/* dive.c */

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

#define ASPECT (3.0 / 4.0)
#define OFFSET (1.0 /  8.0)

int ul_x0;
int ul_y0;
int ul_x1;
int ul_y1;

int ll_x0;
int ll_y0;
int ll_x1;
int ll_y1;

int printline(
char tag[],
int  x0,
int  y0,
int  x1,
int  y1)
{
   fprintf(stderr, "%s: (%d, %d) (%d, %d) \n",
                 tag, x0, y0, x1, y1);
}

int make_line_defs(
int w,
int h)
{
   int pixoff = w * OFFSET;

   ul_x0 = pixoff;
   ul_y0 = h - 1;
   ul_x1 = w - 1;
   ul_y1 = pixoff;

   printline("Upper",  ul_x0, ul_y0, ul_x1, ul_y1);

   ll_x0 = 0;
   ll_y0 = h - 1 - pixoff;
   ll_x1 = w - 1 - pixoff;
   ll_y1 = 0;
   printline("Lower", ll_x0, ll_y0, ll_x1, ll_y1);


}

int write_red_pixel()
{
   fprintf(stdout, "%c%c%c", 250, 0, 0);
}

int write_white_pixel()
{
   fprintf(stdout, "%c%c%c", 250, 250, 250);
}


int make_pixel(
int x,
int y)
{
    if (isAbove(x, y, ul_x0, ul_y0, ul_x1, ul_y1))
       write_red_pixel();
    else if (isAbove(x, y, ll_x0, ll_y0, ll_x1, ll_y1))
       write_white_pixel();
    else
       write_red_pixel();
}

int write_row(
int w,
int h,
int row)
{
   int x;
   int y;

   y = row;
   x = 0;
   while (x < w)
   {
      make_pixel(x, y);
      x = x + 1;
   }
}

int make_ppm_hdr(
int w,
int h)
{
   fprintf(stdout, "P6\n");
   fprintf(stdout, "%d %d %d\n", w, h, 255);
}

int main(
int argc,
char *argv[])
{
   int width = 0;
   int height;
   int row;
   int col;

   if (argc < 2)
   {
      fprintf(stderr, "usage is: dive width-of-flag \n");
      exit(-1);
   }

   sscanf(argv[1], "%d", &width);
   height = width * ASPECT;
   fprintf(stderr, "%d %d\n", width, height);

   make_ppm_hdr(width, height);
   make_line_defs(width, height);

   row = height - 1;
   while (row >= 0)
   {
      write_row(width, height, row);
      row = row - 1;
   }
}