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 * modification, are permitted provided that the following conditions are met:
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 *       derived from this software without specific prior written permission.
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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using OpenSim.Framework;
using OpenSim.Region.PhysicsModules.SharedBase;

using OMV = OpenMetaverse;

namespace OpenSim.Region.PhysicsModule.BulletS
{
    public class BSActorAvatarMove : BSActor
    {
        BSVMotor m_velocityMotor;

        // Set to true if we think we're going up stairs.
        //    This state is remembered because collisions will turn on and off as we go up stairs.
        int m_walkingUpStairs;
        // The amount the step up is applying. Used to smooth stair walking.
        float m_lastStepUp;

        // There are times the velocity or force is set but we don't want to inforce
        //    stationary until some tick in the future and the real velocity drops.
        int m_waitingForLowVelocityForStationary = 0;

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

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

        // Release any connections and resources used by the actor.
        // BSActor.Dispose()
        public override void Dispose()
        {
            base.SetEnabled(false);
            DeactivateAvatarMove();
        }

        // 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},BSActorAvatarMove,refresh", m_controllingPrim.LocalID);
    
            // If the object is physically active, add the hoverer prestep action
            if (isActive)
            {
                ActivateAvatarMove();
            }
            else
            {
                DeactivateAvatarMove();
            }
        }

        // 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.
        }

        // Usually called when target velocity changes to set the current velocity and the target
        //     into the movement motor.
        public void SetVelocityAndTarget(OMV.Vector3 vel, OMV.Vector3 targ, bool inTaintTime)
        {
            m_physicsScene.TaintedObject(inTaintTime, m_controllingPrim.LocalID, "BSActorAvatarMove.setVelocityAndTarget", delegate()
            {
                if (m_velocityMotor != null)
                {
                    m_velocityMotor.Reset();
                    m_velocityMotor.SetTarget(targ);
                    m_velocityMotor.SetCurrent(vel);
                    m_velocityMotor.Enabled = true;
                    m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,SetVelocityAndTarget,vel={1}, targ={2}",
                                m_controllingPrim.LocalID, vel, targ);
                    m_waitingForLowVelocityForStationary = 0;
                }
            });
        }

        public void SuppressStationayCheckUntilLowVelocity()
        {
            m_waitingForLowVelocityForStationary = 1;
        }

        public void SuppressStationayCheckUntilLowVelocity(int waitTicks)
        {
            m_waitingForLowVelocityForStationary = waitTicks;
        }

        // If a movement motor has not been created, create one and start the movement
        private void ActivateAvatarMove()
        {
            if (m_velocityMotor == null)
            {
                // Infinite decay and timescale values so motor only changes current to target values.
                m_velocityMotor = new BSVMotor("BSCharacter.Velocity",
                                                    0.2f,                       // time scale
                                                    BSMotor.Infinite,           // decay time scale
                                                    1f                          // efficiency
                );
                m_velocityMotor.ErrorZeroThreshold = BSParam.AvatarStopZeroThreshold;
                // m_velocityMotor.PhysicsScene = m_controllingPrim.PhysScene; // DEBUG DEBUG so motor will output detail log messages.
                SetVelocityAndTarget(m_controllingPrim.RawVelocity, m_controllingPrim.TargetVelocity, true /* inTaintTime */);
    
                m_physicsScene.BeforeStep += Mover;
                m_controllingPrim.OnPreUpdateProperty += Process_OnPreUpdateProperty;
    
                m_walkingUpStairs = 0;
                m_waitingForLowVelocityForStationary = 0;
            }
        }

        private void DeactivateAvatarMove()
        {
            if (m_velocityMotor != null)
            {
                m_controllingPrim.OnPreUpdateProperty -= Process_OnPreUpdateProperty;
                m_physicsScene.BeforeStep -= Mover;
                m_velocityMotor = null;
            }
        }

        // Called just before the simulation step.
        private void Mover(float timeStep)
        {
            // Don't do movement while the object is selected.
            if (!isActive)
                return;
    
            // TODO: Decide if the step parameters should be changed depending on the avatar's
            //     state (flying, colliding, ...). There is code in ODE to do this.
    
