#ifndef _tls_TankResponseUtilities_h_
#define _tls_TankResponseUtilities_h_

#include <utl/Math.h>
#include <utl/AugerUnits.h>

namespace tls {

  static const double kTankRadius = 1.784*utl::meter;
  static const double kTankHeight = 1.2*utl::meter;

  /// Perpendicular area of Auger tank seen by muon with zenith angle theta
  inline
  double
  TankPerpendicularArea(const double theta)
  {
    const double a1 = utl::kPi*kTankRadius*kTankRadius;
    const double a2 = 2.0*kTankRadius*kTankHeight;
    return a1 * std::cos(theta) + a2 * std::sin(theta);
  }

  /// Projected ground area of Auger tank seen by muon with zenith angle theta
  inline
  double
  TankGroundArea(const double theta)
  {
    const double tanTheta = std::tan(theta);
    return utl::kPi*kTankRadius*kTankRadius + 2*kTankRadius*kTankHeight*tanTheta;
  }

  /// Mean track length of particle piercing Auger tank with zenith angle theta
  inline
  double
  TankMeanTrackLength(const double theta)
  {
    // average length = Volume/PerpendicularArea (from Ines Valino)
    const double volume = kTankHeight*utl::kPi*kTankRadius*kTankRadius;
    return volume/TankPerpendicularArea(theta);
  }

} // NS tls

#endif