/*************************************************************************

 *                                                                       *

 * Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith.       *

 * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          *

 *                                                                       *

 * This library is free software; you can redistribute it and/or         *

 * modify it under the terms of EITHER:                                  *

 *   (1) The GNU Lesser General Public License as published by the Free  *

 *       Software Foundation; either version 2.1 of the License, or (at  *

 *       your option) any later version. The text of the GNU Lesser      *

 *       General Public License is included with this library in the     *

 *       file LICENSE.TXT.                                               *

 *   (2) The BSD-style license that is included with this library in     *

 *       the file LICENSE-BSD.TXT.                                       *

 *                                                                       *

 * This library is distributed in the hope that it will be useful,       *

 * but WITHOUT ANY WARRANTY; without even the implied warranty of        *

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *

 * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *

 *                                                                       *

 *************************************************************************/

#include <ode/ode.h>

#include "object.h"

#include "joint.h"

#include "util.h"

#include <ode/lookup_tables.h>

//#define ALLOCA dALLOCA16

//****************************************************************************

// Auto disabling

void dInternalHandleAutoDisabling (dxWorld *world, dReal stepsize)

{

	dxBody *bb;

	for ( bb=world->firstbody; bb; bb=(dxBody*)bb->next )

	{

		// don't freeze objects mid-air (patch 1586738)

		if ( bb->firstjoint == NULL ) continue;

		// nothing to do unless this body is currently enabled and has

		// the auto-disable flag set

		if ( (bb->flags & (dxBodyAutoDisable|dxBodyDisabled)) != dxBodyAutoDisable ) continue;

		// if sampling / threshold testing is disabled, we can never sleep.

		if ( bb->adis.average_samples == 0 ) continue;

		//

		// see if the body is idle

		//

#ifndef dNODEBUG

		// sanity check

		if ( bb->average_counter >= bb->adis.average_samples )

		{

			// something is going wrong, reset the average-calculations

			bb->average_ready = 0; // not ready for average calculation

			bb->average_counter = 0; // reset the buffer index

		}

#endif // dNODEBUG

		// sample the linear and angular velocity

		bb->average_lvel_buffer[bb->average_counter][0] = bb->lvel[0];

		bb->average_lvel_buffer[bb->average_counter][1] = bb->lvel[1];

		bb->average_lvel_buffer[bb->average_counter][2] = bb->lvel[2];

		bb->average_avel_buffer[bb->average_counter][0] = bb->avel[0];

		bb->average_avel_buffer[bb->average_counter][1] = bb->avel[1];

		bb->average_avel_buffer[bb->average_counter][2] = bb->avel[2];

		bb->average_counter++;

		// buffer ready test

		if ( bb->average_counter >= bb->adis.average_samples )

		{

			bb->average_counter = 0; // fill the buffer from the beginning

			bb->average_ready = 1; // this body is ready now for average calculation

		}

		int idle = 0; // Assume it's in motion unless we have samples to disprove it.

		// enough samples?

		if ( bb->average_ready )

		{

			idle = 1; // Initial assumption: IDLE

			// the sample buffers are filled and ready for calculation

			dVector3 average_lvel, average_avel;

			// Store first velocity samples

			average_lvel[0] = bb->average_lvel_buffer[0][0];

			average_avel[0] = bb->average_avel_buffer[0][0];

			average_lvel[1] = bb->average_lvel_buffer[0][1];

			average_avel[1] = bb->average_avel_buffer[0][1];

			average_lvel[2] = bb->average_lvel_buffer[0][2];

			average_avel[2] = bb->average_avel_buffer[0][2];

			// If we're not in "instantaneous mode"

			if ( bb->adis.average_samples > 1 )

			{

				// add remaining velocities together

				for ( unsigned int i = 1; i < bb->adis.average_samples; ++i )

				{

					average_lvel[0] += bb->average_lvel_buffer[i][0];

					average_avel[0] += bb->average_avel_buffer[i][0];

					average_lvel[1] += bb->average_lvel_buffer[i][1];

					average_avel[1] += bb->average_avel_buffer[i][1];

					average_lvel[2] += bb->average_lvel_buffer[i][2];

					average_avel[2] += bb->average_avel_buffer[i][2];

				}

				// make average

				dReal r1 = dDIV(REAL( 1.0 ),REAL( bb->adis.average_samples ));

				average_lvel[0] = dMUL(average_lvel[0],r1);

				average_avel[0] = dMUL(average_avel[0],r1);

				average_lvel[1] = dMUL(average_lvel[1],r1);

				average_avel[1] = dMUL(average_avel[1],r1);

				average_lvel[2] = dMUL(average_lvel[2],r1);

				average_avel[2] = dMUL(average_avel[2],r1);

