// This code example is created for educational purpose
// by Thorsten Thormaehlen (contact: www.thormae.de).
// It is distributed without any warranty.

#include <QApplication>
#include <QOpenGLWidget>
#include <QOpenGLFunctions_2_0>
#include <QKeyEvent>
#include <QTimer>
#include <QMessageBox>

#include <fstream>
#include <iostream>
using namespace std;

#include <gl/glu.h>

class Renderer : protected QOpenGLFunctions_2_0 {

private:
  struct Vertex
  {
    float position[3];
    float color[4];
    float texCoord[2];
    float normal[3];
  };

public:
  float t;
  int mode;
private:
  GLuint vertBufID;
  GLuint texID;
  int vertNo;

public:
  // constructor
  Renderer() : t(0.0), mode(0),
               vertBufID(0), texID(0), vertNo(0) {}
public:
 void init() {
    initializeOpenGLFunctions();
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_DEPTH);

    // generating VBO input data
    float vertexData[] = {
       0.0f, 0.0f, 2.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.5f, 1.0f, 0.0000f,-0.9701f, 0.2425f,
      -0.5f,-0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0000f,-0.9701f, 0.2425f,
       0.5f,-0.5f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0000f,-0.9701f, 0.2425f,
       0.0f, 0.0f, 2.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.5f, 1.0f, 0.9701f, 0.0000f, 0.2425f,
       0.5f,-0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.9701f, 0.0000f, 0.2425f,
       0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.9701f, 0.0000f, 0.2425f,
       0.0f, 0.0f, 2.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.5f, 1.0f, 0.0000f, 0.9701f, 0.2425f,
       0.5f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 0.0000f, 0.9701f, 0.2425f,
      -0.5f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 0.0f, 0.0000f, 0.9701f, 0.2425f,
       0.0f, 0.0f, 2.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.5f, 1.0f,-0.9701f, 0.0000f, 0.2425f,
      -0.5f, 0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f,-0.9701f, 0.0000f, 0.2425f,
      -0.5f,-0.5f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f,-0.9701f, 0.0000f, 0.2425f
    };

    vertNo = 12;

    // generating vertex VBO
    glGenBuffers(1, &vertBufID);
    glBindBuffer(GL_ARRAY_BUFFER, vertBufID);
    glBufferData(GL_ARRAY_BUFFER, vertNo*sizeof(Vertex),
                 vertexData, GL_STATIC_DRAW);

    std::string fileName(findFile("checkerboard.ppm", "qt", 5));
    texID = loadTexture(fileName);
  }


  void resize(int w, int h) {
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective (30.0, (float)w/(float)h, 2.0, 10.0);
  }

  void display() {
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    // set camera
    gluLookAt(3.0, -1.0, 4.5, 0.0, 0.0, 1.0, 0.0, 0.0, 1.0);
    // draw scene
    glRotatef(t, 0.0f, 0.0f, 1.0f);

    // activating VBO
    glBindBuffer(GL_ARRAY_BUFFER, vertBufID);
    int stride = sizeof(Vertex); // stride in bytes
    int offset = 0; // offset in bytes

    // position
    glVertexPointer(3, GL_FLOAT, stride, (const void*)(intptr_t)offset);
    glEnableClientState(GL_VERTEX_ARRAY);

    // color
    offset = 3 * sizeof(float);
    glColorPointer(4, GL_FLOAT, stride, (const void*)(intptr_t)offset);
    glEnableClientState(GL_COLOR_ARRAY);

    // texture
    offset = (3 + 4) * sizeof(float);
    glTexCoordPointer(2, GL_FLOAT, stride, (const void*)(intptr_t)offset);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);

    // normals
    offset = (3 + 4 + 2) * sizeof(float);
    glNormalPointer(GL_FLOAT, stride, (const void*)(intptr_t)offset);
    glEnableClientState(GL_NORMAL_ARRAY);

    // bind texture
    if(mode == 0) {
      glEnable(GL_TEXTURE_2D);
      glBindTexture(GL_TEXTURE_2D, texID);
    }else{
      glDisable(GL_TEXTURE_2D);
      glBindTexture(GL_TEXTURE_2D, 0);
    }

    // render data
    glDrawArrays(GL_TRIANGLES, 0, vertNo);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_NORMAL_ARRAY);
    glDisable(GL_TEXTURE_2D);
  }

  void dispose() {
    if(vertBufID !=0) glDeleteBuffers( 1, &vertBufID);
    if(texID !=0) glDeleteTextures( 1, &texID);
  }

private:
   // returns a valid textureID on success, otherwise 0
  GLuint loadTexture(std::string &filename) {

    unsigned width;
    unsigned height;
    int level = 0;
    int border = 0;
    std::vector<unsigned char> imgData;

