from __future__ import annotations

import copy

import numpy as np
import open3d as o3d


class GaussianNoiseAdder:
    """Add Gaussian noise to an Open3D point cloud."""

    def __init__(self, noise_std: float = 4.0, seed: int | None = None) -> None:
        self.noise_std = noise_std
        self.seed = seed

    def apply(self, pointcloud: o3d.geometry.PointCloud) -> o3d.geometry.PointCloud:
        noisy = copy.deepcopy(pointcloud)
        points = np.asarray(noisy.points)
        rng = np.random.default_rng(self.seed)
        noise = rng.normal(0, self.noise_std, points.shape)
        noisy.points = o3d.utility.Vector3dVector(points + noise)
        return noisy

    def noise_level(self, clean: o3d.geometry.PointCloud, noisy: o3d.geometry.PointCloud) -> float:
        clean_points = np.asarray(clean.points)
        noisy_points = np.asarray(noisy.points)
        if clean_points.shape != noisy_points.shape:
            raise ValueError("Clean and noisy point clouds must have the same point count.")
        return float(np.mean(np.linalg.norm(noisy_points - clean_points, axis=1)))