/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkOpenGLTexture.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
/**
 * @class   vtkOpenGLShaderCache
 * @brief   manage Shader Programs within a context
 *
 * vtkOpenGLShaderCache manages shader program compilation and binding
 */

#ifndef vtkOpenGLShaderCache_h
#define vtkOpenGLShaderCache_h

#include "vtkObject.h"
#include "vtkRenderingOpenGL2Module.h" // For export macro
#include "vtkShader.h"                 // for vtkShader::Type
#include <map>                         // for methods

class vtkTransformFeedback;
class vtkShaderProgram;
class vtkWindow;
class vtkOpenGLRenderWindow;

class VTKRENDERINGOPENGL2_EXPORT vtkOpenGLShaderCache : public vtkObject
{
public:
  static vtkOpenGLShaderCache* New();
  vtkTypeMacro(vtkOpenGLShaderCache, vtkObject);
  void PrintSelf(ostream& os, vtkIndent indent) override;

  // make sure the specified shaders are compiled, linked, and bound
  virtual vtkShaderProgram* ReadyShaderProgram(const char* vertexCode, const char* fragmentCode,
    const char* geometryCode, vtkTransformFeedback* cap = nullptr);

  // make sure the specified shaders are compiled, linked, and bound
  // will increment the reference count on the shaders if it
  // needs to keep them around
  virtual vtkShaderProgram* ReadyShaderProgram(
    std::map<vtkShader::Type, vtkShader*> shaders, vtkTransformFeedback* cap = nullptr);

  // make sure the specified shaders are compiled, linked, and bound
  virtual vtkShaderProgram* ReadyShaderProgram(
    vtkShaderProgram* shader, vtkTransformFeedback* cap = nullptr);

  /**
   * Release the current shader.  Basically go back to
   * having no shaders loaded.  This is useful for old
   * legacy code that relies on no shaders being loaded.
   */
  void ReleaseCurrentShader();

  /**
   * Free up any resources being used by the provided shader
   */
  virtual void ReleaseGraphicsResources(vtkWindow* win);

  /**
   * Get/Clear the last Shader bound, called by shaders as they release
   * their graphics resources
   */
  virtual void ClearLastShaderBound() { this->LastShaderBound = nullptr; }
  vtkGetObjectMacro(LastShaderBound, vtkShaderProgram);

  // Set the time in seconds elapsed since the first render
  void SetElapsedTime(float val) { this->ElapsedTime = val; }

protected:
  vtkOpenGLShaderCache();
  ~vtkOpenGLShaderCache() override;

  // perform System and Output replacements in place. Returns
  // the number of outputs
  virtual unsigned int ReplaceShaderValues(
    std::string& VSSource, std::string& FSSource, std::string& GSSource);

  virtual vtkShaderProgram* GetShaderProgram(
    const char* vertexCode, const char* fragmentCode, const char* geometryCode);
  virtual vtkShaderProgram* GetShaderProgram(std::map<vtkShader::Type, vtkShader*> shaders);
  virtual int BindShader(vtkShaderProgram* shader);

  class Private;
  Private* Internal;
  vtkShaderProgram* LastShaderBound;

  int OpenGLMajorVersion;
  int OpenGLMinorVersion;

  float ElapsedTime;

private:
  vtkOpenGLShaderCache(const vtkOpenGLShaderCache&) = delete;
  void operator=(const vtkOpenGLShaderCache&) = delete;
};

#endif