Extract the property value related to a certain edge of a box, from its shorthand syntax

extrac-edge.scss

@function string-split($string, $delimiter: " ") {
    $list: ();
    $sum: str-length($string);

    @while str-length($string) > 0 {
        $delimiter-index: str-index($string, $delimiter);

        @if str-length($string) >= 1 and $delimiter-index == null {
            $list: append($list, $string);
            $string: "";
        }

        @if type-of($delimiter-index) == number {
            $each: str-slice($string, 0, ($delimiter-index - 1));
            $list: append($list, $each);
            $string: str-slice($string, ($delimiter-index + 1), $sum);
        }
    }
    @return $list;
}

@function extract-edge($values, $edge) {
    $list: $values;

    @if type-of($values) == string {
        $list: string-split($values);
    }

    $length: length($list);

    $map: (top: nth($list, 1));

    @if $length == 4 {
        $map: map-merge($map, (
            right: nth($list, 2),
            bottom: nth($list, 3),
            left: nth($list, 4)
        ));
    } @else if $length == 3 {
        $map: map-merge($map, (
            left: nth($list, 2),
            right: nth($list, 2),
            bottom: nth($list, 3)
        ));
    } @else if $length == 2 {
        $map: map-merge($map, (
            bottom: nth($list, 1),
            left: nth($list, 2),
            right: nth($list, 2)
        ));
    } @else if $length == 1 {
        $map: map-merge($map, (
            right: nth($list, 1),
            bottom: nth($list, 1),
            left: nth($list, 1)
        ));
    }

    @return map-get($map, $edge);
}

@debug extract-edge(1px 2px 3px 4px, "left");
@debug extract-edge(1px 2px 3px, "left");
@debug extract-edge(1px 2px, "left");
@debug extract-edge(1px, "left");

@debug extract-edge("1px 2px 3px 4px", "left");
@debug extract-edge("1px 2px 3px", "left");
@debug extract-edge("1px 2px", "left");
@debug extract-edge("1px", "left");