<?php
namespace Automattic\WooCommerce\StoreApi\Schemas\V1;

use Automattic\WooCommerce\Enums\ProductType;
use Automattic\WooCommerce\StoreApi\SchemaController;
use Automattic\WooCommerce\StoreApi\Schemas\ExtendSchema;
use Automattic\WooCommerce\StoreApi\Utilities\QuantityLimits;
use Automattic\WooCommerce\Blocks\Utils\ProductAvailabilityUtils;
use Automattic\WooCommerce\Enums\ProductStockStatus;

/**
 * ProductSchema class.
 */
class ProductSchema extends AbstractSchema {
	/**
	 * The schema item name.
	 *
	 * @var string
	 */
	protected $title = 'product';

	/**
	 * The schema item identifier.
	 *
	 * @var string
	 */
	const IDENTIFIER = 'product';

	/**
	 * Image attachment schema instance.
	 *
	 * @var ImageAttachmentSchema
	 */
	protected $image_attachment_schema;

	/**
	 * Constructor.
	 *
	 * @param ExtendSchema     $extend Rest Extending instance.
	 * @param SchemaController $controller Schema Controller instance.
	 */
	public function __construct( ExtendSchema $extend, SchemaController $controller ) {
		parent::__construct( $extend, $controller );
		$this->image_attachment_schema = $this->controller->get( ImageAttachmentSchema::IDENTIFIER );
	}

