Sharing a maintainable and scalable media query mixin generator for SASS

////////////////////////////////////////////
// function for finding next value in map //
////////////////////////////////////////////
@function nextKey($current-value, $mapped-list:$sizes__map) {
    // get current key from list
    $the-list: map-keys($mapped-list);

    //find index of current value and add 1
    $the-index: ( index( $the-list, $current-value) ) + 1;

    // get value from list with new index
    $new-value : nth($the-list, $the-index);

    @return $new-value;

}

///////////////////////
// Media breakpoints //
///////////////////////
$sizes__map : (
    small: 1px,
    medium: 768px,
    large: 960px,
    largest: 1080px,
    xlargest: 1240px
);

///////////////
// The mixin //
///////////////
@mixin media($breakpoint, $breakpoint__two:null) {
    // setting up variables for the second query, if needed
    $first-query: map-get($sizes__map, $breakpoint);
    $second-query: map-get($sizes__map, $breakpoint__two);

    // checks for single or dual arguement inputted
    @if $breakpoint__two == null {
        $mapped__keys : map-keys($sizes__map);

        // get current index of breakpoint to decide what query to run
        $index : index($mapped__keys, $breakpoint);
        @if $index {
            // if it is not the last item in the map, run this
            @if $index < length($sizes__map) {
                @media screen and (min-width : map-get($sizes__map, $breakpoint ) ) and (max-width: map-get($sizes__map, nextKey($breakpoint) )  - 1 ) {
                    @content;
                }
            }
            // if it is the last in the map, run this
            @elseif $index == length($sizes__map) {
                @media screen and (min-width : map-get($sizes__map, $breakpoint) ) {
                    @content;
                }
            }
        }
        // if key does not exsist, run this
        @else {
            @error "Sorry but #{$breakpoint} is not a breakpoint in your setup";
        }
    }
    // will call if two arguements inputted are the same type
    @elseif type-of($breakpoint) == type-of($breakpoint__two)  {
        body {
            color: purple!important;
        }
        // if breakpoint is a string
        @if type-of($breakpoint) == string {

            // if both values are in the $sizes__map
            @if $first-query and $second-query {

                // corrects ordering of variables for correct media query output
                @if $first-query < $second-query {
                    @media screen and (min-width: $first-query) and (max-width: $second-query - 1) {
                        @content;
                    }
                }
                @else {
                    @media screen and (min-width: $second-query) and (max-width: $first-query - 1) {
                        @content;
                    }
                }
            }
            @else {
                $mapped__keys : map-keys($sizes__map);
                @error "The given arguments are not valid you must choose from: #{$mapped__keys}";
            } 
        }
        @elseif type-of($breakpoint) == number {
            // corrects ordering of variables for correct media query output
            @if $breakpoint < $breakpoint__two {
                @media screen and (min-width: $breakpoint) and (max-width: $breakpoint__two) {
                    @content;
                }
            }
            @else {
                @media screen and (min-width: $breakpoint__two) and (max-width: $breakpoint) {
                    @content;
                }
            }
        }
        @else {
            $the-type: type-of($breakpoint);
            @error "passed invalid arguement type #{$the-type}";
        }
    }
    // if neither breakpoint is of the same type
    @else {
        @error "Inputted values are invlaid. Must be array variables or matching unit types";
    }
}
////////////////////////////
// Ways to call the mixin //
////////////////////////////

@include media(small) {
   body {
      background: blue;
   }
}

@include media(small, large) {
   section {
      background: orange;
   }
}

@include media(640px, 1080px) {
   footer {
      background: green;
   }
}

@include media(30em, 60em) {
   header {
      background: red;
   }
}

@media screen and (min-width: 1px) and (max-width: 767px) {
  body {
    background: blue; } }
body {
  color: purple !important; }

@media screen and (min-width: 1px) and (max-width: 959px) {
  section {
    background: orange; } }
body {
  color: purple !important; }

@media screen and (min-width: 640px) and (max-width: 1080px) {
  footer {
    background: green; } }
body {
  color: purple !important; }

@media screen and (min-width: 30em) and (max-width: 60em) {
  header {
    background: red; } }