<?php
/**
 * Unique single-use coupons for messages.
 *
 * @package Rahkar\WP
 */

declare( strict_types = 1 );

namespace Rahkar\WP\Coupons;

use Rahkar\WP\Notifications\Message;
use Rahkar\WP\Notifications\PhoneNumber;
use Rahkar\WP\Support\Events;
use Rahkar\WP\Support\Logger;
use WC_Coupon;

defined( 'ABSPATH' ) || exit;

/**
 * Makes one WooCommerce coupon per recipient: unique code, one use, an expiry
 * and an optional minimum spend.
 *
 * A shared code ("CART10") ends up on a coupon site within a week and is then
 * a discount for everyone. A code made for one message and usable once costs the
 * shop only when that customer uses it, which is what the dashboard measures.
 *
 * Each coupon carries `_rahkar_issued_by`, which the connector reports as
 * `coupon.upserted.issued_by`; `coupon.issued` adds what the coupon itself
 * cannot say: to whom, and for which flow.
 */
final class Issuer {

	/**
	 * Meta key naming the module that made a coupon.
	 */
	public const META_ISSUER = '_rahkar_issued_by';

	/**
	 * Days an expired, unused coupon is kept before {@see self::purge()} removes it.
	 */
	public const KEEP_DAYS = 30;

	/**
	 * Letters and digits that cannot be misread on a phone screen: no 0/O, 1/I/L.
	 */
	private const ALPHABET = 'ABCDEFGHJKMNPQRSTUVWXYZ23456789';

	/**
	 * Make a coupon.
	 *
	 * @param string                $module  Issuing module, e.g. `abandoned_cart`.
	 * @param string                $flow    Flow slug, or empty.
	 * @param string                $phone   Recipient, in any form.
	 * @param array<string, mixed>  $spec    `type` (`percent` or `fixed_cart`), `amount`, `minimum` (0 for none),
	 *                                       `hours` (validity), `prefix` (two to four letters, default `RK`).
	 * @param array<string, string> $context Ids for the event, e.g. `cart_id`.
	 *
	 * @return array{id: int, code: string, expires: int}|null Null when WooCommerce is missing or the spec is unusable.
	 */
	public static function issue( string $module, string $flow, string $phone, array $spec, array $context = [] ): ?array {
		if ( ! class_exists( WC_Coupon::class ) ) {
			return null;
		}

		$type    = 'fixed_cart' === ( $spec['type'] ?? '' ) ? 'fixed_cart' : 'percent';
		$amount  = (float) ( $spec['amount'] ?? 0 );
		$minimum = max( 0.0, (float) ( $spec['minimum'] ?? 0 ) );
		$hours   = max( 1, (int) ( $spec['hours'] ?? 48 ) );
		$prefix  = strtoupper( (string) preg_replace( '/[^A-Za-z]/', '', (string) ( $spec['prefix'] ?? 'RK' ) ) );
		$prefix  = '' === $prefix ? 'RK' : substr( $prefix, 0, 4 );

		if ( $amount <= 0 || ( 'percent' === $type && $amount > 100 ) ) {
			return null;
		}

		$expires = time() + ( $hours * HOUR_IN_SECONDS );

		for ( $try = 0; $try < 3; $try++ ) {
			$code = $prefix . '-' . self::randomPart();

			if ( wc_get_coupon_id_by_code( $code ) > 0 ) {
				continue;
			}

			$coupon = new WC_Coupon();
			$coupon->set_code( $code );
			$coupon->set_discount_type( $type );
			$coupon->set_amount( $amount );
			$coupon->set_minimum_amount( $minimum > 0 ? $minimum : '' );
			$coupon->set_usage_limit( 1 );
			$coupon->set_usage_limit_per_user( 1 );
			$coupon->set_individual_use( true );
			$coupon->set_date_expires( $expires );
			/* translators: %s: module slug */
			$coupon->set_description( sprintf( __( 'کوپن یکتای ماژول %s (راهکار)', 'rahkar-toolkit' ), $module ) );
			$coupon->update_meta_data( self::META_ISSUER, sanitize_key( $module ) );

