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

 Copyright (c) 2018  GeometryFactory Sarl (France).
 Copyright (C) 2002-2014 Gilles Debunne. All rights reserved.

 This file is part of a fork of the QGLViewer library version 2.7.0.

*****************************************************************************/
// $URL: https://github.com/CGAL/cgal/blob/v5.5.2/GraphicsView/include/CGAL/Qt/keyFrameInterpolator_impl.h $
// $Id: keyFrameInterpolator_impl.h 5efa544 2021-02-22T17:19:40+01:00 Mael Rouxel-Labbé
// SPDX-License-Identifier: GPL-3.0-only
#ifdef CGAL_HEADER_ONLY
#define CGAL_INLINE_FUNCTION inline

#include <CGAL/license/GraphicsView.h>

#else
#define CGAL_INLINE_FUNCTION
#endif

#include <CGAL/Qt/keyFrameInterpolator.h>

namespace CGAL{
namespace qglviewer{


/*! Creates a KeyFrameInterpolator, with \p frame as associated frame().

  The frame() can be set or changed using setFrame().

  interpolationTime(), interpolationSpeed() and interpolationPeriod() are set to
  their default values. */
CGAL_INLINE_FUNCTION
KeyFrameInterpolator::KeyFrameInterpolator(Frame *frame)
    : frame_(nullptr), period_(40), interpolationTime_(0.0),
      interpolationSpeed_(1.0), interpolationStarted_(false),
      closedPath_(false), loopInterpolation_(false), pathIsValid_(false),
      valuesAreValid_(true), currentFrameValid_(false)
{
  setFrame(frame);
  for (int i = 0; i < 4; ++i)
    currentFrame_[i] = new QMutableListIterator<KeyFrame *>(keyFrame_);
  connect(&timer_, SIGNAL(timeout()), SLOT(update()));
}

/*! Virtual destructor. Clears the keyFrame path. */
CGAL_INLINE_FUNCTION
KeyFrameInterpolator::~KeyFrameInterpolator() {
  deletePath();
  for (int i = 0; i < 4; ++i)
    delete currentFrame_[i];
}

/*! Sets the frame() associated to the KeyFrameInterpolator. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::setFrame(Frame *const frame) {
  if (this->frame())
    disconnect(this, SIGNAL(interpolated()), this->frame(),
               SIGNAL(interpolated()));

  frame_ = frame;

  if (this->frame())
    connect(this, SIGNAL(interpolated()), this->frame(),
            SIGNAL(interpolated()));
}

/*! Updates frame() state according to current interpolationTime(). Then adds
  interpolationPeriod()*interpolationSpeed() to interpolationTime().

  This internal method is called by a timer when interpolationIsStarted(). It
  can be used for debugging purpose. stopInterpolation() is called when
  interpolationTime() reaches firstTime() or lastTime(), unless
  loopInterpolation() is \c true. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::update() {
  interpolateAtTime(interpolationTime());

  interpolationTime_ += interpolationSpeed() * interpolationPeriod() / 1000.0;

  if (interpolationTime() > keyFrame_.last()->time()) {
    if (loopInterpolation())
      setInterpolationTime(keyFrame_.first()->time() + interpolationTime_ -
                           keyFrame_.last()->time());
    else {
      // Make sure last KeyFrame is reached and displayed
      interpolateAtTime(keyFrame_.last()->time());
      stopInterpolation();
    }
    Q_EMIT endReached();
  } else if (interpolationTime() < keyFrame_.first()->time()) {
    if (loopInterpolation())
      setInterpolationTime(keyFrame_.last()->time() -
                           keyFrame_.first()->time() + interpolationTime_);
    else {
      // Make sure first KeyFrame is reached and displayed
      interpolateAtTime(keyFrame_.first()->time());
      stopInterpolation();
    }
    Q_EMIT endReached();
  }
}

/*! Starts the interpolation process.

  A timer is started with an interpolationPeriod() period that updates the
  frame()'s position and orientation. interpolationIsStarted() will return \c
  true until stopInterpolation() or toggleInterpolation() is called.

  If \p period is positive, it is set as the new interpolationPeriod(). The
  previous interpolationPeriod() is used otherwise (default).

  If interpolationTime() is larger than lastTime(), interpolationTime() is reset
  to firstTime() before interpolation starts (and inversely for negative
  interpolationSpeed()).

