esun3d/app/code/Esun3d/LanguageUrlStoreResolver/Model/UrlPathConverter.php

<?php
declare(strict_types=1);

namespace Esun3d\LanguageUrlStoreResolver\Model;

use Magento\Framework\UrlInterface;
use Magento\Store\Model\StoreManagerInterface;

class UrlPathConverter
{
    /**
     * @var Config
     */
    private $config;

    /**
     * @var StoreCodeMapper
     */
    private $storeCodeMapper;

    /**
     * @var StoreViewRegistry
     */
    private $storeViewRegistry;

    /**
     * @var StoreManagerInterface
     */
    private $storeManager;

    public function __construct(
        Config $config,
        StoreCodeMapper $storeCodeMapper,
        StoreViewRegistry $storeViewRegistry,
        StoreManagerInterface $storeManager
    ) {
        $this->config = $config;
        $this->storeCodeMapper = $storeCodeMapper;
        $this->storeViewRegistry = $storeViewRegistry;
        $this->storeManager = $storeManager;
    }

    public function toLanguageUrl(string $url, string $language): string
    {
        $parts = parse_url($url);
        if ($parts === false) {
            return $url;
        }

        if ($this->isExternalUrl($parts)) {
            return $url;
        }

        $path = $parts['path'] ?? '/';
        $path = $path === '' ? '/' : $path;
        $basePath = $this->getBasePath();
        $relativePath = $this->stripBasePath($path, $basePath);

        if ($this->config->shouldSkipPath($relativePath)) {
            return $url;
        }

        $parts['path'] = $this->prependBasePath(
            $basePath,
            $this->convertRelativePath($relativePath, strtolower($language))
        );

        return $this->buildUrl($parts);
    }

    /**
     * @param mixed[] $parts
     */
    private function isExternalUrl(array $parts): bool
    {
        if (!isset($parts['host'])) {
            return false;
        }

        $baseParts = parse_url($this->storeManager->getStore()->getBaseUrl(UrlInterface::URL_TYPE_WEB));
        $baseHost = isset($baseParts['host']) ? strtolower($baseParts['host']) : '';

        return strtolower((string)$parts['host']) !== $baseHost;
    }

    private function convertRelativePath(string $path, string $language): string
    {
        $path = '/' . ltrim($path, '/');
        $segments = explode('/', trim($path, '/'), 2);
        $firstSegment = $segments[0] ?? '';
        $remainingPath = $segments[1] ?? '';

        if ($this->storeCodeMapper->isRealStoreCodeInScope($firstSegment)) {
            $language = $this->storeCodeMapper->languageFromStoreCode($firstSegment) ?? $language;
            $path = $remainingPath === '' ? '/' : '/' . ltrim($remainingPath, '/');
        }

        if ($this->storeCodeMapper->isLanguageAllowed(strtolower($firstSegment))) {
            $path = $remainingPath === '' ? '/' : '/' . ltrim($remainingPath, '/');
        }

        if ($this->storeCodeMapper->isDefaultLanguage($language)) {
            return $path;
        }

        return $path === '/' ? '/' . $language . '/' : '/' . $language . $path;
    }

    private function getBasePath(): string
    {
        $baseParts = parse_url($this->storeManager->getStore()->getBaseUrl(UrlInterface::URL_TYPE_WEB));
        $basePath = isset($baseParts['path']) ? rtrim($baseParts['path'], '/') : '';

        return $basePath !== '' ? $basePath : '/';
    }

    private function stripBasePath(string $path, string $basePath): string
    {
        if ($basePath === '/' || $basePath === '') {
            return '/' . ltrim($path, '/');
        }

        if ($path === $basePath) {
            return '/';
        }

        if (strpos($path, $basePath . '/') === 0) {
            return '/' . ltrim(substr($path, strlen($basePath)), '/');
        }

        return '/' . ltrim($path, '/');
    }

    private function prependBasePath(string $basePath, string $path): string
    {
        $path = '/' . ltrim($path, '/');

        if ($basePath === '/' || $basePath === '') {
            return $path;
        }

        return rtrim($basePath, '/') . $path;
    }

    /**
     * @param mixed[] $parts
     */
    private function buildUrl(array $parts): string
    {
        $url = '';

        if (isset($parts['host'])) {
            $url .= isset($parts['scheme']) ? $parts['scheme'] . '://' : '//';

            if (isset($parts['user'])) {
                $url .= $parts['user'];
                if (isset($parts['pass'])) {
                    $url .= ':' . $parts['pass'];
                }
                $url .= '@';
            }

            $url .= $parts['host'];

            if (isset($parts['port'])) {
                $url .= ':' . $parts['port'];
            }
        }

        $url .= $parts['path'] ?? '/';

        if (isset($parts['query']) && $parts['query'] !== '') {
            $url .= '?' . $parts['query'];
        }

        if (isset($parts['fragment']) && $parts['fragment'] !== '') {
            $url .= '#' . $parts['fragment'];
        }

        return $url;
    }
}