pub/graphlib/lib/src/layout/charted/intersect/polygon.dart

library graphlib.layout.charted.intersect.polygon;

import "dart:math" as Math;
import "line.dart";

/// Returns the point ({x, y}) at which the point argument intersects with the
/// node argument assuming that it has the shape specified by polygon.
intersectPolygon(node, polyPoints, point) {
  var x1 = node.x;
  var y1 = node.y;

  var intersections = [];

  var minX = double.INFINITY,
      minY = double.INFINITY;
  polyPoints.forEach((entry) {
    minX = Math.min(minX, entry.x);
    minY = Math.min(minY, entry.y);
  });

  var left = x1 - node.width / 2 - minX;
  var top =  y1 - node.height / 2 - minY;

  for (var i = 0; i < polyPoints.length; i++) {
    var p1 = polyPoints[i];
    var p2 = polyPoints[i < polyPoints.length - 1 ? i + 1 : 0];
    var intersect = intersectLine(node, point,
      {"x": left + p1.x, "y": top + p1.y}, {"x": left + p2.x, "y": top + p2.y});
    if (intersect) {
      intersections.push(intersect);
    }
  }

  if (!intersections.length) {
    print("NO INTERSECTION FOUND, RETURN NODE CENTER: $node");
    return node;
  }

  if (intersections.length > 1) {
    // More intersections, find the one nearest to edge end point
    intersections.sort((p, q) {
      var pdx = p.x - point.x,
          pdy = p.y - point.y,
          distp = Math.sqrt(pdx * pdx + pdy * pdy),

          qdx = q.x - point.x,
          qdy = q.y - point.y,
          distq = Math.sqrt(qdx * qdx + qdy * qdy);

      return (distp < distq) ? -1 : (distp == distq ? 0 : 1);
    });
  }
  return intersections[0];
}