<?php
/**
 * Product data extractor.
 *
 * Extracts and normalizes WooCommerce product data into a platform-agnostic
 * structure suitable for all feed formats. Includes memory management
 * by unsetting product objects after extraction.
 *
 * @package AICommerce\Feed
 */

declare(strict_types=1);

namespace AICommerce\Feed;

/**
 * Extracts normalized product data from WC_Product objects.
 */
class ProductDataExtractor {

	/**
	 * Memory threshold in bytes (32 MB). Triggers wp_cache_flush().
	 *
	 * @var int
	 */
	private const MEMORY_THRESHOLD = 33554432;

	/**
	 * Extract normalized data from a single product.
	 *
	 * @param \WC_Product $product The WooCommerce product.
	 *
	 * @return array Normalized product data.
	 */
	public function extract( \WC_Product $product ): array {
		$data = array(
			'id'                => $product->get_id(),
			'title'             => $product->get_name(),
			'description'       => wp_strip_all_tags( $product->get_description() ),
			'short_description' => wp_strip_all_tags( $product->get_short_description() ),
			'url'               => get_permalink( $product->get_id() ),
			'sku'               => $product->get_sku(),
			'price'             => $product->get_price(),
			'regular_price'     => $product->get_regular_price(),
			'sale_price'        => $product->get_sale_price(),
			'currency'          => get_woocommerce_currency(),
			'availability'      => $this->map_availability( $product->get_stock_status() ),
			'stock_quantity'    => $product->get_stock_quantity(),
			'condition'         => 'new',
			'brand'             => $this->get_brand( $product ),
			'gtin'              => $this->get_gtin( $product ),
			'mpn'               => $this->get_mpn( $product ),
			'isbn'              => $this->get_isbn( $product ),
			'images'            => $this->get_images( $product ),
			'categories'        => $this->get_categories( $product ),
			'weight'            => $product->get_weight(),
			'weight_unit'       => get_option( 'woocommerce_weight_unit', 'kg' ),
			'dimensions'        => $this->get_dimensions( $product ),
			'attributes'        => $this->get_attributes( $product ),
			'rating_value'      => $this->get_rating_value( $product ),
			'rating_count'      => $this->get_rating_count( $product ),
			'shipping_free'     => $this->is_free_shipping( $product ),
			'return_policy_url' => get_option( 'aicommerce_return_policy_url', '' ),
			'variants'          => array(),
			'is_variable'       => $product->is_type( 'variable' ),
			'parent_id'         => $product->get_parent_id(),
			'date_created'      => $product->get_date_created() ? $product->get_date_created()->format( 'c' ) : null,
			'date_modified'     => $product->get_date_modified() ? $product->get_date_modified()->format( 'c' ) : null,
		);

		// Group variants for variable products.
		if ( $product->is_type( 'variable' ) && $product instanceof \WC_Product_Variable ) {
			$data['variants'] = $this->extract_variants( $product );
		}

		/**
		 * Filters the normalized product data for feed generation.
		 *
		 * @param array       $data    Normalized product data.
		 * @param \WC_Product $product The WooCommerce product.
		 */
		return apply_filters( 'aicommerce_feed_product_data', $data, $product );
	}

	/**
	 * Extract data from multiple products with memory management.
	 *
	 * Unsets each product after extraction and flushes the object cache
	 * if memory usage exceeds the threshold.
	 *
	 * @param array $products Array of WC_Product objects.
	 *
	 * @return array Array of normalized product data.
	 */
	public function extract_batch( array $products ): array {
		$extracted = array();

		foreach ( $products as $key => $product ) {
			if ( ! $product instanceof \WC_Product ) {
				continue;
			}

			$extracted[] = $this->extract( $product );

			// Memory management: release product reference.
			unset( $products[ $key ] );

			// Flush object cache if memory usage is high.
			if ( memory_get_usage( true ) > self::MEMORY_THRESHOLD ) {
				wp_cache_flush();
			}
		}

		return $extracted;
	}

	/**
	 * Map WooCommerce stock status to feed availability values.
	 *
	 * @param string $stock_status WC stock status.
	 *
	 * @return string Feed-compatible availability value.
	 */
	private function map_availability( string $stock_status ): string {
		$map = array(
			'instock'     => 'in_stock',
			'outofstock'  => 'out_of_stock',
			'onbackorder' => 'backorder',
		);

		return $map[ $stock_status ] ?? 'out_of_stock';
	}

	/**
	 * Get brand with fallback chain.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return string Brand name or empty string.
	 */
	private function get_brand( \WC_Product $product ): string {
		$brand = $product->get_meta( '_aicommerce_brand' );
		if ( empty( $brand ) ) {
			$brand = $product->get_meta( '_wc_brand' );
		}
		if ( empty( $brand ) && taxonomy_exists( 'product_brand' ) ) {
			$brand_terms = get_the_terms( $product->get_id(), 'product_brand' );
			if ( is_array( $brand_terms ) && ! empty( $brand_terms ) ) {
				$brand = $brand_terms[0]->name;
			}
		}
		if ( empty( $brand ) ) {
			$brand = get_option( 'aicommerce_default_brand', '' );
		}

		return (string) $brand;
	}

	/**
	 * Get GTIN with fallback chain.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return string GTIN or empty string.
	 */
	private function get_gtin( \WC_Product $product ): string {
		$gtin = $product->get_meta( '_aicommerce_gtin' );
		if ( empty( $gtin ) && method_exists( $product, 'get_global_unique_id' ) ) {
			$gtin = $product->get_global_unique_id();
		}
		if ( empty( $gtin ) ) {
			$gtin = $product->get_meta( '_global_unique_id' );
		}

		return (string) $gtin;
	}

	/**
	 * Get MPN with fallback chain.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return string MPN or empty string.
	 */
	private function get_mpn( \WC_Product $product ): string {
		$mpn = $product->get_meta( '_aicommerce_mpn' );
		if ( empty( $mpn ) ) {
			$mpn = $product->get_meta( '_mpn' );
		}

		return (string) $mpn;
	}

	/**
	 * Get ISBN from product meta.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return string ISBN or empty string.
	 */
	private function get_isbn( \WC_Product $product ): string {
		$isbn = $product->get_meta( '_aicommerce_isbn' );
		if ( empty( $isbn ) ) {
			$isbn = $product->get_meta( '_isbn' );
		}

		return (string) $isbn;
	}

	/**
	 * Get all product images with alt text.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array Array of image data arrays with 'url' and 'alt' keys.
	 */
	private function get_images( \WC_Product $product ): array {
		$images = array();

