import numpy as np


def CalcChassisVelocityFromWheels(wheel_vel):
    """
    Compute chassis body-frame velocity from three wheel angular velocities for a 
    three-wheel omnidirectional chassis.

    Input
    -----
    wheel_vel : np.ndarray, shape (..., 3), float
        Wheel angular velocity array (unit: rad/s).
        Order: [wheel_front_left_velocity, wheel_front_right_velocity, wheel_rear_velocity]

    Output
    ------
    chassis_vel : np.ndarray, shape (..., 3), float
        Chassis body‑frame velocity vector [v_x, v_y, omega_z].
        - v_x: body‑frame linear velocity along x axis (m/s)
        - v_y: body‑frame linear velocity along y axis (m/s)
        - omega_z: body‑frame angular velocity around z axis (rad/s)
        Output shape matches input batch dimensions.

    Constants
    ---------
    SQRT3_OVER_2 : float
        √3 / 2 ≈ 0.8660254037844386, geometric coefficient for wheel layout.
    RWHEEL : float
        Wheel radius, unit: meter.
    RCHASSIS : float
        Distance from chassis center to each wheel mounting point, unit: meter.
    """
    SQRT3_OVER_2 = 0.8660254037844386
    RWHEEL = 0.101555
    RCHASSIS = 0.32485

    # Initialize output array with same batch dimensions as input
    chassis_vel = np.zeros_like(wheel_vel)

    # Body‑frame v_x (m/s)
    chassis_vel[..., 0] = (
        (wheel_vel[..., 0] - wheel_vel[..., 1]) * RWHEEL / (2.0 * SQRT3_OVER_2)
    )
    # Body‑frame v_y (m/s)
    chassis_vel[..., 1] = (
        (2.0 * wheel_vel[..., 2] - wheel_vel[..., 0] - wheel_vel[..., 1]) * RWHEEL / 3.0
    )
    # Body‑frame angular velocity omega_z (rad/s)
    chassis_vel[..., 2] = (
        -(wheel_vel[..., 0] + wheel_vel[..., 1] + wheel_vel[..., 2])
        * RWHEEL
        / (3.0 * RCHASSIS)
    )
    return chassis_vel