<?php
namespace Advently\Coupon;

use Advently\Calendar\Schedule;
use Advently\Door\Contracts\CouponIssuer;

defined( 'ABSPATH' ) || exit;

/**
 * Turns a door's coupon settings into real WooCommerce coupons.
 *
 * Coupons are created when a door is opened, never ahead of time, and carry
 * _advently_door / _advently_start meta so orders that use them can be
 * attributed to the calendar.
 */
final class Issuer implements CouponIssuer {

	const META_DOOR  = '_advently_door';
	const META_START = '_advently_start';

	/** @var Schedule */
	private $schedule;

	/** @var string */
	private $prefix;

	/** @var string Y-m-d of the calendar run. */
	private $start;

	/** @var \DateTimeImmutable */
	private $now;

	public function __construct( Schedule $schedule, string $prefix, string $start, \DateTimeImmutable $now ) {
		$this->schedule = $schedule;
		$this->prefix   = $prefix;
		$this->start    = $start;
		$this->now      = $now;
	}

	public function issue( array $door, int $doorNo, ?string $email ): array {
		$coupon = $this->build( $door, $doorNo );
		$coupon->set_usage_limit( 1 );
		$coupon->set_usage_limit_per_user( 1 );
		if ( $email ) {
			$coupon->set_email_restrictions( [ $email ] );
		}
		$coupon->set_date_expires( $this->expiry( $door )->getTimestamp() );
		$coupon->save();
		return self::shape( $coupon );
	}

	public function shared( array $door, int $doorNo ): array {
		$option   = self::sharedOption( $this->start, $doorNo );
		$storedId = (int) get_option( $option, 0 );
		$existing = $this->load( $storedId );

		if ( ! $existing ) {
			if ( $storedId ) {
				// The shop owner deleted the coupon; start over with a new one.
				delete_option( $option );
			}
			$coupon = $this->build( $door, $doorNo );
			$coupon->set_date_expires( $this->expiry( $door )->getTimestamp() );
			$coupon->save();
			if ( self::claim( $option, $coupon->get_id() ) ) {
				return self::shape( $coupon );
			}
			$this->discard( $coupon->get_id() );
			$existing = $this->load( (int) get_option( $option, 0 ) );
			if ( ! $existing ) {
				throw new \RuntimeException( 'Shared coupon could not be created.' );
			}
		}

		// Late visitors (missed days allowed) still get a code that works for the full validity.
		$expires = $this->expiry( $door )->getTimestamp();
		$current = $existing->get_date_expires();
		if ( $current && $current->getTimestamp() < $expires ) {
			$existing->set_date_expires( $expires );
			$existing->save();
		}
		return self::shape( $existing );
	}

	/**
	 * Option holding the id of a door's shared (open mode) coupon for one calendar run.
	 */
	public static function sharedOption( string $start, int $doorNo ): string {
		return 'advently_shared_' . str_replace( '-', '', $start ) . '_' . $doorNo;
	}

	public function find( int $couponId ): ?array {
		$coupon = $this->load( $couponId );
		return $coupon ? self::shape( $coupon ) : null;
	}

	public function discard( int $couponId ): void {
		if ( $this->load( $couponId ) ) {
			wp_delete_post( $couponId, true );
		}
	}

	private function build( array $door, int $doorNo ): \WC_Coupon {
		$settings = $door['coupon'];
		$coupon   = new \WC_Coupon();
		$coupon->set_code( $this->uniqueCode( $doorNo ) );
		/* translators: %d: door number. */
		$coupon->set_description( sprintf( __( 'Advently advent calendar – door %d', 'advently' ), $doorNo ) );
		$coupon->set_individual_use( $settings['individual_use'] );
		$coupon->set_minimum_amount( $settings['min_spend'] > 0 ? (string) $settings['min_spend'] : '' );
		$coupon->set_product_categories( $settings['category_ids'] );
		$coupon->set_product_ids( $settings['product_ids'] );

		switch ( $settings['kind'] ) {
			case 'fixed_cart':
				$coupon->set_discount_type( 'fixed_cart' );
				$coupon->set_amount( $settings['amount'] );
				break;
			case 'free_shipping':
				$coupon->set_discount_type( 'fixed_cart' );
				$coupon->set_amount( 0 );
				$coupon->set_free_shipping( true );
				break;
			default:
				$coupon->set_discount_type( 'percent' );
				$coupon->set_amount( $settings['amount'] );
		}

		$coupon->update_meta_data( self::META_DOOR, $doorNo );
		$coupon->update_meta_data( self::META_START, $this->start );
		/**
		 * Fires before a door's coupon is saved, for coupon kinds that add-ons register.
		 *
		 * @param \WC_Coupon $coupon   Unsaved coupon.
		 * @param array      $settings The door's coupon settings.
		 * @param int        $doorNo   Door number.
		 */
		do_action( 'advently_build_coupon', $coupon, $settings, $doorNo );
		return $coupon;
	}

	/**
	 * Validity hours after now, or the end of the calendar when set to 0.
	 */
	private function expiry( array $door ): \DateTimeImmutable {
		$hours = (int) $door['coupon']['validity_hours'];
		return $hours > 0 ? $this->now->modify( '+' . $hours . ' hours' ) : $this->schedule->end();
	}

	private function uniqueCode( int $doorNo ): string {
		for ( $i = 0; $i < 5; $i++ ) {
			$code = CodeGenerator::generate( $this->prefix, $doorNo );
			if ( ! wc_get_coupon_id_by_code( $code ) ) {
				return $code;
			}
		}
		throw new \RuntimeException( 'No free coupon code after 5 attempts.' );
	}

	/**
	 * Stores the shared coupon id only if no parallel request stored one first.
	 * add_option() cannot do this: it upserts and reports success either way.
	 */
	private static function claim( string $option, int $couponId ): bool {
		global $wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery -- atomic insert-if-absent, no API offers it.
		$inserted = $wpdb->query(
			$wpdb->prepare(
				"INSERT IGNORE INTO {$wpdb->options} (option_name, option_value, autoload) VALUES (%s, %s, 'no')",
				$option,
				(string) $couponId
			)
		);
		wp_cache_delete( $option, 'options' );
		wp_cache_delete( 'notoptions', 'options' );
		return 1 === $inserted;
	}

	private function load( int $couponId ): ?\WC_Coupon {
		if ( $couponId <= 0 || 'shop_coupon' !== get_post_type( $couponId ) || 'trash' === get_post_status( $couponId ) ) {
			return null;
		}
		$coupon = new \WC_Coupon( $couponId );
		return $coupon->get_id() ? $coupon : null;
	}

	private static function shape( \WC_Coupon $coupon ): array {
		$expires = $coupon->get_date_expires();
		return [
			'id'      => $coupon->get_id(),
			'code'    => strtoupper( $coupon->get_code() ),
			'expires' => $expires ? $expires->format( DATE_ATOM ) : null,
		];
	}
}