	/**
	 * Product schema properties.
	 *
	 * @return array
	 */
	public function get_properties() {
		return [
			'id'                    => [
				'description' => __( 'Unique identifier for the resource.', 'woocommerce' ),
				'type'        => 'integer',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'name'                  => [
				'description' => __( 'Product name.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
			],
			'slug'                  => [
				'description' => __( 'Product slug.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
			],
			'parent'                => [
				'description' => __( 'ID of the parent product, if applicable.', 'woocommerce' ),
				'type'        => 'integer',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'type'                  => [
				'description' => __( 'Product type.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'variation'             => [
				'description' => __( 'Product variation attributes, if applicable.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
			],
			'permalink'             => [
				'description' => __( 'Product URL.', 'woocommerce' ),
				'type'        => 'string',
				'format'      => 'uri',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'short_description'     => [
				'description' => __( 'Product short description in HTML format.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
			],
			'description'           => [
				'description' => __( 'Product full description in HTML format.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
			],
			'on_sale'               => [
				'description' => __( 'Is the product on sale?', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'sku'                   => [
				'description' => __( 'Unique identifier.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
			],
			'prices'                => [
				'description' => __( 'Price data provided using the smallest unit of the currency.', 'woocommerce' ),
				'type'        => 'object',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
				'properties'  => array_merge(
					$this->get_store_currency_properties(),
					[
						'price'         => [
							'description' => __( 'Current product price.', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'regular_price' => [
							'description' => __( 'Regular product price.', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'sale_price'    => [
							'description' => __( 'Sale product price, if applicable.', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'price_range'   => [
							'description' => __( 'Price range, if applicable.', 'woocommerce' ),
							'type'        => [ 'object', 'null' ],
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
							'properties'  => [
								'min_amount' => [
									'description' => __( 'Price amount.', 'woocommerce' ),
									'type'        => 'string',
									'context'     => [ 'view', 'edit', 'embed' ],
									'readonly'    => true,
								],
								'max_amount' => [
									'description' => __( 'Price amount.', 'woocommerce' ),
									'type'        => 'string',
									'context'     => [ 'view', 'edit', 'embed' ],
									'readonly'    => true,
								],
							],
						],
					]
				),
			],
			'price_html'            => array(
				'description' => __( 'Price string formatted as HTML.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => array( 'view', 'edit', 'embed' ),
				'readonly'    => true,
			),
			'average_rating'        => [
				'description' => __( 'Reviews average rating.', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'review_count'          => [
				'description' => __( 'Amount of reviews that the product has.', 'woocommerce' ),
				'type'        => 'integer',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'images'                => [
				'description' => __( 'List of images.', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'type'       => 'object',
					'properties' => $this->image_attachment_schema->get_properties(),
				],
			],
			'categories'            => [
				'description' => __( 'List of categories, if applicable.', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'type'       => 'object',
					'properties' => [
						'id'   => [
							'description' => __( 'Category ID', 'woocommerce' ),
							'type'        => 'number',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'name' => [
							'description' => __( 'Category name', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'slug' => [
							'description' => __( 'Category slug', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'link' => [
							'description' => __( 'Category link', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
					],
				],
			],
			'tags'                  => [
				'description' => __( 'List of tags, if applicable.', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'type'       => 'object',
					'properties' => [
						'id'   => [
							'description' => __( 'Tag ID', 'woocommerce' ),
							'type'        => 'number',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'name' => [
							'description' => __( 'Tag name', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'slug' => [
							'description' => __( 'Tag slug', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'link' => [
							'description' => __( 'Tag link.', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
					],
				],
			],
			'brands'                => [
				'description' => __( 'List of brands, if applicable.', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'type'       => 'object',
					'properties' => [
						'id'   => [
							'description' => __( 'Brand ID', 'woocommerce' ),
							'type'        => 'number',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'name' => [
							'description' => __( 'Brand name', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'slug' => [
							'description' => __( 'Brand slug', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'link' => [
							'description' => __( 'Brand link', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
					],
				],
			],
			'attributes'            => [
				'description' => __( 'List of attributes (taxonomy terms) assigned to the product. For variable products, these are mapped to variations (see the `variations` field).', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'type'       => 'object',
					'properties' => [
						'id'             => [
							'description' => __( 'The attribute ID, or 0 if the attribute is not taxonomy based.', 'woocommerce' ),
							'type'        => 'integer',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'name'           => [
							'description' => __( 'The attribute name.', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'taxonomy'       => [
							'description' => __( 'The attribute taxonomy, or null if the attribute is not taxonomy based.', 'woocommerce' ),
							'type'        => 'string',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'has_variations' => [
							'description' => __( 'True if this attribute is used by product variations.', 'woocommerce' ),
							'type'        => 'boolean',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'terms'          => [
							'description' => __( 'List of assigned attribute terms.', 'woocommerce' ),
							'type'        => 'array',
							'context'     => [ 'view', 'edit', 'embed' ],
							'items'       => [
								'type'       => 'object',
								'properties' => [
									'id'      => [
										'description' => __( 'The term ID, or 0 if the attribute is not a global attribute.', 'woocommerce' ),
										'type'        => 'integer',
										'context'     => [ 'view', 'edit', 'embed' ],
										'readonly'    => true,
									],
									'name'    => [
										'description' => __( 'The term name.', 'woocommerce' ),
										'type'        => 'string',
										'context'     => [ 'view', 'edit', 'embed' ],
