/** Resident RAM query projection; PostgreSQL is the only persistent data source. */
import { spawn } from 'node:child_process';
import { fileURLToPath } from 'node:url';
import { createInterface } from 'node:readline';

export function unifiedReader({ python, unifiedConfig, timeoutMs = 120000 } = {}) {
  let child, nextId = 0, closed = false;
  const pending = new Map();
  function start() {
    const worker = spawn(python, ['-B', '-X', 'utf8', fileURLToPath(new URL('./voc-library/unified_worker.py', import.meta.url))],
      { windowsHide: true, stdio: ['pipe', 'pipe', 'pipe'],
        env: { ...process.env, KSF_UNIFIED_DB_CONFIG: unifiedConfig } });
    child = worker;
    worker.stderr.resume();
    worker.stdin.on('error', () => {});
    const terminate = () => {
      if (child !== worker) return;
      for (const item of pending.values()) { clearTimeout(item.timer); item.reject(Error('UNIFIED_WORKER_UNAVAILABLE')); }
      pending.clear(); child = undefined;
    };
    worker.on('error', terminate); worker.on('exit', terminate);
    const lines = createInterface({ input: worker.stdout });
    lines.on('line', line => {
      if (child !== worker) return;
      if (Buffer.byteLength(line) > 6000000) return worker.kill();
      try {
        const data = JSON.parse(line), item = pending.get(data.id);
        if (item) { clearTimeout(item.timer); pending.delete(data.id); item.resolve(data.result); }
      } catch { worker.kill(); }
    });
  }
  const read = (engine, config, request) => new Promise((resolve, reject) => {
    if (closed) return reject(Error('UNIFIED_WORKER_CLOSED'));
    if (pending.size >= 4) return reject(Error('LIBRARY_BUSY'));
    if (!child) start();
    const id = ++nextId;
    const worker = child;
    const timer = setTimeout(() => { worker.kill(); }, timeoutMs);
    pending.set(id, { resolve, reject, timer });
    child.stdin.write(JSON.stringify({ id, engine, config, request }) + '\n');
  });
  read.close = () => { closed = true; child?.kill(); };
  return read;
}