API
        // ============================================================

        /// <summary>
        /// 从数据源提取边界点（世界坐标）。与 GroundBuilder 逻辑一致。
        /// </summary>
        public List<List<Vector3>> GetBoundaryPaths()
        {
            var paths = new List<List<Vector3>>();

            if (polygonCollider != null)
            {
                for (int i = 0; i < polygonCollider.pathCount; i++)
                {
                    Vector2[] path = polygonCollider.GetPath(i);
                    var worldPath = new List<Vector3>();
                    foreach (var p in path)
                    {
                        Vector3 world = polygonCollider.transform.TransformPoint(p.x, p.y, 0f);
                        worldPath.Add(world);
                    }
                    if (worldPath.Count >= 3)
                        paths.Add(worldPath);
                }
            }
            else if (groundSprite != null && groundSprite.sprite != null)
            {
                Sprite sprite = groundSprite.sprite;
                int shapeCount = sprite.GetPhysicsShapeCount();

                for (int i = 0; i < shapeCount; i++)
                {
                    var shape = new List<Vector2>();
                    sprite.GetPhysicsShape(i, shape);

                    var worldPath = new List<Vector3>();
                    foreach (var p in shape)
                    {
                        Vector3 world = groundSprite.transform.TransformPoint(p.x, p.y, 0f);
                        worldPath.Add(world);
                    }
                    if (worldPath.Count >= 3)
                        paths.Add(worldPath);
                }
            }

            return paths;
        }

        /// <summary>
        /// 生成碰撞墙。
        /// </summary>
        [ContextMenu("Build Walls")]
        public void Build()
        {
            var paths = GetBoundaryPaths();

            if (paths.Count == 0)
            {
                Debug.LogWarning("[BoundaryWallGenerator] 没有找到边界数据。\n" +
                    "请指定 groundSprite（Sprite 需有 Physics Shape）或 polygonCollider。");
                return;
            }

            // 简化
            if (simplifyTolerance > 0f)
            {
                for (int i = 0; i < paths.Count; i++)
                    paths[i] = SimplifyClosedPath(paths[i], simplifyTolerance);
            }

            // 清除旧的
            ClearGenerated();

            // 创建容器（放在场景根层级，确保 mesh 世界坐标 = 本地坐标）
            GameObject container = new GameObject(GENERATED);
            container.transform.position = Vector3.zero;
            container.transform.rotation = Quaternion.identity;
            container.transform.localScale = Vector3.one;
            container.layer = wallLayer;
            container.isStatic = true;

            switch (colliderMode)
            {
                case ColliderMode.MeshCollider:
                    BuildMeshColliders(container, paths);
                    break;
                case ColliderMode.BoxColliderArray:
                    BuildBoxColliders(container, paths);
                    break;
            }

            int totalEdges = 0;
            foreach (var p in paths) totalEdges += p.Count;
            Debug.Log($"[BoundaryWallGenerator] 生成完成：{paths.Count} 条路径，{totalEdges} 个边界点，" +
                      $"碰撞模式 {colliderMode}，墙高 {wallHeight}，厚度 {wallThickness}。");
        }

        /// <summary>
        /// 清除所有已生成的碰撞墙。
        /// </summary>
        [ContextMenu("Clear Walls")]
        public void ClearGenerated()
        {
            // 容器在场景根层级（非子物体），用 FindObjectOfType 查找
            GameObject old = GameObject.Find(GENERATED);
            if (old != null)
            {
                if (Application.isPlaying)
                    Destroy(old);
                else
                    DestroyImmediate(old);
            }
        }

        // ============================================================
        // MeshCollider 模式
        // ============================================================

        void BuildMeshColliders(GameObject container, List<List<Vector3>> paths)
        {
            for (int i = 0; i < paths.Count; i++)
            {
                var path = paths[i];
                GameObject wallObj = new GameObject($"BoundaryWall_{i}");
                wallObj.transform.SetParent(container.transform, false);
                wallObj.layer = wallLayer;
                wallObj.isStatic = true;

                MeshFilter mf = wallObj.AddComponent<MeshFilter>();
                mf.sharedMesh = GenerateWallMesh(path);