  Use setInterpolationTime() before calling this method to change the starting
  interpolationTime().

  See the <a href="../examples/keyFrames.html">keyFrames example</a> for an
  illustration.

  You may also be interested in CGAL::QGLViewer::animate() and
  CGAL::QGLViewer::startAnimation().

  \attention The keyFrames must be defined (see addKeyFrame()) \e before you
  startInterpolation(), or else the interpolation will naturally immediately
  stop. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::startInterpolation(int period) {
  if (period >= 0)
    setInterpolationPeriod(period);

  if (!keyFrame_.isEmpty()) {
    if ((interpolationSpeed() > 0.0) &&
        (interpolationTime() >= keyFrame_.last()->time()))
      setInterpolationTime(keyFrame_.first()->time());
    if ((interpolationSpeed() < 0.0) &&
        (interpolationTime() <= keyFrame_.first()->time()))
      setInterpolationTime(keyFrame_.last()->time());
    timer_.start(interpolationPeriod());
    interpolationStarted_ = true;
    update();
  }
}

/*! Stops an interpolation started with startInterpolation(). See
 * interpolationIsStarted() and toggleInterpolation(). */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::stopInterpolation() {
  timer_.stop();
  interpolationStarted_ = false;
}

/*! Stops the interpolation and resets interpolationTime() to the firstTime().

If desired, call interpolateAtTime() after this method to actually move the
frame() to firstTime(). */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::resetInterpolation() {
  stopInterpolation();
  setInterpolationTime(firstTime());
}

/*! Appends a new keyFrame to the path, with its associated \p time (in
  seconds).

  The keyFrame is given as a pointer to a Frame, which will be connected to the
  KeyFrameInterpolator: when \p frame is modified, the KeyFrameInterpolator path
  is updated accordingly. This allows for dynamic paths, where keyFrame can be
  edited, even during the interpolation. See the <a
  href="../examples/keyFrames.html">keyFrames example</a> for an illustration.

  \c nullptr \p frame pointers are silently ignored. The keyFrameTime() has to be
  monotonously increasing over keyFrames.

  Use addKeyFrame(const Frame&, qreal) to add keyFrame by values. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::addKeyFrame(const Frame *const frame, qreal time) {
  if (!frame)
    return;

  if (keyFrame_.isEmpty())
    interpolationTime_ = time;

  if ((!keyFrame_.isEmpty()) && (keyFrame_.last()->time() > time))
    qWarning(
        "Error in KeyFrameInterpolator::addKeyFrame: time is not monotone");
  else
    keyFrame_.append(new KeyFrame(frame, time));
  connect(frame, SIGNAL(modified()), SLOT(invalidateValues()));
  valuesAreValid_ = false;
  pathIsValid_ = false;
  currentFrameValid_ = false;
  resetInterpolation();
}

/*! Appends a new keyFrame to the path, with its associated \p time (in
  seconds).

  The path will use the current \p frame state. If you want the path to change
  when \p frame is modified, you need to pass a \e pointer to the Frame instead
  (see addKeyFrame(const Frame*, qreal)).

  The keyFrameTime() have to be monotonously increasing over keyFrames. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::addKeyFrame(const Frame &frame, qreal time) {
  if (keyFrame_.isEmpty())
    interpolationTime_ = time;

  if ((!keyFrame_.isEmpty()) && (keyFrame_.last()->time() > time))
    qWarning(
        "Error in KeyFrameInterpolator::addKeyFrame: time is not monotone");
  else
    keyFrame_.append(new KeyFrame(frame, time));

  valuesAreValid_ = false;
  pathIsValid_ = false;
  currentFrameValid_ = false;
  resetInterpolation();
}

/*! Appends a new keyFrame to the path.

 Same as addKeyFrame(const Frame* frame, qreal), except that the keyFrameTime()
 is set to the previous keyFrameTime() plus one second (or 0.0 if there is no
 previous keyFrame). */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::addKeyFrame(const Frame *const frame) {
  qreal time;
  if (keyFrame_.isEmpty())
    time = 0.0;
  else
    time = lastTime() + 1.0;

  addKeyFrame(frame, time);
}

/*! Appends a new keyFrame to the path.

