<?php
/**
 * Statistics + failed-send ring buffer.
 *
 * Counts of verified / unverified / grandfathered users are computed via
 * indexed user-meta queries cached in a 5-minute transient. Failed wp_mail
 * attempts are recorded in a bounded option-based ring buffer (last 100
 * entries) so the admin can see what's failing without a custom log table.
 *
 * @package WPCoreToolsEmailVerify
 */

defined( 'ABSPATH' ) || exit;

class WPCEV_Stats {

	const COUNT_TRANSIENT = 'wpcev_stats_v1';
	const COUNT_TTL       = 5 * MINUTE_IN_SECONDS;

	const FAIL_LOG_OPTION = 'wpcev_fail_log';
	const FAIL_LOG_MAX    = 100;

	/* ─── Counts ─────────────────────────────────────────────────────────── */

	/**
	 * @return array{verified:int,unverified:int,grandfathered:int,total:int}
	 */
	public static function counts() {
		$cached = get_transient( self::COUNT_TRANSIENT );
		if ( is_array( $cached ) ) {
			return $cached;
		}
		global $wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- aggregate count over indexed user meta; no WP_User_Query primitive does this.
		$verified = (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(DISTINCT user_id) FROM {$wpdb->usermeta} WHERE meta_key = %s AND meta_value = %s",
				WPCEV_Tokens::META_VERIFIED,
				'1'
			)
		);
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery
		$unverified    = (int) $wpdb->get_var(
			$wpdb->prepare(
				"SELECT COUNT(DISTINCT user_id) FROM {$wpdb->usermeta} WHERE meta_key = %s AND meta_value = %s",
				WPCEV_Tokens::META_VERIFIED,
				'0'
			)
		);
		$total         = count_users();
		$total_users   = isset( $total['total_users'] ) ? (int) $total['total_users'] : 0;
		$grandfathered = max( 0, $total_users - $verified - $unverified );

		$out = array(
			'verified'      => $verified,
			'unverified'    => $unverified,
			'grandfathered' => $grandfathered,
			'total'         => $total_users,
		);
		set_transient( self::COUNT_TRANSIENT, $out, self::COUNT_TTL );
		return $out;
	}

	public static function bust_count_cache() {
		delete_transient( self::COUNT_TRANSIENT );
	}

	/**
	 * Recent unverified users (most recently registered first), capped.
	 *
	 * @param int $limit
	 * @return array<int,WP_User>
	 */
	public static function recent_unverified( $limit = 5 ) {
		// phpcs:ignore WordPress.DB.SlowDBQuery -- one indexed meta key on a single column; admin-only widget capped at 50 results.
		$query = new WP_User_Query(
			array(
				'meta_key'    => WPCEV_Tokens::META_VERIFIED, // phpcs:ignore WordPress.DB.SlowDBQuery
				'meta_value'  => '0', // phpcs:ignore WordPress.DB.SlowDBQuery
				'orderby'     => 'registered',
				'order'       => 'DESC',
				'number'      => max( 1, min( 50, (int) $limit ) ),
				'count_total' => false,
			)
		);
		return $query->get_results();
	}

	/**
	 * Return ALL unverified user IDs — used by the CSV export. No paging
	 * because (a) unverified counts are typically small and (b) the export
	 * is a one-shot admin action; if a site really has tens of thousands
	 * of unverified users, the export endpoint streams.
	 *
	 * @return array<int,int>
	 */
	public static function all_unverified_ids() {
		// phpcs:ignore WordPress.DB.SlowDBQuery -- admin-only CSV export; same indexed key as the dashboard widget.
		$query = new WP_User_Query(
			array(
				'meta_key'    => WPCEV_Tokens::META_VERIFIED, // phpcs:ignore WordPress.DB.SlowDBQuery
				'meta_value'  => '0', // phpcs:ignore WordPress.DB.SlowDBQuery
				'fields'      => 'ID',
				'number'      => -1,
				'count_total' => false,
			)
		);
		return array_map( 'intval', (array) $query->get_results() );
	}

	/* ─── Failed-send ring buffer ────────────────────────────────────────── */

	/**
	 * Record a failed send. Trims the buffer to FAIL_LOG_MAX entries (oldest
	 * dropped). Stored as autoload=no so it doesn't bloat the autoload pool.
	 *
	 * @param int    $user_id
	 * @param string $email
	 * @param string $code     'wp_mail_failed' | 'invalid_user' | …
	 * @param string $context  'register' | 'profile_update' | 'resend' | 'cli' | …
	 */
	public static function log_failure( $user_id, $email, $code, $context = '' ) {
		$log   = self::get_failures();
		$log[] = array(
			'time'    => time(),
			'user_id' => (int) $user_id,
			'email'   => substr( (string) $email, 0, 254 ),
			'code'    => sanitize_key( $code ),
			'context' => sanitize_key( $context ),
		);
		// Drop oldest entries beyond the cap.
		if ( count( $log ) > self::FAIL_LOG_MAX ) {
			$log = array_slice( $log, -self::FAIL_LOG_MAX );
		}
		update_option( self::FAIL_LOG_OPTION, $log, false );
	}

	/**
	 * @return array<int,array{time:int,user_id:int,email:string,code:string,context:string}>
	 */
	public static function get_failures() {
		$log = get_option( self::FAIL_LOG_OPTION, array() );
		return is_array( $log ) ? $log : array();
	}

	public static function clear_failures() {
		delete_option( self::FAIL_LOG_OPTION );
	}
}