            // COMMENTARY: when the user is making the avatar walk, except for falling, the velocity
            //   specified for the avatar is the one that should be used. For falling, if the avatar
            //   is not flying and is not colliding then it is presumed to be falling and the Z
            //   component is not fooled with (thus allowing gravity to do its thing).
            // When the avatar is standing, though, the user has specified a velocity of zero and
            //   the avatar should be standing. But if the avatar is pushed by something in the world
            //   (raising elevator platform, moving vehicle, ...) the avatar should be allowed to
            //   move. Thus, the velocity cannot be forced to zero. The problem is that small velocity
            //   errors can creap in and the avatar will slowly float off in some direction.
            // So, the problem is that, when an avatar is standing, we cannot tell creaping error
            //   from real pushing.
            // The code below uses whether the collider is static or moving to decide whether to zero motion.
    
            m_velocityMotor.Step(timeStep);
            m_controllingPrim.IsStationary = false;
    
            // If we're not supposed to be moving, make sure things are zero.
            if (m_velocityMotor.ErrorIsZero() && m_velocityMotor.TargetValue == OMV.Vector3.Zero)
            {
                // The avatar shouldn't be moving
                m_velocityMotor.Zero();
    
                if (m_controllingPrim.IsColliding)
                {
                    // if colliding with something stationary and we're not doing volume detect .
                    if (!m_controllingPrim.ColliderIsMoving && !m_controllingPrim.ColliderIsVolumeDetect)
                    {
                        if (m_waitingForLowVelocityForStationary-- <= 0)
                        {
                            // if waiting for velocity to drop and it has finally dropped, we can be stationary
                            // m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,waitingForLowVelocity {1}",
                            //             m_controllingPrim.LocalID, m_waitingForLowVelocityForStationary);
                            if (m_controllingPrim.RawVelocity.LengthSquared() < BSParam.AvatarStopZeroThresholdSquared)
                            {
                                m_waitingForLowVelocityForStationary = 0;
                            }
                        }
                        if (m_waitingForLowVelocityForStationary <= 0)
                        {
                            m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,collidingWithStationary,zeroingMotion", m_controllingPrim.LocalID);
                            m_controllingPrim.IsStationary = true;
                            m_controllingPrim.ZeroMotion(true /* inTaintTime */);
                        }
                        else
                        {
                            m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,waitingForLowVel,rawvel={1}",
                                        m_controllingPrim.LocalID, m_controllingPrim.RawVelocity.Length());
                        }
                    }
    
                    // Standing has more friction on the ground
                    if (m_controllingPrim.Friction != BSParam.AvatarStandingFriction)
                    {
                        m_controllingPrim.Friction = BSParam.AvatarStandingFriction;
                        m_physicsScene.PE.SetFriction(m_controllingPrim.PhysBody, m_controllingPrim.Friction);
                    }
                }
                else
                {
                    if (m_controllingPrim.Flying)
                    {
                        // Flying and not colliding and velocity nearly zero.
                        m_controllingPrim.ZeroMotion(true /* inTaintTime */);
                    }
                    else
                    {
                        //We are falling but are not touching any keys make sure not falling too fast
                        if (m_controllingPrim.RawVelocity.Z < BSParam.AvatarTerminalVelocity)
                        {
    
                            OMV.Vector3 slowingForce = new OMV.Vector3(0f, 0f, BSParam.AvatarTerminalVelocity - m_controllingPrim.RawVelocity.Z) * m_controllingPrim.Mass;
                            m_physicsScene.PE.ApplyCentralImpulse(m_controllingPrim.PhysBody, slowingForce);
                        }
    
                    }
                }
    
                m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,taint,stopping,target={1},colliding={2},isStationary={3}",
                                m_controllingPrim.LocalID, m_velocityMotor.TargetValue, m_controllingPrim.IsColliding,m_controllingPrim.IsStationary);
            }
            else
            {
                // Supposed to be moving.
                OMV.Vector3 stepVelocity = m_velocityMotor.CurrentValue;
    
                if (m_controllingPrim.Friction != BSParam.AvatarFriction)
                {
                    // Probably starting to walk. Set friction to moving friction.
                    m_controllingPrim.Friction = BSParam.AvatarFriction;
                    m_physicsScene.PE.SetFriction(m_controllingPrim.PhysBody, m_controllingPrim.Friction);
                }
    
                // 'm_velocityMotor is used for walking, flying, and jumping and will thus have the correct values
                //    for Z. But in come cases it must be over-ridden. Like when falling or jumping.
    
                float realVelocityZ = m_controllingPrim.RawVelocity.Z;
    
                // If not flying and falling, we over-ride the stepping motor so we can fall to the ground
                if (!m_controllingPrim.Flying && realVelocityZ < 0)
                {
                    // Can't fall faster than this
                    if (realVelocityZ < BSParam.AvatarTerminalVelocity)
                    {
                        realVelocityZ = BSParam.AvatarTerminalVelocity;
                    }
    
                    stepVelocity.Z = realVelocityZ;
                }
                // m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,DEBUG,motorCurrent={1},realZ={2},flying={3},collid={4},jFrames={5}",
                //     m_controllingPrim.LocalID, m_velocityMotor.CurrentValue, realVelocityZ, m_controllingPrim.Flying, m_controllingPrim.IsColliding, m_jumpFrames);
    
