#include <stdlib.h>
#include <stdio.h>
#include <GL/glut.h>
#include <math.h>

#define W 7                       /* 地面の幅*/
#define D 8                        /* 地面の長さ */
#define FRONT 0
#define HIGHANGLE 1
#define UPSIDE 2
int ViewPoint = HIGHANGLE;

/*
 * 地面を描く
 */
static void myGround(double height)
{
  const static GLfloat ground[][4] = {
    { 0.6, 0.6, 0.6, 1.0 },
    { 0.3, 0.3, 0.3, 1.0 }
  };

  int i, j;

  glBegin(GL_QUADS);
  glNormal3d(0.0, 1.0, 0.0);
  for (j = -D; j < D; ++j) {
    for (i = -W; i < W; ++i) {
      glMaterialfv(GL_FRONT, GL_DIFFUSE, ground[(i + j) & 1]);
      glVertex3d((GLdouble)i, height, (GLdouble)j);
      glVertex3d((GLdouble)i, height, (GLdouble)(j + 1));
      glVertex3d((GLdouble)(i + 1), height, (GLdouble)(j + 1));
      glVertex3d((GLdouble)(i + 1), height, (GLdouble)j);
    }
  }
  glEnd();
}

void idle(void)
{
  glutPostRedisplay();
}

/*
 * 画面表示
 */
void display(void)
{
  static GLfloat lightpos[] = { 3.0, 4.0, 5.0, 1.0 }; /*  光源の位置 */
  static GLfloat color[] = { 0.5, 1.0, 1.0, 1.0 };   /* やかんの色 */
  static GLdouble px = 0.0 ,pz = 0.0;
  static GLdouble r = 0.0;
  pz = 6.0*sin((GLfloat)glutGet(GLUT_ELAPSED_TIME)/300)*cos((GLfloat)glutGet(GLUT_ELAPSED_TIME)/600); 
  px = 6.0*sin((GLfloat)glutGet(GLUT_ELAPSED_TIME)/300)*sin((GLfloat)glutGet(GLUT_ELAPSED_TIME)/600);

  /* 画面クリア */
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  
  /* モデルビュー変換行列の初期化 */
  glLoadIdentity();
  
  /* 光源の位置を設定 */
  glLightfv(GL_LIGHT0, GL_POSITION, lightpos);
  
  /* 視点の移動（物体の方を奥に移す) */
  glTranslated(0.0, 0.0, -25.0);

  switch(ViewPoint){
  case FRONT:
    gluLookAt(7.0, 7.0, 7.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0);
    glRotated(30.0, 30.0, 30.0, 0.0);
    break;
  case HIGHANGLE:
    gluLookAt(0.0, 7.0, 7.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0);
    break;
  case UPSIDE:
    gluLookAt(0.0, 10.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0);
    break;
  default:
    break;
  }

    glRotated(0.0, 2.0, 0.0, 0.0);
  /* シーンの描画 */
  myGround(0.0);
  glPushMatrix();
  glRotated(r - 90.0, 0.0, 1.0, 0.0);
  glTranslated(px, 1.0, pz);
  glMaterialfv(GL_FRONT, GL_DIFFUSE, color);
  glutSolidTeapot(1.0);
  glPopMatrix();

  glutSwapBuffers();
}

void resize(int w, int h)
{
  /* ウィンドウ全体をビューポートにする */
  glViewport(0, 0, w, h);

  /* 透視変換行列の指定 */
  glMatrixMode(GL_PROJECTION);
  
  /*  透視変換行列の初期化 */
  glLoadIdentity();
  gluPerspective(30.0, (double)w / (double)h, 1.0, 100.0);
  
  /* モデルビュー変換行列の指定 */
  glMatrixMode(GL_MODELVIEW);
}

static void keyboard(unsigned char key, int x, int y)
{
  /* ESC か q をタイプしたら終了 */
  if (key == '\033' || key == 'q') {
    exit(0);
  }
}

void mouse(int button, int state, int x, int y)
{
  switch (button) {
  case GLUT_LEFT_BUTTON:
    if (state == GLUT_DOWN) {
    }
    else {
    }
    break;
  case GLUT_RIGHT_BUTTON:
    if(state == GLUT_DOWN){
      if(ViewPoint == FRONT) ViewPoint = HIGHANGLE;
      else if(ViewPoint == HIGHANGLE) ViewPoint = UPSIDE;
      else ViewPoint = FRONT;
      glutPostRedisplay();
    }
    break;
  default:
    break;
  }
}
void init(void)
{
  /* 初期設定 */
  glClearColor(1.0, 1.0, 1.0, 0.0);
  glEnable(GL_DEPTH_TEST);
  glDisable(GL_CULL_FACE);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
  glutCreateWindow(argv[0]);
  glutDisplayFunc(display);
  glutReshapeFunc(resize);
  glutKeyboardFunc(keyboard);
  glutMouseFunc(mouse);
  init();
  glutIdleFunc(idle);
  glutMainLoop();
  return 0;
}