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

#include <GL/glew.h>
#include <GL/freeglut.h> // we use glut here as window manager

#define _USE_MATH_DEFINES
#include <math.h>

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;

class Renderer {

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

public:
  float t;
  int modeVal;
  std::string shaderFilename;
  int shaderFile;

private:
  enum {Scene, numVAOs};
  enum {SceneAll, numVBOs};
  GLuint vaoID[numVAOs];
  GLuint bufID[numVBOs];
  int sceneVertNo;
  GLuint progID;
  GLuint vertID;
  GLuint fragID;
  GLint vertexLoc;
  GLint texCoordLoc;
  GLint normalLoc;
  GLint projectionLoc;
  GLint modelviewLoc;
  GLint normalMatrixLoc;
  GLint modeLoc;
  GLint lightDirectionLoc;
  GLint camPosLoc;
  GLint lookAtLoc;
  GLint camProjectionLoc;
  GLint meshTransformLoc, meshTransformTransposeInvLoc;

  float projection[16];  // projection matrix
  float modelview[16];  // modelview matrix
  std::string filename;
  int file;

public:
  // constructor
  Renderer() : t(0.0), modeVal(1), shaderFilename("PhongBrdfCameraSpace"), shaderFile(0),
               sceneVertNo(0), progID(0), vertID(0), fragID(0),
               vertexLoc(-1), texCoordLoc(-1), normalLoc(-1),
               projectionLoc(-1), modelviewLoc(-1), normalMatrixLoc(-1), modeLoc(-1),
               lightDirectionLoc(-1), camPosLoc(-1), lookAtLoc(-1), 
               meshTransformLoc(-1), meshTransformTransposeInvLoc(-1),
               camProjectionLoc(-1),
               filename("./knot.vbo"), file(0)
               {}
  //destructor
  ~Renderer() {
     deleteAll();
  }

public:
  void nextModel() {
    file++;
    if(file > 4) file = 0;
    if(file == 0) filename = "./knot.vbo";
    if(file == 1) filename = "./teapot.vbo";
    if(file == 2) filename = "./sphere.vbo";
    if(file == 3) filename = "./cube.vbo";
    if(file == 4) filename = "./hose.vbo";
    reload();
  }

  void reload() {
    deleteAll();
    init();
  }

  void init() {
    glEnable(GL_DEPTH_TEST);

    setupShaders();

    // create a Vertex Array Objects (VAO)
    glGenVertexArrays(numVAOs, vaoID);

    // generate a Vertex Buffer Object (VBO)
    glGenBuffers(numVBOs, bufID);

    // binding the pyramid VAO
    glBindVertexArray(vaoID[Scene]);

    std::vector <float> data;
    loadVertexData(filename, data);

    sceneVertNo = int(data.size()) / (3+2+3);

    glBindBuffer(GL_ARRAY_BUFFER, bufID[SceneAll]);
    glBufferData(GL_ARRAY_BUFFER, sceneVertNo*sizeof(Vertex),
                 &data[0], GL_STATIC_DRAW);

    int stride = sizeof(Vertex); // stride in bytes
    int offset = 0; // offset in bytes

    // position
    if (vertexLoc != -1) {
      glVertexAttribPointer(vertexLoc, 3, GL_FLOAT, GL_FALSE, stride, (const void*)(intptr_t)offset);
      glEnableVertexAttribArray(vertexLoc);
    }

    // texCoord
    if (texCoordLoc != -1) {
      offset = 3 * sizeof(float);
      glVertexAttribPointer(texCoordLoc, 2, GL_FLOAT, GL_FALSE, stride, (const void*)(intptr_t)offset);
      glEnableVertexAttribArray(texCoordLoc);
    }

    // normal
    if (normalLoc != -1) {
      offset = (3 + 2) * sizeof(float);
      glVertexAttribPointer(normalLoc, 3, GL_FLOAT, GL_FALSE, stride, (const void*)(intptr_t)offset);
      glEnableVertexAttribArray(normalLoc);
    }

    printf("Press 1-5 to switch mode, 9 to switch shader, 0 to switch 3D mesh\n");
  }


  void resize(int w, int h) {
    glViewport(0, 0, w, h);

