import trimesh
from trimesh import intersections as inter
import open3d as o3d
import numpy as np


def extract_points(segment_list):
  point_list = np.asarray(segment_list[0])
  for segment in segment_list:
    found = False
    for new_point in segment:
      for point in point_list:
        comparison = new_point == point
        if comparison.all():
          found = True
          break
      if not found:
        point_list = np.concatenate((point_list, [new_point]))
  return point_list


def point_cloud_to_mesh(point_list, normal_list):
  pcd = o3d.geometry.PointCloud()
  pcd.points = o3d.utility.Vector3dVector(point_list)
  pcd.normals = o3d.utility.Vector3dVector(normal_list)
  distances = pcd.compute_nearest_neighbor_distance()
  avg_dist = np.mean(distances)
  radius = 3 * avg_dist
  bpa_mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_ball_pivoting(
           pcd,
           o3d.utility.DoubleVector([radius, radius * 2]))
  mesh_result = trimesh.Trimesh(vertices=np.asarray(bpa_mesh.vertices), faces=np.asarray(bpa_mesh.triangles))
  return mesh_result


def merge_meshes(mesh1, mesh2):
  v_1 = mesh1.vertices
  f_1 = mesh1.faces
  v_2 = mesh2.vertices
  f_2 = mesh2.faces
  length = len(v_1)
  v_merge = np.concatenate((v_1, v_2))
  f_merge = np.asarray(f_1)

  for item in f_2:
    point1 = item.item(0) + length
    point2 = item.item(1) + length
    point3 = item.item(2) + length
    surface = np.asarray([point1, point2, point3])
    f_merge = np.concatenate((f_merge, [surface]))

  mesh_merge = trimesh.Trimesh(vertices=v_merge, faces=f_merge)

  return mesh_merge


# example
vertices = [[0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 1, 1], [1, 0, 0], [1, 0, 1], [1, 1, 0], [1, 1, 1]]
faces = [[0, 1, 2], [1, 3, 2], [1, 5, 3], [5, 3, 7], [0, 4, 1], [4, 5, 1], [4, 6, 5], [5, 6, 7], [0, 2, 4], [2, 6, 4],
         [3, 7, 6], [2, 3, 6]]
mesh = trimesh.Trimesh(vertices=vertices, faces=faces)
normal_plane = [0, 0, 1]
point_plane = [0, 0, 0.5]
normal_plane_opp = [0, 0, -1]

# Step 1: division and extraction of segments
mesh_1 = inter.slice_mesh_plane(mesh, normal_plane, point_plane)
mesh_1_segments = inter.mesh_plane(mesh, normal_plane, point_plane)

# Step 2: create mesh from point cloud
points = extract_points(mesh_1_segments)
normals = np.empty((len(points), 3))
for i in range(0, len(normals)):
  normals[i] = normal_plane_opp
mesh_2 = point_cloud_to_mesh(points, normals)

# Step 3: merge both meshes
mesh_final = merge_meshes(mesh_1, mesh_2)


print(mesh_final.vertices, mesh_final.faces)