<?php
/**
 * Database clean-up: expired transients.
 *
 * @package AdminPowerups
 */

namespace SmartWP\AdminPowerups\Modules\DatabaseCleanup\Checks;

use SmartWP\AdminPowerups\Modules\DatabaseCleanup\BaseCheck;
use SmartWP\AdminPowerups\Support\Owners;

defined( 'ABSPATH' ) || exit;

/**
 * Transients of this site (and, on a single site, site transients) whose timeout has passed.
 * Each one is deleted with delete_transient() / delete_site_transient(), which clears the
 * options caches, after its timeout was read again. Unavailable with a persistent object cache:
 * transients then live in the cache, which expires them itself (core's
 * delete_expired_transients() refuses then too). Network `sitemeta` is never touched. Samples
 * show names and dates, never values.
 *
 * @since 1.0.0
 */
class ExpiredTransients extends BaseCheck {

	/**
	 * Names per query.
	 */
	const BATCH = 500;

	/**
	 * {@inheritDoc}
	 */
	public function unavailable(): string {
		if ( wp_using_ext_object_cache() ) {
			return __( 'This site keeps transients in a persistent object cache, which removes expired ones itself.', 'admin-powerups-for-woocommerce' );
		}
		return parent::unavailable();
	}

	/**
	 * Timeout-row prefixes counted here.
	 *
	 * @return string[]
	 */
	private static function prefixes(): array {
		return is_multisite() ? array( '_transient_timeout_' ) : array( '_transient_timeout_', '_site_transient_timeout_' );
	}

	/**
	 * WHERE for expired timeout rows (one LIKE per prefix, on the option_name index).
	 *
	 * @return array{0: string, 1: array<int, mixed>}
	 */
	private static function where(): array {
		global $wpdb;
		$parts = array();
		$args  = array();
		foreach ( self::prefixes() as $prefix ) {
			$parts[] = 'option_name LIKE %s';
			$args[]  = $wpdb->esc_like( $prefix ) . '%';
		}
		$args[] = time();
		return array( '(' . implode( ' OR ', $parts ) . ') AND CAST(option_value AS UNSIGNED) < %d', $args );
	}

	/**
	 * {@inheritDoc}
	 *
	 * @param array<string, mixed> $state  State from the last call.
	 * @param float                $budget Seconds to spend.
	 * @return array{count: int, done: bool, state: array<string, mixed>}
	 */
	public function count( array $state, float $budget ): array {
		global $wpdb;
		list( $where, $args ) = self::where();
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, PluginCheck.Security.DirectDB.UnescapedDBParameter -- live count; $where holds placeholders only.
		$count = (int) $wpdb->get_var( $wpdb->prepare( "SELECT COUNT(*) FROM %i WHERE {$where}", array_merge( array( $wpdb->options ), $args ) ) );
		return array(
			'count' => $count,
			'done'  => true,
			'state' => array(),
		);
	}

	/**
	 * Expired timeout rows.
	 *
	 * @param int $limit Rows.
	 * @return array<int, object>
	 */
	private static function expired( int $limit ): array {
		global $wpdb;
		list( $where, $args ) = self::where();
		$args[]               = $limit;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, PluginCheck.Security.DirectDB.UnescapedDBParameter -- live read; $where holds placeholders only.
		return (array) $wpdb->get_results( $wpdb->prepare( "SELECT option_name, option_value FROM %i WHERE {$where} ORDER BY option_name LIMIT %d", array_merge( array( $wpdb->options ), $args ) ) );
	}

	/**
	 * Transient name and whether it is a site transient, from a timeout row name.
	 *
	 * @param string $option Timeout option name.
	 * @return array{0: string, 1: bool}
	 */
	private static function parse( string $option ): array {
		if ( str_starts_with( $option, '_site_transient_timeout_' ) ) {
			return array( substr( $option, strlen( '_site_transient_timeout_' ) ), true );
		}
		return array( substr( $option, strlen( '_transient_timeout_' ) ), false );
	}