			}

			// threshold test

			dReal av_lspeed, av_aspeed;

			av_lspeed = dDOT( average_lvel, average_lvel );

			if ( av_lspeed > bb->adis.linear_average_threshold )

			{

				idle = 0; // average linear velocity is too high for idle

			}

			else

			{

				av_aspeed = dDOT( average_avel, average_avel );

				if ( av_aspeed > bb->adis.angular_average_threshold )

				{

					idle = 0; // average angular velocity is too high for idle

				}

			}

		}

		// if it's idle, accumulate steps and time.

		// these counters won't overflow because this code doesn't run for disabled bodies.

		if (idle) {

			bb->adis_stepsleft--;

			bb->adis_timeleft -= stepsize;

		}

		else {

			// Reset countdowns

			bb->adis_stepsleft = bb->adis.idle_steps;

			bb->adis_timeleft = bb->adis.idle_time;

		}

		// disable the body if it's idle for a long enough time

		if ( bb->adis_stepsleft <= 0 && bb->adis_timeleft <= 0 )

		{

			bb->flags |= dxBodyDisabled; // set the disable flag

			// disabling bodies should also include resetting the velocity

			// should prevent jittering in big "islands"

			bb->lvel[0] = 0;

			bb->lvel[1] = 0;

			bb->lvel[2] = 0;

			bb->avel[0] = 0;

			bb->avel[1] = 0;

			bb->avel[2] = 0;

		}

	}

}

//****************************************************************************

// body rotation

// return sin(x)/x. this has a singularity at 0 so special handling is needed

// for small arguments.

static inline dReal sinc (dReal x)

{

  // if |x| < 1e-4 then use a taylor series expansion. this two term expansion

  // is actually accurate to one LS bit within this range if double precision

  // is being used - so don't worry!

  if (dFabs(x) < REAL(1.0e-4)) return REAL(1.0) - dMUL(dMUL(x,x),REAL(0.166666666666666666667));

  else return dDIV(dSin(x),x);

}

// given a body b, apply its linear and angular rotation over the time

// interval h, thereby adjusting its position and orientation.

void dxStepBody (dxBody *b, dReal h)

{

  int j;

  // handle linear velocity

  for (j=0; j<3; j++) b->posr.pos[j] += dMUL(h,b->lvel[j]);

  if (b->flags & dxBodyFlagFiniteRotation) {

    dVector3 irv;	// infitesimal rotation vector

    dQuaternion q;	// quaternion for finite rotation

    if (b->flags & dxBodyFlagFiniteRotationAxis) {

      // split the angular velocity vector into a component along the finite

      // rotation axis, and a component orthogonal to it.

      dVector3 frv;		// finite rotation vector

      dReal k = dDOT (b->finite_rot_axis,b->avel);

      frv[0] = dMUL(b->finite_rot_axis[0],k);

      frv[1] = dMUL(b->finite_rot_axis[1],k);

      frv[2] = dMUL(b->finite_rot_axis[2],k);

      irv[0] = b->avel[0] - frv[0];

      irv[1] = b->avel[1] - frv[1];

      irv[2] = b->avel[2] - frv[2];

      // make a rotation quaternion q that corresponds to frv * h.

      // compare this with the full-finite-rotation case below.

      h = dMUL(h,REAL(0.5));

      dReal theta = dMUL(k,h);

      q[0] = dCos(theta);

      dReal s = dMUL(sinc(theta),h);

      q[1] = dMUL(frv[0],s);

      q[2] = dMUL(frv[1],s);

      q[3] = dMUL(frv[2],s);

    }

    else {

      // make a rotation quaternion q that corresponds to w * h

      dReal wlen = dSqrt (dMUL(b->avel[0],b->avel[0]) + dMUL(b->avel[1],b->avel[1]) +

			  dMUL(b->avel[2],b->avel[2]));

      h = dMUL(h,REAL(0.5));

      dReal theta = dMUL(wlen,h);

      q[0] = dCos(theta);

      dReal s = dMUL(sinc(theta),h);

      q[1] = dMUL(b->avel[0],s);

      q[2] = dMUL(b->avel[1],s);

      q[3] = dMUL(b->avel[2],s);

    }

    // do the finite rotation

    dQuaternion q2;

    dQMultiply0 (q2,q,b->q);

    for (j=0; j<4; j++) b->q[j] = q2[j];

