/*
 *  Portions Copyright (C) 2000-2001 Tim Angus
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under the terms of the OSML - Open Source Modification License v1.0 as
 *  described in the file COPYING which is distributed with this source
 *  code.
 *
 *  This program 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.
 */

#include "cg_local.h"

/*
===============
CG_RunLerpFrame

Sets cg.snap, cg.oldFrame, and cg.backlerp
cg.time should be between oldFrameTime and frameTime after exit
===============
*/
void CG_RunLerpFrame( lerpFrame_t *lf )
{
  int     f, numFrames;
  animation_t *anim;

  // debugging tool to get no animations
  if( cg_animSpeed.integer == 0 )
  {
    lf->oldFrame = lf->frame = lf->backlerp = 0;
    return;
  }

  // if we have passed the current frame, move it to
  // oldFrame and calculate a new frame
  if( cg.time >= lf->frameTime )
  {
    lf->oldFrame = lf->frame;
    lf->oldFrameTime = lf->frameTime;

    // get the next frame based on the animation
    anim = lf->animation;
    if( !anim->frameLerp )
      return;   // shouldn't happen

    if( cg.time < lf->animationTime )
      lf->frameTime = lf->animationTime;    // initial lerp
    else
      lf->frameTime = lf->oldFrameTime + anim->frameLerp;

    f = ( lf->frameTime - lf->animationTime ) / anim->frameLerp;
    numFrames = anim->numFrames;
    if( anim->flipflop )
      numFrames *= 2;

    if( f >= numFrames )
    {
      f -= numFrames;
      if( anim->loopFrames )
      {
        f %= anim->loopFrames;
        f += anim->numFrames - anim->loopFrames;
      }
      else
      {
        f = numFrames - 1;
        // the animation is stuck at the end, so it
        // can immediately transition to another sequence
        lf->frameTime = cg.time;
      }
    }

    if( anim->reversed )
      lf->frame = anim->firstFrame + anim->numFrames - 1 - f;
    else if( anim->flipflop && f >= anim->numFrames )
      lf->frame = anim->firstFrame + anim->numFrames - 1 - ( f % anim->numFrames );
    else
      lf->frame = anim->firstFrame + f;

    if( cg.time > lf->frameTime )
    {
      lf->frameTime = cg.time;
      if( cg_debugAnim.integer )
        CG_Printf( "Clamp lf->frameTime\n" );
    }
  }

  if( lf->frameTime > cg.time + 200 )
    lf->frameTime = cg.time;

  if( lf->oldFrameTime > cg.time )
    lf->oldFrameTime = cg.time;

  // calculate current lerp value
  if( lf->frameTime == lf->oldFrameTime )
    lf->backlerp = 0;
  else
    lf->backlerp = 1.0 - (float)( cg.time - lf->oldFrameTime ) / ( lf->frameTime - lf->oldFrameTime );
}