	/**
	 * {@inheritDoc} In batches of expired timeout rows (option_name index order): the values
	 * go first, then the timeouts, and each DELETE checks again that the timeout has passed, so a
	 * transient set anew meanwhile stays. The options caches of the names are cleared.
	 *
	 * @param array<string, mixed> $state  State from the last call.
	 * @param int                  $batch  Rows per statement.
	 * @param float                $budget Seconds to spend.
	 * @return array{deleted: int, skipped: int, notes: array<string, int>, done: bool, state: array<string, mixed>}
	 */
	public function clean( array $state, int $batch, float $budget ): array {
		global $wpdb;
		$out   = self::cleaned( $state, false );
		$start = microtime( true );
		$limit = min( self::BATCH, max( 1, $batch ) );
		do {
			$rows  = self::expired( $limit );
			$now   = time();
			$names = array(
				'_transient_'      => array(),
				'_site_transient_' => array(),
			);
			foreach ( $rows as $row ) {
				list( $name, $site )                                   = self::parse( (string) $row->option_name );
				$names[ $site ? '_site_transient_' : '_transient_' ][] = $name;
			}
			$gone = 0;
			foreach ( $names as $prefix => $list ) {
				if ( ! $list ) {
					continue;
				}
				$timeout  = $prefix . 'timeout_';
				$values   = array_map( static fn( $name ) => $prefix . $name, $list );
				$timeouts = array_map( static fn( $name ) => $timeout . $name, $list );
				$in       = self::placeholders( count( $list ), '%s' );
				// phpcs:disable WordPress.DB.DirectDatabaseQuery, WordPress.DB.PreparedSQL.InterpolatedNotPrepared, WordPress.DB.PreparedSQLPlaceholders.ReplacementsWrongNumber, WordPress.DB.PreparedSQLPlaceholders.UnfinishedPrepare, PluginCheck.Security.DirectDB.UnescapedDBParameter -- $in is one %s placeholder per name (values passed to prepare()); the timeout is checked again inside each DELETE; caches are cleared below.
				$wpdb->query(
					$wpdb->prepare(
						"DELETE v FROM %i v INNER JOIN %i t ON t.option_name = CONCAT( %s, SUBSTRING( v.option_name, %d ) ) WHERE v.option_name IN ({$in}) AND CAST( t.option_value AS UNSIGNED ) < %d",
						array_merge( array( $wpdb->options, $wpdb->options, $timeout, strlen( $prefix ) + 1 ), $values, array( $now ) )
					)
				);
				$gone += (int) $wpdb->query(
					$wpdb->prepare(
						"DELETE FROM %i WHERE option_name IN ({$in}) AND CAST( option_value AS UNSIGNED ) < %d",
						array_merge( array( $wpdb->options ), $timeouts, array( $now ) )
					)
				);
				// phpcs:enable
				self::forget( array_merge( $values, $timeouts ) );
			}
			$out['deleted'] += $gone;
			if ( $rows ) {
				$out['progress'] = true; // Rows looked at (even if all were renewed meanwhile).
			}
			if ( count( $rows ) < $limit || 0 === $gone || '' !== $wpdb->last_error ) {
				$out['done'] = '' === $wpdb->last_error;
				break;
			}
		} while ( self::time_left( $start, $budget ) );
		return $out;
	}

	/**
	 * Clear the options caches of deleted option names.
	 *
	 * @param string[] $names Option names.
	 * @return void
	 */
	private static function forget( array $names ): void {
		$all     = wp_cache_get( 'alloptions', 'options' );
		$changed = false;
		foreach ( $names as $name ) {
			wp_cache_delete( $name, 'options' );
			if ( is_array( $all ) && isset( $all[ $name ] ) ) {
				unset( $all[ $name ] );
				$changed = true;
			}
		}
		if ( $changed ) {
			wp_cache_set( 'alloptions', $all, 'options' );
		}
	}

	/**
	 * {@inheritDoc} Name, expiry and probable owner; never the value.
	 *
	 * @param int $limit Rows (at most 10).
	 * @return array{columns: array<string, string>, rows: array<int, array<string, string>>}
	 */
	public function sample( int $limit = 10 ): array {
		$out = array();
		foreach ( self::expired( max( 1, min( 10, $limit ) ) ) as $row ) {
			list( $name ) = self::parse( (string) $row->option_name );
			$owner        = Owners::guess( $name, 'option' );
			$out[]        = array(
				'name'    => self::value_cell( $name ),
				'expired' => self::date_cell( (int) $row->option_value ),
				'owner'   => self::cell( self::owner_label( $owner ) ),
			);
		}
		return array(
			'columns' => array(
				'name'    => __( 'Transient', 'admin-powerups-for-woocommerce' ),
				'expired' => __( 'Expired', 'admin-powerups-for-woocommerce' ),
				'owner'   => __( 'Probable owner', 'admin-powerups-for-woocommerce' ),
			),
			'rows'    => $out,
		);
	}

	/**
	 * Owner as text.
	 *
	 * @param array<string, string> $owner Owners::guess() result.
	 * @return string
	 */
	private static function owner_label( array $owner ): string {
		switch ( $owner['type'] ?? '' ) {
			case 'core':
				return __( 'WordPress', 'admin-powerups-for-woocommerce' );
			case 'woocommerce':
				return __( 'WooCommerce', 'admin-powerups-for-woocommerce' );
			case 'plugin':
			case 'theme':
				return '' !== ( $owner['name'] ?? '' ) ? (string) $owner['name'] : (string) ( $owner['slug'] ?? '' );
			default:
				return __( 'Unknown', 'admin-powerups-for-woocommerce' );
		}
	}
}