/*  raptor.c
 *   Plots out tragectory of three raptors targeting a victim at the center
 *     of an equilateral triangle. Raptors/person can be set to any initial
 *     coordinates by editing the source.
 *   Options are available to display (crummy) graphical output.
 *
 *   See http://xkcd.com/135/
 *
 *   Have fun!
 *
 *  Copyright 2009       Andrew Poelstra
 *      Do what you want, but please leave my name attached
 *      to this code for as long as it's reasonably intact.
 */

#include <stdio.h>
#include <stdlib.h>

#include <math.h>

/* Don't set DRAW_GRAPHIC and CHECK_ALL ANGLES; you'll regret it. */
#define DRAW_GRAPHIC		1
#define CHECK_ALL_ANGLES	0
#define ANGLE_STEP		0.1
#define DEFAULT_ANGLE		54.4

#define G_WIDTH   200
#define G_HEIGHT  200


#define MIN_DISPLAY_TIME	3500   /* Minimum time needed to output "Caught at (x, y) message */
#define DISPLAY_STEP		5      /* Number of ms required to add another space before the | for the bar-graph display */


typedef struct raptor {
  double x;
  double y;
  double vx;
  double vy;
  double v;
} Raptor;


long magnitude(long x, long y) {
  return sqrt(x * x + y * y);
}

void print_raptor(Raptor *r) {
  printf("At (%f, %f), velocity (%f, %f)\nTotal velocity %f\n\n", r->x, r->y, r->vx, r->vy, r->v);
}


/* Units used are mm and msec */
int main(void) {
  size_t i, x, y;
  double angle;
  double x_ratio, y_ratio;
  unsigned long time_elapsed = 0;
  char marks[G_WIDTH][G_HEIGHT];
  Raptor r[3], you;

 /* Blank out graphic */
  for(x = 0; x < G_WIDTH; ++x)
    for(y = 0; y < G_HEIGHT; ++y)
      marks[x][y] = ' ';

 /* try all angles */
#if CHECK_ALL_ANGLES
  for(angle = 0; angle <= 360; angle += ANGLE_STEP) {
#else
  angle = DEFAULT_ANGLE;
  {
#endif

 /* Set nobody moving initially */
  r[0].vx = r[0].vy = r[0].v =
    r[1].vx = r[1].vy = r[1].v =
    r[2].vx = r[2].vy = r[2].v =
    you.vx = you.vy = you.v = 0;

 /* Place raptors */
 /* For 20m sides, use coordinates
  *    (0, 0)
  *    (0, 11547)
  *    (10000, -5773)
  *    (-10000, -5773)
  * For 20m between self and raptors, use
  *    (0, 0)
  *    (0, 20000)
  *    (17321, -10000)
  *    (-17321, -10000)
  */
  you.x = 0;
  you.y = 0;
  r[0].x = 0;
  r[0].y = 11547;
  r[1].x = 10000;
  r[1].y = -5773;
  r[2].x = -10000;
  r[2].y = -5773;

 /* Set victim velocity based on angle */
  you.v  = 6000;
  you.vx = you.v * sin(angle * 3.141592 / 180);
  you.vy = you.v * cos(angle * 3.141592 / 180);

 /* Step for 5 000 msec */
  time_elapsed = 0;
  while(time_elapsed < 5000) {
   /* Set accelleration */
    r[0].v += 4 * (r[0].v < 10000);
    r[1].v += 4 * (r[1].v < 25000);
    r[2].v += 4 * (r[2].v < 25000);

   /* Set velocity */
    if(magnitude(r[0].x - you.x, r[0].y - you.y) < 100 ||
       magnitude(r[1].x - you.x, r[1].y - you.y) < 100 ||
       magnitude(r[2].x - you.x, r[2].y - you.y) < 100) {
      break;
    }

    x_ratio = (you.x - r[0].x) / magnitude(r[0].x - you.x, r[0].y - you.y);
    y_ratio = (you.y - r[0].y) / magnitude(r[0].x - you.x, r[0].y - you.y);
    r[0].vx = r[0].v * x_ratio;
    r[0].vy = r[0].v * y_ratio;

    x_ratio = (you.x - r[1].x) / magnitude(r[1].x - you.x, r[1].y - you.y);
    y_ratio = (you.y - r[1].y) / magnitude(r[1].x - you.x, r[1].y - you.y);
    r[1].vx = r[1].v * x_ratio;
    r[1].vy = r[1].v * y_ratio;

    x_ratio = (you.x - r[2].x) / magnitude(r[2].x - you.x, r[2].y - you.y);
    y_ratio = (you.y - r[2].y) / magnitude(r[2].x - you.x, r[2].y - you.y);
    r[2].vx = r[2].v * x_ratio;
    r[2].vy = r[2].v * y_ratio;

   /* Move raptors */
    r[0].x += r[0].vx / 1000;
    r[0].y += r[0].vy / 1000;
    r[1].x += r[1].vx / 1000;
    r[1].y += r[1].vy / 1000;
    r[2].x += r[2].vx / 1000;
    r[2].y += r[2].vy / 1000;

   /* Move you */
    you.x += you.vx / 1000;
    you.y += you.vy / 1000;

   /* mark everybody */
#if DRAW_GRAPHIC
    if(time_elapsed % 10 == 0) {
      marks[(int) (G_WIDTH / 2 + r[0].x / 3 / G_WIDTH)][(int) (G_HEIGHT / 3 - r[0].y / 2 / G_HEIGHT)] = '1';
      marks[(int) (G_WIDTH / 2 + r[1].x / 3 / G_WIDTH)][(int) (G_HEIGHT / 3 - r[1].y / 2 / G_HEIGHT)] = '2';
      marks[(int) (G_WIDTH / 2 + r[2].x / 3 / G_WIDTH)][(int) (G_HEIGHT / 3 - r[2].y / 2 / G_HEIGHT)] = '3';
      marks[(int) (G_WIDTH / 2 + you.x / 3 / G_WIDTH)][(int) (G_HEIGHT / 3 - you.y / 2 / G_HEIGHT)] = 'y';
    }
#endif

    ++time_elapsed;
  }

  if(time_elapsed > MIN_DISPLAY_TIME) {
    printf("Caught at (%.2f, %.2f)   \tAngle: %.2f\tTime elapsed: %ld", you.x / 1000, you.y / 1000, angle, time_elapsed);
    for(i = MIN_DISPLAY_TIME; i < time_elapsed; i += DISPLAY_STEP)
      printf(" ");
    puts("|");
  }

 /* end try all angles */
  }

#if DRAW_GRAPHIC
printf("You are at %3f, %3f.\n", you.x / 1000, you.y / 1000);
  for(y = 0; y < G_HEIGHT; ++y) {
    for(x = 0; x < G_WIDTH; ++x) {
      printf("%c", marks[x][y]);
    }
    puts("");
  }
#endif

  return 0;
}