import { chmodSync, copyFileSync, existsSync, mkdirSync } from 'node:fs';
import { homedir } from 'node:os';
import { join } from 'node:path';

// The iris sidecar: a builder wearing a supervisor's clothes.
//
// The install pipeline installs packages and fetches release binaries, but deliberately runs no build
// step — so compiling a Rust crate is this plugin's own job, and the sidecar is the only process the
// platform starts for a plugin. First start pays for the build (minutes — watch `pm2 logs officer-iris`);
// every later start finds the binary and settles into a heartbeat.
//
// Everything lands where the platform already looks: `~/.local/bin` is first on the probe path in
// os-deps.ts, so `iris` and `iris-browser` are found by whoever asks, without anyone's PATH changing.

const name = 'officer-iris';
const CRATE = 'iris-screenshot';
// Upstream's declared rust-version. Distro cargo lags real Rust by a year or more, so this is checked
// BEFORE building — a clear refusal with instructions beats cargo's own MSRV error buried in build spam.
const MSRV: readonly [number, number] = [1, 88];

const home = homedir();
const localBin = join(home, '.local', 'bin');

// `Bun.which` alone reads the PATH this process started with, which under PM2 is minimal. Look where
// things actually are: our install target first, rustup's home second, then whatever PATH says.
const searchPath = (): string => `${localBin}:${join(home, '.cargo', 'bin')}:${process.env.PATH ?? ''}`;
const which = (binary: string): string | null => Bun.which(binary, { PATH: searchPath() });

const log = (message: string): void => console.log(`[${name}] ${message}`);

/** The wrapper ships in this repository; agents need it on a path they can name. Overwrite = upgrade. */
function installWrapper(): void {
  const source = join(import.meta.dir, '..', 'bin', 'iris-browser');
  const target = join(localBin, 'iris-browser');
  mkdirSync(localBin, { recursive: true });
  copyFileSync(source, target);
  chmodSync(target, 0o755);
  log(`iris-browser installed to ${target}`);
}

/** `cargo 1.75.0 (…)` → [1, 75], or null when it will not even say. */
function cargoVersion(cargo: string): [number, number] | null {
  try {
    const out = Bun.spawnSync([cargo, '--version'], { stdout: 'pipe', stderr: 'pipe' });
    const match = new TextDecoder().decode(out.stdout).match(/cargo (\d+)\.(\d+)/);
    return match ? [Number(match[1]), Number(match[2])] : null;
  } catch {
    return null;
  }
}

const meetsMsrv = ([major, minor]: [number, number]): boolean =>
  major > MSRV[0] || (major === MSRV[0] && minor >= MSRV[1]);

/**
 * Build iris into ~/.local/bin. Streams cargo's output straight to PM2's log, because a silent
 * multi-minute compile is indistinguishable from a hang.
 *
 * `--locked` builds against upstream's committed lockfile rather than re-resolving dependencies at
 * install time — the platform's frozen-lockfile rule, honoured one language over.
 */
async function build(cargo: string): Promise<boolean> {
  log(`building ${CRATE} — first start only, takes a few minutes`);
  const proc = Bun.spawn([cargo, 'install', CRATE, '--locked', '--root', join(home, '.local')], {
    stdout: 'inherit',
    stderr: 'inherit',
  });
  const code = await proc.exited;
  if (code !== 0) {
    log(`build failed (cargo exited ${code}) — read the output above; restart this process to retry`);
    return false;
  }
  return true;
}

/** True when the binary is usable. Says why not, with the fix, when it is not. */
async function ensureIris(): Promise<boolean> {
  const present = which('iris');
  if (present) {
    log(`iris ready at ${present}`);
    return true;
  }

  const cargo = which('cargo');
  if (!cargo) {
    log('cargo is not on PATH — the install should have provided it; install rust and restart this process');
    return false;
  }

  const version = cargoVersion(cargo);
  if (!version || !meetsMsrv(version)) {
    log(`${cargo} is ${version ? `cargo ${version.join('.')}` : 'unidentifiable'}, and ${CRATE} needs ${MSRV.join('.')}+`);
    log('your distribution\'s rust is too old. Install rustup as the user officer runs as:');
    log("  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal");
    log('then restart this process: pm2 restart officer-iris');
    return false;
  }

  if (!(await build(cargo))) return false;

  const built = which('iris');
  if (!built) {
    log('cargo reported success but iris is not in ~/.local/bin — read the build output above');
    return false;
  }
  log(`iris built and ready at ${built}`);
  return true;
}

log(`started (pid ${process.pid})`);
installWrapper();
let ready = await ensureIris();

// The heartbeat re-probes rather than repeating a remembered answer: a binary deleted out from under us
// shows up here, and a rustup installed after a refusal turns the next restart into a build — which the
// log has already told the owner. Building inside the interval is deliberately avoided: a periodic
// compile that nobody asked for is not a heartbeat.
const beat = setInterval(() => {
  const present = which('iris');
  if (present && !ready) {
    ready = true;
    log(`iris appeared at ${present}`);
  } else if (!present && ready) {
    ready = false;
    log('iris is GONE from PATH — restart this process to rebuild');
  } else {
    log(`alive — iris ${present ? 'ready' : 'missing'}`);
  }
}, 300_000);

const shutdown = (signal: string): void => {
  log(`${signal} — exiting`);
  clearInterval(beat);
  process.exit(0);
};

process.on('SIGTERM', () => shutdown('SIGTERM'));
process.on('SIGINT', () => shutdown('SIGINT'));