 Same as addKeyFrame(const Frame& frame, qreal), except that the keyFrameTime()
 is automatically set to previous keyFrameTime() plus one second (or 0.0 if
 there is no previous keyFrame). */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::addKeyFrame(const Frame &frame) {
  qreal time;
  if (keyFrame_.isEmpty())
    time = 0.0;
  else
    time = keyFrame_.last()->time() + 1.0;

  addKeyFrame(frame, time);
}

/*! Removes all keyFrames from the path. The numberOfKeyFrames() is set to 0. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::deletePath() {
  stopInterpolation();
  qDeleteAll(keyFrame_);
  keyFrame_.clear();
  pathIsValid_ = false;
  valuesAreValid_ = false;
  currentFrameValid_ = false;
}


CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::updateModifiedFrameValues() {
  Quaternion prevQ = keyFrame_.first()->orientation();
  KeyFrame *kf;
  for (int i = 0; i < keyFrame_.size(); ++i) {
    kf = keyFrame_.at(i);
    if (kf->frame())
      kf->updateValuesFromPointer();
    kf->flipOrientationIfNeeded(prevQ);
    prevQ = kf->orientation();
  }

  KeyFrame *prev = keyFrame_.first();
  kf = keyFrame_.first();
  int index = 1;
  while (kf) {
    KeyFrame *next = (index < keyFrame_.size()) ? keyFrame_.at(index) : nullptr;
    index++;
    if (next)
      kf->computeTangent(prev, next);
    else
      kf->computeTangent(prev, kf);
    prev = kf;
    kf = next;
  }
  valuesAreValid_ = true;
}

/*! Returns the Frame associated with the keyFrame at index \p index.

 See also keyFrameTime(). \p index has to be in the range
 0..numberOfKeyFrames()-1.

 \note If this keyFrame was defined using a pointer to a Frame (see
 addKeyFrame(const Frame* const)), the \e current pointed Frame state is
 returned. */
CGAL_INLINE_FUNCTION
Frame KeyFrameInterpolator::keyFrame(int index) const {
  const KeyFrame *const kf = keyFrame_.at(index);
  return Frame(kf->position(), kf->orientation());
}

/*! Returns the time corresponding to the \p index keyFrame.

 See also keyFrame(). \p index has to be in the range 0..numberOfKeyFrames()-1.
 */
CGAL_INLINE_FUNCTION
qreal KeyFrameInterpolator::keyFrameTime(int index) const {
  return keyFrame_.at(index)->time();
}

/*! Returns the duration of the KeyFrameInterpolator path, expressed in seconds.

 Simply corresponds to lastTime() - firstTime(). Returns 0.0 if the path has
 fewer than 2 keyFrames. See also keyFrameTime(). */
CGAL_INLINE_FUNCTION
qreal KeyFrameInterpolator::duration() const {
  return lastTime() - firstTime();
}

/*! Returns the time corresponding to the first keyFrame, expressed in seconds.

Returns 0.0 if the path is empty. See also lastTime(), duration() and
keyFrameTime(). */
CGAL_INLINE_FUNCTION
qreal KeyFrameInterpolator::firstTime() const {
  if (keyFrame_.isEmpty())
    return 0.0;
  else
    return keyFrame_.first()->time();
}

/*! Returns the time corresponding to the last keyFrame, expressed in seconds.

Returns 0.0 if the path is empty. See also firstTime(), duration() and
keyFrameTime(). */
CGAL_INLINE_FUNCTION
qreal KeyFrameInterpolator::lastTime() const {
  if (keyFrame_.isEmpty())
    return 0.0;
  else
    return keyFrame_.last()->time();
}

CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::updateCurrentKeyFrameForTime(qreal time) {
  // Assertion: times are sorted in monotone order.
  // Assertion: keyFrame_ is not empty

  // TODO: Special case for loops when closed path is implemented !!
  if (!currentFrameValid_)
    // Recompute everything from scrach
    currentFrame_[1]->toFront();

  while (currentFrame_[1]->peekNext()->time() > time) {
    currentFrameValid_ = false;
    if (!currentFrame_[1]->hasPrevious())
      break;
    currentFrame_[1]->previous();
  }

  if (!currentFrameValid_)
    *currentFrame_[2] = *currentFrame_[1];

  while (currentFrame_[2]->peekNext()->time() < time) {
    currentFrameValid_ = false;
    if (!currentFrame_[2]->hasNext())
      break;
    currentFrame_[2]->next();
  }

  if (!currentFrameValid_) {
    *currentFrame_[1] = *currentFrame_[2];
    if ((currentFrame_[1]->hasPrevious()) &&
        (time < currentFrame_[2]->peekNext()->time()))
      currentFrame_[1]->previous();

