//----------------------------------------------------------------------------//
//                                                                            //
// ozz-animation is hosted at http://github.com/guillaumeblanc/ozz-animation  //
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// Copyright (c) Guillaume Blanc                                              //
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//----------------------------------------------------------------------------//

#ifndef OZZ_OZZ_ANIMATION_RUNTIME_TRACK_TRIGGERING_JOB_H_
#define OZZ_OZZ_ANIMATION_RUNTIME_TRACK_TRIGGERING_JOB_H_

#include "ozz/base/platform.h"

namespace ozz {
namespace animation {

class FloatTrack;

// Track edge triggering job implementation. Edge triggering wording refers to
// signal processing, where a signal edge is a transition from low to high or
// from high to low. It is called an "edge" because of the square wave which
// represents a signal has edges at those points. A rising edge is the
// transition from low to high, a falling edge is from high to low.
// TrackTriggeringJob detects when track curve crosses a threshold value,
// triggering dated events that can be processed as state changes.
// Only FloatTrack is supported, because comparing to a threshold for other
// track types isn't possible.
// The job execution actually performs a lazy evaluation of edges. It builds an
// iterator that will process the next edge on each call to ++ operator.
struct TrackTriggeringJob {
  TrackTriggeringJob();

  // Validates job parameters.
  bool Validate() const;

  // Validates and executes job. Execution is lazy. Iterator operator ++ is
  // actually doing the processing work.
  bool Run() const;

  // Input range. 0 is the beginning of the track, 1 is the end.
  // from and to can be of any sign, any order, and any range. The job will
  // perform accordingly:
  // - if difference between from and to is greater than 1, the iterator will
  // loop multiple times on the track.
  // - if from is greater than to, then the track is processed backward (rising
  // edges in forward become falling ones).
  float from;
  float to;

  // Edge detection threshold value.
  // A rising edge is detected as soon as the track value becomes greater than
  // the threshold.
  // A falling edge is detected as soon as the track value becomes smaller or
  // equal than the threshold.
  float threshold;

  // Track to sample.
  const FloatTrack* track;

  // Job output iterator.
  class Iterator;
  Iterator* iterator;

  // Returns an iterator referring to the past-the-end element. It should only
  // be used to test if iterator loop reached the end (using operator !=), and
  // shall not be dereferenced.
  Iterator end() const;

  // Structure of an edge as detected by the job.
  struct Edge {
    float ratio;  // Ratio at which track value crossed threshold.
    bool rising;  // true is edge is rising (getting higher than threshold).
  };
};

// Iterator implementation. Calls to ++ operator will compute the next edge. It
// should be compared (using operator !=) to job's end iterator to test if the
// last edge has been reached.
class TrackTriggeringJob::Iterator {
 public:
  Iterator() : job_(nullptr), outer_(0.f), inner_(0) {}

  // Evaluate next edge.
  // Calling this function on an end iterator results in an assertion in debug,
  // an undefined behavior otherwise.
  const Iterator& operator++();
  Iterator operator++(int) {
    Iterator prev = *this;
    ++*this;
    return prev;
  }

  // Compare with other iterators.
  bool operator!=(const Iterator& _it) const {
    return inner_ != _it.inner_ || outer_ != _it.outer_ || job_ != _it.job_;
  }
  bool operator==(const Iterator& _it) const {
    return job_ == _it.job_ && outer_ == _it.outer_ && inner_ == _it.inner_;
  }

  // Dereferencing operators.
  const Edge& operator*() const {
    assert(*this != job_->end() && "Can't dereference end iterator.");
    return edge_;
  }
  const Edge* operator->() const {
    assert(*this != job_->end() && "Can't dereference end iterator.");
    return &edge_;
  }

 private:
  friend struct TrackTriggeringJob;

  // Constructors used by the job.
  explicit Iterator(const TrackTriggeringJob* _job);
  struct End {};
  Iterator(const TrackTriggeringJob* _job, End)
      : job_(_job),
        outer_(0.f),
        inner_(-2) {  // Can never be reached while looping.
  }

  // Job this iterator works on.
  const TrackTriggeringJob* job_;

  // Current value of the outer loop, aka a ratio cursor between from and to.
  float outer_;

  // Current value of the inner loop, aka a key frame index.
  ptrdiff_t inner_;

  // Latest evaluated edge.
  Edge edge_;
};

// end() job function inline implementation.
inline TrackTriggeringJob::Iterator TrackTriggeringJob::end() const {
  return Iterator(this, Iterator::End());
}
}  // namespace animation
}  // namespace ozz
#endif  // OZZ_OZZ_ANIMATION_RUNTIME_TRACK_TRIGGERING_JOB_H_