// glut_example.c
// Stanford University, CS248, Fall 2000
//
// Demonstrates basic use of GLUT toolkit for CS248 video game assignment.
// More GLUT details at http://reality.sgi.com/mjk_asd/spec3/spec3.html
// Here you'll find examples of initialization, basic viewing transformations,
// mouse and keyboard callbacks, menus, some rendering primitives, lighting,
// double buffering, Z buffering, and texturing.
//
// Matt Ginzton -- magi@cs.stanford.edu
#include <GL/glew.h>
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
	
const char *vertex_shader_source =
  "attribute vec4 in_position;    \n"
  "attribute vec4 in_color;    \n"
  "\n"
  "varying vec4 vVaryingColor;         \n"
  "                             \n"
  "void main()                  \n"
  "{                            \n"
  "    gl_Position = in_position;\n"
  "    vVaryingColor = in_color;\n"
  "}                            \n";

const char *fragment_shader_source =
  "precision mediump float;     \n"
  "                             \n"
  "varying vec4 vVaryingColor;         \n"
  "                             \n"
  "void main()                  \n"
  "{                            \n"
  "    gl_FragColor = vVaryingColor;   \n"
  "}                            \n";

GLfloat vVertices[] = {
  // front
  -1.0f, -1.0f, +1.0f, // point blue
  +1.0f, -1.0f, +1.0f, // point magenta
  -1.0f, +1.0f, +1.0f, // point cyan
  +1.0f, +1.0f, +1.0f, // point white
};

GLfloat vColors[] = {
  // front
  0.0f,  0.0f,  1.0f, // blue
  1.0f,  0.0f,  1.0f, // magenta
  0.0f,  1.0f,  1.0f, // cyan
  1.0f,  1.0f,  1.0f, // white
};

#define VERTEX_BUFFER_SIZE 0x60000
#define COMPONENTS_PER_VERTEX (3)
#define NUM_VERTICES (4)

GLint modelviewmatrix_handle;
GLint modelviewprojectionmatrix_handle;
GLint normalmatrix_handle;
GLuint vertex_shader;
GLuint fragment_shader;
GLuint program;

#define VIEWING_DISTANCE_MIN  3.0
#define TEXTURE_ID_CUBE 1
enum {
  MENU_LIGHTING = 1,
  MENU_POLYMODE,
  MENU_TEXTURING,
  MENU_EXIT
};
typedef int BOOL;
#define TRUE 1
#define FALSE 0
static BOOL g_bLightingEnabled = TRUE;
static BOOL g_bFillPolygons = TRUE;
static BOOL g_bTexture = FALSE;
static BOOL g_bButton1Down = FALSE;
static GLfloat g_fTeapotAngle = 0.0;
static GLfloat g_fTeapotAngle2 = 0.0;
static GLfloat g_fViewDistance = 3 * VIEWING_DISTANCE_MIN;
static GLfloat g_nearPlane = 1;
static GLfloat g_farPlane = 1000;
static int g_Width = 600;                          // Initial window width
static int g_Height = 600;                         // Initial window height
static int g_yClick = 0;
static float g_lightPos[4] = { 10, 10, -100, 1 };  // Position of light
#ifdef _WIN32
static DWORD last_idle_time;
#else
static struct timeval last_idle_time;
#endif
void DrawCubeFace(float fSize)
{
  fSize /= 2.0;
  glBegin(GL_QUADS);
  glVertex3f(-fSize, -fSize, fSize);    glTexCoord2f (0, 0);
  glVertex3f(fSize, -fSize, fSize);     glTexCoord2f (1, 0);
  glVertex3f(fSize, fSize, fSize);      glTexCoord2f (1, 1);
  glVertex3f(-fSize, fSize, fSize);     glTexCoord2f (0, 1);
  glEnd();
}
void DrawCubeWithTextureCoords (float fSize)
{
  glPushMatrix();
  DrawCubeFace (fSize);
  glRotatef (90, 1, 0, 0);
  DrawCubeFace (fSize);
  glRotatef (90, 1, 0, 0);
  DrawCubeFace (fSize);
  glRotatef (90, 1, 0, 0);
  DrawCubeFace (fSize);
  glRotatef (90, 0, 1, 0);
  DrawCubeFace (fSize);
  glRotatef (180, 0, 1, 0);
  DrawCubeFace (fSize);
  glPopMatrix();
}
void RenderObjects(void)
{
  float colorBronzeDiff[4] = { 0.8, 0.6, 0.0, 1.0 };
  float colorBronzeSpec[4] = { 1.0, 1.0, 0.4, 1.0 };
  float colorBlue[4]       = { 0.0, 0.2, 1.0, 1.0 };
  float colorNone[4]       = { 0.0, 0.0, 0.0, 0.0 };
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  // Main object (cube) ... transform to its coordinates, and render
  glRotatef(15, 1, 0, 0);
  glRotatef(45, 0, 1, 0);
  glRotatef(g_fTeapotAngle, 0, 0, 1);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, colorBlue);
  glMaterialfv(GL_FRONT, GL_SPECULAR, colorNone);
  glColor4fv(colorBlue);
  glBindTexture(GL_TEXTURE_2D, TEXTURE_ID_CUBE);
  DrawCubeWithTextureCoords(1.0);
  // Child object (teapot) ... relative transform, and render
  glPushMatrix();
  glTranslatef(2, 0, 0);
  glRotatef(g_fTeapotAngle2, 1, 1, 0);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, colorBronzeDiff);
  glMaterialfv(GL_FRONT, GL_SPECULAR, colorBronzeSpec);
  glMaterialf(GL_FRONT, GL_SHININESS, 50.0);
  glColor4fv(colorBronzeDiff);
  glBindTexture(GL_TEXTURE_2D, 0);
  glutSolidTeapot(0.3);
  glPopMatrix(); 
  glPopMatrix();
}
void display(void)
{
   // Clear frame buffer and depth buffer
    glClearColor(0.5, 0.5, 0.5, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glEnable(GL_CULL_FACE);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    glDrawArrays(GL_TRIANGLE_STRIP, 4, 4);
    glDrawArrays(GL_TRIANGLE_STRIP, 8, 4);
    glDrawArrays(GL_TRIANGLE_STRIP, 12, 4);
    glDrawArrays(GL_TRIANGLE_STRIP, 16, 4);
    glDrawArrays(GL_TRIANGLE_STRIP, 20, 4);

