core/src/Search/ProductIndexer.php

<?php

namespace Modules\Core\Search;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Lunar\Models\Currency;
use Lunar\Models\Product;
use Lunar\Search\ProductIndexer as BaseProductIndexer;

/**
 * Extends Lunar's own indexer to add fields needed for storefront listing/filtering
 * (Modules\Core\Catalog\ProductService) that aren't part of Lunar's default document:
 * collection membership and a comparable price. Neither is filterable in Meilisearch
 * until `php artisan lunar:meilisearch:setup` re-syncs index settings and the index is
 * refreshed — see docs/product-listing.md.
 */
class ProductIndexer extends BaseProductIndexer
{
    public function getFilterableFields(): array
    {
        return [
            ...parent::getFilterableFields(),
            'brand',
            'collections',
            'price',
        ];
    }

    public function makeAllSearchableUsing(Builder $query): Builder
    {
        return parent::makeAllSearchableUsing($query)->with(['collections', 'variants.prices']);
    }

    public function toSearchableArray(Model $model): array
    {
        /** @var Product $model */
        $data = parent::toSearchableArray($model);

        $data['collections'] = $model->collections->pluck('id')->map(fn ($id) => (string) $id)->all();
        $data['price'] = $this->cheapestPrice($model);

        return $data;
    }

    /**
     * The cheapest variant's base price (no customer group) in the default currency,
     * as a float in major units — e.g. 19.99, not 1999. Null if the product has no
     * variant with a price in that currency yet, so it's excluded from price filters
     * rather than sorting to the bottom as if it were free.
     */
    private function cheapestPrice(Product $model): ?float
    {
        $currency = Currency::getDefault();

        $price = $model->variants
            ->flatMap(fn ($variant) => $variant->prices)
            ->filter(fn ($price) => $price->currency_id === $currency->id && $price->customer_group_id === null)
            ->min(fn ($price) => $price->price->value);

        return $price !== null ? $price / (10 ** $currency->decimal_places) : null;
    }
}