<?php
/**
 * When must an advert come down because its shop item is no longer for sale? Pure rules over plain facts.
 *
 * @package Tidelist
 */

namespace Tidelist\Sync;

/**
 * Takedown rules.
 */
final class TakedownRules {

	const ITEM_DELETED       = 'item_deleted';
	const ITEM_TRASHED       = 'item_trashed';
	const ITEM_UNPUBLISHED   = 'item_unpublished';
	const PARENT_DELETED     = 'parent_deleted';
	const PARENT_TRASHED     = 'parent_trashed';
	const PARENT_UNPUBLISHED = 'parent_unpublished';
	const OUT_OF_STOCK       = 'out_of_stock';
	const STOCK_ZERO         = 'stock_zero';

	/**
	 * Reason the advert must come down, or "" if it stays up.
	 *
	 * Facts: item_exists, item_status (the product or variation), parent_exists and parent_status (the parent
	 * product of a variation; for a simple product they repeat the item), manage_stock, stock, stock_status.
	 *
	 * Several pieces of an item stay up until its stock reaches 0: only stock <= 0 (or "out of stock") takes
	 * the advert down.
	 *
	 * @param array $facts Current facts about the item and its product.
	 */
	public static function reason( array $facts ): string {
		if ( empty( $facts['item_exists'] ) ) {
			return self::ITEM_DELETED;
		}
		if ( 'trash' === (string) ( $facts['item_status'] ?? '' ) ) {
			return self::ITEM_TRASHED;
		}
		if ( empty( $facts['parent_exists'] ) ) {
			return self::PARENT_DELETED;
		}
		$parent_status = (string) ( $facts['parent_status'] ?? '' );
		if ( 'trash' === $parent_status ) {
			return self::PARENT_TRASHED;
		}
		if ( 'publish' !== $parent_status ) {
			return self::PARENT_UNPUBLISHED;
		}
		if ( 'publish' !== (string) ( $facts['item_status'] ?? '' ) ) {
			return self::ITEM_UNPUBLISHED;
		}
		if ( 'outofstock' === (string) ( $facts['stock_status'] ?? '' ) ) {
			return self::OUT_OF_STOCK;
		}
		if ( ! empty( $facts['manage_stock'] ) && (int) ( $facts['stock'] ?? 0 ) <= 0 ) {
			return self::STOCK_ZERO;
		}
		return '';
	}

	/**
	 * Why an item cannot be advertised right now: "" when it can, "out_of_stock" when it has no stock (an advert for it would
	 * be a paid placement for something the shop cannot sell), "not_published" for any other reason it is not for sale.
	 *
	 * @param array $facts Current facts about the item and its product.
	 */
	public static function listing_block( array $facts ): string {
		$reason = self::reason( $facts );
		if ( self::OUT_OF_STOCK === $reason || self::STOCK_ZERO === $reason ) {
			return 'out_of_stock';
		}
		if ( '' !== $reason ) {
			return 'not_published';
		}
		// Not out of stock by the takedown rules, but still not "in stock" (for example on backorder).
		return self::can_relist( $facts ) ? '' : 'out_of_stock';
	}

	/**
	 * Whether an item that was taken down could be listed again: it is for sale and in stock.
	 *
	 * @param array $facts Current facts.
	 */
	public static function can_relist( array $facts ): bool {
		if ( '' !== self::reason( $facts ) ) {
			return false;
		}
		if ( ! empty( $facts['manage_stock'] ) ) {
			return (int) ( $facts['stock'] ?? 0 ) > 0;
		}
		return 'instock' === (string) ( $facts['stock_status'] ?? '' );
	}
}