add_action('rest_api_init', function () {
    register_rest_route('myaio/v1', '/sitemap-update', [
        'methods'             => 'POST',
        'callback'            => 'myaio_sac_update_sitemap_api',
        'permission_callback' => 'myaio_sac_rest_permission_check',
    ]);
});

function myaio_sac_update_sitemap_api(WP_REST_Request $request) {
    try {
        $sitemap_url = esc_url_raw((string) $request->get_param('sitemap_url'));
        $url         = esc_url_raw((string) $request->get_param('url'));
        $priority    = trim((string) $request->get_param('priority'));
        $changefreq  = trim((string) $request->get_param('changefreq'));
        $action      = strtolower(trim((string) $request->get_param('action')));

        if (!$sitemap_url || !$url || !in_array($action, ['add', 'remove'], true)) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Required params: sitemap_url, url, action(add/remove).',
            ], 400);
        }

        if ($priority === '') {
            $priority = '0.5';
        }

        if ($changefreq === '') {
            $changefreq = 'monthly';
        }

        if (!preg_match('/^(0(\.\d+)?|1(\.0)?)$/', $priority)) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Priority must be between 0.0 and 1.0.',
            ], 400);
        }

        $allowed_freq = ['always', 'hourly', 'daily', 'weekly', 'monthly', 'yearly', 'never'];

        if (!in_array($changefreq, $allowed_freq, true)) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Invalid changefreq.',
            ], 400);
        }

        $file_path = myaio_sac_sitemap_url_to_local_path($sitemap_url);

        if (!$file_path) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Only local sitemap URLs from this website can be updated.',
            ], 400);
        }

        if (!file_exists($file_path)) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Sitemap file does not exist.',
                'file_path' => $file_path,
            ], 404);
        }

        if (!is_writable($file_path)) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Sitemap file is not writable.',
                'file_path' => $file_path,
            ], 403);
        }

        $xml_string = file_get_contents($file_path);

        if (!$xml_string) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Unable to read sitemap file.',
            ], 500);
        }

        libxml_use_internal_errors(true);
        $xml = simplexml_load_string($xml_string);
        libxml_clear_errors();

        if (!$xml) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Invalid XML sitemap.',
            ], 500);
        }

        $type = myaio_sac_dashboard_parse_sitemap_type($xml);

        if ($type !== 'urlset') {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Only URL sitemap files can be updated. Sitemap index files cannot directly contain page URLs.',
            ], 400);
        }

        $result = myaio_sac_update_urlset_xml($xml, $url, $priority, $changefreq, $action);

        $dom = dom_import_simplexml($xml)->ownerDocument;
        $dom->formatOutput = true;

        $saved = file_put_contents($file_path, $dom->saveXML());

        if ($saved === false) {
            return new WP_REST_Response([
                'success' => false,
                'message' => 'Failed to save sitemap file.',
            ], 500);
        }

        return rest_ensure_response([
            'success'     => true,
            'action'      => $action,
            'message'     => $result['message'],
            'sitemap_url' => $sitemap_url,
            'url'         => $url,
            'priority'    => $priority,
            'changefreq'  => $changefreq,
            'lastmod'     => gmdate('c'),
        ]);

    } catch (Throwable $e) {
        return new WP_REST_Response([
            'success' => false,
            'message' => $e->getMessage(),
        ], 500);
    }
}

function myaio_sac_update_urlset_xml(SimpleXMLElement $xml, $url, $priority, $changefreq, $action) {
    $target_norm = myaio_sac_dashboard_normalize_url($url);

    $nodes = $xml->xpath('/*[local-name()="urlset"]/*[local-name()="url"]');

    foreach ((array) $nodes as $node) {
        $loc_nodes = $node->xpath('./*[local-name()="loc"]');
        $loc = $loc_nodes ? trim((string) $loc_nodes[0]) : '';

        if (myaio_sac_dashboard_normalize_url($loc) !== $target_norm) {
            continue;
        }

        if ($action === 'remove') {
            $dom_node = dom_import_simplexml($node);
            $dom_node->parentNode->removeChild($dom_node);

            return [
                'message' => 'URL removed from sitemap.',
            ];
        }

        myaio_sac_set_or_update_xml_child($node, 'lastmod', gmdate('c'));
        myaio_sac_set_or_update_xml_child($node, 'changefreq', $changefreq);
        myaio_sac_set_or_update_xml_child($node, 'priority', $priority);

        return [
            'message' => 'URL already existed. Sitemap entry updated.',
        ];
    }

    if ($action === 'remove') {
        return [
            'message' => 'URL was not found in sitemap. Nothing removed.',
        ];
    }

    $new = $xml->addChild('url');
    $new->addChild('loc', esc_url_raw($url));
    $new->addChild('lastmod', gmdate('c'));
    $new->addChild('changefreq', $changefreq);
    $new->addChild('priority', $priority);

    return [
        'message' => 'URL added to sitemap.',
    ];
}

function myaio_sac_set_or_update_xml_child(SimpleXMLElement $node, $child_name, $value) {
    $children = $node->xpath('./*[local-name()="' . $child_name . '"]');

    if ($children && isset($children[0])) {
        $children[0][0] = $value;
        return;
    }

    $node->addChild($child_name, $value);
}

function myaio_sac_sitemap_url_to_local_path($sitemap_url) {
    $site_url = home_url('/');

    $site_parts    = wp_parse_url($site_url);
    $sitemap_parts = wp_parse_url($sitemap_url);

    if (empty($site_parts['host']) || empty($sitemap_parts['host'])) {
        return false;
    }

    if (strtolower($site_parts['host']) !== strtolower($sitemap_parts['host'])) {
        return false;
    }

    $path = $sitemap_parts['path'] ?? '';

    if ($path === '') {
        return false;
    }

    $path = ltrim($path, '/');

    if (strpos($path, '..') !== false) {
        return false;
    }

    if (!preg_match('/sitemap.*\.xml$/i', basename($path))) {
        return false;
    }

    return trailingslashit(ABSPATH) . $path;
}