    *currentFrame_[0] = *currentFrame_[1];
    if (currentFrame_[0]->hasPrevious())
      currentFrame_[0]->previous();

    *currentFrame_[3] = *currentFrame_[2];
    if (currentFrame_[3]->hasNext())
      currentFrame_[3]->next();

    currentFrameValid_ = true;
    splineCacheIsValid_ = false;
  }

  // cout << "Time = " << time << " : " << currentFrame_[0]->peekNext()->time()
  // << " , " << currentFrame_[1]->peekNext()->time() << " , " <<
  // currentFrame_[2]->peekNext()->time() << " , " <<
  // currentFrame_[3]->peekNext()->time() << endl;
}

CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::updateSplineCache() {
  Vec delta = currentFrame_[2]->peekNext()->position() -
              currentFrame_[1]->peekNext()->position();
  v1 = 3.0 * delta - 2.0 * currentFrame_[1]->peekNext()->tgP() -
       currentFrame_[2]->peekNext()->tgP();
  v2 = -2.0 * delta + currentFrame_[1]->peekNext()->tgP() +
       currentFrame_[2]->peekNext()->tgP();
  splineCacheIsValid_ = true;
}

/*! Interpolate frame() at time \p time (expressed in seconds).
  interpolationTime() is set to \p time and frame() is set accordingly.

  If you simply want to change interpolationTime() but not the frame() state,
  use setInterpolationTime() instead.

  Emits the interpolated() signal and makes the frame() emit the
  Frame::interpolated() signal. */
CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::interpolateAtTime(qreal time) {
  setInterpolationTime(time);

  if ((keyFrame_.isEmpty()) || (!frame()))
    return;

  if (!valuesAreValid_)
    updateModifiedFrameValues();

  updateCurrentKeyFrameForTime(time);

  if (!splineCacheIsValid_)
    updateSplineCache();

  qreal alpha;
  qreal dt = currentFrame_[2]->peekNext()->time() -
             currentFrame_[1]->peekNext()->time();
  if (dt == 0.0)
    alpha = 0.0;
  else
    alpha = (time - currentFrame_[1]->peekNext()->time()) / dt;

  // Linear interpolation - debug
  // Vec pos = alpha*(currentFrame_[2]->peekNext()->position()) +
  // (1.0-alpha)*(currentFrame_[1]->peekNext()->position());
  Vec pos =
      currentFrame_[1]->peekNext()->position() +
      alpha * (currentFrame_[1]->peekNext()->tgP() + alpha * (v1 + alpha * v2));
  Quaternion q = Quaternion::squad(
      currentFrame_[1]->peekNext()->orientation(),
      currentFrame_[1]->peekNext()->tgQ(), currentFrame_[2]->peekNext()->tgQ(),
      currentFrame_[2]->peekNext()->orientation(), alpha);
  frame()->setPositionAndOrientationWithConstraint(pos, q);

  Q_EMIT interpolated();
}


#ifndef DOXYGEN

//////////// KeyFrame private class implementation /////////
CGAL_INLINE_FUNCTION
KeyFrameInterpolator::KeyFrame::KeyFrame(const Frame &fr, qreal t)
    : time_(t), frame_(nullptr) {
  p_ = fr.position();
  q_ = fr.orientation();
}

CGAL_INLINE_FUNCTION
KeyFrameInterpolator::KeyFrame::KeyFrame(const Frame *fr, qreal t)
    : time_(t), frame_(fr) {
  updateValuesFromPointer();
}

CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::KeyFrame::updateValuesFromPointer() {
  p_ = frame()->position();
  q_ = frame()->orientation();
}

CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::KeyFrame::computeTangent(
    const KeyFrame *const prev, const KeyFrame *const next) {
  tgP_ = 0.5 * (next->position() - prev->position());
  tgQ_ = Quaternion::squadTangent(prev->orientation(), q_, next->orientation());
}

CGAL_INLINE_FUNCTION
void KeyFrameInterpolator::KeyFrame::flipOrientationIfNeeded(
    const Quaternion &prev) {
  if (Quaternion::dot(prev, q_) < 0.0)
    q_.negate();
}
#endif // DOXYGEN

}}
