<?php
declare(strict_types=1);

namespace Esun3d\LanguageUrlStoreResolver\Model;

class HtmlLinkProcessor
{
    /**
     * @var UrlPathConverter
     */
    private $urlPathConverter;

    /**
     * @param UrlPathConverter $urlPathConverter
     */
    public function __construct(UrlPathConverter $urlPathConverter)
    {
        $this->urlPathConverter = $urlPathConverter;
    }

    /**
     * Convert internal anchor URLs in complete page HTML.
     *
     * @param string $html
     * @param string $language
     * @return string
     */
    public function process(string $html, string $language): string
    {
        if (stripos($html, '<a') === false) {
            return $html;
        }

        $result = preg_replace_callback(
            '~(<a\b[^>]*\bhref\s*=\s*)(["\'])(.*?)\2~is',
            function (array $matches) use ($language): string {
                $href = $matches[3];
                $normalizedHref = trim($href);

                if (!$this->isConvertibleHref($normalizedHref)) {
                    return $matches[0];
                }

                $convertedHref = $this->urlPathConverter->toLanguageUrl($normalizedHref, $language);
                if ($convertedHref === $normalizedHref) {
                    return $matches[0];
                }

                return $matches[1] . $matches[2] . $convertedHref . $matches[2];
            },
            $html
        );

        return is_string($result) ? $result : $html;
    }

    /**
     * Check whether an href represents a navigational HTTP URL.
     *
     * @param string $href
     * @return bool
     */
    private function isConvertibleHref(string $href): bool
    {
        if ($href === '' || $href[0] === '#' || $href[0] === '?') {
            return false;
        }

        if (strpos($href, '{{') !== false || strpos($href, '${') !== false) {
            return false;
        }

        return !preg_match('~^[a-z][a-z0-9+.-]*:~i', $href)
            || preg_match('~^https?:~i', $href) === 1;
    }
}