"""
This module is for functions which perform measurements.
"""

import numpy as np

def calculate_distance(rA, rB):
    """
    Calculate the distance between two points.

    Optional extended summary.

    Parameters
    ----------
    rA : np.ndarray
        The coordinates of each point.
    rB

    Returns
    -------
    dist : float
        The distance between the two points.

    Examples
    --------
    >>> r1 = np.array([0, 0, 0])
    >>> r2 = np.array([0, 0.1, 0])
    >>> calculate_distance(r1, r2)
    0.1
    """
    # This function calculates the distance between two points given as numpy arrays.
    d = (rA - rB)
    dist = np.linalg.norm(d)
    return dist


def calculate_angle(rA, rB, rC, degrees=False):
    # Calculate the angle between three points. Answer is given in radians by default, but can be given in degrees
    # by setting degrees=True
    AB = rB - rA
    BC = rB - rC
    theta = np.arccos(np.dot(AB, BC) / (np.linalg.norm(AB) * np.linalg.norm(BC)))

    if degrees:
        return np.degrees(theta)
    else:
        return theta