										'readonly'    => true,
									],
									'slug'    => [
										'description' => __( 'The term slug.', 'woocommerce' ),
										'type'        => 'string',
										'context'     => [ 'view', 'edit', 'embed' ],
										'readonly'    => true,
									],
									'default' => [
										'description' => __( 'If this is a default attribute', 'woocommerce' ),
										'type'        => 'boolean',
										'context'     => [ 'view', 'edit', 'embed' ],
										'readonly'    => true,
									],
								],
							],
						],
					],
				],
			],
			'variations'            => [
				'description' => __( 'List of variation IDs, if applicable.', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'type'       => 'object',
					'properties' => [
						'id'         => [
							'description' => __( 'The attribute ID, or 0 if the attribute is not taxonomy based.', 'woocommerce' ),
							'type'        => 'integer',
							'context'     => [ 'view', 'edit', 'embed' ],
							'readonly'    => true,
						],
						'attributes' => [
							'description' => __( 'List of variation attributes.', 'woocommerce' ),
							'type'        => 'array',
							'context'     => [ 'view', 'edit', 'embed' ],
							'items'       => [
								'type'       => 'object',
								'properties' => [
									'name'  => [
										'description' => __( 'The attribute name.', 'woocommerce' ),
										'type'        => 'string',
										'context'     => [ 'view', 'edit', 'embed' ],
										'readonly'    => true,
									],
									'value' => [
										'description' => __( 'The assigned attribute.', 'woocommerce' ),
										'type'        => 'string',
										'context'     => [ 'view', 'edit', 'embed' ],
										'readonly'    => true,
									],
								],
							],
						],
					],
				],
			],
			'grouped_products'      => [
				'description' => __( 'List of grouped product IDs, if applicable.', 'woocommerce' ),
				'type'        => 'array',
				'context'     => [ 'view', 'edit', 'embed' ],
				'items'       => [
					'description' => __( 'List of grouped product ids.', 'woocommerce' ),
					'type'        => 'integer',
					'context'     => [ 'view', 'edit', 'embed' ],
					'readonly'    => true,
				],
			],
			'has_options'           => [
				'description' => __( 'Does the product have additional options before it can be added to the cart?', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'is_purchasable'        => [
				'description' => __( 'Is the product purchasable?', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'is_in_stock'           => [
				'description' => __( 'Is the product in stock?', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'is_on_backorder'       => [
				'description' => __( 'Is the product stock backordered? This will also return false if backorder notifications are turned off.', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'stock_availability'    => [
				'description' => __( 'Information about the product\'s availability.', 'woocommerce' ),
				'type'        => 'object',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
				'properties'  => [
					'text'  => [
						'description' => __( 'Stock availability text.', 'woocommerce' ),
						'type'        => 'string',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
					'class' => [
						'description' => __( 'Stock availability class.', 'woocommerce' ),
						'type'        => 'string',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
				],
			],
			'low_stock_remaining'   => [
				'description' => __( 'Quantity left in stock if stock is low, or null if not applicable.', 'woocommerce' ),
				'type'        => [ 'number', 'null' ],
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'sold_individually'     => [
				'description' => __( 'If true, only one item of this product is allowed for purchase in a single order.', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			'weight'                => [
				'description' => sprintf(
					/* translators: %s: weight unit */
					__( 'Product weight (%s).', 'woocommerce' ),
					get_option( 'woocommerce_weight_unit' )
				),
				'type'        => 'string',
				'context'     => [ 'view', 'edit' ],
				'readonly'    => true,
			],
			'dimensions'            => [
				'description' => __( 'Product dimensions.', 'woocommerce' ),
				'type'        => 'object',
				'context'     => [ 'view', 'edit' ],
				'readonly'    => true,
				'properties'  => [
					'length' => [
						'description' => sprintf(
							/* translators: %s: dimension unit */
							__( 'Product length (%s).', 'woocommerce' ),
							get_option( 'woocommerce_dimension_unit' )
						),
						'type'        => 'string',
						'context'     => [ 'view', 'edit' ],
						'readonly'    => true,
					],
					'width'  => [
						'description' => sprintf(
							/* translators: %s: dimension unit */
							__( 'Product width (%s).', 'woocommerce' ),
							get_option( 'woocommerce_dimension_unit' )
						),
						'type'        => 'string',
						'context'     => [ 'view', 'edit' ],
						'readonly'    => true,
					],
					'height' => [
						'description' => sprintf(
							/* translators: %s: dimension unit */
							__( 'Product height (%s).', 'woocommerce' ),
							get_option( 'woocommerce_dimension_unit' )
						),
						'type'        => 'string',
						'context'     => [ 'view', 'edit' ],
						'readonly'    => true,
					],
				],
			],
			'formatted_weight'      => [
				'description' => __( 'Product weight formatted for display (e.g. "2.5 kg").', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit' ],
				'readonly'    => true,
			],
			'formatted_dimensions'  => [
				'description' => __( 'Product dimensions formatted for display (e.g. "10 × 5 × 3 cm").', 'woocommerce' ),
				'type'        => 'string',
				'context'     => [ 'view', 'edit' ],
				'readonly'    => true,
			],
			'add_to_cart'           => [
				'description' => __( 'Add to cart button parameters.', 'woocommerce' ),
				'type'        => 'object',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
				'properties'  => [
					'text'        => [
						'description' => __( 'Button text.', 'woocommerce' ),
						'type'        => 'string',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
					'description' => [
						'description' => __( 'Button description.', 'woocommerce' ),
						'type'        => 'string',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
					'url'         => [
						'description' => __( 'Add to cart URL.', 'woocommerce' ),
						'type'        => 'string',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
					'minimum'     => [
						'description' => __( 'The minimum quantity that can be added to the cart.', 'woocommerce' ),
						'type'        => 'number',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
					'maximum'     => [
						'description' => __( 'The maximum quantity that can be added to the cart.', 'woocommerce' ),
						'type'        => 'number',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
					'multiple_of' => [
						'description' => __( 'The amount that quantities increment by. Quantity must be an multiple of this value.', 'woocommerce' ),
						'type'        => 'number',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
						'default'     => 1,
					],
					'single_text' => [
						'description' => __( 'Button text in the single product page.', 'woocommerce' ),
						'type'        => 'string',
						'context'     => [ 'view', 'edit', 'embed' ],
						'readonly'    => true,
					],
				],
			],
			'is_password_protected' => [
				'description' => __( 'Whether the product requires a password to access its content.', 'woocommerce' ),
				'type'        => 'boolean',
				'context'     => [ 'view', 'edit', 'embed' ],
				'readonly'    => true,
			],
			self::EXTENDING_KEY     => $this->get_extended_schema( self::IDENTIFIER ),
		];
	}

