<?php
/**
 * Scan continuation.
 *
 * @package Consentfold
 */

declare(strict_types=1);

namespace Consentfold\Scanner;

/**
 * Runs the static scan from cron (docs/subsystems.md §5.6): a scan that does not finish in one run schedules a single
 * `consentfold_scan_chunk` event, which picks up where the last run stopped. This class has no schedule of its own:
 * it only removes the recurring `consentfold_scan` event that an earlier version scheduled.
 */
final class Cron {

	/**
	 * The recurring event an earlier version scheduled; it is only ever removed.
	 */
	public const SCAN_HOOK  = 'consentfold_scan';
	public const CHUNK_HOOK = 'consentfold_scan_chunk';

	/**
	 * Seconds between the chunks of one scan.
	 */
	private const CHUNK_DELAY = 30;

	/**
	 * Static scan.
	 *
	 * @var StaticScanner
	 */
	private StaticScanner $scanner;

	/**
	 * Seconds one run may spend scanning.
	 *
	 * @var float
	 */
	private float $budget;

	/**
	 * Constructor.
	 *
	 * @param StaticScanner $scanner Static scan.
	 * @param float         $budget  Seconds one run may spend scanning.
	 */
	public function __construct( StaticScanner $scanner, float $budget = StaticScanner::BUDGET ) {
		$this->scanner = $scanner;
		$this->budget  = $budget;
	}

	/**
	 * Hook the event that continues a scan.
	 */
	public function register(): void {
		add_action( self::CHUNK_HOOK, array( $this, 'run' ) );
	}

	/**
	 * Run one chunk of the scan, and schedule the next when the scan is not complete and none is scheduled yet, which
	 * keeps a run that lost the lock to another from queuing a second event.
	 */
	public function run(): void {
		if ( ! $this->scanner->advance( $this->budget ) && $this->scanner->running() && false === wp_next_scheduled( self::CHUNK_HOOK ) ) {
			wp_schedule_single_event( time() + self::CHUNK_DELAY, self::CHUNK_HOOK );
		}
	}

	/**
	 * Remove the recurring event left over from an earlier schedule.
	 */
	public function remove_recurring(): void {
		if ( false !== wp_next_scheduled( self::SCAN_HOOK ) ) {
			wp_unschedule_hook( self::SCAN_HOOK );
		}
	}

	/**
	 * Remove both events.
	 */
	public function unschedule(): void {
		wp_unschedule_hook( self::SCAN_HOOK );
		wp_unschedule_hook( self::CHUNK_HOOK );
	}
}