#include <stdio.h>
#include <math.h>

#include "mygraph.h"
#include "mydebug.h"
#include "point.h"

extern int DEBUG;

#define ZERO_DELTA 0.0000001

void read_line( line * the_line){

     if ( DEBUG & LINE_LEVEL ) {
	fprintf(stderr,"DEBUG: Entering read_line\n");
     }

     printf ("Enter the endpoints of a line\n");
     read_point(&(the_line->e1));
     read_point(&(the_line->e2));


     if ( DEBUG & LINE_LEVEL ) {
	fprintf(stderr,"DEBUG: Exiting read_line, (%f, %f) to ( %f, %f)\n",
	      the_line->e1.x,the_line->e1.y,the_line->e2.x,the_line->e2.y);
     }
}

void print_line ( line a_line) {

     if ( DEBUG & LINE_LEVEL ) {
	fprintf(stderr,"DEBUG: Entering print_line\n");
     }

     printf ("The line is : ");
     print_point (a_line.e1);
     print_point (a_line.e2);
     printf ("\n");

     if ( DEBUG & LINE_LEVEL ) {
	fprintf(stderr,"DEBUG: Exiting print_line\n");
     }
}

int calculate_slope (line aline, float * slope){
    float deltax, deltay;

     if ( DEBUG_LINE ) {
	fprintf(stderr,"DEBUG: Entering calculate_slope\n");
	fprintf(stderr,"DEBUG: The line is, (%f, %f) to ( %f, %f)\n",
	      aline.e1.x,aline.e1.y,aline.e2.x,aline.e2.y);
     }

     deltax = aline.e1.x - aline.e2.x;
     deltay = aline.e1.y - aline.e2.y;

     if ( DEBUG_LINE &&  DEBUG_MED ) {
	fprintf(stderr,"Delta x = %f, Delta y = %f\n",deltax, deltay);
     }

     if (fabs(deltax) < ZERO_DELTA) {
         if ( DEBUG_LINE &&  DEBUG_MED ) {
	    fprintf(stderr,
		  "DEBUG: This represents a 0 delta x, slope infinity\n");
         }
	 return (-1);
     }

     *slope = deltay/deltax; 
    
     if ( DEBUG_LINE ) {
	fprintf(stderr,"DEBUG: Exiting calculate_slope\n");
     }

     return(0);
}