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 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
// Ubit Umarov 2012
using System;
using System.Collections.Generic;
using OpenSim.Region.PhysicsModules.SharedBase;
using OpenMetaverse;

namespace OpenSim.Region.PhysicsModule.ubOde
{
    /// <summary>
    /// </summary>
    public class ODESitAvatar
    {
        private readonly ODEScene m_scene;
        private readonly ODERayCastRequestManager m_raymanager;

        public ODESitAvatar(ODEScene pScene, ODERayCastRequestManager raymanager)
        {
            m_scene = pScene;
            m_raymanager = raymanager;
        }

        private static readonly Vector3 SitAjust = new(0, 0, 0.4f);
        private const RayFilterFlags RaySitFlags = RayFilterFlags.AllPrims | RayFilterFlags.ClosestHit;

        private void RotAroundZ(float x, float y, ref Quaternion ori)
        {
            float ang = 0.5f * MathF.Atan2(y, x);
            float s = MathF.Sin(ang);
            float c = MathF.Cos(ang);

            ori.X = 0;
            ori.Y = 0;
            ori.Z = s;
            ori.W = c;
        }


        public void Sit(PhysicsActor actor, Vector3 avPos, Vector3 avCameraPosition, Vector3 offset, Vector3 avOffset, SitAvatarCallback PhysicsSitResponse)
        {
            if (!m_scene.haveActor(actor) || actor is not OdePrim || ((OdePrim)actor).m_prim_geom == IntPtr.Zero)
            {
                PhysicsSitResponse(-1, actor.LocalID, offset, Quaternion.Identity);
                return;
            }

            IntPtr geom = ((OdePrim)actor).m_prim_geom;

            Vector3 geopos = UBOdeNative.GeomGetPositionOMV(geom);
            Quaternion geomOri = UBOdeNative.GeomGetQuaternionOMV(geom);

            //Vector3 geopos = actor.Position;
            //Quaternion geomOri = actor.Orientation;

            Quaternion geomInvOri = Quaternion.Conjugate(geomOri);
            Quaternion ori = Quaternion.Identity;

            Vector3 rayDir = geopos + offset - avCameraPosition;

            float raylen = rayDir.Length();
            if (raylen < 0.001f)
            {
                PhysicsSitResponse(-1, actor.LocalID, offset, Quaternion.Identity);
                return;
            }

            float t = 1 / raylen;
            rayDir.X *= t;
            rayDir.Y *= t;
            rayDir.Z *= t;

            raylen += 30f; // focal point may be far

            List<ContactResult> rayResults = m_scene.RaycastActor(actor, avCameraPosition, rayDir, raylen, 1, RaySitFlags);
            if (rayResults.Count == 0)
            {
                /* if this fundamental ray failed, then just fail so user can try another spot and not be sitted far on a big prim
                d.AABB aabb;
                d.GeomGetAABB(geom, out aabb);
                offset = new Vector3(avOffset.X, 0, aabb.MaxZ + avOffset.Z - geopos.Z);
                ori = geomInvOri;
                offset *= geomInvOri;
                PhysicsSitResponse(1, actor.LocalID, offset, ori);
                */
                PhysicsSitResponse(0, actor.LocalID, offset, ori);
                return;
            }

            int status = 1;

            offset = rayResults[0].Pos - geopos;

            UBOdeNative.GeomClassID geoclass = UBOdeNative.GeomGetClass(geom);

            if (geoclass == UBOdeNative.GeomClassID.SphereClass)
            {
                float r = UBOdeNative.GeomSphereGetRadius(geom);

                offset.Normalize();
                offset *= r;

                RotAroundZ(offset.X, offset.Y, ref ori);

                if (r < 0.4f)
                {
                    offset = new Vector3(0, 0, r);
                }
                else
                {
                    if (offset.Z < 0.4f)
                    {
                        t = offset.Z;
                        float rsq = r * r;

                        t = 1.0f / (rsq - t * t);
                        offset.X *= t;
                        offset.Y *= t;
                        offset.Z = 0.4f;
                        t = rsq - 0.16f;
                        offset.X *= t;
                        offset.Y *= t;
                    }
                    else if (r > 0.8f && offset.Z > 0.8f * r)
                    {
                        status = 3;
                        avOffset.X = -avOffset.X;
                        avOffset.Z *= 1.6f;
                    }
                }

                offset += avOffset * ori;

                ori = geomInvOri * ori;
                offset *= geomInvOri;

                PhysicsSitResponse(status, actor.LocalID, offset, ori);
                return;
            }

            Vector3 norm = rayResults[0].Normal;

            if (norm.Z < -0.4f)
            {
                PhysicsSitResponse(0, actor.LocalID, offset, Quaternion.Identity);
                return;
            }


            float SitNormX = -rayDir.X;
            float SitNormY = -rayDir.Y;