	/**
	 * Convert a WooCommerce product into an object suitable for the response.
	 *
	 * @param \WC_Product $product Product instance.
	 * @return array
	 */
	public function get_item_response( $product ) {
		$availability      = ProductAvailabilityUtils::get_product_availability( $product );
		$password_required = post_password_required( $product->get_id() );
		$short_description = $password_required ? '' : $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_short_description() ) ) );
		$description       = $password_required ? '' : $this->prepare_html_response( wc_format_content( wp_kses_post( $product->get_description() ) ) );

		return [
			'id'                    => $product->get_id(),
			'name'                  => $this->prepare_html_response( $product->get_title() ),
			'slug'                  => $product->get_slug(),
			'parent'                => $product->get_parent_id(),
			'type'                  => $product->get_type(),
			'variation'             => $this->prepare_html_response( $product->is_type( ProductType::VARIATION ) ? wc_get_formatted_variation( $product, true, true, false ) : '' ),
			'permalink'             => $product->get_permalink(),
			'sku'                   => $this->prepare_html_response( $product->get_sku() ),
			'short_description'     => $short_description,
			'description'           => $description,
			'on_sale'               => $product->is_on_sale(),
			'prices'                => (object) $this->prepare_product_price_response( $product ),
			'price_html'            => $this->prepare_html_response( $product->get_price_html() ),
			'average_rating'        => (string) $product->get_average_rating(),
			'review_count'          => $product->get_review_count(),
			'images'                => $this->get_images( $product ),
			'categories'            => $this->get_term_list( $product, 'product_cat' ),
			'tags'                  => $this->get_term_list( $product, 'product_tag' ),
			'brands'                => $this->get_term_list( $product, 'product_brand' ),
			'attributes'            => $this->get_attributes( $product ),
			'variations'            => $this->get_variations( $product ),
			'grouped_products'      => $this->get_grouped_products( $product ),
			'has_options'           => $product->has_options(),
			'is_purchasable'        => $product->is_purchasable(),
			'is_in_stock'           => $product->is_in_stock(),
			'is_on_backorder'       => ProductStockStatus::ON_BACKORDER === $product->get_stock_status(),
			'low_stock_remaining'   => $this->get_low_stock_remaining( $product ),
			'stock_availability'    => (object) array(
				'text'  => $availability['availability'] ?? '',
				'class' => $availability['class'] ?? '',
			),
			'sold_individually'     => $product->is_sold_individually(),
			'weight'                => $product->get_weight(),
			'dimensions'            => (object) [
				'length' => $product->get_length(),
				'width'  => $product->get_width(),
				'height' => $product->get_height(),
			],
			'formatted_weight'      => wc_format_weight( (float) $product->get_weight() ),
			'formatted_dimensions'  => html_entity_decode( wc_format_dimensions( (array) $product->get_dimensions( false ) ), ENT_QUOTES, get_bloginfo( 'charset' ) ),
			'add_to_cart'           => (object) array_merge(
				[
					'text'        => $this->prepare_html_response( $product->add_to_cart_text() ),
					'description' => $this->prepare_html_response( $product->add_to_cart_description() ),
					'url'         => $this->prepare_html_response( $product->add_to_cart_url() ),
					'single_text' => $this->prepare_html_response( $product->single_add_to_cart_text() ),
				],
				( new QuantityLimits() )->get_add_to_cart_limits( $product )
			),
			'is_password_protected' => '' !== $product->get_post_password(),
			self::EXTENDING_KEY     => $this->get_extended_data( self::IDENTIFIER, $product ),

		];
	}

	/**
	 * Get list of product images.
	 *
	 * @param \WC_Product $product Product instance.
	 * @return array
	 */
	protected function get_images( \WC_Product $product ) {
		$attachment_ids = array_merge( [ $product->get_image_id() ], $product->get_gallery_image_ids() );

		return array_values( array_filter( array_map( [ $this->image_attachment_schema, 'get_item_response' ], $attachment_ids ) ) );
	}

