BEV Selector Parsing

bev.scss

// BEVM Selector Processing

// Quick string replace function
@function str-replace($string, $search, $replace: '') {
  $index: str-index($string, $search);
  
  @if $index {
    @return str-slice($string, 1, $index - 1) + $replace + str-replace(str-slice($string, $index + str-length($search)), $search, $replace);
  }
  @return $string;
}

// Check if a chunk has any variations
@function hasVariation($chunk) {
  $output: str-index($chunk, '--');
  @return $output;
}

// Check if a chunk has any elements
@function hasElement($chunk) {
  $output: str-index($chunk, '__');
  @return $output;
}

@function stripSelectorType($chunk) {
  $output: str-replace($chunk,'%','');
  $output: str-replace($output,'.','');
  @return $output;
}

// If the BEVM isn't assuming any parents, we parse it alone.
@function parseParentlessBEVM($chunk) {
  $block: $chunk;
  $variation: null;
  @if hasVariation($chunk) {
    $variationIndex: str-index($chunk, '--');
    $variation: str-slice($chunk, $variationIndex, -1);
    @if hasElement($variation) {
      $variation: null;
    }
    @else {
      $block: str-slice($chunk, 1, $variationIndex - 1);
      @if hasVariation($variation) {
        $variationIndex: str-index($variation, '--');
        $block: #{$block}#{str-slice($variation, 1, $variationIndex - 1)};
        $variation: str-slice($variation, $variationIndex, -1);
      }
    }
  }
  @return (
    type: mixed,
    block: $block,
    variation: $variation,
    modifier: null
  );
}

@function parseBEVMSelector($selector) {
  // Default BEVM model 
  $BEVM: (
    block: $selector,
    variation: null,
    modifier: null,
    type: basic
  );
  @if str-index($selector, '-') == 1 and str-index($selector, '--') != 1 {
    // If the selector is a -modifier of its parent
    $block: stripSelectorType('#{&}');
    $BEVM: map-merge($BEVM, (
      block: '#{$block} .#{$selector}',
      variation: null,
      modifier: #{$selector},
      type: modifier
    ));
  } 
  @else if str-index($selector, '--') == 1 {
    // If the selector is a --variation requiring its parent as part of the class name
    $variation: $selector;
    $block: stripSelectorType('#{&}');
    // If there's an element declared after the variation delimiter, it's just a variation.
    @if hasElement($variation) {
      $block: #{$block}#{$selector};
      $variation: null;
    }
    $BEVM: map-merge($BEVM, (
      block: $block,
      variation: $variation,
      modifier: null,
      type: variation
    ));
  } 
  @else {
    @if str-index($selector, '__') == 1 {
      // If the selector is an __element requiring its parent as part of the class name
      $block: stripSelectorType('#{&}');
      $BEVM: map-merge($BEVM, (
        block: #{$block}#{$selector},
        variation: null,
        type: element
      ));
    } 
    // If the selector is not assuming any parents
    @else {
      $BEVM: parseParentlessBEVM($selector);
    }
  }
  @return $BEVM;
}

@mixin _($selector, $buildClass: null) {
  $BEVM: parseBEVMSelector($selector);
  $type: map-get($BEVM, type);
  $block: map-get($BEVM, block);
  $variation: map-get($BEVM, variation);
  $modifier: map-get($BEVM, modifier);
  @at-root {
    // Every new model gets a placeholder.
    %#{$block}#{$variation} {
      @if $variation {
        @extend %#{$block};
      };
      @content;
    }
    // If we want to build a class.
    @if $buildClass or $modifier {
      .#{$block}#{$variation} {
        @if $variation {
          @extend %#{$block};
        };
        @content;
      }
    }
  }
}