// ======================================
// 
//            create-selector
//
// ======================================


// Create valid CSS selector
// @author Yum<ym.jsng@gmail.com>
// @access public
// @param  {String} $type
// @param  {String} $namestring
// @return {String} 
@function create-selector($type, $namestring, $options:null) {

  @if ($type == "block") {
    @return _create-selector-block($namestring, map-get($options, level));
  }

  @if ($type == "element") {
    @return _create-selector-element($namestring, map-get($options, in-a-modifier));
  }

  @if ($type == "modifier") {
    @return _create-selector-modifier($namestring, map-get($options, value), map-get($options, in-an-element));
  }

  @if ($type == "shared-rule") {
    @return _create-selector-shared-rules($namestring, map-get($options, context));
  }

  @error "`#{$type}` is not a valid type for create-selector";
}


// Create valid CSS selector for BEM block
// @author Yum<ym.jsng@gmail.com>
// @access private 
// @param  {String}  $name
// @param  {String=} $type - a block type
// @return {String} 
@function _create-selector-block($name, $level:null) {
  @return (
    "." + _get-block-prefix-by-type($level) + $name
  );
}


// Create valid CSS selector for BEM element
// @author Yum<ym.jsng@gmail.com>
// @access private 
// @param  {String}  $name
// @param  {String=} $in-a-modifier - Test if the statement is in a modifier context
// @return {String} 
@function _create-selector-element($name, $in-a-modifier:false) {
  @if ($in-a-modifier) {
    @return (
      & + ">" + _create-selector-element($name)
    );
  }

  @return (
    get-block(&) + bem-sass-get("config", "element-sep") + $name
  );
}


// Create valid CSS selector for BEM element
// @author Yum<ym.jsng@gmail.com>
// @access private 
// @param  {String}  $name
// @param  {String=} $in-an-element- Test if the statement is in a element context
// @return {String} 
@function _create-selector-modifier($name, $value:null, $in-an-element:false) {
  @if ($value) {
    @return (
      _attach-value-to-modifier(
        _create-selector-modifier($name), 
        $value
      )
    );
  }

  @if ($in-an-element) {
    @return (
      & + bem-sass-get("config", "modifier-sep") + $name 
    )
  }

  @return (
    get-block(&) + bem-sass-get("config", "modifier-sep") + $name 
  );
} 


// Create namespaced placeholder for common rules inside a block
// @author Yum<ym.jsng@gmail.com>
// @access private 
// @param  {String} 
// @param  {List} $context - parent selector
// @return {String} 
@function _create-selector-shared-rules($name-partial, $context) {
  @return "%" + str-slice(get-block($context), 2) + "__CRS__" + $name-partial;
} 


// Add a value string to given BEM modifier selector string
// @author  Yum<ym.jsng@gmail.com>
// @access  private 
// @param   {String} the modifier name
// @param   {String} the value 
// @return  {String} a value attached BEM modifier

@function _attach-value-to-modifier($BEM-modifier-selector-string, $value) {
  @return ( 
    $BEM-modifier-selector-string + bem-sass-get("config", "modifier-sep") + $value
  );
} 


// Get BEM block prefix by given type
// @author  Yum<ym.jsng@gmail.com>
// @access  private 
// @param   {String} the type of the block
// @return  {String} the prefix of the block type
@function _get-block-prefix-by-type($type: null) { 
  @if ($type == null) {
    @return bem-sass-get("config", "default-prefix");
  } 

  @if (
    bem-sass-get(
      "config", 
      "block-levels", 
      $type
    )  == null
  ) {
    @error "block type `#{$type}` has not been declared";
  }

  @return bem-sass-get("config", "block-levels", $type);
}