                // 不添加 MeshRenderer —— 空气墙只需要碰撞，不需要渲染（无阴影、无绘制开销）

                MeshCollider mc = wallObj.AddComponent<MeshCollider>();
                mc.sharedMesh = mf.sharedMesh;
                mc.convex = false;
            }
        }

        /// <summary>
        /// 沿闭合路径生成垂直墙体 Mesh（双面），用于 MeshCollider。
        /// 直接使用世界坐标（容器物体与 BoundaryWallGenerator 同 Transform，本地偏移为零）。
        /// </summary>
        Mesh GenerateWallMesh(List<Vector3> worldPoints)
        {
            int n = worldPoints.Count;

            // 顶点：top ring (0..n-1) + bottom ring (n..2n-1)
            Vector3[] verts = new Vector3[n * 2];
            Vector3[] norms = new Vector3[n * 2];

            for (int i = 0; i < n; i++)
            {
                int next = (i + 1) % n;

                verts[i] = worldPoints[i] + new Vector3(0, wallHeight, 0);  // 顶部
                verts[n + i] = worldPoints[i];                                // 底部（地面高度）

                // 法线：边的垂直方向，朝外
                Vector3 edge = worldPoints[next] - worldPoints[i];
                Vector3 normal = Vector3.Cross(edge, Vector3.down).normalized;
                norms[i] = normal;
                norms[n + i] = normal;
            }

            // 三角形：双面
            var tris = new List<int>(n * 12);
            for (int i = 0; i < n; i++)
            {
                int next = (i + 1) % n;
                int ti = i, tj = next, bi = n + i, bj = n + next;

                // 正面
                tris.Add(ti); tris.Add(bi); tris.Add(bj);
                tris.Add(ti); tris.Add(bj); tris.Add(tj);
                // 背面（反绕）
                tris.Add(ti); tris.Add(bj); tris.Add(bi);
                tris.Add(ti); tris.Add(tj); tris.Add(bj);
            }

            Mesh mesh = new Mesh { name = "BoundaryWall" };
            mesh.SetVertices(verts);
            mesh.SetNormals(norms);
            mesh.SetTriangles(tris, 0);
            mesh.RecalculateBounds();
            return mesh;
        }

        // ============================================================
        // BoxCollider 阵列模式
        // ============================================================

        void BuildBoxColliders(GameObject container, List<List<Vector3>> paths)
        {
            int segIndex = 0;

            for (int p = 0; p < paths.Count; p++)
            {
                var path = paths[p];
                int n = path.Count;

                for (int i = 0; i < n; i++)
                {
                    int next = (i + 1) % n;
                    Vector3 a = path[i];
                    Vector3 b = path[next];

                    // 边段中点（世界坐标）
                    Vector3 mid = (a + b) * 0.5f;
                    float length = Vector3.Distance(a, b);
                    if (length < 0.001f) continue;

                    // 边段方向（投影到 XZ 平面，忽略 Y 分量）
                    Vector3 dir = (b - a).normalized;
                    dir.y = 0f;
                    if (dir.sqrMagnitude < 0.0001f) continue;
                    dir.Normalize();

                    // 创建子物体
                    GameObject segObj = new GameObject($"WallSeg_{segIndex}");
                    segObj.transform.SetParent(container.transform, false);
                    segObj.layer = wallLayer;
                    segObj.isStatic = true;

                    // 定位到中点，Y 偏移到墙高一半
                    segObj.transform.position = mid + new Vector3(0, wallHeight * 0.5f, 0);

                    // 旋转使 Z 轴沿边段方向（LookRotation: forward=Z 对齐 dir，up=Y 保持朝上）
                    segObj.transform.rotation = Quaternion.LookRotation(dir, Vector3.up);

                    // 添加 BoxCollider：X=厚度, Y=墙高, Z=边段长度
                    BoxCollider bc = segObj.AddComponent<BoxCollider>();
                    bc.size = new Vector3(wallThickness, wallHeight, length);
                    bc.center = Vector3.zero;