    // this function replaces gluPerspective
    mat4Perspective(projection, 45.0f, (float)w/(float)h, 0.5f, 4.0f);
    // mat4Print(projection);
  }

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

    float lightDirection[4] = { 0.0, -1.0, -1.0, 0.0};
    float cameraPos[3] = { 1.5, 0.0, 1.5 };
    float lightDirectionTrans[4];
    float modelviewInv[16];
    float normalmatrix[16];
    float lookAt[16], lookAtInv[16], m[16];
    float meshTransform[16], meshTransformInv[16], meshTransformTransposeInv[16];

    // mat4LookAt replaces gluLookAt
    mat4LookAt(lookAt, cameraPos[0], cameraPos[1], cameraPos[2], // eye
      0.0f, 0.0f, 0.0f, // look at
      0.0f, 0.0f, 1.0f); // up

    // apply lookAt matrix to light direction
    mat4Invert(lookAt, lookAtInv);
    mat4Transpose(lookAtInv, m);
    applyMatrixToVec4(m, lightDirection, lightDirectionTrans);
    
    // rotate mesh
    rotateZ(meshTransform, -t);

    // compute meshTransformTransposeInv
    mat4Invert(meshTransform, meshTransformInv);
    mat4Transpose(meshTransformInv, meshTransformTransposeInv);
    
    // compute modelview and normalmatrix
    mat4Multiply(lookAt, meshTransform, modelview);
    mat4Invert(modelview, modelviewInv);
    mat4Transpose(modelviewInv, normalmatrix);    

    glUseProgram(progID);
    // load the current projection and modelview matrix into the
    // corresponding UNIFORM variables of the shader
    if(projectionLoc != -1) glUniformMatrix4fv(projectionLoc, 1, false, projection);
    if(camProjectionLoc != -1) glUniformMatrix4fv(camProjectionLoc, 1, false, projection);
    if(modelviewLoc != -1) glUniformMatrix4fv(modelviewLoc, 1, false, modelview);
    if(normalMatrixLoc != -1) glUniformMatrix4fv(normalMatrixLoc, 1, false, normalmatrix);
    if(modeLoc != -1) glUniform1i(modeLoc, modeVal);
    if(lightDirectionLoc != -1) glUniform3fv(lightDirectionLoc, 1, lightDirectionTrans);
    if(camPosLoc != -1) glUniform3fv(camPosLoc, 1, cameraPos);
    if(lookAtLoc != -1) glUniformMatrix4fv(lookAtLoc, 1, false, lookAt);
    if(meshTransformLoc != -1) glUniformMatrix4fv(meshTransformLoc, 1, false, meshTransform);
    if(meshTransformTransposeInvLoc != -1) glUniformMatrix4fv(meshTransformTransposeInvLoc, 1, false, meshTransformTransposeInv);

    // bind Triangle VAO
    glBindVertexArray(vaoID[Scene]);
    // render data
    glDrawArrays(GL_TRIANGLES, 0, sceneVertNo);
  }
private:

  void setupShaders() {

    // create shader
    vertID = glCreateShader(GL_VERTEX_SHADER);
    fragID = glCreateShader(GL_FRAGMENT_SHADER);

    // load shader source from file
    std::string vs = loadShaderSrc("./"+shaderFilename+".vert");
    const char* vss = vs.c_str();
    std::string fs = loadShaderSrc("./"+shaderFilename+".frag");
    const char* fss = fs.c_str();

    // specify shader source
    glShaderSource(vertID, 1, &(vss), NULL);
    glShaderSource(fragID, 1, &(fss), NULL);

    // compile the shader
    glCompileShader(vertID);
    glCompileShader(fragID);

    // check for errors
    printShaderInfoLog(vertID);
    printShaderInfoLog(fragID);

    // create program and attach shaders
    progID = glCreateProgram();
    glAttachShader(progID, vertID);
    glAttachShader(progID, fragID);

