<?php
namespace AntivirusAI\V1;

/** WP-Cron is a best-effort wake-up, not a promise of exact execution time. */
final class Scheduler {
	public static function register(): void {
		add_action( 'antivirus_ai_tick', array( self::class, 'tick' ) );
		add_action( 'antivirus_ai_daily', array( self::class, 'daily' ) );
	}
	public static function scheduleTick( string $id, int $delay = 10 ): bool {
		if ( ! wp_next_scheduled( 'antivirus_ai_tick', array( $id ) ) ) {
			$scheduled = wp_schedule_single_event( time() + max( 1, min( 900, $delay ) ), 'antivirus_ai_tick', array( $id ), true );
			if ( is_wp_error( $scheduled ) || false === $scheduled ) {
				( new Store() )->activity(
					'scheduler_error',
					array(
						'scan_id' => $id,
						'message' => 'WordPress did not accept the scan wake-up. Use Continue batch or WP-CLI.',
					)
				);
				return false;
			}
		}
		return true;
	}
	public static function settingsChanged( array $settings ): void {
		wp_clear_scheduled_hook( 'antivirus_ai_daily' );
		if ( empty( $settings['daily'] ) ) {
			$state = get_option( 'antivirus_ai_schedule_state', array() );
			$state = is_array( $state ) ? $state : array();
			$state['enabled'] = false;
			$state['next_due'] = 0;
			$state['retry_due'] = 0;
			$state['consecutive_failures'] = 0;
			update_option( 'antivirus_ai_schedule_state', $state, false );
			return;
		}
		$state = get_option( 'antivirus_ai_schedule_state', array() );
		$state = is_array( $state ) ? $state : array();
		$state['retry_due'] = 0; $state['consecutive_failures'] = 0;
		unset( $state['blocking_scan_id'] );
		update_option( 'antivirus_ai_schedule_state', $state, false );
		self::nextDaily( time() + self::interval() );
	}
	public static function interval(): int {
		return max( 900, min( 86400, (int) apply_filters( 'antivirus_ai_scan_interval', 86400 ) ) );
	}
	private static function nextDaily( int $due ): void {
		$state               = get_option( 'antivirus_ai_schedule_state', array() );
		$state = is_array( $state ) ? $state : array();
		$state['enabled']    = true;
		$state['next_due']   = $due;
		$state['interval']   = self::interval();
		$result              = wp_schedule_single_event( $due, 'antivirus_ai_daily', array(), true );
		// Accepting a future wake-up does not prove the previous scan start succeeded.
		$state['execution_error'] = $state['execution_error'] ?? ( $state['last_error'] ?? '' );
		$state['schedule_error']  = is_wp_error( $result ) ? $result->get_error_message() : ( false === $result ? 'WordPress did not accept the scheduled sweep.' : '' );
		$state['last_error']      = $state['execution_error'] ?: $state['schedule_error'];
		update_option( 'antivirus_ai_schedule_state', $state, false );
	}
	public static function daily(): void {
		$settings = get_option( 'antivirus_ai_settings', array() );
		if ( empty( $settings['daily'] ) ) {
			return; }
		$store = new Store();
		$token = $store->lock( 'daily_scheduler', 60 );
		if ( ! $token ) {
			// A consumed cron wake-up must not disappear just because another request holds the lease.
