using UnityEngine.Assertions;
using UnityEngine;

namespace Rokid.UXR.Interaction {
	public class CylinderSurface : MonoBehaviour, ISurface, IBounds
	{
	    public enum NormalFacing
	    {
	        /// <summary>
	        /// Raycast hit will register on the outside or inside of the cylinder,
	        /// whichever is hit first.
	        /// </summary>
	        Any,
	
	        /// <summary>
	        /// Raycasts will pass through the outside of the cylinder and hit the inside wall.
	        /// </summary>
	        In,
	
	        /// <summary>
	        /// Raycast against the outside wall of the cylinder.
	        /// In this mode, raycasts with an origin inside the cylinder will always fail.
	        /// </summary>
	        Out,
	    }
	
	    [SerializeField]
	    private Cylinder _cylinder;
	
	    [SerializeField]
	    private NormalFacing _facing = NormalFacing.Out;
	
	    [SerializeField, Tooltip("Height of the cylinder. If zero or negative, height will be infinite.")]
	    private float _height = 1f;
	
	    public bool IsValid => _cylinder != null && Radius > 0;
	
	    public float Radius => _cylinder.Radius;
	
	    public Cylinder Cylinder => _cylinder;
	
	    public Transform Transform => _cylinder.transform;
	
	
	    public Bounds Bounds
	    {
	        get
	        {
	            float maxScale = Mathf.Max(Transform.lossyScale.x,
	                Mathf.Max(Transform.lossyScale.y, Transform.lossyScale.z));
	            float maxSize = maxScale * (Height + Radius);
	            return new Bounds(Transform.position,
	                new Vector3(maxSize, maxSize, maxSize));
	        }
	    }
	
	    public NormalFacing Facing
	    {
	        get => _facing;
	        set => _facing = value;
	    }
	
	    public float Height
	    {
	        get => _height;
	        set => _height = value;
	    }
	
	
	    public bool ClosestSurfacePoint(in Vector3 point, out SurfaceHit hit, float maxDistance)
	    {
	        hit = new SurfaceHit();
	
	        if (!IsValid)
	        {
	            return false;
	        }
	
	        Vector3 localPoint = _cylinder.transform.InverseTransformPoint(point);
	        Vector3 clampedOrigin = localPoint;
	
	        if (_height > 0)
	        {
	            clampedOrigin.y = Mathf.Clamp(clampedOrigin.y, -_height / 2f, _height / 2f);
	        }
	
	        Vector3 nearestPointOnCenterAxis = Vector3.Project(clampedOrigin, Vector3.up);
	
	        Vector3 direction = (clampedOrigin == nearestPointOnCenterAxis) ?
	            Vector3.forward : (clampedOrigin - nearestPointOnCenterAxis).normalized;
	
	        bool isOutside = (clampedOrigin - nearestPointOnCenterAxis).magnitude > Radius;
	        Vector3 hitPoint = nearestPointOnCenterAxis + direction * Radius;
	        float hitDistance = Vector3.Distance(localPoint, hitPoint);
	
	        if (maxDistance > 0 && TransformScale(hitDistance) > maxDistance)
	        {
	            return false;
	        }
	
	        Vector3 normal;
	        switch (_facing)
	        {
	            default:
	            case NormalFacing.Any:
	                normal = isOutside ? direction : -direction;
	                break;
	            case NormalFacing.In:
	                normal = -direction;
	                break;
	            case NormalFacing.Out:
	                normal = direction;
	                break;
	        }
	
	        hit.Point = _cylinder.transform.TransformPoint(nearestPointOnCenterAxis + direction * Radius);
	        hit.Normal = _cylinder.transform.TransformDirection(normal);
	        hit.Distance = TransformScale(hitDistance);
	
	        return true;
	    }
	
	    public bool Raycast(in Ray ray, out SurfaceHit hit, float maxDistance)
	    {
	        // Flatten to 2D and find intersection point with circle in local space,
	        // then convert back into 3D world space
	
	        hit = new SurfaceHit();
	
	        if (!IsValid)
	        {
	            return false;
	        }
	
	        Ray localRay3D = new Ray(_cylinder.transform.InverseTransformPoint(ray.origin),
	                                 _cylinder.transform.InverseTransformDirection(ray.direction).normalized);
	
	        Ray localRay2D = new Ray(CancelY(localRay3D.origin), CancelY(localRay3D.direction).normalized);
	
	        Vector3 originToCenter2D = -localRay2D.origin;
	        Vector3 projPoint2D = localRay2D.origin + Vector3.Project(originToCenter2D, localRay2D.direction);
	
	        float magDir2D = Vector3.Magnitude(CancelY(localRay3D.direction));
	        float magProj = Vector3.Magnitude(projPoint2D);
	
	        bool isOutside = originToCenter2D.magnitude > Radius;
	
	        NormalFacing effectiveFacing = _facing == NormalFacing.Any && !isOutside ? NormalFacing.In : _facing;
	
	        bool hasMissed = magProj > Radius || // Aiming toward but missing
	                         Mathf.Approximately(magDir2D, 0f) || // Aiming up or down
	                         (isOutside && Vector3.Dot(originToCenter2D, localRay2D.direction) < 0) || // Aiming away
	                         (!isOutside && effectiveFacing == NormalFacing.Out); // Origin inside with normals out
	
	        if (hasMissed)
	        {
	            return false;
	        }
	
	        float projToWall = Mathf.Sqrt(Mathf.Pow(Radius, 2) - Mathf.Pow(magProj, 2));
	        float tOuter = Vector3.Distance(localRay2D.origin, projPoint2D - localRay2D.direction * projToWall) / magDir2D;
	        float tInner = Vector3.Distance(localRay2D.origin, projPoint2D + localRay2D.direction * projToWall) / magDir2D;
	
	        Vector3 localHitpointOuter = localRay3D.GetPoint(tOuter);
	        Vector3 localHitpointInner = localRay3D.GetPoint(tInner);
	
	        bool hasOuter = (maxDistance <= 0 || TransformScale(tOuter) <= maxDistance) &&
	                        (_height <= 0 || Mathf.Abs(localHitpointOuter.y) <= _height / 2f);
	
	        bool hasInner = (maxDistance <= 0 || TransformScale(tInner) <= maxDistance) &&
	                        (_height <= 0 || Mathf.Abs(localHitpointInner.y) <= _height / 2f);
	
	        if (effectiveFacing != NormalFacing.In && hasOuter)
	        {
	            hit.Point = _cylinder.transform.TransformPoint(localHitpointOuter);
	            hit.Normal = _cylinder.transform.TransformDirection(CancelY(localHitpointOuter).normalized);
	            hit.Distance = TransformScale(tOuter);
	        }
	        else if (hasInner)
	        {
	            hit.Point = _cylinder.transform.TransformPoint(localHitpointInner);
	            hit.Normal = _cylinder.transform.TransformDirection(CancelY(-localHitpointInner).normalized);
	            hit.Distance = TransformScale(tInner);
	        }
	        else
	        {
	            return false;
	        }
	
	        return true;
	    }
	
	    /// <summary>
	    /// Local to world transformation of a float, assuming uniform scale.
	    /// </summary>
	    private float TransformScale(float val)
	    {
	        return val * _cylinder.transform.lossyScale.x;
	    }
	
	    /// <summary>
	    /// Cancel the Y component of a vector
	    /// </summary>
	    private static Vector3 CancelY(in Vector3 vector)
	    {
	        return new Vector3(vector.x, 0, vector.z);
	    }
	}
}