    // "outColor" is a user-provided OUT variable
    // of the fragment shader.
    // Its output is bound to the first color buffer
    // in the framebuffer
    glBindFragDataLocation(progID, 0, "outColor");

    // link the program
    glLinkProgram(progID);
    // output error messages
    printProgramInfoLog(progID);

    // retrieve the location of the IN variables of the vertex shaders
    vertexLoc = glGetAttribLocation(progID,"position");
    texCoordLoc = glGetAttribLocation(progID,"texcoord");
    normalLoc = glGetAttribLocation(progID, "normal");

    // retrieve the location of the UNIFORM variables of the shaders
    
    camProjectionLoc = glGetUniformLocation(progID, "cameraProjection");
    projectionLoc = glGetUniformLocation(progID, "projection");
    modelviewLoc = glGetUniformLocation(progID, "modelview");
    normalMatrixLoc = glGetUniformLocation(progID, "normalMat");
    modeLoc = glGetUniformLocation(progID, "mode");
    lightDirectionLoc = glGetUniformLocation(progID, "lightDirection");
    camPosLoc = glGetUniformLocation(progID, "cameraPosition");
    lookAtLoc = glGetUniformLocation(progID, "cameraLookAt");
    meshTransformLoc = glGetUniformLocation(progID, "meshTransform");
    meshTransformTransposeInvLoc = glGetUniformLocation(progID, "meshTransformTransposedInverse");
  }

  void deleteAll() {
    glDeleteVertexArrays(numVAOs, vaoID);
    glDeleteBuffers(numVBOs, bufID);
    glDeleteProgram(progID);
    glDeleteShader(vertID);
    glDeleteShader(fragID);
  }

  void printShaderInfoLog(GLuint obj) {
    int infoLogLength = 0;
    int returnLength  = 0;
    char *infoLog;
    glGetShaderiv(obj, GL_INFO_LOG_LENGTH,&infoLogLength);
    if (infoLogLength > 0) {
      infoLog = (char *)malloc(infoLogLength);
      glGetShaderInfoLog(obj, infoLogLength, &returnLength, infoLog);
      printf("%s\n",infoLog);
      free(infoLog);
    }
  }

  void printProgramInfoLog(GLuint obj) {
    int infoLogLength = 0;
    int returnLength  = 0;
    char *infoLog;
    glGetProgramiv(obj, GL_INFO_LOG_LENGTH,&infoLogLength);
    if (infoLogLength > 0) {
      infoLog = (char *)malloc(infoLogLength);
      glGetProgramInfoLog(obj, infoLogLength, &returnLength, infoLog);
      printf("%s\n",infoLog);
      free(infoLog);
    }
  }

  std::string loadShaderSrc(const std::string& filename) {
    std::ifstream is(filename);
    if (is.is_open()) {
      std::stringstream buffer;
      buffer << is.rdbuf();
      return buffer.str();
    }
    cerr << "Unable to open file " << filename << endl;
    exit(1);
  }

  // the following functions are some matrix and vector helpers,
  // which work for this demo but in general it is recommended
  // to use more advanced matrix libraries,
  // e.g. OpenGL Mathematics (GLM)
  float vec3Dot( float *a, float *b) {
    return a[0]*b[0] + a[1]*b[1] + a[2]*b[2];
  }

  void vec3Cross( float *a, float *b, float *res) {
    res[0] = a[1] * b[2]  -  b[1] * a[2];
    res[1] = a[2] * b[0]  -  b[2] * a[0];
    res[2] = a[0] * b[1]  -  b[0] * a[1];
  }

  void vec3Normalize(float *a) {
    float mag = sqrt(a[0] * a[0]  +  a[1] * a[1]  +  a[2] * a[2]);
    a[0] /= mag; a[1] /= mag; a[2] /= mag;
  }

  void mat4Identity( float *a) {
    for (int i = 0; i < 16; ++i) a[i] = 0.0f;
    for (int i = 0; i < 4; ++i) a[i + i * 4] = 1.0f;
  }

