/**
 * Sorts products by price, using their currency-specific prices.
 * 
 * HOW TO USE THIS CODE
 * This code shows how to override the "sort by price" logic used by WooCommerce, to ensure that products
 * are sorted using their currency-specific price.
 *
 * DISCLAIMER
 * THE USE OF THIS CODE IS AT YOUR OWN RISK. You remain fully liable for compliance with tax laws.
 * This code is offered free of charge and there is no warranty for it, to the extent permitted by applicable law.
 * Except when otherwise stated in writing the copyright holders and/or other parties provide the program "as is"
 * without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of
 * merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the program
 * is with you. Should the program prove defective, you assume the cost of all necessary servicing, repair or correction.
 *
 * The code is provided as an example and it's not covered by our support service. We won't be able to offer free support
 * in relation to it. Should you need a consultation, or assistance to customise this code, you can contact us to avail
 * of our paid consultation services: https://aelia.co/hire_us 
 */
class Aelia_Live_Product_Sort {
	protected static $query_order = '';
	protected static $query_limits = array();

	/**
	 * Fetches the prices of all the products in the catalogue.
	 *
	 * @param string currency
	 * @return array
	 */
	protected static function fetch_product_prices(string $currency = null) {
		$transient_id = implode('_', array(
			'wc_aelia_get_all_product_prices',
			$currency ?? get_woocommerce_currency(),
			WC_Cache_Helper::get_transient_version('product'),
		));
		$product_prices = get_transient($transient_id);
		if($product_prices === false) {
			global $wpdb;

			$sql = "
				SELECT DISTINCT product_id
				FROM {$wpdb->wc_product_meta_lookup}
			";

			$product_prices = array();
			foreach(wp_list_pluck($wpdb->get_results($sql), 'product_id') as $product_id) {
				$product = wc_get_product($product_id);

				// Skip invalid products and variations
				if(!$product instanceof \WC_Product || $product instanceof \WC_Product_Variation) {
					continue;
				}

				$product_prices[$product_id] = array();

				if($product instanceof \WC_Product_Variable) {
					$children_prices = array();
					// Fetch the price of each variation
					foreach($product->get_visible_children() as $child_product_id) {
						$children_prices[] = apply_filters('wc_aelia_cs_get_product_base_price_in_currency', get_post_meta('_price', $child_product_id, true), $child_product_id);
					}

					$product_prices[$product_id]['min'] = !empty($children_prices) ? min($children_prices) : '';
					$product_prices[$product_id]['max'] = !empty($children_prices) ? max($children_prices) : '';
				}
				else {
					$product_prices[$product_id]['max'] = $product_prices[$product_id]['min'] = apply_filters('wc_aelia_cs_get_product_base_price_in_currency', get_post_meta('_price', $product_id, true), $product_id);
				}
			}
			if(is_array($product_prices)) {
				// Cache the products, for performance
				set_transient($transient_id, $product_prices, HOUR_IN_SECONDS);
			}
		}

		return $product_prices;
	}

	/**
	 * Given a "LIMIT x, y" clause, returns an array with the start and length.
	 *
	 * @param string $limits
	 * @return array
	 */
	protected static function extract_query_limits(string $limits): array {
		$limit_parts = explode(',', str_replace('LIMIT ', '', $limits));
		$limit_parts = array_filter(array_map(function($value) {
			$value = trim($value);
			return is_numeric($value) ? (int)$value : '';
		}, $limit_parts));

		if(empty($limit_parts)) {
			return array(
				'start' => 0,
				'length' => null,
			);
		}

		return array(
			'start' => (count($limit_parts) > 1) ? array_shift($limit_parts) : 0,
			'length' => array_shift($limit_parts),
		);
	}

	/**
	 * Overrides the limits set against a WP_Query, so that it always returns
	 * all the products.
	 *
	 * @param string $limits
	 * @param WP_Query $query
	 * @return string
	 */
	public static function post_limits_request($limits, $query): string {
		self::$query_limits = self::extract_query_limits($limits);

		remove_filter('post_limits_request', array(__CLASS__, 'post_limits_request'), 10, 2);

		return '';
	}

	/**
	 * Filters the list of posts returned by a WP_Query, doing the following:
	 * - Sorts them by the applicable price in the active currency.
	 * - Returns only the posts that fall into the LIMITS set for the query.
	 *
	 * @param array $posts
	 * @param WP_Query $wp_query
	 * @return array
	 */
	public static function posts_results($posts, $wp_query) {
		remove_filter('posts_results', array(__CLASS__, 'posts_results'), 99, 2);

		$price_type = (self::$query_order === 'DESC') ? 'max' : 'min';

		// Fetch all the product prices
		$product_prices = wp_list_pluck(self::fetch_product_prices(), $price_type);
		// Extract the numeric prices
		$numeric_prices = array_filter($product_prices, 'is_numeric');

		// Sort the numeric prices in ascending or descending order
		if(self::$query_order === 'DESC') {
			arsort($numeric_prices, SORT_NUMERIC);
		}
		else {
			asort($numeric_prices, SORT_NUMERIC);
		}

		// Return a list of post, sorted as follows
		// - All the products with a numeric price, in ascending or descending order
		// - All the product with a non-numeric price, in any order
		$ordered_product_ids = array_flip(array_keys($numeric_prices + array_diff_key($product_prices, $numeric_prices)));

		uasort($posts, function($a, $b) use ($ordered_product_ids) {
			$a_pos = $ordered_product_ids[$a->ID] ?? -1;
			$b_pos = $ordered_product_ids[$b->ID] ?? -1;

			return $a_pos <=> $b_pos;
		});

		return array_slice($posts, self::$query_limits['start'], self::$query_limits['length']);
	}

	/**
	 * Intercepts the ordering arguments set against a WC_Query, to enable the sorting
	 * by price in active currency.
	 *
	 * @param array $args
	 * @param string $orderby
	 * @param string $order
	 * @return array
	 */
	public static function woocommerce_get_catalog_ordering_args($args, $orderby, $order) {
		if($orderby === 'price') {
			self::$query_order = $order;

			add_filter('post_limits_request', array(__CLASS__, 'post_limits_request'), 10, 2);
			add_filter('posts_results', array(__CLASS__, 'posts_results'), 99, 2);
		}
		return $args;
	}

	public static function init() {
		add_filter('woocommerce_get_catalog_ordering_args', array(__CLASS__, 'woocommerce_get_catalog_ordering_args'), 99, 3);
	}
}

Aelia_Live_Product_Sort::init();