    // load image data
    if(!loadPPMImageFlipped(filename, width, height, imgData)) return 0;

    // data is aligned in byte order
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    //request textureID
    GLuint textureID;
    glGenTextures( 1, &textureID);

    // bind texture
    glBindTexture( GL_TEXTURE_2D, textureID);

    //define how to filter the texture (important but ignore for now)
    glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

    //texture colors should modulate the original color values
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

    // specify the 2D texture map
    glTexImage2D(GL_TEXTURE_2D, level, GL_RGB, width, height, border, GL_RGB, GL_UNSIGNED_BYTE, &imgData[0]);

    // return unique texture identifier
    return textureID;
  }

  bool loadPPMImageFlipped(std::string &filename, unsigned &width, unsigned &height, std::vector<unsigned char> &imgData) {

    ifstream input(filename.c_str(), ifstream::in | ifstream::binary);
    if(!input) { // cast istream to bool to see if something went wrong
      QMessageBox msgBox;
      msgBox.setText(QString("Can not find texture data file ")+QString(filename.c_str()));
      msgBox.exec();
      return false;
    }
    input.unsetf(std::ios_base::skipws);

    string line;
    input >> line >> std::ws;
    if (line != "P6") {
      QMessageBox msgBox;
      msgBox.setText("File is not PPM P6 raw format");
      msgBox.exec();
      return false;
    }

    width = 0;
    height = 0;
    unsigned depth = 0;
    unsigned readItems = 0;
    unsigned char lastCharBeforeBinary;

    while (readItems < 3) {
      input >> std::ws;
      if(input.peek() != '#') {
        if (readItems == 0) input >> width;
        if (readItems == 1) input >> height;
        if (readItems == 2) input >> depth >> lastCharBeforeBinary;
        readItems++;
      }else{ // skip comments
        std::getline(input, line);
      }
    }

    if(depth >= 256) {
      QMessageBox msgBox;
      msgBox.setText("Only 8-bit PPM format is supported");
      msgBox.exec();
      return false;
    }

    unsigned byteCount = width * height * 3;
    imgData.resize(byteCount);
    input.read((char*)&imgData[0], byteCount*sizeof(unsigned char));

    // vertically flip the image because the image origin
    // in OpenGL is the lower-left corner
    unsigned char tmpData;
    for(unsigned y=0; y < height / 2; y++) {
      int sourceIndex = y * width * 3;
      int targetIndex = (height-1-y) * width *3;
      for(unsigned x=0; x < width*3; x++) {
          tmpData = imgData[targetIndex];
          imgData[targetIndex] = imgData[sourceIndex];
          imgData[sourceIndex] = tmpData;
          sourceIndex++;
          targetIndex++;
      }
    }

    return true;
  }

  bool fileExists(const std::string& filename)
  {
    ifstream myfile(filename.c_str());
    if (!myfile.is_open()) {
      return false;
    }
    myfile.close();
    return true;
  }

  std::string findFile(const std::string& filename, const std::string& subdir, int depth)
  {
    int counter = 0;
    std::string path("");

    while (counter < depth) {
      if (fileExists(path + filename)) return path + filename;
      if (fileExists(path + "/" + subdir + "/" + filename)) return path + "/" + subdir + "/" + filename;
      path += "../";
      counter++;
    }
    return filename;
  }
};


class MyWidget : public QOpenGLWidget {

private:
  Renderer *renderer;
  QTimer *timer;

public:
  MyWidget(QWidget *parent = NULL) : QOpenGLWidget(parent) {
    this->setWindowTitle("VBO Stride Demo");
    this->resize(320, 320);
    renderer = new Renderer();
    timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(update()));
    timer->start(30);
  }

  ~MyWidget() {
    makeCurrent();
    renderer->dispose();
    doneCurrent();
    delete renderer;
    delete timer;
  }

protected:
  void initializeGL() { renderer->init(); }
  void resizeGL(int w, int h){ renderer->resize(w, h); }
  void paintGL() {
      float offset = 1.0f;
      renderer->t += offset;
      renderer->display();
  }
  void keyPressEvent(QKeyEvent* event){
    bool redraw = false;
    switch(event->key()) {
    case '1':
      if(renderer->mode == 1) renderer->mode = 0;
      else renderer->mode = 1;
      redraw = true;
      break;
    }
    if(redraw) {
      this->update();
    }
  }
};

int main (int argc, char* argv[]) {
    // create a QApplication object that handles initialization,
    // finalization, and the main event loop
    QApplication appl(argc, argv);
    MyWidget widget;  // create a widget
    widget.show(); //show the widget and its children
    return appl.exec(); // execute the application
}