// lib/snapshot.js — headless-chromium homepage screenshots of deployed apps.
// One chromium at a time (module-level promise chain); duplicate requests for
// a project that is already queued/running are skipped. Never throws — all
// errors are caught and logged to the console.
import fs from 'node:fs';
import path from 'node:path';
import { config, NAME_RE } from './config.js';
import { runCmd } from './paas.js';

// Domain is embedded in chromium args — must be a plain hostname, nothing else.
const SNAP_DOMAIN_RE = /^[a-z0-9]([a-z0-9.-]*[a-z0-9])?$/;

let chain = Promise.resolve();
const inFlight = new Set();

export function snapshotPath(projectName) {
  if (!NAME_RE.test(projectName)) throw new Error(`invalid app name: ${projectName}`);
  return path.join(config.snapshotDir, `${projectName}.png`);
}

// Fire-and-forget friendly: resolves true when a fresh snapshot was written,
// false when skipped or failed. Never rejects.
export function takeSnapshot(projectName, primaryDomain) {
  try {
    if (!NAME_RE.test(String(projectName || ''))) return Promise.resolve(false);
    const domain = String(primaryDomain || '').trim().toLowerCase();
    if (!SNAP_DOMAIN_RE.test(domain)) return Promise.resolve(false);
    if (inFlight.has(projectName)) return Promise.resolve(false);
    inFlight.add(projectName);
    const job = chain
      .then(() => run(projectName, domain))
      .catch((err) => {
        console.error(`[snapshot] ${projectName}: ${(err && err.message) || err}`);
        return false;
      })
      .finally(() => inFlight.delete(projectName));
    chain = job;
    return job;
  } catch (err) {
    console.error(`[snapshot] ${projectName}: ${(err && err.message) || err}`);
    return Promise.resolve(false);
  }
}

async function run(projectName, domain) {
  fs.mkdirSync(config.snapshotDir, { recursive: true });
  const outFile = snapshotPath(projectName);
  const args = [
    '--headless=new',
    '--no-sandbox',
    // the render is pinned to 127.0.0.1 — cert validity is irrelevant for a
    // thumbnail, and freshly created apps have no certificate yet at all
    '--ignore-certificate-errors',
    '--disable-gpu',
    '--hide-scrollbars',
    '--window-size=1366,900',
    `--screenshot=${outFile}`,
    `--host-resolver-rules=MAP ${domain} 127.0.0.1`,
    '--virtual-time-budget=15000',
    `https://${domain}/`,
  ];
  // niced: a snapshot render must never compete with request serving
  const res = await runCmd('nice', ['-n', '19', config.chromiumBin, ...args], { timeout: 60000 });
  if (res.code !== 0) {
    const detail = res.timedOut ? 'timed out after 60s' : `exited with code ${res.code}`;
    console.error(`[snapshot] ${projectName}: chromium ${detail}: ${res.stderr.trim().slice(-300)}`);
    return false;
  }
  return true;
}