// @category  utilities

// simplify checking if a value is defined before outputting it to a property
// @mixin     if-set
// @param     $property {String} css property to define
// @param     $value {String} a valid css value for property
// @param     $ignore {List} a list of "falsy" values
// @usage
// =if-set(margin, $margin, $ignore: (5px 10px)); // will only output margin if it is not 5px or 10px
@mixin if-set($property, $value: false, $ignore: false) {
  @if($ignore == false) {
    $ignore: (0 0px);
  }
  @if($value != false and not index(-compass-list($ignore), $value)) {
    #{$property}: $value;
  }
}

$REGISTRY_DO_ONCE: () !default;
// a function to prevent routines from executing multiple times
// @function  do-once
// @param     $name {String} name of the identifier
// @return    {Bool} true if the first time invoked, false otherwise
@function do-once($name) {
  @if index($REGISTRY_DO_ONCE, $name) {
    @return false;
  }
  $REGISTRY_DO_ONCE: append($REGISTRY_DO_ONCE, $name);
  @return true;
}

// helper to determine if a sprite is already set or sprites are disabled
// @function  _shouldSetSprite
// @private
// @param     $sprite {SpriteMap} the sprite map to check against
// @return    {Boolean} should the sprite be set
@function _shouldSetSprite($sprite) {
  @return not $CONFIG_DISABLE_STYLEGUIDE_SPRITES and not $sprite;
}

// check that a sprite isn't nil or false
// @function  styleguide-check-sprite
// @param     $map {SpriteMap} the sprite map to check against
// @return    {Boolean} is the sprite set
@function styleguide-check-sprite($map) {
  @return not ($CONFIG_DISABLE_STYLEGUIDE_SPRITES and index(false nil, $map));
}

// wrapper for sprite()
// @function  styleguide-sprite
// @param     $map {SpriteMap} the sprite map
// @param     $sprite {Sprite} the sprite name
// @param     $offset-x {Number} the horizontal offset of the sprite position
// @param     $offset-y {Number} the vertical offset of the sprite position
// @return    {Sprite} the sprite object or nil
@function styleguide-sprite($map, $sprite, $offset-x: 0, $offset-y: 0) {
  @if not styleguide-check-sprite($map) { @return nil; }
  @return sprite($map, $sprite, $offset-x, $offset-y);
}

// wrapper for sprite-position()
// @function  styleguide-sprite-position
// @param     $map {SpriteMap} the sprite map
// @param     $sprite {Sprite} the sprite name
// @param     $offset-x {Number} the horizontal offset of the sprite position
// @param     $offset-y {Number} the vertical offset of the sprite position
// @return    {List} the sprite position or nil
@function styleguide-sprite-position($map, $sprite, $offset-x: 0, $offset-y: 0) {
  @if not styleguide-check-sprite($map) { @return nil; }
  @return sprite-position($map, $sprite, $offset-x, $offset-y);
}

// wrapper for sprite-url()
// @function  styleguide-sprite-url
// @param     $map {SpriteMap} the sprite map
// @return    {String} the sprite URL or nil
@function styleguide-sprite-url($map) {
  @if not styleguide-check-sprite($map) { @return nil; }
  @return sprite-url($map);
}

// wrapper for sprite-file()
// @function  styleguide-sprite-file
// @param     $map {SpriteMap} the sprite map
// @param     $sprite {Sprite} the sprite name
// @return    {ImageFile} the image or nil
@function styleguide-sprite-file($map, $sprite) {
  @if not styleguide-check-sprite($map) { @return nil; }
  @return sprite-file($map, $sprite);
}

// wrapper for image-width()
// @function  styleguide-image-width
// @param     $image {ImageFile} the image
// @return    {Number} the width of the image or nil
@function styleguide-image-width($image) {
  @if $image == nil { @return nil; }
  @return image-width($image);
}

// wrapper for image-height()
// @function  styleguide-image-height
// @param     $image {ImageFile} the image
// @return    {Number} the height of the image or nil
@function styleguide-image-height($image) {
  @if $image == nil { @return nil; }
  @return image-height($image);
}