///Returns `$list` as a string, prettified if `$pre` is set to true.
///@ignore Documentation: http://sassylists.com/documentation.html#sl-debug
///@param {List}   $list          - list to debug
///@param {Bool}   $pre   (false) - enable/disable variables type and proper indentation
///@param {Number} $level (1)     - internal variable for recursion
///@requires sl-is-empty
///@requires sl-is-single
///@requires sl-has-multiple-values
///
///@example
///   sl-debug(a b c)
///   // '("a", "b", "c")'
///@return {String}

@function sl-debug($list, $pre: false, $level: 1) {
  @if sl-missing-dependencies(sl-is-empty, sl-is-single, sl-has-multiple-values) == true { @return null; }

  @if sl-is-empty($list) {
    @return "( )";
  }

  @if sl-is-single($list) {
    @return if($pre,  "(" + type-of($list) + ") ", "") + $list;
  }

  $tab: "    ";
  $indent: "";
  $break: if($pre, "\A ", "");
  $length: length($list);

  @for $i from 1 to $level {
    $indent: $indent + $tab;
  }

  $result: "[" + $break;

  @for $i from 1 through $length {
    $item: nth($list, $i);
    $result: $result + if($pre, $indent + $tab, " ");

    @if sl-has-multiple-values($item) {
      $result: $result
        + if($pre, "(list: " + length($item) + ") ", "")
        + sl-debug($item, $pre, $level + 1);
    }

    @else {
      @if $pre {
        $result: $result + "(" + type-of($item) + ") ";
      }

      @if sl-is-empty($item) {
        $result: $result + "( )";
      }

      @else if type-of($item) == "string" {
        $result: $result + quote($item);
      }

      @else if $item == null {
        $result: $result + "null";
      }

      @else {
        $result: $result + $item;
      }
    }

    @if $i != $length {
      $result: $result + "," + $break;
    }
  }

  $result: $result + $break + if($pre, if($level > 1, $indent, ""), " ") + "]";

  @return quote($result);
}

///Mixin displaying clean debug
///@param {List} $list - list
///@requires sl-debug

@mixin sl-debug($list) {
  body:before {
    content: sl-debug($list, true)            !important;

    display: block                            !important;
    margin: 1em                               !important;
    padding: .5em                             !important; 

    background: #EFEFEF                       !important;
    border: 1px solid #DDD                    !important;
    border-radius: .2em                       !important;

    color: #333                               !important;
    font: .75em/1.5 "Courier New", monospace  !important;
    text-shadow: 0 1px white                  !important;
    white-space: pre-wrap                     !important;
  }
}