	/**
	 * Gets remaining stock amount for a product.
	 *
	 * @param \WC_Product $product Product instance.
	 * @return int|float|null
	 */
	protected function get_remaining_stock( \WC_Product $product ) {
		if ( is_null( $product->get_stock_quantity() ) ) {
			return null;
		}
		return $product->get_stock_quantity();
	}

	/**
	 * If a product has low stock, return the remaining stock amount for display.
	 *
	 * @param \WC_Product $product Product instance.
	 * @return int|float|null
	 */
	protected function get_low_stock_remaining( \WC_Product $product ) {
		$remaining_stock = $this->get_remaining_stock( $product );
		$stock_format    = get_option( 'woocommerce_stock_format' );

		// Don't show the low stock badge if the settings doesn't allow it.
		if ( 'no_amount' === $stock_format ) {
			return null;
		}

		// Show the low stock badge if the remaining stock is below or equal to the threshold.
		if ( ! is_null( $remaining_stock ) && $remaining_stock <= wc_get_low_stock_amount( $product ) ) {
			return max( $remaining_stock, 0 );
		}

		return null;
	}

	/**
	 * Returns true if the given attribute is valid.
	 *
	 * @param mixed $attribute Object or variable to check.
	 * @return boolean
	 */
	protected function filter_valid_attribute( $attribute ) {
		return is_a( $attribute, '\WC_Product_Attribute' );
	}

	/**
	 * Returns true if the given attribute is valid and used for variations.
	 *
	 * @param mixed $attribute Object or variable to check.
	 * @return boolean
	 */
	protected function filter_variation_attribute( $attribute ) {
		return $this->filter_valid_attribute( $attribute ) && $attribute->get_variation();
	}

	/**
	 * Get variation IDs and attributes from the DB.
	 *
	 * @param \WC_Product $product Product instance.
	 * @returns array
	 */
	protected function get_variations( \WC_Product $product ) {
		$variation_ids = $product->is_type( ProductType::VARIABLE ) ? $product->get_visible_children() : [];

		if ( ! count( $variation_ids ) ) {
			return [];
		}

		/**
		 * Gets default variation data which applies to all of this products variations.
		 */
		$attributes                  = array_filter( $product->get_attributes(), [ $this, 'filter_variation_attribute' ] );
		$default_variation_meta_data = array_reduce(
			$attributes,
			function ( $defaults, $attribute ) use ( $product ) {
				$meta_key              = wc_variation_attribute_name( $attribute->get_name() );
				$defaults[ $meta_key ] = [
					'name'  => wc_attribute_label( $attribute->get_name(), $product ),
					'value' => null,
				];
				return $defaults;
			},
			[]
		);
		$default_variation_meta_keys = array_keys( $default_variation_meta_data );

		/**
		 * Gets individual variation data from the database, using cache where possible.
		 */
		$cache_group   = 'product_variation_meta_data';
		$cache_value   = wp_cache_get( $product->get_id(), $cache_group );
		$last_modified = get_the_modified_date( 'U', $product->get_id() );

		if ( false === $cache_value || $last_modified !== $cache_value['last_modified'] ) {
			global $wpdb;
			// phpcs:disable WordPress.DB.PreparedSQL.NotPrepared
			$variation_meta_data = $wpdb->get_results(
				"
				SELECT post_id as variation_id, meta_key as attribute_key, meta_value as attribute_value
				FROM {$wpdb->postmeta}
				WHERE post_id IN (" . implode( ',', array_map( 'esc_sql', $variation_ids ) ) . ")
				AND meta_key IN ('" . implode( "','", array_map( 'esc_sql', $default_variation_meta_keys ) ) . "')
			"
			);
			// phpcs:enable

			wp_cache_set(
				$product->get_id(),
				[
					'last_modified' => $last_modified,
					'data'          => $variation_meta_data,
				],
				$cache_group
			);
		} else {
			$variation_meta_data = $cache_value['data'];
		}

