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 * modification, are permitted provided that the following conditions are met:
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 *       notice, this list of conditions and the following disclaimer.
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 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
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 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
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 * 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
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 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using OpenSim.Region.PhysicsModules.SharedBase;

using OMV = OpenMetaverse;

namespace OpenSim.Region.PhysicsModule.BulletS
{
    public class BSActorHover : BSActor
    {
        private BSFMotor m_hoverMotor;

        public BSActorHover(BSScene physicsScene, BSPhysObject pObj, string actorName)
            : base(physicsScene, pObj, actorName)
        {
            m_hoverMotor = null;
            m_physicsScene.DetailLog("{0},BSActorHover,constructor", m_controllingPrim.LocalID);
        }

        // BSActor.isActive
        public override bool isActive
        {
            get { return Enabled; }
        }

        // Release any connections and resources used by the actor.
        // BSActor.Dispose()
        public override void Dispose()
        {
            Enabled = false;
            DeactivateHover();
        }

        // Called when physical parameters (properties set in Bullet) need to be re-applied.
        // Called at taint-time.
        // BSActor.Refresh()
        public override void Refresh()
        {
            m_physicsScene.DetailLog("{0},BSActorHover,refresh", m_controllingPrim.LocalID);
    
            // If not active any more, turn me off
            if (!m_controllingPrim.HoverActive)
            {
                SetEnabled(false);
            }
    
            // If the object is physically active, add the hoverer prestep action
            if (isActive)
            {
                ActivateHover();
            }
            else
            {
                DeactivateHover();
            }
        }

        // The object's physical representation is being rebuilt so pick up any physical dependencies (constraints, ...).
        //     Register a prestep action to restore physical requirements before the next simulation step.
        // Called at taint-time.
        // BSActor.RemoveDependencies()
        public override void RemoveDependencies()
        {
            // Nothing to do for the hoverer since it is all software at pre-step action time.
        }

        // If a hover motor has not been created, create one and start the hovering.
        private void ActivateHover()
        {
            if (m_hoverMotor == null)
            {
                // Turning the target on
                m_hoverMotor = new BSFMotor("BSActorHover",
                                            m_controllingPrim.HoverTau,               // timeScale
                                            BSMotor.Infinite,           // decay time scale
                                            1f                          // efficiency
                );
                m_hoverMotor.SetTarget(ComputeCurrentHoverHeight());
                m_hoverMotor.SetCurrent(m_controllingPrim.RawPosition.Z);
                m_hoverMotor.PhysicsScene = m_physicsScene; // DEBUG DEBUG so motor will output detail log messages.
    
                m_physicsScene.BeforeStep += Hoverer;
            }
        }

        private void DeactivateHover()
        {
            if (m_hoverMotor != null)
            {
                m_physicsScene.BeforeStep -= Hoverer;
                m_hoverMotor = null;
            }
        }

        // Called just before the simulation step. Update the vertical position for hoverness.
        private void Hoverer(float timeStep)
        {
            // Don't do hovering while the object is selected.
            if (!isActive)
                return;
    
            m_hoverMotor.SetCurrent(m_controllingPrim.RawPosition.Z);
            m_hoverMotor.SetTarget(ComputeCurrentHoverHeight());
            float targetHeight = m_hoverMotor.Step(timeStep);
    
            // 'targetHeight' is where we'd like the Z of the prim to be at this moment.
            // Compute the amount of force to push us there.
            float moveForce = (targetHeight - m_controllingPrim.RawPosition.Z) * m_controllingPrim.RawMass;
            // Undo anything the object thinks it's doing at the moment
            moveForce = -m_controllingPrim.RawVelocity.Z * m_controllingPrim.Mass;
    
            m_physicsScene.PE.ApplyCentralImpulse(m_controllingPrim.PhysBody, new OMV.Vector3(0f, 0f, moveForce));
            m_physicsScene.DetailLog("{0},BSPrim.Hover,move,targHt={1},moveForce={2},mass={3}",
                            m_controllingPrim.LocalID, targetHeight, moveForce, m_controllingPrim.RawMass);
        }

        // Based on current position, determine what we should be hovering at now.
        // Must recompute often. What if we walked offa cliff>
        private float ComputeCurrentHoverHeight()
        {
            float ret = m_controllingPrim.HoverHeight;
            float groundHeight = m_physicsScene.TerrainManager.GetTerrainHeightAtXYZ(m_controllingPrim.RawPosition);
    
            switch (m_controllingPrim.HoverType)
            {
                case PIDHoverType.Ground:
                    ret = groundHeight + m_controllingPrim.HoverHeight;
                    break;
                case PIDHoverType.GroundAndWater:
                    float waterHeight = m_physicsScene.TerrainManager.GetWaterLevelAtXYZ(m_controllingPrim.RawPosition);
                    if (groundHeight > waterHeight)
                    {
                        ret = groundHeight + m_controllingPrim.HoverHeight;
                    }
                    else
                    {
                        ret = waterHeight + m_controllingPrim.HoverHeight;
                    }
                    break;
            }
            return ret;
        }
    }
}
