using System.Collections.Generic;
using UnityEngine;

namespace IndianOceanAssets.Engine2_5D
{
    /// <summary>
    /// 地面边界生成器 v2 —— 从 Sprite Physics Shape 或 PolygonCollider2D 自动提取边界，
    /// 生成崖壁 Mesh + 边缘发光条带。
    ///
    /// 替代 CliffWallBuilder 的手动摆点方式。
    /// 美术改图后只需重新 Build，无需手动调整边界点。
    ///
    /// 使用方式：
    /// 1. 场景中创建空物体，挂上此脚本（放在地面高度 Y=0）
    /// 2. 把地面 SpriteRenderer 拖到 groundSprite 字段
    ///    （或把 PolygonCollider2D 拖到 polygonCollider 字段）
    /// 3. 指定 wallMaterial（URP Unlit 暗色）
    /// 4. Inspector 点 "Build Ground" 按钮
    /// </summary>
    public class GroundBuilder : MonoBehaviour
    {
        [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;

        [Header("崖壁")]
        [Tooltip("崖壁往下延伸的高度（世界单位）")]
        [SerializeField] float wallHeight = 5f;

        [Tooltip("崖壁材质（建议 URP Unlit，深色，Cull Off 双面）")]
        [SerializeField] Material wallMaterial;

        [Header("边缘发光")]
        [Tooltip("是否生成顶部发光条带")]
        [SerializeField] bool generateEdgeGlow = true;

        [Tooltip("发光条带的高度（世界单位）")]
        [SerializeField] float edgeGlowHeight = 0.3f;

        [Tooltip("发光颜色")]
        [SerializeField] Color edgeGlowColor = new Color(0.2f, 0.6f, 0.9f, 1f);

        [Tooltip("发光亮度")]
        [SerializeField, Range(0.1f, 5f)] float edgeGlowIntensity = 1.5f;

        [Tooltip("渐变：越大上边越亮下边越暗")]
        [SerializeField, Range(0.1f, 3f)] float edgeGlowGradient = 1f;

        [Tooltip("边缘发光材质（使用 AbyssEdgeGlow shader）。留空则自动创建。")]
        [SerializeField] Material edgeGlowMaterial;

        [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;

        [Tooltip("UV 平铺缩放（越大纹理越密）")]
        [SerializeField] float uvScale = 1f;

        private const string GENERATED = "Generated_Ground";

        /// <summary>Editor 脚本读取用。</summary>
        public float SimplifyTolerance => simplifyTolerance;

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

            if (polygonCollider != null)
            {
                // 从 PolygonCollider2D 读取所有路径
                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)
            {
                // 从 Sprite Physics Shape 读取所有轮廓
                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)
                    {
                        // Sprite 局部坐标 → 世界坐标
                        // TransformPoint 自动处理旋转（地面精灵平铺时 X→X, Y→Z）
                        Vector3 world = groundSprite.transform.TransformPoint(p.x, p.y, 0f);
                        worldPath.Add(world);
                    }
                    if (worldPath.Count >= 3)
                        paths.Add(worldPath);
                }
            }

            return paths;
        }

        /// <summary>
        /// 生成崖壁 + 发光条带。
        /// </summary>
        [ContextMenu("Build Ground")]
        public void Build()
        {
            var paths = GetBoundaryPaths();

            if (paths.Count == 0)
            {
                Debug.LogWarning("[GroundBuilder] 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);
            }

            // 清除旧生成物
            ClearGenerated();

            // 创建容器
            GameObject container = new GameObject(GENERATED);
            container.transform.SetParent(transform, false);

            int totalPoints = 0;

            // 为每条路径生成崖壁和发光
            for (int i = 0; i < paths.Count; i++)
            {
                var path = paths[i];
                totalPoints += path.Count;

                // ---- 崖壁 Mesh ----
                GameObject wallObj = new GameObject($"CliffWall_{i}");
                wallObj.transform.SetParent(container.transform, false);
                MeshFilter wallMF = wallObj.AddComponent<MeshFilter>();
                MeshRenderer wallMR = wallObj.AddComponent<MeshRenderer>();
                wallMF.sharedMesh = GenerateWallMesh(path);
                wallMR.sharedMaterial = wallMaterial;

                // ---- 边缘发光 Mesh ----
                if (generateEdgeGlow)
                {
                    GameObject glowObj = new GameObject($"EdgeGlow_{i}");
                    glowObj.transform.SetParent(container.transform, false);
                    MeshFilter glowMF = glowObj.AddComponent<MeshFilter>();
                    MeshRenderer glowMR = glowObj.AddComponent<MeshRenderer>();
                    glowMF.sharedMesh = GenerateEdgeGlowMesh(path);

                    if (edgeGlowMaterial != null)
                    {
                        glowMR.sharedMaterial = edgeGlowMaterial;
                    }
                    else
                    {
                        Shader glowShader = Shader.Find("IndianOcean/AbyssEdgeGlow");
                        if (glowShader != null)
                        {
                            Material mat = new Material(glowShader);
                            mat.SetColor("_Color", edgeGlowColor);
                            mat.SetFloat("_Intensity", edgeGlowIntensity);
                            mat.SetFloat("_Gradient", edgeGlowGradient);
                            glowMR.sharedMaterial = mat;
                        }
                        else
                        {
                            Debug.LogWarning("[GroundBuilder] 找不到 IndianOcean/AbyssEdgeGlow shader。");
                        }
                    }
                }
            }

            int totalEdges = 0;
            foreach (var p in paths) totalEdges += p.Count;
            Debug.Log($"[GroundBuilder] 生成完成：{paths.Count} 条路径，{totalEdges} 个边界点，" +
                      $"崖壁高度 {wallHeight}。" +
                      (simplifyTolerance > 0 ? $" 已简化（容差 {simplifyTolerance}）。" : ""));
        }

