/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkResourceProbe_h
#define itkResourceProbe_h

#include "itkMacro.h"
#include "itkIndent.h"
#include "itkIntTypes.h"

#include <iostream> // For cout.
#include <string>
#include <vector>

#include "ITKCommonExport.h"

namespace itk
{
/** \class ResourceProbe
 *  \brief Computes the change of a value between two points in code.
 *
 *   This class is the base class of all the probes (time, memory, etc.)
 *   between the execution of two pieces of code. It can be started and
 *   stopped in order to evaluate the execution over multiple passes.
 *
 *   \sa TimeResourceProbe, MemoryResourceProbe
 *
 * \ingroup ITKCommon
 */
template <typename ValueType, typename MeanType>
class ITK_TEMPLATE_EXPORT ResourceProbe
{
public:
  /** Type for counting how many times the probe has been started and stopped.
   */
  using CountType = SizeValueType;

public:
  /** Constructor */
  ResourceProbe(std::string type, std::string unit);

  /** Destructor */
  virtual ~ResourceProbe() = default;

  /** Returns the type probed value */
  std::string
  GetType() const;

  /** Returns the unit probed value */
  std::string
  GetUnit() const;

  /** Start counting the change of value */
  virtual void
  Start();

  /** Stop counting the change of value.
   *
   * If a matching Start() has not been called before, there is no
   * effect.
   **/
  virtual void
  Stop();

  /** Returns the number of times that the probe has been started */
  CountType
  GetNumberOfStarts() const;

  /** Returns the number of times that the probe has been stopped */
  CountType
  GetNumberOfStops() const;

  /** Returns the number of iteration of the probe */
  CountType
  GetNumberOfIteration() const;

  /** Returns the instant value of the probed system.
   */
  virtual ValueType
  GetInstantValue() const = 0;

  /** Returns the accumulated value changes between the starts and stops
   *  of the probe */
  virtual ValueType
  GetTotal() const;

  /** Returns the average value changes between the starts and stops
   *  of the probe. Stop() has to be called at least once, returns 0 otherwise.
   */
  virtual MeanType
  GetMean() const;

  /** Reset the probe */
  virtual void
  Reset();

  /** Returns the min value changes between the starts and stops
   *  of the probe */
  virtual ValueType
  GetMinimum() const;

  /** Returns the max value changes between the starts and stops
   *  of the probe */
  virtual ValueType
  GetMaximum() const;

  /** Returns the standard deviation value changes between the starts and stops
   *  of the probe. */
  virtual ValueType
  GetStandardDeviation();

  /** Returns the standard deviation value changes between the starts and stops
   *  of the probe. */
  virtual ValueType
  GetStandardError();

  /** Set name of probe */
  virtual void
  SetNameOfProbe(const char * nameOfProbe);

  /** Set name of probe */
  virtual std::string
  GetNameOfProbe() const;

  /** Print System information */
  virtual void
  PrintSystemInformation(std::ostream & os = std::cout);

  /** Print Probe Results. */
  virtual void
  Report(std::ostream & os = std::cout, bool printSystemInfo = true, bool printReportHead = true, bool useTabs = false);

  /** Print Probe Results. */
  virtual void
  ExpandedReport(std::ostream & os = std::cout,
                 bool           printSystemInfo = true,
                 bool           printReportHead = true,
                 bool           useTabs = false);

  /** Print Probe Results. */
  virtual void
  JSONReport(std::ostream & os = std::cout);

  /** Print Probe Results. */
  virtual void
  PrintJSONSystemInformation(std::ostream & os = std::cout);

protected:
  /** Update the Min and Max values with an input value */
  virtual void
  UpdateMinimumMaximumMeasuredValue(ValueType value);

  /** Print Probe Results. */
  virtual void
  PrintReportHead(std::ostream & os = std::cout, bool useTabs = false);

  /** Print Probe Results. */
  virtual void
  PrintExpandedReportHead(std::ostream & os = std::cout, bool useTabs = false);

  /** Prints a varName: varValue pair. */
  template <typename T>
  void
  PrintJSONvar(std::ostream & os, const char * varName, T varValue, unsigned int indent = 4, bool comma = true);

  /** Cause the object to print itself out. */
  virtual void
  Print(std::ostream & os, Indent indent) const;

private:
  ValueType m_StartValue{};
  ValueType m_TotalValue{};
  ValueType m_MinimumValue{};
  ValueType m_MaximumValue{};
  ValueType m_StandardDeviation{};
  ValueType m_StandardError{};

  CountType m_NumberOfStarts{};
  CountType m_NumberOfStops{};
  CountType m_NumberOfIteration{};

  std::vector<ValueType> m_ProbeValueList{};

  std::string m_NameOfProbe{};
  std::string m_TypeString{};
  std::string m_UnitString{};

  static constexpr unsigned int tabwidth = 15;
};
} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#  include "itkResourceProbe.hxx"
#endif

#endif // itkResourceProbe_h
