import { sidecarPort } from '@@/sidecar-registry';
import { snapshotPlugins } from '@@/plugins/mount';

/*
  Where a plugin's socket actually goes.

  A target is an ADDRESS — a host and a port — never a URL a manifest wrote. The relay turns it into
  `ws://<host>:<port>/ws`, and `/ws` is a convention rather than a setting for the same reason the host is
  not configurable: every value here has to be one the platform derived, not one a plugin asserted.

  The target is always a SIDECAR. A fixed-port form was written and removed the same day: nothing stops a
  manifest naming a port it does not own, so `{ port: 5432 }` plus a grant would be a raw TCP relay onto
  Postgres for anyone that plugin reaches. Verifying the host is loopback is not verifying the port belongs
  to the plugin, and only the second question matters.

  A sidecar's port is different in kind, not degree: the platform watched it arrive at registration, so the
  association is observed rather than asserted. It is also the SAME port the sidecar serves its HTTP on —
  one announcement, one listener, `/ws` alongside the routes. That is what the relay's move to
  websocket-to-websocket bought, and why a plugin wanting a socket no longer has to choose between having
  one and having ordinary routes.

  **Host is always loopback and is not configurable.** A plugin socket that could name an arbitrary host
  would be a request-forgery primitive handed to every plugin author and reachable by anyone the plugin is
  granted to. There is no case for it that a sidecar does not already serve.
*/

export type PluginWsTarget = { host: string; port: number };

export async function pluginWsTargetFor(appName: string): Promise<PluginWsTarget | null> {
  const { states } = await snapshotPlugins();
  // Installed, not merely present on disk. A plugin directory that exists but is not installed has no
  // routes and no permission, so it must have no socket either.
  const state = states.find((st) => st.plugin.appName === appName && st.install);
  const socket = state?.plugin.manifest.websocket;
  if (!socket) return null;

  // A sidecar that has not announced its port yet is indistinguishable from one that never will, and both
  // are correctly a refusal — there is nothing to relay onto. The caller says "not accepting connections",
  // which is true either way.
  const port = sidecarPort(socket.sidecar);
  return port ? { host: '127.0.0.1', port } : null;
}