#include <vtkSmartPointer.h>

#include <vtkCamera.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkActor.h>
#include <vtkOpenGLPolyDataMapper.h>
#include <vtkPLYReader.h>
#include <vtkProperty.h>
#include <vtkPolyDataNormals.h>
#include <vtkTriangleMeshPointNormals.h>
#include <vtkNamedColors.h>
#include <vtkRenderWindowInteractor.h>

#include <vtksys/SystemTools.hxx>
#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyDataReader.h>
#include <vtkSTLReader.h>
#include <vtkXMLPolyDataReader.h>
#include <vtkSphereSource.h>

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);
}

//----------------------------------------------------------------------------
int main(int argc, char *argv[])
{
  vtkSmartPointer<vtkPolyData> polyData =
    ReadPolyData(argc > 1 ? argv[1] : "");

  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  vtkSmartPointer<vtkActor> actor =
    vtkSmartPointer<vtkActor>::New();
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkOpenGLPolyDataMapper> mapper =
    vtkSmartPointer<vtkOpenGLPolyDataMapper>::New();
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize(640, 480);
  renderWindow->AddRenderer(renderer);
  renderer->AddActor(actor);

  vtkSmartPointer<vtkRenderWindowInteractor>  interactor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  interactor->SetRenderWindow(renderWindow);

  vtkSmartPointer<vtkTriangleMeshPointNormals> norms =
    vtkSmartPointer<vtkTriangleMeshPointNormals>::New();
  norms->SetInputData(polyData);

  mapper->SetInputConnection(norms->GetOutputPort());
  actor->SetMapper(mapper);
  actor->GetProperty()->SetAmbientColor(0.2, 0.2, 1.0);
  actor->GetProperty()->SetDiffuseColor(1.0, 0.65, 0.7);
  actor->GetProperty()->SetSpecularColor(1.0, 1.0, 1.0);
  actor->GetProperty()->SetSpecular(0.5);
  actor->GetProperty()->SetDiffuse(0.7);
  actor->GetProperty()->SetAmbient(0.5);
  actor->GetProperty()->SetSpecularPower(20.0);
  actor->GetProperty()->SetOpacity(1.0);

  // Modify the shader to color based on model normal
  // To do this we have to modify the vertex shader
  // to pass the normal in model coordinates
  // through to the fragment shader. By default the normal
  // is converted to View coordinates and then passed on.
  // We keep that, but add a varying for the original normal.
  // Then we modify the fragment shader to set the diffuse color
  // based on that normal. First lets modify the vertex
  // shader
  mapper->AddShaderReplacement(
    vtkShader::Vertex,
    "//VTK::Normal::Dec", // replace the normal block
    true, // before the standard replacements
    "//VTK::Normal::Dec\n" // we still want the default
    "  varying vec3 myNormalMCVSOutput;\n", //but we add this
    false // only do it once
    );
  mapper->AddShaderReplacement(
    vtkShader::Vertex,
    "//VTK::Normal::Impl", // replace the normal block
    true, // before the standard replacements
    "//VTK::Normal::Impl\n" // we still want the default
    "  myNormalMCVSOutput = normalMC;\n", //but we add this
    false // only do it once
    );
  mapper->AddShaderReplacement(
    vtkShader::Vertex,
    "//VTK::Color::Impl", // dummy replacement for testing clear method
    true,
    "VTK::Color::Impl\n",
    false
    );
  mapper->ClearShaderReplacement(
    vtkShader::Vertex,     // clear our dummy replacement
    "//VTK::Color::Impl",
    true
    );

  // now modify the fragment shader
  mapper->AddShaderReplacement(
    vtkShader::Fragment,  // in the fragment shader
    "//VTK::Normal::Dec", // replace the normal block
    true, // before the standard replacements
    "//VTK::Normal::Dec\n" // we still want the default
    "  varying vec3 myNormalMCVSOutput;\n", //but we add this
    false // only do it once
    );
  mapper->AddShaderReplacement(
    vtkShader::Fragment,  // in the fragment shader
    "//VTK::Normal::Impl", // replace the normal block
    true, // before the standard replacements
    "//VTK::Normal::Impl\n" // we still want the default calc
    "  diffuseColor = abs(myNormalMCVSOutput);\n", //but we add this
    false // only do it once
    );

  renderWindow->Render();
  renderer->GetActiveCamera()->SetPosition(1.0,1.0, -1.0);
  renderer->GetActiveCamera()->SetFocalPoint(0,1,0);
  renderer->GetActiveCamera()->SetViewUp(0,1,0);
  renderer->GetActiveCamera()->Elevation(30.0);
  renderer->ResetCamera();
  renderer->GetActiveCamera()->Zoom(1.3);
  renderWindow->Render();

  interactor->Start();

  return EXIT_SUCCESS;
}

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension = vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
  if (extension == ".ply")
  {
    vtkSmartPointer<vtkPLYReader> reader =
      vtkSmartPointer<vtkPLYReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    vtkSmartPointer<vtkXMLPolyDataReader> reader =
      vtkSmartPointer<vtkXMLPolyDataReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    vtkSmartPointer<vtkOBJReader> reader =
      vtkSmartPointer<vtkOBJReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    vtkSmartPointer<vtkSTLReader> reader =
      vtkSmartPointer<vtkSTLReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    vtkSmartPointer<vtkPolyDataReader> reader =
      vtkSmartPointer<vtkPolyDataReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g")
  {
    vtkSmartPointer<vtkBYUReader> reader =
      vtkSmartPointer<vtkBYUReader>::New();
    reader->SetGeometryFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else
  {
    vtkSmartPointer<vtkSphereSource> source =
      vtkSmartPointer<vtkSphereSource>::New();
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}
}