   // Make sure changes appear onscreen
   glutSwapBuffers();
}
void reshape(GLint width, GLint height)
{
   g_Width = width;
   g_Height = height;
   glViewport(0, 0, g_Width, g_Height);
}
void InitGraphics(void)
{
        GLint ret;
        printf("GL Extensions \"%s\"\n", glGetString(GL_EXTENSIONS));

	vertex_shader = glCreateShader(GL_VERTEX_SHADER);
	if (!vertex_shader) {
		exit(1);
	}


	glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
	glCompileShader(vertex_shader);

	glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &ret);
	if (!ret) {
		char *log;

		printf("Error: vertex shader compilation failed!:\n");
		glGetShaderiv(vertex_shader, GL_INFO_LOG_LENGTH, &ret);

		if (ret > 1) {
			log = malloc(ret);
			glGetShaderInfoLog(vertex_shader, ret, NULL, log);
			printf("%s", log);
		}
		exit(1);
	} else
		printf("Vertex shader compilation succeeded!\n");

	fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
	if (!fragment_shader) {
		exit(1);
	}


	glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
	glCompileShader(fragment_shader);

	glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &ret);
	if (!ret) {
		char *log;

		printf("Error: fragment shader compilation failed!:\n");
		glGetShaderiv(fragment_shader, GL_INFO_LOG_LENGTH, &ret);

		if (ret > 1) {
			log = malloc(ret);
			glGetShaderInfoLog(fragment_shader, ret, NULL, log);
			printf("%s", log);
		}
		exit(-1);
	} else
		printf("Fragment shader compilation succeeded!\n");

	program = glCreateProgram();
	if (!program) {
		printf("Error: failed to create program!\n");
		exit(-1);
	}

	glAttachShader(program, vertex_shader);
	glAttachShader(program, fragment_shader);

	glBindAttribLocation(program, 0, "in_position");
	glBindAttribLocation(program, 1, "in_color");

	glLinkProgram(program);

	glGetProgramiv(program, GL_LINK_STATUS, &ret);
	if (!ret) {
		char *log;

		printf("Error: program linking failed!:\n");
		glGetProgramiv(program, GL_INFO_LOG_LENGTH, &ret);

		if (ret > 1) {
			log = malloc(ret);
			glGetProgramInfoLog(program, ret, NULL, log);
			printf("%s", log);
		}
		exit(-1);
	} else
		printf("program linking succeeded!\n");

	glUseProgram(program);

        /* Make vertex buffer object */
        float vtx_logical[NUM_VERTICES * COMPONENTS_PER_VERTEX * 3];
        size_t stride = COMPONENTS_PER_VERTEX * 3;

        for(int vert=0; vert<NUM_VERTICES; ++vert)
        {
            int src_idx = vert * COMPONENTS_PER_VERTEX;
            int dest_idx = vert * stride;
            for(int comp=0; comp<COMPONENTS_PER_VERTEX; ++comp)
            {
                vtx_logical[dest_idx+comp+0] = vVertices[src_idx + comp]; /* 0 */
                vtx_logical[dest_idx+comp+6] = vColors[src_idx + comp]; /* 2 */
            }
        }
        
        int vbo = 0;
        glGenBuffers(1, &vbo);
        glBindBuffer(GL_ARRAY_BUFFER, vbo);
        glBufferData(GL_ARRAY_BUFFER, sizeof(vtx_logical), (void*)vtx_logical, GL_STREAM_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, stride*4, (void*)(0*4));
	glEnableVertexAttribArray(0);