			$id = $coupon->save();

			if ( $id <= 0 ) {
				break;
			}

			self::report( $coupon, $module, $flow, $phone, $context );

			return [
				'id'      => $id,
				'code'    => $coupon->get_code(),
				'expires' => $expires,
			];
		}

		Logger::error( 'coupons', 'Could not create a coupon.', [ 'module' => $module ] );

		return null;
	}

	/**
	 * Delete unused coupons a module made that expired long ago.
	 *
	 * Used coupons stay: an order points at them. Deleted for good, which the
	 * connector reports as `coupon.deleted`.
	 *
	 * @param int $limit Coupons per call.
	 *
	 * @return int Coupons deleted.
	 */
	public static function purge( int $limit = 50 ): int {
		// phpcs:disable WordPress.DB.SlowDBQuery.slow_db_query_meta_query -- Runs from a periodic job, a few dozen rows at most.
		$ids = get_posts(
			[
				'post_type'      => 'shop_coupon',
				'post_status'    => 'any',
				'posts_per_page' => $limit,
				'fields'         => 'ids',
				'no_found_rows'  => true,
				'meta_query'     => [
					'relation' => 'AND',
					[
						'key'     => self::META_ISSUER,
						'compare' => 'EXISTS',
					],
					[
						'key'     => 'date_expires',
						'value'   => time() - ( self::KEEP_DAYS * DAY_IN_SECONDS ),
						'compare' => '<',
						'type'    => 'NUMERIC',
					],
					[
						'key'     => 'usage_count',
						'value'   => 0,
						'compare' => '=',
						'type'    => 'NUMERIC',
					],
				],
			]
		);
		// phpcs:enable WordPress.DB.SlowDBQuery.slow_db_query_meta_query

		$deleted = 0;

		foreach ( $ids as $id ) {
			if ( wp_delete_post( (int) $id, true ) ) {
				++$deleted;
			}
		}

		return $deleted;
	}

	/**
	 * Six characters from the readable alphabet.
	 */
	private static function randomPart(): string {
		$part = '';

		for ( $i = 0; $i < 6; $i++ ) {
			$part .= self::ALPHABET[ random_int( 0, strlen( self::ALPHABET ) - 1 ) ];
		}

		return $part;
	}

	/**
	 * Report `coupon.issued` (EVENTS-v1.md §9).
	 *
	 * @param WC_Coupon             $coupon  The new coupon.
	 * @param string                $module  Issuing module.
	 * @param string                $flow    Flow slug, or empty.
	 * @param string                $phone   Recipient.
	 * @param array<string, string> $context Ids.
	 */
	private static function report( WC_Coupon $coupon, string $module, string $flow, string $phone, array $context ): void {
		if ( ! Events::listening() ) {
			return;
		}

		$number  = PhoneNumber::parse( $phone );
		$minimum = (float) $coupon->get_minimum_amount();
		$expires = $coupon->get_date_expires();
		$data    = [
			'coupon_id'      => (string) $coupon->get_id(),
			'code'           => strtolower( $coupon->get_code() ),
			'module'         => sanitize_key( $module ),
			'flow'           => '' === $flow ? null : sanitize_key( $flow ),
			'discount_type'  => sanitize_key( $coupon->get_discount_type() ),
			'amount'         => self::money( (string) $coupon->get_amount() ),
			'currency'       => strtoupper( get_woocommerce_currency() ),
			'minimum_amount' => $minimum > 0 ? self::money( (string) $minimum ) : null,
			'expires_at'     => null === $expires ? null : gmdate( 'Y-m-d\TH:i:s\Z', $expires->getTimestamp() ),
			'phone'          => null === $number ? null : $number->canonical(),
		];

		$context = Message::context( $context );

		if ( [] !== $context ) {
			$data['context'] = $context;
		}

		Events::emit( 'coupon.issued', $data );
	}

	/**
	 * A decimal string the contract accepts.
	 *
	 * @param string $amount Amount.
	 */
	private static function money( string $amount ): string {
		$value = str_contains( $amount, '.' ) ? rtrim( rtrim( $amount, '0' ), '.' ) : $amount;

		return '' === $value ? '0' : $value;
	}
}