<?php
/**
 * Whether background work keeps up: a verdict from plain facts. Pure PHP.
 *
 * Facts: available (bool), last_success (Unix time, 0 = never), last_failure (Unix time), last_error (text),
 * oldest_overdue (seconds a waiting job is late, 0 = none), overdue (number of late jobs), failed (failed jobs).
 *
 * @package Tidelist
 */

namespace Tidelist\Health;

/**
 * Background work reliability.
 */
final class Reliability {

	const LATE_AFTER     = 1800;   // A job waiting longer than this is late.
	const CRITICAL_AFTER = 10800;  // Three hours late means the queue is not running.
	const STALE_AFTER    = 129600; // The daily job has not finished for a day and a half.

	/**
	 * Facts with every key present.
	 *
	 * @param array $facts Facts.
	 */
	public static function normalise( array $facts ): array {
		return array_merge(
			array(
				'available'      => true,
				'last_success'   => 0,
				'last_failure'   => 0,
				'last_error'     => '',
				'oldest_overdue' => 0,
				'overdue'        => 0,
				'failed'         => 0,
			),
			$facts
		);
	}

	/**
	 * The verdict, in the shape of the other health checks.
	 *
	 * @param array $facts Facts.
	 * @param int   $now   Now (Unix).
	 * @return array{status:string, label:string, description:string}
	 */
	public static function evaluate( array $facts, int $now ): array {
		$f = self::normalise( $facts );
		if ( ! $f['available'] ) {
			return self::result( Checks::CRITICAL, 'Background jobs are not available', 'Tidelist needs Action Scheduler (it comes with WooCommerce) to publish batches and take adverts down. Update WooCommerce.' );
		}
		if ( $f['oldest_overdue'] >= self::CRITICAL_AFTER ) {
			return self::result(
				Checks::CRITICAL,
				'Background jobs are not running',
				sprintf( 'The oldest waiting job is %s late (%d waiting). Adverts are not taken down or updated on time. WP-Cron probably does not run: see the troubleshooting guide, or ask your host to call wp-cron.php every 5 minutes.', self::duration( $f['oldest_overdue'] ), $f['overdue'] )
			);
		}
		if ( $f['oldest_overdue'] >= self::LATE_AFTER ) {
			return self::result(
				Checks::RECOMMENDED,
				'Background jobs are running late',
				sprintf( 'The oldest waiting job is %s late (%d waiting). On a quiet site WP-Cron only runs when someone visits: a real cron job fixes that.', self::duration( $f['oldest_overdue'] ), $f['overdue'] )
			);
		}
		if ( $f['failed'] > 0 ) {
			$why = '' !== $f['last_error'] ? ' Last error: ' . $f['last_error'] : '';
			return self::result( Checks::RECOMMENDED, 'Some background jobs failed', sprintf( '%d job(s) failed.%s Open WooCommerce → Status → Scheduled Actions → Failed to see them.', $f['failed'], $why ) );
		}
		if ( $f['last_success'] > 0 && $now - $f['last_success'] > self::STALE_AFTER ) {
			return self::result( Checks::RECOMMENDED, 'No background job has finished lately', sprintf( 'The last job finished %s ago. The daily upkeep should run every day. Check that WP-Cron works.', self::duration( $now - $f['last_success'] ) ) );
		}
		return self::result( Checks::GOOD, 'Background jobs are running', 'Waiting jobs are on time and none failed.' );
	}

	/**
	 * A length of time in words: "45 min", "3 h 10 min", "2 days".
	 *
	 * @param int $seconds Seconds.
	 */
	public static function duration( int $seconds ): string {
		$seconds = max( 0, $seconds );
		if ( $seconds < 3600 ) {
			return max( 1, (int) round( $seconds / 60 ) ) . ' min';
		}
		if ( $seconds < 172800 ) {
			$hours   = intdiv( $seconds, 3600 );
			$minutes = intdiv( $seconds % 3600, 60 );
			return $hours . ' h' . ( $minutes > 0 ? ' ' . $minutes . ' min' : '' );
		}
		return intdiv( $seconds, 86400 ) . ' days';
	}

	/**
	 * Result array.
	 *
	 * @param string $status      Status.
	 * @param string $label       Label.
	 * @param string $description Description.
	 */
	private static function result( string $status, string $label, string $description ): array {
		return array(
			'status'      => $status,
			'label'       => $label,
			'description' => $description,
		);
	}
}