<?php
/**
 * Links a new fatal error to the change that most likely came before it.
 *
 * @package Keepwatch
 */

namespace Keepwatch\Changes;

defined( 'ABSPATH' ) || exit;

/**
 * Pure logic, no WordPress calls. The result is a "possible" link, never a verdict:
 *  - same_component: the error comes from a plugin/theme changed in the 24 hours before the error first appeared;
 *  - timing: the error comes from elsewhere but started within 60 minutes after a change.
 */
final class Correlator {

	public const COMPONENT_WINDOW = DAY_IN_SECONDS;
	public const TIMING_WINDOW    = HOUR_IN_SECONDS;

	/** Change kinds that can introduce an error. */
	private const KINDS = array( 'update', 'install', 'activate', 'theme_switch' );

	/**
	 * Component of a (redacted) file path: "plugin:slug", "theme:slug", "core" or null.
	 *
	 * @param string $file File path.
	 */
	public static function component( string $file ): ?string {
		$file = str_replace( '\\', '/', $file );
		if ( 1 === preg_match( '#/(?:mu-)?plugins/([^/]+)/#', $file, $m ) ) {
			return 'plugin:' . strtolower( $m[1] );
		}
		if ( 1 === preg_match( '#/themes/([^/]+)/#', $file, $m ) ) {
			return 'theme:' . strtolower( $m[1] );
		}
		if ( 1 === preg_match( '#(?:^|/|\})wp-(?:includes|admin)/#', $file ) ) {
			return 'core';
		}
		return null;
	}

	/**
	 * Best matching change for an error, or null.
	 *
	 * @param string|null                                                                                                              $component  Error component.
	 * @param int                                                                                                                      $first_seen When the error first happened.
	 * @param array<int, array{time: int, kind: string, type: string, slug: string, name: string, from: string|null, to: string|null}> $changes Changes.
	 * @return array{change: array{time: int, kind: string, type: string, slug: string, name: string, from: string|null, to: string|null}, reason: string}|null
	 */
	public static function match( ?string $component, int $first_seen, array $changes ): ?array {
		$best_same   = null;
		$best_timing = null;
		foreach ( $changes as $change ) {
			if ( ! in_array( $change['kind'], self::KINDS, true ) || $change['time'] > $first_seen ) {
				continue;
			}
			$age  = $first_seen - $change['time'];
			$name = 'core' === $change['type'] ? 'core' : $change['type'] . ':' . $change['slug'];
			if ( null !== $component && $name === $component && $age <= self::COMPONENT_WINDOW ) {
				if ( null === $best_same || $change['time'] > $best_same['time'] ) {
					$best_same = $change;
				}
			} elseif ( $age <= self::TIMING_WINDOW && ( null === $best_timing || $change['time'] > $best_timing['time'] ) ) {
				$best_timing = $change;
			}
		}
		if ( null !== $best_same ) {
			return array(
				'change' => $best_same,
				'reason' => 'same_component',
			);
		}
		if ( null !== $best_timing ) {
			return array(
				'change' => $best_timing,
				'reason' => 'timing',
			);
		}
		return null;
	}
}