/*
 * Copyright (c) 1991, 1992, 1993 Silicon Graphics, Inc.
 *
 * Permission to use, copy, modify, distribute, and sell this software and
 * its documentation for any purpose is hereby granted without fee, provided
 * that (i) the above copyright notices and this permission notice appear in
 * all copies of the software and related documentation, and (ii) the name of
 * Silicon Graphics may not be used in any advertising or
 * publicity relating to the software without the specific, prior written
 * permission of Silicon Graphics.
 *
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF
 * ANY KIND,
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 *
 * IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR
 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include "GL/gl.h"
#include "GL/glu.h"
#include <GL/gltk.h>

#ifndef PI
#define PI 3.141592657
#endif

enum {
  NORMAL = 0,
  WEIRD = 1
};

enum {
  STREAK = 0,
  CIRCLE = 1
};

#define MAXSTARS 400
#define MAXPOS 10000
#define MAXWARP 10
#define MAXANGLES 6000

typedef struct _starRec {
  GLint type;
  float x[2], y[2], z[2];
  float offsetX, offsetY, offsetR, rotation;
} starRec;

GLenum doubleBuffer, directRender;
GLint windW, windH;

GLenum flag = NORMAL;
GLint starCount = MAXSTARS / 2;
float speed = 1.0;
GLint nitro = 0;
starRec stars[MAXSTARS];
float sinTable[MAXANGLES];

float Sin(float angle)
{

  return (sinTable[(GLint) angle]);
}

float Cos(float angle)
{

  return (sinTable[((GLint) angle + (MAXANGLES / 4)) % MAXANGLES]);
}

void NewStar(GLint n, GLint d)
{

  if (rand() % 4 == 0) {
    stars[n].type = CIRCLE;
  }
  else {
    stars[n].type = STREAK;
  }
  stars[n].x[0] = (float)(rand() % MAXPOS - MAXPOS / 2);
  stars[n].y[0] = (float)(rand() % MAXPOS - MAXPOS / 2);
  stars[n].z[0] = (float)(rand() % MAXPOS + d);
  if (rand() % 4 == 0 && flag == WEIRD) {
    stars[n].offsetX = (float)(rand() % 100 - 100 / 2);
    stars[n].offsetY = (float)(rand() % 100 - 100 / 2);
    stars[n].offsetR = (float)(rand() % 25 - 25 / 2);
  }
  else {
    stars[n].offsetX = 0.0;
    stars[n].offsetY = 0.0;
    stars[n].offsetR = 0.0;
  }
}

void RotatePoint(float *x, float *y, float rotation)
{
  float tmpX, tmpY;

  tmpX = *x * Cos(rotation) - *y * Sin(rotation);
  tmpY = *y * Cos(rotation) + *x * Sin(rotation);
  *x = tmpX;
  *y = tmpY;
}

void MoveStars(void)
{
  float offset;
  GLint n;

  offset = speed * 60.0;

  for (n = 0; n < starCount; n++) {
    stars[n].x[1] = stars[n].x[0];
    stars[n].y[1] = stars[n].y[0];
    stars[n].z[1] = stars[n].z[0];
    stars[n].x[0] += stars[n].offsetX;
    stars[n].y[0] += stars[n].offsetY;
    stars[n].z[0] -= offset;
    stars[n].rotation += stars[n].offsetR;
    if (stars[n].rotation > MAXANGLES) {
      stars[n].rotation = 0.0;
    }
  }
}

GLenum StarPoint(GLint n)
{
  float x0, y0, x1, y1, width;
  GLint i;

  x0 = stars[n].x[0] * windW / stars[n].z[0];
  y0 = stars[n].y[0] * windH / stars[n].z[0];
  RotatePoint(&x0, &y0, stars[n].rotation);
  x0 += windW / 2.0;
  y0 += windH / 2.0;

  if (x0 >= 0.0 && x0 < windW && y0 >= 0.0 && y0 < windH) {
    if (stars[n].type == STREAK) {
      x1 = stars[n].x[1] * windW / stars[n].z[1];
      y1 = stars[n].y[1] * windH / stars[n].z[1];
      RotatePoint(&x1, &y1, stars[n].rotation);
      x1 += windW / 2.0;
      y1 += windH / 2.0;

