<?php
namespace Strikewise\Display;

use Strikewise\Calculator\Reference;
use Strikewise\Calculator\ReferenceService;
use Strikewise\Pricing\Perishable;
use Strikewise\Pricing\PriceResolver;

defined( 'ABSPATH' ) || exit;

/**
 * CJEU mode (judgment C-330/23, Aldi Süd, 26.09.2024), on by default.
 *
 * An announced price reduction must refer to the lowest price of the 30 days
 * before the reduction. In CJEU mode:
 * - the strike-through price is that lowest price instead of the regular price,
 * - a "reduction" that is not below that lowest price is not shown as one
 *   (no strike-through price, no sale badge, no notice),
 * - so is a reduction without a known earlier price (unless the shop chose to
 *   keep it) and one of a product that was never offered at a higher price.
 * Price comparisons with a UVP and reductions of perishable goods (§ 11 Abs. 4
 * PAngV) are left alone.
 *
 * Only the displayed values change ("view" context). Stored prices, the price
 * history and the calculation always use the real values ("edit" context).
 * Because WooCommerce builds strike-through prices, badges, Store API data and
 * most product feeds from the regular price, filtering it covers all of them.
 */
final class CjeuMode {

	const OPTION_ENABLED    = 'strikewise_cjeu_mode';
	const OPTION_NO_HISTORY = 'strikewise_cjeu_no_history';

	const ACTION_NONE         = 'none';
	const ACTION_REPLACE      = 'replace';
	const ACTION_NO_REDUCTION = 'no_reduction';

	/** @var ReferenceService */
	private $references;

	/** @var array<string,array{action:string,regular:string}> Decisions per product and price state, for this request. */
	private $decisions = array();

	public function __construct( ReferenceService $references ) {
		$this->references = $references;
	}

	public function register(): void {
		add_filter( 'strikewise_settings', array( $this, 'settings' ) );

		if ( ! self::is_enabled() ) {
			return;
		}

		add_action( 'strikewise_reference_refreshed', array( $this, 'forget' ) );
		add_filter( 'woocommerce_product_get_regular_price', array( $this, 'filter_regular_price' ), 20, 2 );
		add_filter( 'woocommerce_product_variation_get_regular_price', array( $this, 'filter_regular_price' ), 20, 2 );
		add_filter( 'woocommerce_product_is_on_sale', array( $this, 'filter_is_on_sale' ), 20, 2 );
		add_filter( 'woocommerce_variation_prices_regular_price', array( $this, 'filter_variation_prices_regular' ), 20, 3 );
		add_filter( 'woocommerce_get_variation_prices_hash', array( $this, 'filter_prices_hash' ), 20, 3 );
	}

	public static function is_enabled(): bool {
		return 'yes' === get_option( self::OPTION_ENABLED, 'yes' );
	}

	/**
	 * Reductions without a known earlier price are not shown, unless the shop chose to keep them.
	 */
	public static function hides_unknown(): bool {
		return 'keep' !== get_option( self::OPTION_NO_HISTORY, 'hide' );
	}

	/**
	 * What CJEU mode does with this product right now.
	 *
	 * @return array{action:string,regular:string} regular = the regular price to show, in the basis prices are entered in.
	 */
	public function decide( \WC_Product $product ): array {
		$sale    = $product->get_sale_price( 'edit' );
		$regular = $product->get_regular_price( 'edit' );
		$key     = $product->get_id() . '|' . $regular . '|' . $sale;
		$none    = array(
			'action'  => self::ACTION_NONE,
			'regular' => (string) $regular,
		);

		// Re-checked on every call, so switching the option off takes effect immediately.
		if ( ! self::is_enabled() ) {
			return $none;
		}

		if ( isset( $this->decisions[ $key ] ) ) {
			return $this->decisions[ $key ];
		}

		$decision = $none;

		// 'edit' context: the stored sale, without our own is_on_sale filter.
		// A UVP comparison is not a reduction of the own price, and perishable goods are exempt.
		if ( '' !== $sale && $product->is_on_sale( 'edit' ) && ! $product->is_type( array( 'variable', 'grouped' ) )
			&& ! Perishable::applies( $product ) && ! (bool) apply_filters( 'strikewise_is_price_comparison', false, $product ) ) {
			$reference = $this->references->get( $product );
			$current   = PriceResolver::to_gross( $product, (float) $sale );

			if ( $reference->has_price() && null !== $reference->t0 ) {
				$decision = (float) $reference->price - $current > 0.005
					? array(
						'action'  => self::ACTION_REPLACE,
						'regular' => self::format( PriceResolver::from_gross( $product, (float) $reference->price ) ),
					)
					: array(
						'action'  => self::ACTION_NO_REDUCTION,
						'regular' => (string) $sale,
					);
			} elseif ( Reference::STATUS_NO_HISTORY === $reference->status && ( self::hides_unknown() || ReferenceService::launched_reduced( $product, $reference ) ) ) {
				// Never offered at a higher price, or no earlier price known: no reduction to announce.
				$decision = array(
					'action'  => self::ACTION_NO_REDUCTION,
					'regular' => (string) $sale,
				);
			}
		}

