/**
 * Determines visibility of a celestial body relative to the Sun, as seen from the Earth.
 *
 * This function returns an [ElongationInfo] object, which provides the following
 * information about the given celestial body at the given time:
 *
 * - `visibility` is an enumerated type that specifies whether the body is more easily seen
 *    in the morning before sunrise, or in the evening after sunset.
 *
 * - `elongation` is the angle in degrees between two vectors: one from the center of the Earth to the
 *    center of the Sun, the other from the center of the Earth to the center of the specified body.
 *    This angle indicates how far away the body is from the glare of the Sun.
 *    The elongation angle is always in the range [0, 180].
 *
 * - `eclipticSeparation` is the absolute value of the difference between the body's ecliptic longitude
 *   and the Sun's ecliptic longitude, both as seen from the center of the Earth. This angle measures
 *   around the plane of the Earth's orbit, and ignores how far above or below that plane the body is.
 *   The ecliptic separation is measured in degrees and is always in the range [0, 180].
 *
 * @param body
 * The celestial body whose visibility is to be calculated.
 *
 * @param time
 * The date and time of the observation.
 */
fun elongation(body: Body, time: Time): ElongationInfo {
    val relativeLongitude = pairLongitude(body, Body.Sun, time)
    val elongation = angleFromSun(body, time)
    return if (relativeLongitude > 180.0)
        ElongationInfo(time, Visibility.Morning, elongation, 360.0 - relativeLongitude)
    else
        ElongationInfo(time, Visibility.Evening, elongation, relativeLongitude)
}