			if ( ! wp_next_scheduled( 'antivirus_ai_daily' ) ) { wp_schedule_single_event( time() + 60, 'antivirus_ai_daily', array(), true ); }
			return; }
		try {
			if ( empty( Store::freshOption( 'antivirus_ai_settings', array() )['daily'] ) ) {
				return; }
			$state               = get_option( 'antivirus_ai_schedule_state', array() );
			$state = is_array( $state ) ? $state : array();
			$state['last_run'] = time();
			if ( empty( $state['retry_due'] ) ) { $state['consecutive_failures'] = 0; }
			$state['attempt_due'] = (int) ( $state['retry_due'] ?? 0 ) > 0 ? (int) ( $state['attempt_due'] ?? $state['next_due'] ?? time() ) : (int) ( $state['next_due'] ?? time() );
			$state['last_delay_seconds'] = max( 0, time() - $state['attempt_due'] );
			update_option( 'antivirus_ai_schedule_state', $state, false );
			try {
				$scanner = new Scanner( $store );
				$latest = $store->list( 'scan', 'queued', 1 )[0] ?? $store->list( 'scan', 'running', 1 )[0] ?? null;
				$resuming = $latest && in_array( $latest['_status'], array( 'queued', 'running' ), true );
				$id = $resuming ? $latest['_id'] : $scanner->start( (string) apply_filters( 'antivirus_ai_scheduled_scan_mode', 'full' ) );
				// Re-read the returned scan: start() may encounter a concurrently created targeted scan.
				$selected = $store->get( $id );
				if ( ! $selected || 'scan' !== ( $selected['_kind'] ?? '' ) ) { throw new \RuntimeException( 'The scheduled scan could not be confirmed in local storage.' ); }
				if ( ! empty( $selected['target_finding_id'] ) || 'targeted' === ( $selected['mode'] ?? '' ) ) {
					self::scheduleTick( $id );
					$state['last_scan_action'] = 'deferred_targeted';
					$state['blocking_scan_id'] = $id;
					$state['last_deferred_at'] = time();
					$state['retry_due'] = time() + 120;
					unset( $state['last_scan_id'], $state['last_scan_requested_at'] );
					Store::saveOption( 'antivirus_ai_schedule_state', $state );
					if ( ! empty( Store::freshOption( 'antivirus_ai_settings', array() )['daily'] ) ) {
						wp_clear_scheduled_hook( 'antivirus_ai_daily' );
						self::nextDaily( $state['retry_due'] );
					}
					return;
				}
				if ( ! self::scheduleTick( $id ) ) { throw new \RuntimeException( 'The scan was retained but its next batch could not be scheduled. A bounded retry will resume it.' ); }
				$state['retry_due'] = 0;
				$state['consecutive_failures'] = 0;
				unset( $state['blocking_scan_id'] );
				$state['last_scan_id'] = $id;
				$state['last_scan_action'] = $resuming ? 'resumed' : 'requested';
				$state['last_scan_requested_at'] = time();
				$state['execution_error'] = '';
				$state['last_error']      = $state['schedule_error'] ?? '';
				update_option( 'antivirus_ai_schedule_state', $state, false );
			} catch ( \Throwable $error ) {
				$state['last_error'] = substr( $error->getMessage(), 0, 300 );
				$state['execution_error'] = $state['last_error'];
				$state['consecutive_failures'] = (int) ( $state['consecutive_failures'] ?? 0 ) + 1;
				$state['retry_due'] = $state['consecutive_failures'] < 3 ? time() + 120 * $state['consecutive_failures'] : 0;
				update_option( 'antivirus_ai_schedule_state', $state, false );
				$store->activity( 'scheduler_error', array( 'message' => $state['last_error'] ) );
			}
			// Always leave a future wake-up after a transient scan-start failure.
