/**
 * The per-session port band the loopback pages share.
 *
 * `serve` draws the session's one port from it, so every page that session serves
 * clusters where a person's bookmarks already point. The band is one product decision,
 * stated here once: a number repeated in each extension's config is several chances to
 * move one of them, and nothing would notice until a bookmark landed outside the range.
 *
 * A pick is a guess, not a reservation. `serveHttp` binds it and falls back to whatever
 * free port the OS gives, so a port another process holds costs a retry rather than a
 * start.
 */

import { randomInt } from "node:crypto";

/** Base of the per-session port range. */
export const PORT_BASE = 4780;

/** Number of ports in the per-session range. */
export const PORT_RANGE = 1000;

/** A random port in the per-session range `PORT_BASE`–`PORT_BASE + PORT_RANGE - 1`. */
export function randomPort(): number {
	return PORT_BASE + randomInt(PORT_RANGE);
}