export default {
async fetch(request, env) {
const targetBinding = request.headers.get("MF-Binding");
if (targetBinding) {
const originalHeaders = new Headers();
for (const [name, value] of request.headers) {
if (name.startsWith("mf-header-")) {
originalHeaders.set(name.slice("mf-header-".length), value);
} else if (name === "upgrade") {
// The `Upgrade` header needs to be special-cased to prevent:
// TypeError: Worker tried to return a WebSocket in a response to a request which did not contain the header "Upgrade: websocket"
originalHeaders.set(name, value);
}
}
let fetcher = env[targetBinding];
// Special case the Dispatch Namespace binding because it has a top-level synchronous .get() call
const dispatchNamespaceOptions = originalHeaders.get(
"MF-Dispatch-Namespace-Options"
);
if (dispatchNamespaceOptions) {
const { name, args, options } = JSON.parse(dispatchNamespaceOptions);
fetcher = (env[targetBinding] as DispatchNamespace).get(
name,
args,
options
);
}
return (fetcher as Fetcher).fetch(
request.headers.get("MF-URL")!,
new Request(request, {
redirect: "manual",
headers: originalHeaders,
})
);
}
return new Response("Provide a binding", { status: 400 });
},
} satisfies ExportedHandler<Record<string, Fetcher | DispatchNamespace>>;