  void mat4Multiply(float *a, float *b, float *res) {
    for (int i = 0; i < 4; ++i) {
      for (int j = 0; j < 4; ++j) {
        res[j*4 + i] = 0.0f;
        for (int k = 0; k < 4; ++k) {
          res[j*4 + i] += a[k*4 + i] * b[j*4 + k];
        }
      }
    }
  }

  void mat4Perspective(float *a, float fov, float aspect, float zNear, float zFar) {
    float f = 1.0f / float(tan (fov/2.0f * (M_PI / 180.0f)));
    mat4Identity(a);
    a[0] = f / aspect;
    a[1 * 4 + 1] = f;
    a[2 * 4 + 2] = (zFar + zNear)  / (zNear - zFar);
    a[3 * 4 + 2] = (2.0f * zFar * zNear) / (zNear - zFar);
    a[2 * 4 + 3] = -1.0f;
    a[3 * 4 + 3] = 0.0f;
  }

  void mat4LookAt(float *viewMatrix,
                  float eyeX, float eyeY, float eyeZ,
                  float centerX, float centerY, float centerZ,
                  float upX, float upY, float upZ) {

    float dir[3], right[3], up[3], eye[3];
    up[0]=upX; up[1]=upY; up[2]=upZ;
    eye[0]=eyeX; eye[1]=eyeY; eye[2]=eyeZ;

    dir[0]=centerX-eyeX; dir[1]=centerY-eyeY; dir[2]=centerZ-eyeZ;
    vec3Normalize(dir);
    vec3Cross(dir,up,right);
    vec3Normalize(right);
    vec3Cross(right,dir,up);
    vec3Normalize(up);
    // first row
    viewMatrix[0]  = right[0];
    viewMatrix[4]  = right[1];
    viewMatrix[8]  = right[2];
    viewMatrix[12] = -vec3Dot(right, eye);
    // second row
    viewMatrix[1]  = up[0];
    viewMatrix[5]  = up[1];
    viewMatrix[9]  = up[2];
    viewMatrix[13] = -vec3Dot(up, eye);
    // third row
    viewMatrix[2]  = -dir[0];
    viewMatrix[6]  = -dir[1];
    viewMatrix[10] = -dir[2];
    viewMatrix[14] =  vec3Dot(dir, eye);
    // forth row
    viewMatrix[3]  = 0.0f;
    viewMatrix[7]  = 0.0f;
    viewMatrix[11] = 0.0f;
    viewMatrix[15] = 1.0f;
  }

  void mat4Print(float* a) {
    // opengl uses column major order
    for (int i = 0; i < 4; ++i) {
      for (int j = 0; j < 4; ++j) {
        cout << a[j * 4 + i] << " ";
      }
      cout << endl;
    }
  }

  void mat4Transpose(float* a, float *transposed) {
    int t = 0;
    for (int i = 0; i < 4; ++i) {
      for (int j = 0; j < 4; ++j) {
        transposed[t++] = a[j * 4 + i];
      }
    }
  }