	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, stride*4, (void*)(6*4));
	glEnableVertexAttribArray(1);
            
        modelviewmatrix_handle = glGetUniformLocation(program, "modelviewMatrix");
        modelviewprojectionmatrix_handle = glGetUniformLocation(program, "modelviewprojectionMatrix");
        normalmatrix_handle = glGetUniformLocation(program, "normalMatrix");
}
void MouseButton(int button, int state, int x, int y)
{
  // Respond to mouse button presses.
  // If button1 pressed, mark this state so we know in motion function.
  if (button == GLUT_LEFT_BUTTON)
    {
      g_bButton1Down = (state == GLUT_DOWN) ? TRUE : FALSE;
      g_yClick = y - 3 * g_fViewDistance;
    }
}
void MouseMotion(int x, int y)
{
  // If button1 pressed, zoom in/out if mouse is moved up/down.
  if (g_bButton1Down)
    {
      g_fViewDistance = (y - g_yClick) / 3.0;
      if (g_fViewDistance < VIEWING_DISTANCE_MIN)
         g_fViewDistance = VIEWING_DISTANCE_MIN;
      glutPostRedisplay();
    }
}
void AnimateScene(void)
{
  float dt;
#ifdef _WIN32
  DWORD time_now;
  time_now = GetTickCount();
  dt = (float) (time_now - last_idle_time) / 1000.0;
#else
  // Figure out time elapsed since last call to idle function
  struct timeval time_now;
  gettimeofday(&time_now, NULL);
  dt = (float)(time_now.tv_sec  - last_idle_time.tv_sec) +
  1.0e-6*(time_now.tv_usec - last_idle_time.tv_usec);
#endif
  // Animate the teapot by updating its angles
  g_fTeapotAngle += dt * 30.0;
  g_fTeapotAngle2 += dt * 100.0;
  // Save time_now for next time
  last_idle_time = time_now;
  // Force redraw
  glutPostRedisplay();
}
void SelectFromMenu(int idCommand)
{
  switch (idCommand)
    {
    case MENU_LIGHTING:
      g_bLightingEnabled = !g_bLightingEnabled;
      if (g_bLightingEnabled)
         glEnable(GL_LIGHTING);
      else
         glDisable(GL_LIGHTING);
      break;
    case MENU_POLYMODE:
      g_bFillPolygons = !g_bFillPolygons;
      glPolygonMode (GL_FRONT_AND_BACK, g_bFillPolygons ? GL_FILL : GL_LINE);
      break;      
    case MENU_TEXTURING:
      g_bTexture = !g_bTexture;
      if (g_bTexture)
         glEnable(GL_TEXTURE_2D);
      else
         glDisable(GL_TEXTURE_2D);
      break;    
    case MENU_EXIT:
      exit (0);
      break;
    }
  // Almost any menu selection requires a redraw
  glutPostRedisplay();
}
void Keyboard(unsigned char key, int x, int y)
{
  switch (key)
  {
  case 27:             // ESCAPE key
	  exit (0);
	  break;
  case 'l':
	  SelectFromMenu(MENU_LIGHTING);
	  break;
  case 'p':
	  SelectFromMenu(MENU_POLYMODE);
	  break;
  case 't':
	  SelectFromMenu(MENU_TEXTURING);
	  break;
  }
}
int BuildPopupMenu (void)
{
  int menu;
  menu = glutCreateMenu (SelectFromMenu);
  glutAddMenuEntry ("Toggle lighting\tl", MENU_LIGHTING);
  glutAddMenuEntry ("Toggle polygon fill\tp", MENU_POLYMODE);
  glutAddMenuEntry ("Toggle texturing\tt", MENU_TEXTURING);
  glutAddMenuEntry ("Exit demo\tEsc", MENU_EXIT);
  return menu;
}
int main(int argc, char** argv)
{
  // GLUT Window Initialization:
  glutInit (&argc, argv);
  glutInitWindowSize (g_Width, g_Height);
  glutInitDisplayMode ( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
  glutCreateWindow ("Orientation check");

    GLenum err = glewInit();
    if (GLEW_OK != err)
    {
        /* Problem: glewInit failed, something is seriously wrong. */
        fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
        exit(1);
    }
    fprintf(stdout, "Status: Using GLEW %s\n", glewGetString(GLEW_VERSION));

  // Initialize OpenGL graphics state
  InitGraphics();
  // Register callbacks:
  glutDisplayFunc (display);
  glutReshapeFunc (reshape);
  glutKeyboardFunc (Keyboard);
  glutMouseFunc (MouseButton);
  glutMotionFunc (MouseMotion);
  glutIdleFunc (AnimateScene);
  // Create our popup menu
  BuildPopupMenu ();
  glutAttachMenu (GLUT_RIGHT_BUTTON);
  // Get the initial time, for use by animation
#ifdef _WIN32
  last_idle_time = GetTickCount();
#else
  gettimeofday (&last_idle_time, NULL);
#endif
  // Turn the flow of control over to GLUT
  glutMainLoop ();
  return 0;
}