/*
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

#ifndef __SIM_TIME_INTERVAL_HH__
#define __SIM_TIME_INTERVAL_HH__

#include "BLI_utildefines.h"

namespace blender::sim {

/**
 * The start time is exclusive and the end time is inclusive. If the duration is zero, the interval
 * describes a single point in time.
 */
class TimeInterval {
 private:
  float start_;
  float duration_;

 public:
  TimeInterval(float start, float duration) : start_(start), duration_(duration)
  {
    BLI_assert(duration_ >= 0.0f);
  }

  float start() const
  {
    return start_;
  }

  float stop() const
  {
    return start_ + duration_;
  }

  float duration() const
  {
    return duration_;
  }

  float time_at_factor(float factor) const
  {
    return start_ + factor * duration_;
  }

  float factor_at_time(float time) const
  {
    BLI_assert(duration_ > 0.0f);
    return (time - start_) / duration_;
  }

  float safe_factor_at_time(float time) const
  {
    if (duration_ > 0.0f) {
      return this->factor_at_time(time);
    }
    return 0.0f;
  }

  void compute_uniform_samples(MutableSpan<float> r_samples) const
  {
    int64_t amount = r_samples.size();
    if (amount == 0) {
      return;
    }
    if (amount == 1) {
      r_samples[0] = this->time_at_factor(0.5f);
      return;
    }

    const float step = duration_ / (float)(amount - 1);
    for (int64_t i : r_samples.index_range()) {
      r_samples[i] = start_ + i * step;
    }
  }
};

}  // namespace blender::sim

#endif /* __SIM_TIME_INTERVAL_HH__ */