            Vector3 pivot = geopos + offset;

            float edgeNormalX = norm.X;
            float edgeNormalY = norm.Y;
            float edgeDirX = -rayDir.X;
            float edgeDirY = -rayDir.Y;
            Vector3 edgePos = rayResults[0].Pos;
            float edgeDist = float.MaxValue;

            bool foundEdge = false;

            if (norm.Z < 0.5f)
            {
                float rayDist = 4.0f;

                for (int i = 0; i < 6; i++)
                {
                    pivot.X -= 0.01f * norm.X;
                    pivot.Y -= 0.01f * norm.Y;
                    pivot.Z -= 0.01f * norm.Z;

                    rayDir.X = -norm.X * norm.Z;
                    rayDir.Y = -norm.Y * norm.Z;
                    rayDir.Z = 1.0f - norm.Z * norm.Z;
                    rayDir.Normalize();

                    rayResults = m_scene.RaycastActor(actor, pivot, rayDir, rayDist, 1, RayFilterFlags.AllPrims);
                    if (rayResults.Count == 0)
                        break;

                    if (MathF.Abs(rayResults[0].Normal.Z) < 0.7f)
                    {
                        rayDist -= rayResults[0].Depth;
                        if (rayDist < 0f)
                            break;

                        pivot = rayResults[0].Pos;
                        norm = rayResults[0].Normal;
                        edgeNormalX = norm.X;
                        edgeNormalY = norm.Y;
                        edgeDirX = -rayDir.X;
                        edgeDirY = -rayDir.Y;
                    }
                    else
                    {
                        foundEdge = true;
                        edgePos = rayResults[0].Pos;
                        break;
                    }
                }

                if (!foundEdge)
                {
                    PhysicsSitResponse(0, actor.LocalID, offset, ori);
                    return;
                }
                avOffset.X *= 0.5f;
            }

            else if (norm.Z > 0.866f)
            {
                float toCamBaseX = avCameraPosition.X - pivot.X;
                float toCamBaseY = avCameraPosition.Y - pivot.Y;
                float toCamX = toCamBaseX;
                float toCamY = toCamBaseY;

                for (int j = 0; j < 4; j++)
                {
                    float rayDist = 1.0f;
                    float curEdgeDist = 0.0f;

                    for (int i = 0; i < 3; i++)
                    {
                        pivot.Z -= 0.01f;
                        rayDir.X = toCamX;
                        rayDir.Y = toCamY;
                        rayDir.Z = (-toCamX * norm.X - toCamY * norm.Y) / norm.Z;
                        rayDir.Normalize();

                        rayResults = m_scene.RaycastActor(actor, pivot, rayDir, rayDist, 1, RayFilterFlags.AllPrims);
                        if (rayResults.Count == 0)
                            break;

                        curEdgeDist += rayResults[0].Depth;

                        if (rayResults[0].Normal.Z > 0.5f)
                        {
                            rayDist -= rayResults[0].Depth;
                            if (rayDist < 0f)
                                break;

                            pivot = rayResults[0].Pos;
                            norm = rayResults[0].Normal;
                        }
                        else
                        {
                            foundEdge = true;
                            if (curEdgeDist < edgeDist)
                            {
                                edgeDist = curEdgeDist;
                                edgeNormalX = rayResults[0].Normal.X;
                                edgeNormalY = rayResults[0].Normal.Y;
                                edgeDirX = rayDir.X;
                                edgeDirY = rayDir.Y;
                                edgePos = rayResults[0].Pos;
                            }
                            break;
                        }
                    }
                    if (foundEdge && edgeDist < 0.2f)
                        break;

                    pivot = geopos + offset;

                    switch (j)
                    {
                        case 0:
                            toCamX = -toCamBaseY;
                            toCamY = toCamBaseX;
                            break;
                        case 1:
                            toCamX = toCamBaseY;
                            toCamY = -toCamBaseX;
                            break;
                        case 2:
                            toCamX = -toCamBaseX;
                            toCamY = -toCamBaseY;
                            break;
                        default:
                            break;
                    }
                }

                if (!foundEdge)
                {
                    avOffset.X = -avOffset.X;
                    avOffset.Z *= 1.6f;

                    RotAroundZ(SitNormX, SitNormY, ref ori);

                    offset += avOffset * ori;

                    ori = geomInvOri * ori;
                    offset *= geomInvOri;

                    PhysicsSitResponse(3, actor.LocalID, offset, ori);
                    return;
                }
                avOffset.X *= 0.5f;
            }

            SitNormX = edgeNormalX;
            SitNormY = edgeNormalY;
            if (edgeDirX * SitNormX + edgeDirY * SitNormY < 0)
            {
                SitNormX = -SitNormX;
                SitNormY = -SitNormY;
            }

            RotAroundZ(SitNormX, SitNormY, ref ori);

            offset = edgePos + avOffset * ori;
            offset -= geopos;

            ori = geomInvOri * ori;
            offset *= geomInvOri;

            PhysicsSitResponse(1, actor.LocalID, offset, ori);
            return;
        }
    }
}