    // do the infitesimal rotation if required

    if (b->flags & dxBodyFlagFiniteRotationAxis) {

      dReal dq[4];

      dWtoDQ (irv,b->q,dq);

      for (j=0; j<4; j++) b->q[j] += dMUL(h,dq[j]);

    }

  }

  else {

    // the normal way - do an infitesimal rotation

    dReal dq[4];

    dWtoDQ (b->avel,b->q,dq);

    for (j=0; j<4; j++) b->q[j] += dMUL(h,dq[j]);

  }

  // normalize the quaternion and convert it to a rotation matrix

  dNormalize4 (b->q);

  dQtoR (b->q,b->posr.R);

  // notify all attached geoms that this body has moved

  for (dxGeom *geom = b->geom; geom; geom = dGeomGetBodyNext (geom))

    dGeomMoved (geom);

}

//****************************************************************************

// island processing

// this groups all joints and bodies in a world into islands. all objects

// in an island are reachable by going through connected bodies and joints.

// each island can be simulated separately.

// note that joints that are not attached to anything will not be included

// in any island, an so they do not affect the simulation.

//

// this function starts new island from unvisited bodies. however, it will

// never start a new islands from a disabled body. thus islands of disabled

// bodies will not be included in the simulation. disabled bodies are

// re-enabled if they are found to be part of an active island.

void dxProcessIslands (dxWorld *world, dReal stepsize, dstepper_fn_t stepper)

{

  dxBody *b,*bb,**body;

  dxJoint *j,**joint;

  // nothing to do if no bodies

  if (world->nb <= 0) return;

  // handle auto-disabling of bodies

  dInternalHandleAutoDisabling (world,stepsize);

  // make arrays for body and joint lists (for a single island) to go into

  body = (dxBody**) malloc (world->nb * sizeof(dxBody*));

  if(body == NULL){

  	return;

  }

  joint = (dxJoint**) malloc (world->nj * sizeof(dxJoint*));

  if(joint == NULL){

  	free(body);

	return;

  }

  int bcount = 0;	// number of bodies in `body'

  int jcount = 0;	// number of joints in `joint'

  // set all body/joint tags to 0

  for (b=world->firstbody; b; b=(dxBody*)b->next) b->tag = 0;

  for (j=world->firstjoint; j; j=(dxJoint*)j->next) j->tag = 0;

  // allocate a stack of unvisited bodies in the island. the maximum size of

  // the stack can be the lesser of the number of bodies or joints, because

  // new bodies are only ever added to the stack by going through untagged

  // joints. all the bodies in the stack must be tagged!

  int stackalloc = (world->nj < world->nb) ? world->nj : world->nb;

  dxBody **stack = (dxBody**) malloc (stackalloc * sizeof(dxBody*));

  if(stack == NULL){

	free(body);

	free(joint);

	return;

  }

  for (bb=world->firstbody; bb; bb=(dxBody*)bb->next) {

    // get bb = the next enabled, untagged body, and tag it

    if (bb->tag || (bb->flags & dxBodyDisabled)) continue;

    bb->tag = 1;

    // tag all bodies and joints starting from bb.

    int stacksize = 0;

    int firsttime = 1;

    b = bb;

    body[0] = bb;

    bcount = 1;

    jcount = 0;

    while (stacksize > 0 || firsttime)

    {

      if (!firsttime)

          {

          b = stack[--stacksize];	// pop body off stack

          body[bcount++] = b;	// put body on body list

          }

      else

          {

          firsttime = 0;

          }

      // traverse and tag all body's joints, add untagged connected bodies

      // to stack

      for (dxJointNode *n=b->firstjoint; n; n=n->next) {

	if (!n->joint->tag) {

	  n->joint->tag = 1;

	  joint[jcount++] = n->joint;

	  if (n->body && !n->body->tag) {

	    n->body->tag = 1;

	    stack[stacksize++] = n->body;

	  }

	}

      }

    }

    // now do something with body and joint lists

    stepper (world,body,bcount,joint,jcount,stepsize);

    // what we've just done may have altered the body/joint tag values.

    // we must make sure that these tags are nonzero.

    // also make sure all bodies are in the enabled state.

    int i;

    for (i=0; i<bcount; i++) {

      body[i]->tag = 1;

      body[i]->flags &= ~dxBodyDisabled;

    }

    for (i=0; i<jcount; i++) joint[i]->tag = 1;

  }

  free(body);

  free(joint);

  free(stack);

}