<?php
namespace Relay\Files;

/**
 * A path relative to a group folder (themes, plugins, mu-plugins, uploads, other) that came from a file list —
 * possibly another site's. Only plain, forward-slash, UTF-8 paths that stay inside the folder are accepted.
 */
final class RelPath
{
    public const GROUPS = ['themes', 'plugins', 'mu-plugins', 'uploads', 'other'];

    public static function valid(string $rel): bool
    {
        if ($rel === '' || strlen($rel) > 1024 || strpbrk($rel, "\0\\") !== false || $rel[0] === '/' || preg_match('#^[A-Za-z]:#', $rel) || !mb_check_encoding($rel, 'UTF-8')) {
            return false;
        }
        foreach (explode('/', $rel) as $segment) {
            if ($segment === '' || $segment === '.' || $segment === '..' || preg_match('/[\x00-\x1f\x7f]/', $segment)) {
                return false;
            }
        }
        return true;
    }

    /** The top-level item a path belongs to: the theme or plugin folder, the uploads year, the file itself... */
    public static function top(string $rel): string
    {
        return explode('/', $rel, 2)[0];
    }

    /** @param string[] $protected "group/top-level" items (see Groups::protected_items()), compared case-insensitively */
    public static function is_protected(string $group, string $rel, array $protected): bool
    {
        $item = strtolower($group . '/' . self::top($rel));
        foreach ($protected as $p) {
            if (strtolower($p) === $item) {
                return true;
            }
        }
        return false;
    }
}