		/**
		 * Merges and formats default variation data with individual variation data.
		 */
		$attributes_by_variation = array_reduce(
			$variation_meta_data,
			function ( $values, $data ) use ( $default_variation_meta_keys ) {
				// The query above only includes the keys of $default_variation_meta_data so we know all of the attributes
				// being processed here apply to this product. However, we need an additional check here because the
				// cache may have been primed elsewhere and include keys from other products.
				// @see AbstractProductGrid::prime_product_variations.
				if ( in_array( $data->attribute_key, $default_variation_meta_keys, true ) ) {
					$values[ $data->variation_id ][ $data->attribute_key ] = $data->attribute_value;
				}
				return $values;
			},
			array_fill_keys( $variation_ids, [] )
		);

		$variations = [];

		foreach ( $variation_ids as $variation_id ) {
			$attribute_data = $default_variation_meta_data;

			foreach ( $attributes_by_variation[ $variation_id ] as $meta_key => $meta_value ) {
				if ( '' !== $meta_value ) {
					$attribute_data[ $meta_key ]['value'] = $meta_value;
				}
			}

			$variations[] = (object) [
				'id'         => $variation_id,
				'attributes' => array_values( $attribute_data ),
			];
		}

		return $variations;
	}

	/**
	 * Get grouped product IDs.
	 *
	 * @param \WC_Product $product Product instance.
	 * @return array
	 */
	protected function get_grouped_products( \WC_Product $product ) {
		if ( $product->is_type( ProductType::GROUPED ) ) {
			return array_map(
				function ( $child ) {
					return $child->get_id();
				},
				$product->get_visible_children(),
			);
		}
		return [];
	}

	/**
	 * Get list of product attributes and attribute terms.
	 *
	 * @param \WC_Product $product Product instance.
	 * @return array
	 */
	protected function get_attributes( \WC_Product $product ) {
		$attributes         = array_filter( $product->get_attributes(), [ $this, 'filter_valid_attribute' ] );
		$default_attributes = $product->get_default_attributes();
		$return             = [];

		foreach ( $attributes as $attribute_slug => $attribute ) {
			// Only visible or variation attributes will be exposed by this API.
			if ( ! $attribute->get_visible() && ! $attribute->get_variation() ) {
				continue;
			}

			$terms = $attribute->is_taxonomy() ? array_map( [ $this, 'prepare_product_attribute_taxonomy_value' ], $attribute->get_terms() ) : array_map( [ $this, 'prepare_product_attribute_value' ], $attribute->get_options() );
			// Custom attribute names are sanitized to be the array keys.
			// So when we do the array_key_exists check below we also need to sanitize the attribute names.

			$sanitized_attribute_name = sanitize_key( $attribute->get_name() );

			if ( array_key_exists( $sanitized_attribute_name, $default_attributes ) ) {
				foreach ( $terms as $term ) {
					$term->default = $term->slug === $default_attributes[ $sanitized_attribute_name ];
				}
			}

			$return[] = (object) [
				'id'             => $attribute->get_id(),
				'name'           => wc_attribute_label( $attribute->get_name(), $product ),
				'taxonomy'       => $attribute->is_taxonomy() ? $attribute->get_name() : null,
				'has_variations' => true === $attribute->get_variation(),
				'terms'          => $terms,
			];
		}

		return $return;
	}

	/**
	 * Prepare an attribute term for the response.
	 *
	 * @param \WP_Term $term Term object.
	 * @return object
	 */
	protected function prepare_product_attribute_taxonomy_value( \WP_Term $term ) {
		return $this->prepare_product_attribute_value( $term->name, $term->term_id, $term->slug );
	}

	/**
	 * Prepare an attribute term for the response.
	 *
	 * @param string $name Attribute term name.
	 * @param int    $id Attribute term ID.
	 * @param string $slug Attribute term slug.
	 * @return object
	 */
	protected function prepare_product_attribute_value( $name, $id = 0, $slug = '' ) {
		return (object) [
			'id'   => (int) $id,
			'name' => $name,
			'slug' => $slug ? $slug : $name,
		];
	}

	/**
	 * Get an array of pricing data.
	 *
	 * @param \WC_Product $product Product instance.
	 * @param string      $tax_display_mode If returned prices are incl or excl of tax.
	 * @return array
	 */
	protected function prepare_product_price_response( \WC_Product $product, $tax_display_mode = '' ) {
		$prices           = [];
		$tax_display_mode = $this->get_tax_display_mode( $tax_display_mode );
		$price_function   = $this->get_price_function_from_tax_display_mode( $tax_display_mode );

