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Merged
Chintanpatel24 merged 1 commit into from
Jun 11, 2026
Merged

feat: add HTML landing page for SVG cards with robust content negotia… #26

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37 changes: 33 additions & 4 deletions src/response.js
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Original file line number Diff line number Diff line change
@@ -1,13 +1,42 @@
/**
* Utility to send SVG response or an HTML wrapper based on the Accept header.
* Utility to send SVG response or an HTML wrapper based on the request context.
*/

function sendResponse(req, res, svg, status = 200) {
const accept = req.headers.accept || "";
const userAgent = req.headers["user-agent"] || "";
const secFetchDest = req.headers["sec-fetch-dest"] || "";
const { format } = req.query || {};

if (accept.includes("text/html")) {
// Force SVG if format=svg is requested
if (format === "svg") {
res.setHeader("Content-Type", "image/svg+xml");
res.status(status).send(svg);
return;
}

// Detect if the request is from GitHub's proxy (Camo)
// GitHub Camo uses "github-camo" in the user agent.
const isGithubCamo = userAgent.toLowerCase().includes("github-camo");

// Modern browsers send sec-fetch-dest: image when loading <img> tags
// and sec-fetch-dest: document when opening in a new tab.
const isImageRequest = secFetchDest === "image" || (accept.includes("image/svg+xml") && !accept.includes("text/html"));

// We serve HTML only if:
// 1. It's NOT from GitHub Camo
// 2. It's NOT an explicit image request from a browser
// 3. The client explicitly accepts text/html (browser navigation)
let serveHtml = !isGithubCamo && !isImageRequest && accept.includes("text/html");

// Extra safety: if sec-fetch-dest is "document", it's definitely a browser navigation
if (secFetchDest === "document") {
serveHtml = true;
}
Comment on lines +33 to +35

if (serveHtml) {
res.setHeader("Content-Type", "text/html");
res.setHeader("Vary", "Accept");
res.setHeader("Vary", "Accept, Sec-Fetch-Dest");
const html = `
Comment on lines 38 to 40
<!DOCTYPE html>
<html lang="en">
Expand Down Expand Up @@ -67,7 +96,7 @@ function sendResponse(req, res, svg, status = 200) {
res.status(status).send(html);
} else {
res.setHeader("Content-Type", "image/svg+xml");
res.setHeader("Vary", "Accept");
res.setHeader("Vary", "Accept, Sec-Fetch-Dest");
res.status(status).send(svg);
Comment on lines 98 to 100
}
}
Expand Down
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