			if ( ! empty( Store::freshOption( 'antivirus_ai_settings', array() )['daily'] ) && ! wp_next_scheduled( 'antivirus_ai_daily' ) ) {
				self::nextDaily( $state['retry_due'] ?: time() + self::interval() ); }
			$store->prune();
		} finally {
			$store->unlock( 'daily_scheduler', $token ); }
	}
	public static function diagnostics(): array {
		$state    = get_option( 'antivirus_ai_schedule_state', array() );
		$worker   = get_option( 'antivirus_ai_worker_state', array() );
		$proWorker = get_option( 'antivirus_ai_pro_worker_state', array() );
		$settings = get_option( 'antivirus_ai_settings', array() );
		$scan     = ( new Scanner( new Store() ) )->latest();
		$active   = $scan && in_array( $scan['_status'], array( 'queued', 'running' ), true );
		$enabled  = ! empty( $settings['daily'] );
		$due      = (int) ( $state['next_due'] ?? 0 );
		$seen     = (int) ( $worker['finished_at'] ?? $worker['started_at'] ?? 0 );
		$scheduledScan = ! empty( $state['last_scan_id'] ) && is_string( $state['last_scan_id'] ) ? ( new Store() )->get( $state['last_scan_id'] ) : null;
		if ( $scheduledScan && 'scan' !== ( $scheduledScan['_kind'] ?? '' ) ) { $scheduledScan = null; }
		return array(
			'enabled'          => $enabled,
			'next_due'         => $due,
			'last_run'         => (int) ( $state['last_run'] ?? 0 ),
			'last_scan_id'     => $scheduledScan['_id'] ?? null,
			'last_scan_action' => in_array( $state['last_scan_action'] ?? '', array( 'requested', 'resumed', 'deferred_targeted' ), true ) ? $state['last_scan_action'] : null,
			'last_scan_requested_at' => (int) ( $state['last_scan_requested_at'] ?? 0 ),
			'last_scan_status' => $scheduledScan['_status'] ?? 'not_recorded',
			'last_scan_completed_at' => $scheduledScan['completed_at'] ?? null,
			'last_delay_seconds' => max( 0, (int) ( $state['last_delay_seconds'] ?? 0 ) ),
			'retry_due' => max( 0, (int) ( $state['retry_due'] ?? 0 ) ),
			'consecutive_failures' => max( 0, (int) ( $state['consecutive_failures'] ?? 0 ) ),
			'overlap_deferred' => $enabled && (int) ( $state['retry_due'] ?? 0 ) > 0 && 'deferred_targeted' === ( $state['last_scan_action'] ?? '' ),
			'scheduled_wakeup' => (int) wp_next_scheduled( 'antivirus_ai_daily' ),
			'last_error'       => substr( (string) ( $state['last_error'] ?? '' ), 0, 300 ),
			'execution_error'  => substr( (string) ( $state['execution_error'] ?? '' ), 0, 300 ),
			'schedule_error'   => substr( (string) ( $state['schedule_error'] ?? '' ), 0, 300 ),
			'overdue'          => $enabled && $due > 0 && $due < time() - max( 300, min( 7200, self::interval() ) ),
			'active_stalled'   => $active && (int) ( $scan['heartbeat'] ?? 0 ) < time() - 900,
			'missing_wakeup'   => ( $enabled && ! wp_next_scheduled( 'antivirus_ai_daily' ) ) || ( $active && ! wp_next_scheduled( 'antivirus_ai_tick', array( $scan['_id'] ) ) ),
			'worker_last_seen' => $seen,
			'worker_stale'     => $seen <= 0 || $seen > time() || $seen < time() - 900,
			'worker_error'     => substr( (string) ( ! empty( $worker['last_error'] ) ? $worker['last_error'] : ( $proWorker['last_error'] ?? '' ) ), 0, 300 ),
		);
	}
	/** Called by the authenticated local CLI, never registered on visitor requests. */
	public static function work( int $maxBatches = 1 ): array {
		$store = new Store();
		$token = $store->lock( 'background_worker', 300 );
		if ( ! $token ) {
			return array( 'busy' => true ) + self::diagnostics(); }
		$worker = array( 'started_at' => time(), 'last_error' => '' );
		update_option( 'antivirus_ai_worker_state', $worker, false );
		try {
			$state = get_option( 'antivirus_ai_schedule_state', array() );
			if ( ! empty( get_option( 'antivirus_ai_settings', array() )['daily'] ) ) {
				$due = wp_next_scheduled( 'antivirus_ai_daily' );
				if ( ( $due && $due <= time() ) || (int) ( $state['next_due'] ?? 0 ) <= time() ) {
					wp_clear_scheduled_hook( 'antivirus_ai_daily' );
					self::daily();
				} elseif ( ! $due ) {
					self::nextDaily( (int) $state['next_due'] );
				}
			}
			for ( $batch = 0; $batch < max( 1, min( 20, $maxBatches ) ); ++$batch ) {
				$scan = ( new Scanner( $store ) )->latest();
				if ( ! $scan || ! in_array( $scan['_status'], array( 'queued', 'running' ), true ) ) {
					break; }
				// A host worker explicitly advances retained work even if its wake-up was lost.
