// ======================================
// 
//               get-block 
//
// ======================================

// Get BEM block selector(e.g "b-block") 
// from given selector list
// @param { List } the selector list
// @return { Unquoted String } the BEM block selector 
@function get-block($selector) { 
  @return (
    _get-block-part-from-string(
      selector-to-string($selector)
    )
  );
} 


// Get block part from given string 
// from given selector string
// @param   { String } the selector as string
// @return  { Unquoted String } selector as unquoted string
// @example
//    _get-block-part-from-string(".b-block_mod") //=> ".b-block"
@function _get-block-part-from-string($selector-string) {
  @return (
    _attach-block-prefix(
      unquote(
        str-slice(
          remove-block-prefix($selector-string), 
          1, 
          _sep-start-at(
            remove-block-prefix($selector-string)
          )
        )
      ), 
      _get-block-prefix($selector-string)
    )
  );
}


// Get block prefix from string
// @param   { String } a selector string
// @return  { String } the block prefix 
@function _get-block-prefix($selector-string) {
  @each $prefix in bem-sass-get("logged-prefixes") {
    @if (str-index($selector-string, $prefix) == 2) {
      @return str-slice($selector-string, 2, 1 + str-length($prefix));
    }
  }
  @return "";
}

// Attach block prefix to selector string
// @param   { String } a selector string
// @param   { String } a block prefix 
// @return  { String } the string which includes the block prefix 
@function _attach-block-prefix($selector-string, $prefix) {
  @return str-insert($selector-string, $prefix, 2);
}


// Get an index of the first elem/modifier separator
// from a given selector string
// @param   { String } the selector as string
// @return  { Number } index of the separator
@function _sep-start-at($selector-string) {
  $index-element-sep: str-index($selector-string, bem-sass-get("config", "element-sep"));
  $index-modifier-sep: str-index($selector-string, bem-sass-get("config", "modifier-sep"));

  @if ($index-element-sep and $index-modifier-sep) {
    @return min($index-element-sep, $index-modifier-sep) - 1;
  } 

  @if ($index-element-sep) {
    @return $index-element-sep - 1;
  } 

  @if ($index-modifier-sep) {
    @return $index-modifier-sep - 1;
  } 

  @return -1; 
}