<?php
/** Short leases with owner-checked release, backed by WordPress's unique option name. @package AccessibleForms */
namespace AccessibleForms;

// phpcs:disable WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Plugin-owned tables and atomic option leases use prepared SQL; live permissions, deletion and queue state must not use stale object-cache rows.

if ( ! defined( 'ABSPATH' ) ) {
	exit();
}
class Locks {
	public static function purge() {
		global $wpdb;
		$rows = $wpdb->get_results(
			$wpdb->prepare(
				'SELECT option_name, option_value FROM %i WHERE option_name LIKE %s AND CAST(option_value AS UNSIGNED) < %d LIMIT 500',
				$wpdb->options,
				$wpdb->esc_like( 'accessible_forms_lock_' ) . '%',
				time()
			),
			ARRAY_A
		);
		foreach ( $rows as $row ) {
			self::release( array( $row['option_name'], $row['option_value'] ) );
		}
		if ( count( $rows ) === 500 && ! wp_next_scheduled( 'accessible_forms_purge_batch' ) ) {
			wp_schedule_single_event( time() + 30, 'accessible_forms_purge_batch' );
		}
	}
	public static function acquire( $key, $seconds = 30 ) {
		global $wpdb;
		$name  = 'accessible_forms_lock_' . hash( 'sha256', $key );
		$owner = time() + $seconds . ':' . bin2hex( random_bytes( 16 ) );
		// Option/object caches are not a concurrency boundary. A long request may
		// retain a lease already released by another PHP process. The unique index
		// and conditional takeover below arbitrate against current database state.
		$inserted = $wpdb->query( $wpdb->prepare( 'INSERT IGNORE INTO %i (option_name, option_value, autoload) VALUES (%s, %s, %s)', $wpdb->options, $name, $owner, 'no' ) );
		if ( false === $inserted ) { return false; }
		$claimed = 1 === $inserted || 1 === $wpdb->query( $wpdb->prepare( "UPDATE %i SET option_value = %s WHERE option_name = %s AND CAST(SUBSTRING_INDEX(option_value, ':', 1) AS UNSIGNED) < %d", $wpdb->options, $owner, $name, time() ) );
		wp_cache_delete( $name, 'options' ); wp_cache_delete( 'notoptions', 'options' );
		return $claimed ? array( $name, $owner ) : false;
	}
	public static function release( $lease ) {
		if ( ! is_array( $lease ) ) {
			return;
		}
		global $wpdb;
		$wpdb->query(
			$wpdb->prepare(
				'DELETE FROM %i WHERE option_name = %s AND option_value = %s',
				$wpdb->options,
				$lease[0],
				$lease[1]
			)
		);
		wp_cache_delete( $lease[0], 'options' );
		wp_cache_delete( 'notoptions', 'options' );
	}
	public static function limit( $purpose, $limit, $seconds ) {
		$key  = 'accessible_forms_limit_' . hash( 'sha256', $purpose . ':' . (int) floor( time() / $seconds ) );
		$lock = self::acquire( $key, 5 );
		if ( ! $lock ) {
			return false;
		}
		try {
			// A different worker may have updated this counter before releasing its lease.
			wp_cache_delete( $key, 'transient' );
			wp_cache_delete( '_transient_' . $key, 'options' );
			wp_cache_delete( '_transient_timeout_' . $key, 'options' );
			$count = (int) get_transient( $key );
			if ( $count >= $limit ) {
				return false;
			}
			return set_transient( $key, $count + 1, $seconds ) && (int) get_transient( $key ) === $count + 1;
		} finally {
			self::release( $lock );
		}
	}
}