        /// <summary>
        /// 清除所有生成物。
        /// </summary>
        [ContextMenu("Clear Generated")]
        public void ClearGenerated()
        {
            Transform old = transform.Find(GENERATED);
            if (old != null)
            {
                if (Application.isPlaying)
                    Destroy(old.gameObject);
                else
                    DestroyImmediate(old.gameObject);
            }
        }

        // ============================================================
        // Mesh 生成（共享顶点 + 距离 UV + 手动法线）
        // ============================================================

        /// <summary>
        /// 生成崖壁 Mesh：闭合路径，每条边一个垂直四边形（双面），共享顶点。
        /// UV.x 按边长累积（纹理不拉伸），UV.y: 1=顶 0=底。
        /// </summary>
        Mesh GenerateWallMesh(List<Vector3> worldPoints)
        {
            int n = worldPoints.Count;

            // 世界坐标 → 本地坐标
            var local = new Vector3[n];
            for (int i = 0; i < n; i++)
                local[i] = transform.InverseTransformPoint(worldPoints[i]);

            // 顶点：top ring (0..n-1) + bottom ring (n..2n-1)
            Vector3[] verts = new Vector3[n * 2];
            Vector2[] uvs = new Vector2[n * 2];
            Vector3[] norms = new Vector3[n * 2];

            float u = 0f;
            for (int i = 0; i < n; i++)
            {
                int next = (i + 1) % n;
                Vector3 top = local[i];
                Vector3 bot = local[i] + new Vector3(0, -wallHeight, 0);

                verts[i] = top;
                verts[n + i] = bot;

                // UV.x 按距离累积
                float edgeLen = Vector3.Distance(local[i], local[next]);
                uvs[i] = new Vector2(u * uvScale, 1f);
                uvs[n + i] = new Vector2(u * uvScale, 0f);
                u += edgeLen;

                // 法线：边的垂直方向，朝外
                Vector3 edge = local[next] - local[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 * 4);
            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(tj); tris.Add(bj);
                tris.Add(ti); tris.Add(bj); tris.Add(bi);
                // 背面（反绕）
                tris.Add(ti); tris.Add(bj); tris.Add(tj);
                tris.Add(ti); tris.Add(bi); tris.Add(bj);
            }

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

        /// <summary>
        /// 生成边缘发光 Mesh：沿边界顶部的细条。
        /// UV.y: 1=顶部(亮) 0=底部(暗)，配合 AbyssEdgeGlow shader。
        /// </summary>
        Mesh GenerateEdgeGlowMesh(List<Vector3> worldPoints)
        {
            int n = worldPoints.Count;

            var local = new Vector3[n];
            for (int i = 0; i < n; i++)
                local[i] = transform.InverseTransformPoint(worldPoints[i]);

            Vector3[] verts = new Vector3[n * 2];
            Vector2[] uvs = new Vector2[n * 2];

            float u = 0f;
            for (int i = 0; i < n; i++)
            {
                int next = (i + 1) % n;
                verts[i] = local[i];                                    // 顶
                verts[n + i] = local[i] + new Vector3(0, -edgeGlowHeight, 0); // 底

                float edgeLen = Vector3.Distance(local[i], local[next]);
                uvs[i] = new Vector2(u * uvScale, 1f);
                uvs[n + i] = new Vector2(u * uvScale, 0f);
                u += edgeLen;
            }

            var tris = new List<int>(n * 4);
            for (int i = 0; i < n; i++)
            {
                int next = (i + 1) % n;
                int ti = i, tj = next, bi = n + i, bj = n + next;

                tris.Add(ti); tris.Add(tj); tris.Add(bj);
                tris.Add(ti); tris.Add(bj); tris.Add(bi);
                tris.Add(ti); tris.Add(bj); tris.Add(tj);
                tris.Add(ti); tris.Add(bi); tris.Add(bj);
            }

            Mesh mesh = new Mesh { name = "EdgeGlow" };
            mesh.SetVertices(verts);
            mesh.SetUVs(0, uvs);
            mesh.SetTriangles(tris, 0);
            mesh.RecalculateBounds();
            return mesh;
        }

        // ============================================================
        // Douglas-Peucker 路径简化
        // ============================================================

        /// <summary>
        /// 对闭合路径做 Douglas-Peucker 简化。
        /// 先找到离起点最远的点，把闭合路径拆成两条开放路径分别简化。
        /// </summary>
        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; }
            }

            // 拆成两段开放路径
            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]); // 闭合

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

            // 合并：arc1 + arc2[1..count-2]（跳过 arc2 首尾，它们和 arc1 重复）
            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;

            // 找离首末连线最远的点
            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
        // ============================================================

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

            Gizmos.color = new Color(0.2f, 0.6f, 0.9f, 0.8f);
            foreach (var path in paths)
            {
                for (int i = 0; i < path.Count; i++)
                {
                    Vector3 cur = path[i];
                    Vector3 next = path[(i + 1) % path.Count];
                    Gizmos.DrawLine(cur, next);
                    Gizmos.DrawSphere(cur, 0.15f);
                }
            }
        }
    }
}