		// If we have a variable product, get the price from the variations (this will use the min value).
		if ( $product->is_type( ProductType::VARIABLE ) ) {
			$regular_price = $product->get_variation_regular_price();
			$sale_price    = $product->get_variation_sale_price();
		} else {
			$regular_price = $product->get_regular_price();
			$sale_price    = $product->get_sale_price();
		}

		$prices['price']         = $this->prepare_money_response( $price_function( $product ), wc_get_price_decimals() );
		$prices['regular_price'] = $this->prepare_money_response( $price_function( $product, [ 'price' => $regular_price ] ), wc_get_price_decimals() );
		$prices['sale_price']    = $this->prepare_money_response( $price_function( $product, [ 'price' => $sale_price ] ), wc_get_price_decimals() );
		$prices['price_range']   = $this->get_price_range( $product, $tax_display_mode );

		return $this->prepare_currency_response( $prices );
	}

	/**
	 * WooCommerce can return prices including or excluding tax; choose the correct method based on tax display mode.
	 *
	 * @param string $tax_display_mode Provided tax display mode.
	 * @return string Valid tax display mode.
	 */
	protected function get_tax_display_mode( $tax_display_mode = '' ) {
		return in_array( $tax_display_mode, [ 'incl', 'excl' ], true ) ? $tax_display_mode : get_option( 'woocommerce_tax_display_shop' );
	}

	/**
	 * WooCommerce can return prices including or excluding tax; choose the correct method based on tax display mode.
	 *
	 * @param string $tax_display_mode If returned prices are incl or excl of tax.
	 * @return string Function name.
	 */
	protected function get_price_function_from_tax_display_mode( $tax_display_mode ) {
		return 'incl' === $tax_display_mode ? 'wc_get_price_including_tax' : 'wc_get_price_excluding_tax';
	}

	/**
	 * Get price range from certain product types.
	 *
	 * @param \WC_Product $product Product instance.
	 * @param string      $tax_display_mode If returned prices are incl or excl of tax.
	 * @return object|null
	 */
	protected function get_price_range( \WC_Product $product, $tax_display_mode = '' ) {
		$tax_display_mode = $this->get_tax_display_mode( $tax_display_mode );

		if ( $product->is_type( ProductType::VARIABLE ) ) {
			$prices = $product->get_variation_prices( true );

			if ( ! empty( $prices['price'] ) && ( min( $prices['price'] ) !== max( $prices['price'] ) ) ) {
				return (object) [
					'min_amount' => $this->prepare_money_response( min( $prices['price'] ), wc_get_price_decimals() ),
					'max_amount' => $this->prepare_money_response( max( $prices['price'] ), wc_get_price_decimals() ),
				];
			}
		}

		if ( $product->is_type( ProductType::GROUPED ) ) {
			$children       = $product->get_visible_children();
			$price_function = 'incl' === $tax_display_mode ? 'wc_get_price_including_tax' : 'wc_get_price_excluding_tax';

			foreach ( $children as $child ) {
				if ( '' !== $child->get_price() ) {
					$child_prices[] = $price_function( $child );
				}
			}

			if ( ! empty( $child_prices ) ) {
				return (object) [
					'min_amount' => $this->prepare_money_response( min( $child_prices ), wc_get_price_decimals() ),
					'max_amount' => $this->prepare_money_response( max( $child_prices ), wc_get_price_decimals() ),
				];
			}
		}

		return null;
	}

	/**
	 * Returns a list of terms assigned to the product.
	 *
	 * @param \WC_Product $product Product object.
	 * @param string      $taxonomy Taxonomy name.
	 * @return array Array of terms (id, name, slug).
	 */
	protected function get_term_list( \WC_Product $product, $taxonomy = '' ) {
		if ( ! $taxonomy ) {
			return [];
		}

		$terms = get_the_terms( $product->get_id(), $taxonomy );

		if ( ! $terms || is_wp_error( $terms ) ) {
			return [];
		}

		$return           = [];
		$default_category = (int) get_option( 'default_product_cat', 0 );

		foreach ( $terms as $term ) {
			$link = get_term_link( $term, $taxonomy );

			if ( is_wp_error( $link ) ) {
				continue;
			}

			if ( $term->term_id === $default_category ) {
				continue;
			}

			$return[] = (object) [
				'id'   => $term->term_id,
				'name' => $term->name,
				'slug' => $term->slug,
				'link' => $link,
			];
		}

		return $return;
	}
}