      glLineWidth(MAXPOS / 100.0 / stars[n].z[0] + 1.0);
      glColor3f(1.0, (MAXWARP - speed) / MAXWARP, (MAXWARP - speed) / MAXWARP);
      if (fabs(x0 - x1) < 1.0 && fabs(y0 - y1) < 1.0) {
	glBegin(GL_POINTS);
	glVertex2f(x0, y0);
	glEnd();
      }
      else {
	glBegin(GL_LINES);
	glVertex2f(x0, y0);
	glVertex2f(x1, y1);
	glEnd();
      }
    }
    else {
      width = MAXPOS / 10.0 / stars[n].z[0] + 1.0;
      glColor3f(1.0, 0.0, 0.0);
      glBegin(GL_POLYGON);
      for (i = 0; i < 8; i++) {
	float x = x0 + width * Cos((float)i * MAXANGLES / 8.0);
	float y = y0 + width * Sin((float)i * MAXANGLES / 8.0);

	glVertex2f(x, y);
      };
      glEnd();
    }
    return GL_TRUE;
  }
  else {
    return GL_FALSE;
  }
}

void ShowStars(void)
{
  GLint n;

  glClear(GL_COLOR_BUFFER_BIT);

  for (n = 0; n < starCount; n++) {
    if (stars[n].z[0] > speed || (stars[n].z[0] > 0.0 && speed < MAXWARP)) {
      if (StarPoint(n) == GL_FALSE) {
	NewStar(n, MAXPOS);
      }
    }
    else {
      NewStar(n, MAXPOS);
    }
  }
}

static void Init(void)
{
  float angle;
  GLint n;

  srand((unsigned int)time(NULL));

  for (n = 0; n < MAXSTARS; n++) {
    NewStar(n, 100);
  }

  angle = 0.0;
  for (n = 0; n < MAXANGLES; n++) {
    sinTable[n] = sin(angle);
    angle += PI / (MAXANGLES / 2.0);
  }

  glClearColor(0.0, 0.0, 0.0, 0.0);

  glDisable(GL_DITHER);
}

void Reshape(int width, int height)
{

  windW = (GLint) width;
  windH = (GLint) height;

  glViewport(0, 0, windW, windH);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluOrtho2D(-0.5, windW + 0.5, -0.5, windH + 0.5);
  glMatrixMode(GL_MODELVIEW);
}

static GLenum Key(int key, GLenum mask)
{

  switch (key) {
    case TK_ESCAPE:
      tkQuit();
    case TK_SPACE:
      flag = (flag == NORMAL) ? WEIRD : NORMAL;
      break;
    case TK_t:
      nitro = 1;
      break;
    default:
      return GL_FALSE;
  }
  return GL_TRUE;
}

void Idle(void)
{

  MoveStars();
  ShowStars();
  if (nitro > 0) {
    speed = (float)(nitro / 10) + 1.0;
    if (speed > MAXWARP) {
      speed = MAXWARP;
    }
    if (++nitro > MAXWARP * 10) {
      nitro = -nitro;
    }
  }
  else if (nitro < 0) {
    nitro++;
    speed = (float)(-nitro / 10) + 1.0;
    if (speed > MAXWARP) {
      speed = MAXWARP;
    }
  }

  glFlush();
  if (doubleBuffer) {
    tkSwapBuffers();
  }
}

static GLenum Args(int argc, char **argv)
{
  GLint i;

  doubleBuffer = GL_FALSE;
  directRender = GL_TRUE;

  for (i = 1; i < argc; i++) {
    if (strcmp(argv[i], "-sb") == 0) {
      doubleBuffer = GL_FALSE;
    }
    else if (strcmp(argv[i], "-db") == 0) {
      doubleBuffer = GL_TRUE;
    }
    else if (strcmp(argv[i], "-dr") == 0) {
      directRender = GL_TRUE;
    }
    else if (strcmp(argv[i], "-ir") == 0) {
      directRender = GL_FALSE;
    }
  }
  return GL_TRUE;
}

void main(int argc, char **argv)
{
  GLenum type;

  if (Args(argc, argv) == GL_FALSE) {
    tkQuit();
  }

  windW = 300;
  windH = 300;
  tkInitPosition(0, 0, 300, 300);

  type = TK_RGB;
  type |= (doubleBuffer) ? TK_DOUBLE : TK_SINGLE;
  type |= (directRender) ? TK_DIRECT : TK_INDIRECT;
  tkInitDisplayMode(type);

  if (tkInitWindow("Stars") == GL_FALSE) {
    tkQuit();
  }

  Init();

  tkExposeFunc(Reshape);
  tkReshapeFunc(Reshape);
  tkKeyDownFunc(Key);
  tkIdleFunc(Idle);
  tkExec();
}