<?php
/**
 * Number sequences.
 *
 * @package HostKhata
 */

namespace HostKhata\Support;

defined( 'ABSPATH' ) || exit;

use wpdb;

/**
 * Hands out increasing numbers without ever giving the same number twice, even
 * when two requests ask at the same moment.
 *
 * The counter lives in one row of the options table and is raised with a single
 * `UPDATE ... LAST_INSERT_ID( value + 1 )`. MySQL locks the row for that
 * statement and remembers the new value for this connection, so the following
 * `SELECT LAST_INSERT_ID()` returns exactly the number this request got.
 *
 * @since 0.1.0
 */
final class Sequence {

	/**
	 * Option name prefix.
	 */
	const PREFIX = 'hostkhata_seq_';

	/**
	 * Database object.
	 *
	 * @var wpdb
	 */
	private $wpdb;

	/**
	 * Constructor.
	 *
	 * @param wpdb $wpdb WordPress database object.
	 */
	public function __construct( wpdb $wpdb ) {
		$this->wpdb = $wpdb;
	}

	/**
	 * The next number of a sequence, starting at 1.
	 *
	 * @since 0.1.0
	 *
	 * @param string $name Sequence name, for example `order`.
	 * @return int
	 */
	public function next( string $name ): int {
		$option = self::PREFIX . preg_replace( '/[^a-z0-9_]/', '', strtolower( $name ) );

		// Creating the row is idempotent: add_option() does nothing when it exists.
		add_option( $option, '0', '', 'no' );

		$this->wpdb->query( $this->wpdb->prepare( "UPDATE {$this->wpdb->options} SET option_value = LAST_INSERT_ID( option_value + 1 ) WHERE option_name = %s", $option ) ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.InterpolatedNotPrepared,WordPress.DB.PreparedSQL.NotPrepared,PluginCheck.Security.DirectDB.UnescapedDBParameter -- Options table name; value prepared.

		$number = (int) $this->wpdb->get_var( 'SELECT LAST_INSERT_ID()' ); // phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching

		// The row changed behind WordPress's back, so drop any cached copy.
		wp_cache_delete( $option, 'options' );
		wp_cache_delete( 'alloptions', 'options' );
		wp_cache_delete( 'notoptions', 'options' );

		return $number;
	}
}