chore(vendor): import pi 1.3.0

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0

third_party/pi/packages/chord/src/websocket.ts

@@ -0,0 +1,35 @@
+import type { AcceptOptions } from "./connection.ts";
+import type { Host } from "./host.ts";
+import { type WebSocketLike, webSocketLink } from "./link.ts";
+
+/** A WebSocket server (e.g. `ws`'s `WebSocketServer`), structurally: Chord does not depend on `ws`. */
+export interface WebSocketServerLike<Request> {
+	on(event: "connection", listener: (socket: WebSocketLike, request: Request) => void): unknown;
+}
+
+/** WebSocket peers are always accepted as clients: no roots, no code versions, no reload votes, not addressable. */
+export interface WebSocketAcceptOptions<Request, P = unknown>
+	extends Omit<AcceptOptions<P>, "principal" | "kind" | "name"> {
+	/** The authenticator: the principal of the connecting client, or undefined to refuse it. */
+	principal(request: Request): P | undefined | Promise<P | undefined>;
+}
+
+/** Accepts every connection of `server` on `host` as a client link stamped with the authenticated principal. */
+export function acceptWebSockets<Request, P = unknown>(
+	server: WebSocketServerLike<Request>,
+	host: Host<P>,
+	options: WebSocketAcceptOptions<Request, P>,
+): void {
+	server.on("connection", (socket, request) => {
+		// Wrap at once so frames sent while authenticating are queued, not lost. Large payloads go out deflated; clients
+		// may not send packed frames (a small message could inflate to anything).
+		const link = webSocketLink(socket, { compress: true, acceptPacked: false });
+		Promise.resolve(options.principal(request)).then(
+			(principal) => {
+				if (principal === undefined) link.close("unauthorized");
+				else host.accept(link, { ...options, principal, kind: "client" });
+			},
+			() => link.close("authentication failed"),
+		);
+	});
+}