  bool mat4Invert(float* m, float *inverse) {
    float inv[16];
    inv[0] = m[5]*m[10]*m[15]-m[5]*m[11]*m[14]-m[9]*m[6]*m[15]+
             m[9]*m[7]*m[14]+m[13]*m[6]*m[11]-m[13]*m[7]*m[10];
    inv[4] = -m[4]*m[10]*m[15]+m[4]*m[11]*m[14]+m[8]*m[6]*m[15]-
             m[8]*m[7]*m[14]-m[12]*m[6]*m[11]+m[12]*m[7]*m[10];
    inv[8] = m[4]*m[9]*m[15]-m[4]*m[11]*m[13]-m[8]*m[5]*m[15]+
             m[8]*m[7]*m[13]+m[12]*m[5]*m[11]-m[12]*m[7]*m[9];
    inv[12]= -m[4]*m[9]*m[14]+m[4]*m[10]*m[13]+m[8]*m[5]*m[14]-
             m[8]*m[6]*m[13]-m[12]*m[5]*m[10]+m[12]*m[6]*m[9];
    inv[1] = -m[1]*m[10]*m[15]+m[1]*m[11]*m[14]+m[9]*m[2]*m[15]-
             m[9]*m[3]*m[14]-m[13]*m[2]*m[11]+m[13]*m[3]*m[10];
    inv[5] = m[0]*m[10]*m[15]-m[0]*m[11]*m[14]-m[8]*m[2]*m[15]+
             m[8]*m[3]*m[14]+m[12]*m[2]*m[11]-m[12]*m[3]*m[10];
    inv[9] = -m[0]*m[9]*m[15]+m[0]*m[11]*m[13]+m[8]*m[1]*m[15]-
             m[8]*m[3]*m[13]-m[12]*m[1]*m[11]+m[12]*m[3]*m[9];
    inv[13]= m[0]*m[9]*m[14]-m[0]*m[10]*m[13]-m[8]*m[1]*m[14]+
             m[8]*m[2]*m[13]+m[12]*m[1]*m[10]-m[12]*m[2]*m[9];
    inv[2] = m[1]*m[6]*m[15]-m[1]*m[7]*m[14]-m[5]*m[2]*m[15]+
             m[5]*m[3]*m[14]+m[13]*m[2]*m[7]-m[13]*m[3]*m[6];
    inv[6] = -m[0]*m[6]*m[15]+m[0]*m[7]*m[14]+m[4]*m[2]*m[15]-
             m[4]*m[3]*m[14]-m[12]*m[2]*m[7]+m[12]*m[3]*m[6];
    inv[10]= m[0]*m[5]*m[15]-m[0]*m[7]*m[13]-m[4]*m[1]*m[15]+
             m[4]*m[3]*m[13]+m[12]*m[1]*m[7]-m[12]*m[3]*m[5];
    inv[14]= -m[0]*m[5]*m[14]+m[0]*m[6]*m[13]+m[4]*m[1]*m[14]-
             m[4]*m[2]*m[13]-m[12]*m[1]*m[6]+m[12]*m[2]*m[5];
    inv[3] = -m[1]*m[6]*m[11]+m[1]*m[7]*m[10]+m[5]*m[2]*m[11]-
             m[5]*m[3]*m[10]-m[9]*m[2]*m[7]+m[9]*m[3]*m[6];
    inv[7] = m[0]*m[6]*m[11]-m[0]*m[7]*m[10]-m[4]*m[2]*m[11]+
             m[4]*m[3]*m[10]+m[8]*m[2]*m[7]-m[8]*m[3]*m[6];
    inv[11]= -m[0]*m[5]*m[11]+m[0]*m[7]*m[9]+m[4]*m[1]*m[11]-
             m[4]*m[3]*m[9]-m[8]*m[1]*m[7]+m[8]*m[3]*m[5];
    inv[15]= m[0]*m[5]*m[10]-m[0]*m[6]*m[9]-m[4]*m[1]*m[10]+
             m[4]*m[2]*m[9]+m[8]*m[1]*m[6]-m[8]*m[2]*m[5];

    float det = m[0]*inv[0]+m[1]*inv[4]+m[2]*inv[8]+m[3]*inv[12];
    if (det == 0) return false;
    det = 1.0f / det;
    for (int i = 0; i < 16; i++) inverse[i] = inv[i] * det;
    return true;
  }

  void applyMatrixToVec4(float* m, float* vector, float* result) {
      result[0] = m[0 + 4 * 0] * vector[0] + m[0 + 4 * 1] * vector[1] + m[0 + 4 * 2] * vector[2] + m[0 + 4 * 3] * vector[3];
      result[1] = m[1 + 4 * 0] * vector[0] + m[1 + 4 * 1] * vector[1] + m[1 + 4 * 2] * vector[2] + m[1 + 4 * 3] * vector[3];
      result[2] = m[2 + 4 * 0] * vector[0] + m[2 + 4 * 1] * vector[1] + m[2 + 4 * 2] * vector[2] + m[2 + 4 * 3] * vector[3];
      result[3] = m[3 + 4 * 0] * vector[0] + m[3 + 4 * 1] * vector[1] + m[3 + 4 * 2] * vector[2] + m[3 + 4 * 3] * vector[3];
  }