		$main_id = $product->get_image_id();
		if ( $main_id ) {
			$url = wp_get_attachment_url( $main_id );
			if ( $url ) {
				$alt      = get_post_meta( $main_id, '_wp_attachment_image_alt', true );
				$images[] = array(
					'url' => $url,
					'alt' => is_string( $alt ) ? $alt : '',
				);
			}
		}

		foreach ( $product->get_gallery_image_ids() as $gallery_id ) {
			$url = wp_get_attachment_url( $gallery_id );
			if ( $url ) {
				$alt      = get_post_meta( $gallery_id, '_wp_attachment_image_alt', true );
				$images[] = array(
					'url' => $url,
					'alt' => is_string( $alt ) ? $alt : '',
				);
			}
		}

		return $images;
	}

	/**
	 * Get product categories with parent info.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array Array of category data.
	 */
	private function get_categories( \WC_Product $product ): array {
		$terms = get_the_terms( $product->get_id(), 'product_cat' );
		if ( ! is_array( $terms ) ) {
			return array();
		}

		$categories = array();
		foreach ( $terms as $term ) {
			$categories[] = array(
				'id'        => $term->term_id,
				'name'      => $term->name,
				'slug'      => $term->slug,
				'parent_id' => $term->parent,
			);
		}

		return $categories;
	}

	/**
	 * Get product dimensions.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array Dimension data.
	 */
	private function get_dimensions( \WC_Product $product ): array {
		return array(
			'length' => $product->get_length(),
			'width'  => $product->get_width(),
			'height' => $product->get_height(),
			'unit'   => get_option( 'woocommerce_dimension_unit', 'cm' ),
		);
	}

	/**
	 * Get product attributes.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return array Array of attribute data.
	 */
	private function get_attributes( \WC_Product $product ): array {
		$attributes = array();

		foreach ( $product->get_attributes() as $key => $attribute ) {
			if ( is_object( $attribute ) && method_exists( $attribute, 'get_options' ) ) {
				$attributes[ $key ] = array(
					'name'    => wc_attribute_label( $key, $product ),
					'options' => $attribute->get_options(),
					'visible' => $attribute->get_visible(),
				);
			}
		}

		return $attributes;
	}

	/**
	 * Get average product rating.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return float Average rating or 0.
	 */
	private function get_rating_value( \WC_Product $product ): float {
		if ( method_exists( $product, 'get_average_rating' ) ) {
			return (float) $product->get_average_rating();
		}

		return 0.0;
	}

	/**
	 * Get number of product ratings/reviews.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return int Rating count.
	 */
	private function get_rating_count( \WC_Product $product ): int {
		if ( method_exists( $product, 'get_rating_count' ) ) {
			return (int) $product->get_rating_count();
		}

		return 0;
	}

	/**
	 * Check if product qualifies for free shipping.
	 *
	 * @param \WC_Product $product The product.
	 *
	 * @return bool True if free shipping applies.
	 */
	private function is_free_shipping( \WC_Product $product ): bool {
		$shipping_class = $product->get_shipping_class();
		return 'free-shipping' === $shipping_class || 'free_shipping' === $shipping_class;
	}

	/**
	 * Extract variants for a variable product.
	 *
	 * @param \WC_Product_Variable $product The variable product.
	 *
	 * @return array Array of variant data.
	 */
	private function extract_variants( \WC_Product_Variable $product ): array {
		$variants      = array();
		$variation_ids = $product->get_children();

		foreach ( $variation_ids as $variation_id ) {
			$variation = wc_get_product( $variation_id );
			if ( ! $variation instanceof \WC_Product_Variation ) {
				continue;
			}

			$image_url = '';
			$image_alt = '';
			if ( $variation->get_image_id() ) {
				$image_url = wp_get_attachment_url( $variation->get_image_id() );
				$alt       = get_post_meta( $variation->get_image_id(), '_wp_attachment_image_alt', true );
				$image_alt = is_string( $alt ) ? $alt : '';
			}

			$variants[] = array(
				'id'             => $variation->get_id(),
				'sku'            => $variation->get_sku(),
				'price'          => $variation->get_price(),
				'regular_price'  => $variation->get_regular_price(),
				'sale_price'     => $variation->get_sale_price(),
				'availability'   => $this->map_availability( $variation->get_stock_status() ),
				'stock_quantity' => $variation->get_stock_quantity(),
				'gtin'           => $this->get_gtin( $variation ),
				'mpn'            => $this->get_mpn( $variation ),
				'image'          => $image_url ?: '',
				'image_alt'      => $image_alt,
				'attributes'     => $variation->get_variation_attributes(),
				'weight'         => $variation->get_weight(),
				'dimensions'     => array(
					'length' => $variation->get_length(),
					'width'  => $variation->get_width(),
					'height' => $variation->get_height(),
				),
			);

			// Release variation reference.
			unset( $variation );
		}

		return $variants;
	}
}