                //Alicia: Maintain minimum height when flying.
                // SL has a flying effect that keeps the avatar flying above the ground by some margin
                if (m_controllingPrim.Flying)
                {
                    float hover_height = m_physicsScene.TerrainManager.GetTerrainHeightAtXYZ(m_controllingPrim.RawPosition)
                                                            + BSParam.AvatarFlyingGroundMargin;
    
                    if( m_controllingPrim.Position.Z < hover_height)
                    {
                        m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,addingUpforceForGroundMargin,height={1},hoverHeight={2}",
                                    m_controllingPrim.LocalID, m_controllingPrim.Position.Z, hover_height);
                        stepVelocity.Z += BSParam.AvatarFlyingGroundUpForce;
                    }
                }
    
                // 'stepVelocity' is now the speed we'd like the avatar to move in. Turn that into an instantanous force.
                OMV.Vector3 moveForce = (stepVelocity - m_controllingPrim.RawVelocity) * m_controllingPrim.Mass;
    
                // Add special movement force to allow avatars to walk up stepped surfaces.
                moveForce += WalkUpStairs();
    
                m_physicsScene.DetailLog("{0},BSCharacter.MoveMotor,move,stepVel={1},vel={2},mass={3},moveForce={4}",
                                m_controllingPrim.LocalID, stepVelocity, m_controllingPrim.RawVelocity, m_controllingPrim.Mass, moveForce);
                m_physicsScene.PE.ApplyCentralImpulse(m_controllingPrim.PhysBody, moveForce);
            }
        }

        // Called just as the property update is received from the physics engine.
        // Do any mode necessary for avatar movement.
        private void Process_OnPreUpdateProperty(ref EntityProperties entprop)
        {
            // Don't change position if standing on a stationary object.
            if (m_controllingPrim.IsStationary)
            {
                entprop.Position = m_controllingPrim.RawPosition;
                entprop.Velocity = OMV.Vector3.Zero;
                m_physicsScene.PE.SetTranslation(m_controllingPrim.PhysBody, entprop.Position, entprop.Rotation);
            }
    
        }

        // Decide if the character is colliding with a low object and compute a force to pop the
        //    avatar up so it can walk up and over the low objects.
        private OMV.Vector3 WalkUpStairs()
        {
            OMV.Vector3 ret = OMV.Vector3.Zero;
    
            m_physicsScene.DetailLog("{0},BSCharacter.WalkUpStairs,IsColliding={1},flying={2},targSpeed={3},collisions={4},avHeight={5}",
                            m_controllingPrim.LocalID, m_controllingPrim.IsColliding, m_controllingPrim.Flying,
                            m_controllingPrim.TargetVelocitySpeed, m_controllingPrim.CollisionsLastTick.Count, m_controllingPrim.Size.Z);
    
            // Check for stairs climbing if colliding, not flying and moving forward
            if ( m_controllingPrim.IsColliding
                        && !m_controllingPrim.Flying
                        && m_controllingPrim.TargetVelocitySpeed > 0.1f )
            {
                // The range near the character's feet where we will consider stairs
                // float nearFeetHeightMin = m_controllingPrim.RawPosition.Z - (m_controllingPrim.Size.Z / 2f) + 0.05f;
                // Note: there is a problem with the computation of the capsule height. Thus RawPosition is off
                //    from the height. Revisit size and this computation when height is scaled properly.
                float nearFeetHeightMin = m_controllingPrim.RawPosition.Z - (m_controllingPrim.Size.Z / 2f) - BSParam.AvatarStepGroundFudge;
                float nearFeetHeightMax = nearFeetHeightMin + BSParam.AvatarStepHeight;
    
