Sass function change text color based on background color

dynamic-color.scss

/* This snippet NEED HSL values to work correctly */
/* Sass variables with HSL values */
$orange: hsl(30, 91, 58, 1);
$blue: hsl(229, 100, 65, 1);
$purple: hsl(251, 54, 49, 1);
$black: hsl(0, 0, 0, 1);
$white: hsl(0, 0, 100, 1);

/* Utilities variables to pass to function */
$bg-color: $purple;
$text-color: dynamic-color(bg-color);

// dynamic color function declaration
@function  dynamic-color($color) {
    $font-color: $black;
    @if (lightness($color) > 50%) {
        $font-color: $black;
    } @else {
        $font-color: $white;
    }
    @return $font-color;
};


// Integration example

.button {
    width: 200px;
    padding: 18px 36px 16px;
    color: black;
    cursor: pointer;
    background-color: $bg-color;
    border: 3px solid black;
    border-radius: 50px;
    box-shadow: 6px 6px 0 black;
    display: flex;
    justify-content: center;
    font-weight: bold;
    font-family: 'arial';
    color: dynamic-color($bg-color);
}