Feat: Adding tags to product filters

src/Catalog/Services/ProductIndexer.php

@@ -90,6 +90,7 @@ class ProductIndexer extends BaseProductIndexer
             'in_stock',
             'recommendations.id',
             'skus',
+            'tags',
         ];
     }
 

src/Catalog/Services/ProductService.php

@@ -78,8 +78,27 @@ class ProductService
         );
 
         $priceBounds = $this->priceSliderBounds($filters, $filters?->minPrice, $filters?->maxPrice);
+        $availableTags = $this->availableTags($filters);
 
-        return new ProductListingResult($products, $priceBounds);
+        return new ProductListingResult($products, $priceBounds, $availableTags);
+    }
+
+    /**
+     * Every distinct `tags` value present on a product matching $filters,
+     * excluding $filters->tag itself — same "scoped but not self-collapsing"
+     * reasoning as priceRange() excluding `price` — so selecting a tag
+     * doesn't shrink the sidebar down to just that one tag. Sorted
+     * alphabetically; Meilisearch's facetDistribution has no defined order
+     * of its own.
+     *
+     * @return array<int, string>
+     */
+    private function availableTags(?ProductFilters $filters): array
+    {
+        $filter = $this->filterBuilder->build($filters, exclude: ['tag']);
+        $tags = $this->rawFacets('tags', $filter)['facetDistribution']['tags'] ?? [];
+
+        return collect($tags)->keys()->sort()->values()->all();
     }
 
     /**
@@ -93,9 +112,12 @@ class ProductService
      * apply that field's own filter separately in the UI/query layer.
      *
      * `$field` must be one of ProductIndexer's filterable fields; only discrete-value
-     * fields make sense here (`brand`, `in_stock`) — a numeric field like `price`
-     * would return one "facet" per exact price, not a usable range bucket. Use
-     * `priceRange()` for `price` instead.
+     * fields make sense here (`brand`, `tags`, `in_stock`) — a numeric field like
+     * `price` would return one "facet" per exact price, not a usable range bucket.
+     * Use `priceRange()` for `price` instead. `facets('tags', $filters)` is how a
+     * category page gets "which tags actually appear on products in this category" —
+     * pass a $filters that omits `tag` (see `build()`'s $exclude) so the tag list
+     * itself doesn't collapse to whichever tag is already selected.
      *
      * @return array<string, int> facet value => matching product count
      */