                // Look for a collision point that is near the character's feet and is oriented the same as the charactor is.
                // Find the highest 'good' collision.
                OMV.Vector3 highestTouchPosition = OMV.Vector3.Zero;
                foreach (KeyValuePair<uint, ContactPoint> kvp in m_controllingPrim.CollisionsLastTick.m_objCollisionList)
                {
                    // Don't care about collisions with the terrain
                    if (kvp.Key > m_physicsScene.TerrainManager.HighestTerrainID)
                    {
                        BSPhysObject collisionObject;
                        if (m_physicsScene.PhysObjects.TryGetValue(kvp.Key, out collisionObject))
                        {
                            if (!collisionObject.IsVolumeDetect)
                            {
                                OMV.Vector3 touchPosition = kvp.Value.Position;
                                m_physicsScene.DetailLog("{0},BSCharacter.WalkUpStairs,min={1},max={2},touch={3}",
                                                m_controllingPrim.LocalID, nearFeetHeightMin, nearFeetHeightMax, touchPosition);
                                if (touchPosition.Z >= nearFeetHeightMin && touchPosition.Z <= nearFeetHeightMax)
                                {
                                    // This contact is within the 'near the feet' range.
                                    // The step is presumed to be more or less vertical. Thus the Z component should
                                    //    be nearly horizontal.
                                    OMV.Vector3 directionFacing = OMV.Vector3.UnitX * m_controllingPrim.RawOrientation;
                                    OMV.Vector3 touchNormal = OMV.Vector3.Normalize(kvp.Value.SurfaceNormal);
                                    const float PIOver2 = 1.571f; // Used to make unit vector axis into approx radian angles
                                    // m_physicsScene.DetailLog("{0},BSCharacter.WalkUpStairs,avNormal={1},colNormal={2},diff={3}",
                                    //             m_controllingPrim.LocalID, directionFacing, touchNormal,
                                    //             Math.Abs(OMV.Vector3.Distance(directionFacing, touchNormal)) );
                                    if ((Math.Abs(directionFacing.Z) * PIOver2) < BSParam.AvatarStepAngle
                                        && (Math.Abs(touchNormal.Z) * PIOver2) < BSParam.AvatarStepAngle)
                                    {
                                        // The normal should be our contact point to the object so it is pointing away
                                        //    thus the difference between our facing orientation and the normal should be small.
                                        float diff = Math.Abs(OMV.Vector3.Distance(directionFacing, touchNormal));
                                        if (diff < BSParam.AvatarStepApproachFactor)
                                        {
                                            if (highestTouchPosition.Z < touchPosition.Z)
                                                highestTouchPosition = touchPosition;
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                m_walkingUpStairs = 0;
                // If there is a good step sensing, move the avatar over the step.
                if (highestTouchPosition != OMV.Vector3.Zero)
                {
                    // Remember that we are going up stairs. This is needed because collisions
                    //    will stop when we move up so this smoothes out that effect.
                    m_walkingUpStairs = BSParam.AvatarStepSmoothingSteps;
    
                    m_lastStepUp = highestTouchPosition.Z - nearFeetHeightMin;
                    ret = ComputeStairCorrection(m_lastStepUp);
                    m_physicsScene.DetailLog("{0},BSCharacter.WalkUpStairs,touchPos={1},nearFeetMin={2},ret={3}",
                            m_controllingPrim.LocalID, highestTouchPosition, nearFeetHeightMin, ret);
                }
            }
            else
            {
                // If we used to be going up stairs but are not now, smooth the case where collision goes away while
                //    we are bouncing up the stairs.
                if (m_walkingUpStairs > 0)
                {
                    m_walkingUpStairs--;
                    ret = ComputeStairCorrection(m_lastStepUp);
                }
            }
    
            return ret;
        }

        private OMV.Vector3 ComputeStairCorrection(float stepUp)
        {
            OMV.Vector3 ret = OMV.Vector3.Zero;
            OMV.Vector3 displacement = OMV.Vector3.Zero;
    
            if (stepUp > 0f)
            {
                // Found the stairs contact point. Push up a little to raise the character.
                if (BSParam.AvatarStepForceFactor > 0f)
                {
                    float upForce = stepUp * m_controllingPrim.Mass * BSParam.AvatarStepForceFactor;
                    ret = new OMV.Vector3(0f, 0f, upForce);
                }
    
                // Also move the avatar up for the new height
                if (BSParam.AvatarStepUpCorrectionFactor > 0f)
                {
                    // Move the avatar up related to the height of the collision
                    displacement = new OMV.Vector3(0f, 0f, stepUp * BSParam.AvatarStepUpCorrectionFactor);
                    m_controllingPrim.ForcePosition = m_controllingPrim.RawPosition + displacement;
                }
                else
                {
                    if (BSParam.AvatarStepUpCorrectionFactor < 0f)
                    {
                        // Move the avatar up about the specified step height
                        displacement = new OMV.Vector3(0f, 0f, BSParam.AvatarStepHeight);
                        m_controllingPrim.ForcePosition = m_controllingPrim.RawPosition + displacement;
                    }
                }
                m_physicsScene.DetailLog("{0},BSCharacter.WalkUpStairs.ComputeStairCorrection,stepUp={1},isp={2},force={3}",
                                            m_controllingPrim.LocalID, stepUp, displacement, ret);
    
            }
            return ret;
        }
    }
}


