# all files / diagram-js/lib/util/ LineIntersection.js

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     import {
      pointDistance
    } from './Geometry';

    import intersectPaths from 'path-intersection';

    var round = Math.round,
        max = Math.max;

    function circlePath(center, r) {
      var x = center.x,
          y = center.y;

      return [
        ['M', x, y],
        ['m', 0, -r],
        ['a', r, r, 0, 1, 1, 0, 2 * r],
        ['a', r, r, 0, 1, 1, 0, -2 * r],
        ['z']
      ];
    }

    function linePath(points) {
      var segments = [];

      points.forEach(function(p, idx) {
        segments.push([ idx === 0 ? 'M' : 'L', p.x, p.y ]);
      });

      return segments;
    }

    var INTERSECTION_THRESHOLD = 10;

    function getBendpointIntersection(waypoints, reference) {

      var i, w;

      for (i = 0; (w = waypoints[i]); i++) {

        if (pointDistance(w, reference) <= INTERSECTION_THRESHOLD) {
          return {
            point: waypoints[i],
            bendpoint: true,
            index: i
          };
        }
      }

      return null;
    }

    function getPathIntersection(waypoints, reference) {

      var intersections = intersectPaths(circlePath(reference, INTERSECTION_THRESHOLD), linePath(waypoints));

      var a = intersections[0],
          b = intersections[intersections.length - 1],
          idx;

      if (!a) {
        // no intersection
        return null;
      }

      Eif (a !== b) {

        Iif (a.segment2 !== b.segment2) {
          // we use the bendpoint in between both segments
          // as the intersection point

          idx = max(a.segment2, b.segment2) - 1;

          return {
            point: waypoints[idx],
            bendpoint: true,
            index: idx
          };
        }

        return {
          point: {
            x: (round(a.x + b.x) / 2),
            y: (round(a.y + b.y) / 2)
          },
          index: a.segment2
        };
      }

      return {
        point: {
          x: round(a.x),
          y: round(a.y)
        },
        index: a.segment2
      };
    }

    /**
     * Returns the closest point on the connection towards a given reference point.
     *
     * @param  {Array<Point>} waypoints
     * @param  {Point} reference
     *
     * @return {Object} intersection data (segment, point)
     */
    export function getApproxIntersection(waypoints, reference) {
      return getBendpointIntersection(waypoints, reference) || getPathIntersection(waypoints, reference);
    }