Extruding along a line programmatically

I'm trying to create a script that will extrude a face along a path but I can't quite get there.
I don't know how I can get the indices of the vertices I created using extrude.

This is what I currently have:


What I want is a full ring without the holes.

This is my code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using System.Linq;
4. using UnityEngine;
5. using UnityEngine.ProBuilder;
6. using UnityEngine.ProBuilder.MeshOperations;
7.  
8. public class ProbuilderProceduralWall : MonoBehaviour
9. {
10.     public int radius = 10;
11.     public int iterations = 20;
12.     public bool FlipNormals = false;
13.     [SerializeField]
14.     List<Vector2> _face = new List<Vector2>();
15.     [SerializeField]
16.     Vector3[] _path = new Vector3[0];
17.  
18.     void OnDrawGizmos()
19.     {
20.         for (int i = 0; i < _face.Count - 1; i++)
21.         {
22.             Debug.DrawLine(_face[i], _face[i + 1]);
23.         }
24.         for (int i = 0; i < _path.Length - 1; i++)
25.         {
26.             Debug.DrawLine(_path[i], _path[i + 1]);
27.         }
28.     }
29.     void Start()
30.     {
31.         if (_path.Length == 0) _path = MakePath(iterations, radius);
32.         if (_face.Count == 0) _face = new List<Vector2>() { new Vector2(-0.5f, 0), new Vector2(-0.25f, .5f), new Vector2(0, 1), new Vector2(0.25f, 0.5f), new Vector2(0.5f, 0) };
33.         Do();
34.     }
35.     void OnGUI()
36.     {
37.         if (GUILayout.Button("Make path"))
38.         {
39.             _path = MakePath(iterations, radius);
40.         }
41.  
42.         if (GUILayout.Button("Do"))
43.         {
44.             Do();
45.         }
46.     }
47.  
48.     static Vector3[] MakePath(int iterations, float radius)
49.     {
50.         var path = new Vector3[iterations];
51.         for (var i = 0; i < iterations; i++)
52.         {
53.             path[i] = new Vector3(Mathf.Sin((1f / iterations * Mathf.PI * 2) * i) * radius, 0, Mathf.Cos((1f / iterations * Mathf.PI * 2) * i) * radius);
54.         }
55.         return path;
56.     }
57.  
58.     void Do()
59.     {
60.         var min = _face.Aggregate(new Vector2(Mathf.Infinity, Mathf.Infinity), (agg, p) => Vector2.Min(agg, p));
61.         var max = _face.Aggregate(new Vector2(Mathf.NegativeInfinity, Mathf.NegativeInfinity), (agg, p) => Vector2.Max(agg, p));
62.  
63.         var mesh = ProBuilderMesh.Create();
64.         var facePoints = new List<Vector3>(_face.Select(p => (Vector3)p));
65.         facePoints.Sort((a, b) => a.x.CompareTo(b.x));
66.         facePoints.Insert(0, new Vector3(min.x, min.y - 1));
67.         facePoints.Add(new Vector3(max.x, min.y - 1));
68.         mesh.CreateShapeFromPolygon(facePoints, 0, FlipNormals);
69.         var instance = GameObject.Instantiate(mesh.gameObject);
70.         var instanceMesh = instance.GetComponent<ProBuilderMesh>();
71.  
72.  
73.         instanceMesh.transform.position = _path[0];
74.         var toModel = instanceMesh.transform.worldToLocalMatrix;
75.         var face = instanceMesh.faces.Last();
76.         var faces = new[] { face };
77.  
78.         for (int i = 0; i < _path.Length - 1; i++)
79.         {
80.             var start = _path[i];
81.             var middle = _path[i + 1];
82.             var end = i + 2 < _path.Length ? _path[i + 2] : _path[i + 1];
83.  
84.             var createdFaces = instanceMesh.Extrude(faces, ExtrudeMethod.FaceNormal, 1);
85.  
86.             var positions = new List<Vector3>(instanceMesh.positions);
87.             var dir = ((middle - start).normalized + (end - middle).normalized);
88.             var rotation = Quaternion.LookRotation(dir, Vector3.up);
89.             var toWorld = Matrix4x4.TRS(middle, rotation, Vector3.one);
90.             Debug.DrawRay(middle, dir.normalized, Color.magenta, 30.0f);
91.          
92.             foreach (var index in face.distinctIndexes)
93.             {
94.                 positions[index] = toModel.MultiplyPoint3x4(toWorld.MultiplyPoint3x4(facePoints[index]));
95.                 Debug.DrawRay(positions[index], Vector3.up * 0.1f, Color.red, 30.0f);
96.             }
97.             instanceMesh.positions = positions;          
98.         }
99.  
100.         instanceMesh.ToMesh();
101.         instanceMesh.Refresh();
102.         instanceMesh.name = $"{name}";
103.         instanceMesh.GetComponentInChildren<Renderer>().sharedMaterial = BuiltinMaterials.defaultMaterial;
104.         Destroy(mesh.gameObject);
105.         Debug.Log("Created mesh", instanceMesh);
106.     }
107.  
108. }
109.