<?php
/**
 * Checks the find/replace rules a user typed on the Scope step before a run is created.
 *
 * @package Shiftora\Migration\FindReplace
 */

declare(strict_types=1);

namespace Shiftora\Migration\FindReplace;

use InvalidArgumentException;

// Prevent direct file access.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

// phpcs:disable WordPress.Security.EscapeOutput.ExceptionNotEscaped -- Exception messages become a WP_Error the REST layer encodes; nothing here prints HTML.

/**
 * A bad rule refuses the whole request instead of being dropped, so what the
 * Review step listed is exactly what runs.
 */
final class CustomRuleValidator {

	public const MAX_RULES  = 50;
	public const MAX_LENGTH = 500;

	/**
	 * @param mixed $rules Raw `find_replace` request value: a list of { find, replace }.
	 *
	 * @return array<int, array{find: string, replace: string, generated: false}> Empty when none were sent.
	 *
	 * @throws InvalidArgumentException With a message fit to show the user.
	 */
	public static function validate( $rules ): array {
		if ( null === $rules || [] === $rules ) {
			return [];
		}

		if ( ! is_array( $rules ) || ! array_is_list( $rules ) ) {
			throw new InvalidArgumentException( __( 'Custom find and replace rules must be a list.', 'shiftora' ) );
		}

		if ( count( $rules ) > self::MAX_RULES ) {
			throw new InvalidArgumentException(
				/* translators: %d: the most rules one migration accepts. */
				sprintf( __( 'A migration accepts at most %d custom find and replace rules.', 'shiftora' ), self::MAX_RULES )
			);
		}

		$clean = [];
		foreach ( $rules as $index => $rule ) {
			$number = $index + 1;
			$find   = is_array( $rule ) && is_string( $rule['find'] ?? null ) ? $rule['find'] : null;
			$to     = is_array( $rule ) && is_string( $rule['replace'] ?? null ) ? $rule['replace'] : null;

			if ( null === $find || null === $to || '' === trim( $find ) ) {
				throw new InvalidArgumentException(
					/* translators: %d: rule number, counted from 1. */
					sprintf( __( 'Custom rule %d needs something in From.', 'shiftora' ), $number )
				);
			}

			if ( strlen( $find ) > self::MAX_LENGTH || strlen( $to ) > self::MAX_LENGTH ) {
				throw new InvalidArgumentException(
					/* translators: 1: rule number, 2: the longest From or To in characters. */
					sprintf( __( 'Custom rule %1$d is too long. From and To can each hold %2$d characters.', 'shiftora' ), $number, self::MAX_LENGTH )
				);
			}

			if ( 1 === preg_match( '/[\x00-\x1F\x7F]/', $find . $to ) ) {
				throw new InvalidArgumentException(
					/* translators: %d: rule number, counted from 1. */
					sprintf( __( 'Custom rule %d contains a control character.', 'shiftora' ), $number )
				);
			}

			if ( $find === $to ) {
				throw new InvalidArgumentException(
					/* translators: %d: rule number, counted from 1. */
					sprintf( __( 'Custom rule %d has the same From and To.', 'shiftora' ), $number )
				);
			}

			// Not a generated URL rule: those run as one pass with host boundaries, and
			// a typed rule gets the plain left-to-right behavior it asked for.
			$clean[] = [ 'find' => $find, 'replace' => $to, 'generated' => false ];
		}

		return $clean;
	}
}