  void rotateZ(float* rot, float degree) {
    mat4Identity(rot);
    float rad = M_PI / 180.0 * degree;
    rot[0 + 4 * 0] = cos(rad);
    rot[1 + 4 * 0] = sin(rad);
    rot[0 + 4 * 1] = -sin(rad); 
    rot[1 + 4  *1] = cos(rad);   
  }


  bool loadVertexData(std::string& filename, std::vector<float>& data) {
    // read vertex data from file
    ifstream input(filename.c_str());
    if (!input) {
      cerr << "Can not find vertex data file " << filename << endl;
      return false;
    }
    else {
      int numFloats;
      double vertData;
      if (input >> numFloats) {
        if (numFloats > 0) {
          data.resize(numFloats);
          int i = 0;
          while (input >> vertData && i < numFloats) {
            // store it in the vector.
            data[i] = float(vertData);
            i++;
          }
          if (i != numFloats || numFloats % (3 + 2 + 3)) data.resize(0);
        }
      }
      input.close();
    }
    return false;
  }
};


//this is a static pointer to a Renderer used in the glut callback functions
static Renderer *renderer;

//glut static callbacks start
static void glutResize(int w, int h) 
{
  renderer->resize(w,h);
}

static void glutDisplay() 
{
  renderer->display();
  glutSwapBuffers();
  glutReportErrors();
}

static void timer(int v) 
{
  float offset = 1.0f;
  renderer->t += offset;
  glutDisplay();
  glutTimerFunc(unsigned(20), timer, ++v);
}

static void glutKeyboard(unsigned char key, int x, int y) {
  bool redraw = false;
  std::string modeStr;
  std::stringstream ss;
  switch(key) {
    case '1':
      renderer->modeVal = 1;
      redraw = true;
      modeStr = string("mode = 1");
      break;
    case '2':
      renderer->modeVal = 2;
      redraw = true;
      modeStr = string("mode = 2");
      break;
    case '3':
      renderer->modeVal = 3;
      redraw = true;
      modeStr = string("mode = 3");
      break;
    case '4':
      renderer->modeVal = 4;
      redraw = true;
      modeStr = string("mode = 4");
      break;
    case '5':
      renderer->modeVal = 5;
      redraw = true;
      modeStr = string("mode = 5");
      break;
    case '9':
      renderer->shaderFile++;
      if(renderer->shaderFile > 4)  renderer->shaderFile = 0;
      if(renderer->shaderFile == 0) renderer->shaderFilename = "PhongBrdfCameraSpace";
      if(renderer->shaderFile == 1) renderer->shaderFilename = "PhongBrdfWorldSpace";
      if(renderer->shaderFile == 2) renderer->shaderFilename = "BlinnPhongBrdfCameraSpace";
      if(renderer->shaderFile == 3) renderer->shaderFilename = "BlinnPhongBrdfWorldSpace";
      if(renderer->shaderFile == 4) renderer->shaderFilename = "PhongBrdfPerVertex";
      renderer->reload();
      redraw = true;
      modeStr = "Shader Light/Material (" + renderer->shaderFilename + ")";
      break;
    case '0':
      renderer->nextModel();
      redraw = true;
      modeStr = string("Shader Light/Material");
      break;
    }
    if(redraw) {
      glutDisplay();
	    cout << modeStr << endl;
      glutSetWindowTitle(modeStr.c_str());
    }
}


int main(int argc, char **argv) 
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
  glutInitWindowPosition(100,100);
  glutInitWindowSize(320, 320);

  glutCreateWindow("Shader Light/Material");
  GLenum err = glewInit();
  if (GLEW_OK != err) {
    fprintf(stderr, "Glew error: %s\n", glewGetErrorString(err));
  }
  glutDisplayFunc(glutDisplay);
  //glutIdleFunc(glutDisplay);
  glutReshapeFunc(glutResize);
  glutKeyboardFunc(glutKeyboard);

  renderer = new Renderer;
  renderer->init();

  glutTimerFunc(unsigned(20), timer, 0);

  glutMainLoop();
}