                    // 调试可视化：添加 Cube 让墙体可见
                    if (showDebugVisuals)
                    {
                        GameObject vis = GameObject.CreatePrimitive(PrimitiveType.Cube);
                        vis.name = "Visual";
                        vis.transform.SetParent(segObj.transform, false);
                        vis.transform.localPosition = Vector3.zero;
                        vis.transform.localRotation = Quaternion.identity;
                        vis.transform.localScale = new Vector3(wallThickness, wallHeight, length);
                        vis.isStatic = false;
                        // 移除 Cube 自带的 Collider，避免双重碰撞
                        var cubeCol = vis.GetComponent<Collider>();
                        if (cubeCol != null) DestroyImmediate(cubeCol);
                    }

                    segIndex++;
                }
            }
        }

        // ============================================================
        // Douglas-Peucker 路径简化（与 GroundBuilder 一致）
        // ============================================================

        List<Vector3> SimplifyClosedPath(List<Vector3> points, float tolerance)
        {
            if (points.Count < 4) return points;

            // 找离 points[0] 最远的点
            float maxDist = 0f;
            int farIdx = 1;
            for (int i = 1; i < points.Count; i++)
            {
                float d = Vector3.Distance(points[0], points[i]);
                if (d > maxDist) { maxDist = d; farIdx = i; }
            }

            var arc1 = new List<Vector3>();
            var arc2 = new List<Vector3>();
            for (int i = 0; i <= farIdx; i++) arc1.Add(points[i]);
            for (int i = farIdx; i < points.Count; i++) arc2.Add(points[i]);
            arc2.Add(points[0]);

            arc1 = DouglasPeucker(arc1, tolerance);
            arc2 = DouglasPeucker(arc2, tolerance);

            var result = new List<Vector3>(arc1);
            for (int i = 1; i < arc2.Count - 1; i++)
                result.Add(arc2[i]);

            return result;
        }

        List<Vector3> DouglasPeucker(List<Vector3> points, float tolerance)
        {
            if (points.Count < 3) return points;

            float maxDist = 0f;
            int maxIdx = 0;
            Vector3 a = points[0];
            Vector3 b = points[points.Count - 1];

            for (int i = 1; i < points.Count - 1; i++)
            {
                float d = PerpDistance(points[i], a, b);
                if (d > maxDist) { maxDist = d; maxIdx = i; }
            }

            if (maxDist > tolerance)
            {
                var left = DouglasPeucker(points.GetRange(0, maxIdx + 1), tolerance);
                var right = DouglasPeucker(points.GetRange(maxIdx, points.Count - maxIdx), tolerance);

                var result = new List<Vector3>(left);
                result.AddRange(right.GetRange(1, right.Count - 1));
                return result;
            }
            else
            {
                return new List<Vector3> { a, b };
            }
        }

        float PerpDistance(Vector3 p, Vector3 lineA, Vector3 lineB)
        {
            Vector3 ab = lineB - lineA;
            float lenSq = ab.sqrMagnitude;
            if (lenSq < 1e-8f) return Vector3.Distance(p, lineA);
            Vector3 ap = p - lineA;
            float t = Vector3.Dot(ap, ab) / lenSq;
            t = Mathf.Clamp01(t);
            Vector3 proj = lineA + t * ab;
            return Vector3.Distance(p, proj);
        }

        // ============================================================
        // Gizmos —— 在 Scene 视图中预览碰撞边界
        // ============================================================

        private void OnDrawGizmosSelected()
        {
            var paths = GetBoundaryPaths();
            if (paths.Count == 0) return;

            Gizmos.color = new Color(1f, 0.4f, 0.2f, 0.8f); // 橙色，区别于 GroundBuilder 的蓝色
            foreach (var path in paths)
            {
                for (int i = 0; i < path.Count; i++)
                {
                    Vector3 cur = path[i];
                    Vector3 next = path[(i + 1) % path.Count];

                    // 底部线
                    Gizmos.DrawLine(cur, next);
                    // 顶部线
                    Vector3 curTop = cur + new Vector3(0, wallHeight, 0);
                    Vector3 nextTop = next + new Vector3(0, wallHeight, 0);
                    Gizmos.DrawLine(curTop, nextTop);
                    // 垂直连接线
                    Gizmos.DrawLine(cur, curTop);

                    Gizmos.DrawSphere(cur, 0.1f);
                }
            }
        }
    }
}