				wp_clear_scheduled_hook( 'antivirus_ai_tick', array( $scan['_id'] ) );
				self::tick( $scan['_id'] );
			}
			try {
				do_action( 'antivirus_ai_worker' );
			} catch ( \Throwable $error ) {
				$worker['last_error'] = substr( $error->getMessage(), 0, 300 );
				$store->activity( 'background_extension_error', array( 'message' => $worker['last_error'] ) );
			}
			$worker['finished_at'] = time();
			update_option( 'antivirus_ai_worker_state', $worker, false );
			return array( 'busy' => false ) + self::diagnostics();
		} catch ( \Throwable $error ) {
			$worker['last_error'] = substr( $error->getMessage(), 0, 300 );
			$worker['failed_at']  = time();
			update_option( 'antivirus_ai_worker_state', $worker, false );
			throw $error;
		} finally {
			$store->unlock( 'background_worker', $token ); }
	}
	public static function tick( string $id ): void {
		if ( ! preg_match( '/^[a-z0-9_]{1,64}$/D', $id ) ) {
			return; }
		$store = new Store();
		$scan  = $store->get( $id );
		if ( ! $scan || 'scan' !== $scan['_kind'] || ! in_array( $scan['_status'], array( 'queued', 'running' ), true ) ) {
			return; }
		$retryId = 'job_' . substr( hash( 'sha256', $id ), 0, 56 );
		try {
			$result = ( new Scanner( $store ) )->tick( $id, 25 );
			$store->put(
				'job',
				$retryId,
				array(
					'scan_id'  => $id,
					'failures' => 0,
				),
				'active'
			);
			if ( in_array( $result['_status'] ?? $result['status'] ?? '', array( 'queued', 'running' ), true ) ) {
				self::scheduleTick( $id, 15 ); } else {
				$store->delete( $retryId );
				$store->prune(); }
		} catch ( \Throwable $error ) {
			$job      = $store->get( $retryId );
			$attempts = (int) ( $job['failures'] ?? 0 ) + 1;
			$after    = $store->get( $id );
			$terminal = ! $after || ! in_array( $after['_status'], array( 'queued', 'running' ), true );
			$store->put(
				'job',
				$retryId,
				array(
					'scan_id'    => $id,
					'failures'   => $attempts,
					'last_error' => substr( $error->getMessage(), 0, 300 ),
				),
				$attempts >= 3 || $terminal ? 'failed' : 'retry'
			);
			$store->activity(
				'scan_batch_error',
				array(
					'scan_id' => $id,
					'attempt' => $attempts,
					'message' => substr( $error->getMessage(), 0, 300 ),
				)
			);
			if ( $terminal ) {
				$store->prune();
				return; }
			if ( $attempts < 3 ) {
				self::scheduleTick( $id, 60 * $attempts ); } else {
				$scan = $store->get( $id );
				if ( $scan && in_array( $scan['_status'], array( 'queued', 'running' ), true ) ) {
					$scan['status']        = 'incomplete';
					$scan['result_state']  = 'confirmed_threat' === ( $scan['result_state'] ?? '' ) || in_array( 'confirmed', $scan['observed_findings'] ?? array(), true ) ? 'confirmed_threat' : 'scan_incomplete';
					$scan['completed_at'] = gmdate( 'c' );
					$scan['limitations'][] = 'Three scheduled batches failed. The scan is incomplete; inspect Activity and start a fresh scan after resolving the error.';
					$store->put( 'scan', $id, $scan, 'incomplete', $scan['_revision'] );
				}
				}
		}
	}
}