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export interface Env { PREVIEWS: R2Bucket }
const MIME: Record<string, string> = {
html: "text/html; charset=utf-8", css: "text/css", js: "text/javascript",
json: "application/json", svg: "image/svg+xml", png: "image/png", jpg: "image/jpeg",
gif: "image/gif", ico: "image/x-icon", txt: "text/plain; charset=utf-8",
xml: "application/xml", pdf: "application/pdf", woff2: "font/woff2", woff: "font/woff",
};
export function mimeFor(key: string): string {
const ext = key.split(".").pop() ?? "";
return MIME[ext] ?? "application/octet-stream";
}
export function keyFor(pathname: string): string {
let key = pathname.replace(/^\//, "");
if (key.endsWith("/") || key === "" ) key += "index.html";
return key;
}
export default {
async fetch(request: Request, env: Env): Promise<Response> {
const key = keyFor(new URL(request.url).pathname);
let obj: R2ObjectBody | null = null;
let resolvedKey = key;
try {
obj = await env.PREVIEWS.get(key);
if (!obj && !key.split("/").pop()?.includes(".")) {
// Extensionless directory URL with no trailing slash (e.g. /en/rolling/cli) —
// keyFor() only appends index.html for trailing-slash/empty paths, so probe the
// directory's index.html before 404ing. Check the LAST path segment only — a dot
// anywhere earlier (e.g. version segment "1.4" in /pr-42/en/1.4/cli) must not skip
// the probe for an otherwise-extensionless final segment.
resolvedKey = `${key}/index.html`;
obj = await env.PREVIEWS.get(resolvedKey);
}
} catch {
// Transient R2/binding error on either probe — fail closed with a controlled 503
// instead of letting an unhandled exception surface as a raw worker error.
return new Response("preview temporarily unavailable", {
status: 503,
headers: { "X-Robots-Tag": "noindex", "Cache-Control": "no-store" },
});
}
if (!obj) {
return new Response("preview not found", {
status: 404,
// no-store on the 404 too — a cached 404 would persist past the preview upload
headers: { "X-Robots-Tag": "noindex", "Cache-Control": "no-store" },
});
}
return new Response(obj.body, {
headers: {
"content-type": obj.httpMetadata?.contentType ?? mimeFor(resolvedKey),
"X-Robots-Tag": "noindex",
"Cache-Control": "no-store",
"X-Content-Type-Options": "nosniff",
},
});
},
} satisfies ExportedHandler<Env>;
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