Connect shortest list of line strings to each other

[mziadd]

[Repost]
This is a problem with almost the same as my problem but I could not understand R language nor the algorithm he used

Suppose I have a list of line strings, I want to connect the green line to the shortest polygon line (The pink line), forming a new closed polygon like in the screenshot below.

This is what I have done so far...

  var gf = JTS.GeometryFactory.defaultPrecision();
  JTS.Point startPoint = gf.createPoint(newCoords.first);
  JTS.Point endPoint = gf.createPoint(newCoords.last);
  JTS.Geometry inSameLine;

  double defaultBuffer = 0.000001;

  int index = 0;

  Map<List<JTS.LineString>, double> shortestPathSeries = {};
  for (int i = 0; i < snappingGeometry.lineSegments.length; i++) {
    List<JTS.LineString> connectedLineSeries = [];
    double connectedLineSeriesDistance = 0;

    JTS.LineString currentLine =
        snappingGeometry.lineSegments[i].toGeometry(gf);

    if (currentLine.getLength() > 0) {
      if (startPoint.intersects(currentLine.buffer(defaultBuffer)) &&
          endPoint.intersects(currentLine.buffer(defaultBuffer))) {
        inSameLine = currentLine;
        shortestPathSeries = {};
        break;
      }

      if (startPoint.intersects(currentLine.buffer(defaultBuffer))) {
       
        JTS.LineString activeLine = currentLine.copy();
  
        List<VisitedNode> visitedLineSegments = [];
        snappingGeometry.lineSegments.forEach((element) {
          visitedLineSegments.add(VisitedNode(element, false, index));
          index++;
        });
 
        while (activeLine != null &&
            (visitedLineSegments
                    .indexWhere((element) => !element.visited) !=
                -1)) {
          JTS.LineString checkGeomActiveChain;

          var checkGeomNull = visitedLineSegments.where((element) {
            var isLineIntersectsActiveLine = element.line
                .toGeometry(gf)
                .intersects(activeLine.buffer(defaultBuffer));

            return !element.visited &&
                element.line.getLength() > 0 &&
                isLineIntersectsActiveLine;
          }).firstOrNull;
          if (checkGeomNull != null) {
            visitedLineSegments[checkGeomNull.index].visited = true;
            checkGeomActiveChain = checkGeomNull.line.toGeometry(gf);

            JTS.Point endPointForChain =
                checkGeomActiveChain.getStartPoint();

            connectedLineSeries.add(checkGeomActiveChain);
            connectedLineSeriesDistance +=
                endPointForChain.distance(activeLine);
          } else if (checkGeomNull == null) {
            int index = visitedLineSegments
                .indexWhere((element) => !element.visited);
            if (index != -1) checkGeomActiveChain = currentLine.copy();
            connectedLineSeries = [];
            connectedLineSeriesDistance = 0;
          }
          activeLine = checkGeomActiveChain;
        }

        if (connectedLineSeries.isNotEmpty)
          shortestPathSeries.putIfAbsent(
              connectedLineSeries, () => connectedLineSeriesDistance);
      }
    }
  }

  if (inSameLine != null) {
    newCoords.addAll(inSameLine.getCoordinates());
    polylineGeometry = gf.createLineString(newCoords);

    print('ADDING ON SAME LINE');
  } else if (shortestPathSeries.isNotEmpty) {
    print('ADDING Connected Edge ${shortestPathSeries.length}');

    var sortedGraphDistances = shortestPathSeries.entries.toList()
      ..sort((e1, e2) {
        var diff = e1.value.compareTo(e2.value);

        return diff;
      });
    shortestPathSeries
      ..clear()
      ..addEntries(sortedGraphDistances);
    List<JTS.LineString> notconnectedLineSeries;
    if (shortestPathSeries.values.first != 0)
      notconnectedLineSeries = shortestPathSeries.keys.first;
    else
      notconnectedLineSeries = shortestPathSeries.keys.elementAt(1);

    List<JTS.Coordinate> newCoordsX = [];
    newCoordsX.add(newCoords[0]);
    newCoordsX.addAll(notconnectedLineSeries
        .map((e) => e.getCoordinates())
        .reduce((value, element) => element)
        .toList());
    for (int i = 1; i < newCoords.length; i++) newCoordsX.add(newCoords[i]);
    testResult(gf.createLineString(newCoordsX).buffer(0.00001), context);
    return;
    polylineGeometry = gf.createLineString(newCoordsX);
  }

The problem is only one line is detected which is not the shortest, not the longest.
I want ideas or hints that solve my problem

Note: I am using dart_jts which is a port to flutter.