		$this->decisions[ $key ] = $decision;

		return $decision;
	}

	/**
	 * Drops cached decisions of a product whose reference price changed in this request.
	 *
	 * @param int $product_id
	 */
	public function forget( $product_id ): void {
		$prefix = (int) $product_id . '|';
		foreach ( array_keys( $this->decisions ) as $key ) {
			if ( 0 === strpos( $key, $prefix ) ) {
				unset( $this->decisions[ $key ] );
			}
		}
	}

	/**
	 * @param string|float $value
	 * @param mixed        $product
	 * @return string|float
	 */
	public function filter_regular_price( $value, $product ) {
		if ( ! $product instanceof \WC_Product || '' === $value ) {
			return $value;
		}

		$decision = $this->decide( $product );

		return self::ACTION_NONE === $decision['action'] ? $value : $decision['regular'];
	}

	/**
	 * @param bool  $on_sale
	 * @param mixed $product
	 */
	public function filter_is_on_sale( $on_sale, $product ): bool {
		if ( ! $on_sale || ! $product instanceof \WC_Product || $product->is_type( 'variable' ) ) {
			return (bool) $on_sale;
		}

		return self::ACTION_NO_REDUCTION !== $this->decide( $product )['action'];
	}

	/**
	 * Price ranges and sale detection of variable products use these cached arrays.
	 *
	 * @param string|float $price
	 * @param mixed        $variation
	 * @param mixed        $product
	 * @return string|float
	 */
	public function filter_variation_prices_regular( $price, $variation, $product ) {
		return $variation instanceof \WC_Product ? $this->filter_regular_price( $price, $variation ) : $price;
	}

	/**
	 * Makes WooCommerce cache the variation prices separately for CJEU mode.
	 *
	 * @param array<int|string,mixed> $hash
	 * @param mixed                   $product
	 * @param bool                    $for_display
	 * @return array<int|string,mixed>
	 */
	public function filter_prices_hash( $hash, $product, $for_display ) {
		$hash[] = 'strikewise-cjeu-1|' . ( self::hides_unknown() ? 'hide' : 'keep' );
		return $hash;
	}

	private static function format( float $amount ): string {
		return (string) round( $amount, wc_get_price_decimals() );
	}

	/**
	 * Settings rows, added to WooCommerce -> Settings -> Products -> Strikewise.
	 *
	 * @param array<int,array<string,mixed>> $settings
	 * @return array<int,array<string,mixed>>
	 */
	public function settings( $settings ) {
		$settings[] = array(
			'title' => __( 'CJEU mode', 'strikewise' ),
			'type'  => 'title',
			'desc'  => __( 'Judgment C-330/23 of the CJEU: an announced reduction must refer to the lowest price of the 30 days before it.', 'strikewise' ),
			'id'    => 'strikewise_cjeu',
		);
		$settings[] = array(
			'title'   => __( 'Enable', 'strikewise' ),
			'desc'    => __( 'Calculate strike-through prices from the lowest price of the 30 days before the reduction (CJEU, C-330/23). A reduction that is not below that price is not shown as one.', 'strikewise' ),
			'id'      => self::OPTION_ENABLED,
			'type'    => 'checkbox',
			'default' => 'yes',
		);
		$settings[] = array(
			'title'   => __( 'Without price history', 'strikewise' ),
			'desc'    => __( 'For reduced products without a known earlier price, e.g. directly after installing Strikewise. A strike-through price without the earlier price is not allowed; you can enter a known earlier price in the product.', 'strikewise' ),
			'id'      => self::OPTION_NO_HISTORY,
			'type'    => 'select',
			'default' => 'hide',
			'options' => array(
				'hide' => __( 'Do not show a reduction (recommended)', 'strikewise' ),
				'keep' => __( 'Keep the regular price as strike-through price', 'strikewise' ),
			),
		);
		$settings[] = array(
			'type' => 'sectionend',
			'id'   => 'strikewise_cjeu',
		);

		return $settings;
	}
}