// Exercises the island's os and diagnostics_channel shims differentially:
// every line must match real Node byte-for-byte. os values bridge to the
// same runtime answers as the static lowerings; diagnostics_channel is
// real pub/sub (publish with no subscribers is a no-op, like Node).
import os, { EOL } from "node:os";
import dc from "diagnostics_channel";

export function report() {
  const lines = [];
  lines.push(`platform=${os.platform()}`);
  lines.push(`arch=${os.arch()}`);
  lines.push(`home=${os.homedir()}`);
  lines.push(`tmp=${os.tmpdir()}`);
  lines.push(`eol=${JSON.stringify(os.EOL)} named=${EOL === os.EOL}`);
  lines.push(`host-ok=${os.hostname().length > 0}`);
  const got = [];
  dc.subscribe("demo", (msg, name) => got.push(`${name}:${msg.n}`));
  const ch = dc.channel("demo");
  lines.push(`has=${ch.hasSubscribers}`);
  ch.publish({ n: 1 });
  dc.channel("demo").publish({ n: 2 });
  lines.push(...got);
  const silent = dc.channel("nobody");
  silent.publish({ n: 3 });
  lines.push(`silent=${silent.hasSubscribers} ${dc.hasSubscribers("nobody")}`);
  const fn = () => {};
  dc.subscribe("once", fn);
  lines.push(`unsub=${dc.unsubscribe("once", fn)} ${dc.unsubscribe("once", fn)}`);
  const tc = dc.tracingChannel("op");
  lines.push(`tc=${tc.hasSubscribers === false}`);
  return lines.join("\n");
}