/* geometry.c
 *
 * Created by Rory Healy (healyr@student.unimelb.edu.au)
 * Created on 9th September 2021
 * Last modified 9th September 2021
 *
 * A small library of functions used in the geometric construction of a 
 * Voronoi diagram.
 *
 */

#ifndef GEOMETRY_HEADER
#include "geometry.h"
#endif

#ifndef COMMON_HEADER
#include "common.h"
#endif

bisector_t getBisector(vertex_t *pointA, vertex_t *pointB) {
    bisector_t newBisector;
    double midpointX = (pointA->x + pointB->x) / 2;
    double midpointY = (pointA->y + pointB->y) / 2;

    newBisector.x = midpointX;
    newBisector.y = midpointY;

    /* Calculating bisector slope according to slope of AB */
    if (pointA->x == pointB->x) {
        /* The line segment AB has an infinite gradient, 
         * so the orthogonal line will have zero slope.
         */
        newBisector.slope = 0;
        newBisector.isSlopeInfinite = 0;
    } else if (pointA->y == pointB->y) {
        /* The line segment AB has gradient of zero, so 
         * the orthogonal line will have an infinite slope. 
         */
        newBisector.isSlopeInfinite = 1;

        /* Not actually zero, just a placeholder to prevent 
         * accidental errors 
         */
        newBisector.slope = 0;
    } else {
        /* Slope of the line segment AB */
        double segmentSlope = \
            (pointB->y - pointA->y) / (pointB->x - pointA->x);

        /* Calculate orthogonal slope */
        newBisector.isSlopeInfinite = 0;
        newBisector.slope = -1 / segmentSlope;
    }

    return newBisector;
}