Function checkServerCapabilities

script.js:1139–1210

(name, url)

// ─── Server Capability Check ─────────────────────────────────────────────────

async function checkServerCapabilities(name, url) {
    showToast('Checking server capabilities...', 'info');

    const testHostname = 'example.com';
    const dnsQuery = buildDNSQuery(testHostname);
    const usesJsonApi = (() => {
        try { return new URL(url).pathname.includes('/resolve'); }
        catch { return false; }
    })();

    const wireGetUrl = (() => {
        const u = new URL(url);
        u.searchParams.set('dns', encodeDnsQueryBase64Url(dnsQuery));
        return u;
    })();

    const jsonGetUrl = (() => {
        const u = new URL(url);
        u.searchParams.set('name', testHostname);
        u.searchParams.set('type', 'A');
        u.searchParams.set('nocache', Date.now());
        return u;
    })();

    const withTimeout = async (input, options = {}) => {
        const controller = new AbortController();
        const timer = setTimeout(() => controller.abort(), 4000);
        try { return await fetch(input, { ...options, signal: controller.signal }); }
        catch (error) { console.error('Capability test error', { input, options, error }); return null; }
        finally { clearTimeout(timer); }
    };

    const testGet = async (mode) => {
        const urlToUse = usesJsonApi ? jsonGetUrl : wireGetUrl;
        const headers = usesJsonApi ? DNS_JSON_HEADERS : DNS_MESSAGE_HEADERS;
        const response = await withTimeout(urlToUse, { method: 'GET', mode, headers });
        if (!response) return { success: false, cors: false };
        if (mode === 'cors') return { success: response.ok, cors: response.type === 'cors' };
        return { success: true, cors: false };
    };

    const testPostCors = async () => {
        if (usesJsonApi) return { success: false, cors: false };
        const response = await withTimeout(url, {
            method: 'POST', mode: 'cors',
            headers: { 'Content-Type': 'application/dns-message', ...DNS_MESSAGE_HEADERS },
            body: dnsQuery
        });
        if (!response) return { success: false, cors: false };
        return { success: response.ok, cors: response.type === 'cors' };
    };

    const [getCors, postCors, getNoCors] = await Promise.all([
        testGet('cors'), testPostCors(), testGet('no-cors')
    ]);

    let chosenType = null;
    let allowCors = false;