<?php
namespace Strikewise\Pricing;

defined( 'ABSPATH' ) || exit;

/**
 * Turns a WooCommerce product into the consumer price that applies right now.
 *
 * Stored prices are final prices incl. VAT ("Gesamtpreis"), based on the
 * shop's base location, so a change of the tax rate is a price change too.
 */
final class PriceResolver {

	/**
	 * The shop's base currency. Currency switchers filter get_woocommerce_currency()
	 * per visitor, so the history is always kept in the currency prices are entered in.
	 */
	public static function currency(): string {
		return (string) get_option( 'woocommerce_currency', 'EUR' );
	}

	/**
	 * Products that carry their own price. Variable and grouped parents do not.
	 */
	public static function is_trackable( \WC_Product $product ): bool {
		$trackable = ! $product->is_type( array( 'variable', 'grouped' ) );

		/**
		 * Filters whether Strikewise records prices for a product.
		 *
		 * @param bool        $trackable
		 * @param \WC_Product $product
		 */
		return (bool) apply_filters( 'strikewise_is_trackable', $trackable, $product );
	}

	/**
	 * @return array{price: float, regular: float|null, reduced: bool}|null Null if the product has no price.
	 */
	public static function snapshot( \WC_Product $product ): ?array {
		$regular = $product->get_regular_price( 'edit' );
		$sale    = $product->get_sale_price( 'edit' );
		$current = $product->get_price( 'edit' );

		if ( '' === $regular && '' === $current ) {
			return null;
		}

		// is_on_sale() checks the sale price and the scheduled sale dates against "now".
		$reduced   = '' !== $sale && $product->is_on_sale( 'edit' );
		$effective = $reduced ? (float) $sale : (float) ( '' !== $regular ? $regular : $current );

		return array(
			'price'   => self::to_gross( $product, $effective ),
			'regular' => '' === $regular ? null : self::to_gross( $product, (float) $regular ),
			'reduced' => $reduced,
		);
	}

	/**
	 * Price as entered in WooCommerce -> final price incl. VAT at the base location.
	 */
	public static function to_gross( \WC_Product $product, float $amount ): float {
		if ( ! wc_tax_enabled() || wc_prices_include_tax() || ! $product->is_taxable() ) {
			return round( $amount, 4 );
		}

		$rates = \WC_Tax::get_base_tax_rates( $product->get_tax_class( 'unfiltered' ) );
		$taxes = \WC_Tax::calc_tax( $amount, $rates, false );

		return round( $amount + array_sum( $taxes ), 4 );
	}

	/**
	 * Final price incl. VAT -> the basis prices are entered in (inverse of to_gross()).
	 */
	public static function from_gross( \WC_Product $product, float $gross ): float {
		if ( ! wc_tax_enabled() || wc_prices_include_tax() || ! $product->is_taxable() ) {
			return $gross;
		}

		$rates = \WC_Tax::get_base_tax_rates( $product->get_tax_class( 'unfiltered' ) );
		$taxes = \WC_Tax::calc_tax( $gross, $rates, true );

		return $gross - array_sum( $taxes );
	}

	/**
	 * Stored gross price -> the way the shop displays prices (incl. or excl. VAT).
	 */
	public static function to_display( \WC_Product $product, float $gross ): float {
		if ( ! wc_tax_enabled() || ! $product->is_taxable() || 'excl' !== get_option( 'woocommerce_tax_display_shop' ) ) {
			return $gross;
		}

		$rates = \WC_Tax::get_base_tax_rates( $product->get_tax_class( 'unfiltered' ) );
		$taxes = \WC_Tax::calc_tax( $gross, $rates, true );

		return $gross - array_sum( $taxes );
	}
}