using UnityEngine;

namespace HotUpdate
{
    /// <summary>
    /// 用地表 MeshCollider 的碰撞高度作为放置 Y。原点在底面中点的物件直接用该值。
    /// </summary>
    public static class GroundSit
    {
        const float RayStartY = 80f;
        const float RayLength = 160f;

        public static float Height(Vector3 xz, Transform searchRoot = null, float fallback = 0f)
        {
            Physics.SyncTransforms();
            var ray = new Ray(new Vector3(xz.x, RayStartY, xz.z), Vector3.down);
            var bestDist = float.MaxValue;
            var y = fallback;
            var hitAny = false;

            foreach (var col in Collect(searchRoot))
            {
                if (col == null || !col.enabled) continue;
                if (!IsGroundCollider(col)) continue;
                if (!col.Raycast(ray, out var hit, RayLength)) continue;
                if (hit.distance >= bestDist) continue;
                bestDist = hit.distance;
                y = hit.point.y;
                hitAny = true;
            }

            if (hitAny) return y;

            foreach (var col in Collect(searchRoot))
            {
                if (col == null || !col.enabled) continue;
                if (!col.Raycast(ray, out var hit, RayLength)) continue;
                if (hit.distance >= bestDist) continue;
                bestDist = hit.distance;
                y = hit.point.y;
                hitAny = true;
            }

            return hitAny ? y : fallback;
        }

        static MeshCollider[] Collect(Transform searchRoot)
        {
            if (searchRoot != null)
                return searchRoot.GetComponentsInChildren<MeshCollider>();
            return Object.FindObjectsByType<MeshCollider>(FindObjectsSortMode.None);
        }

        static bool IsGroundCollider(MeshCollider col)
        {
            for (var t = col.transform; t != null; t = t.parent)
            {
                if (t.name.IndexOf("ground", System.StringComparison.OrdinalIgnoreCase) >= 0)
                    return true;
            }
            return false;
        }
    }
}