// Minimal Chrome DevTools Protocol client (Node 22 global WebSocket, no npm deps).
const fs = require('fs');
const path = require('path');

class CDP {
  constructor(wsUrl) {
    this.wsUrl = wsUrl;
    this.id = 0;
    this.pending = new Map();
    this.closed = false;
  }

  connect(timeoutMs = 10000) {
    return new Promise((resolve, reject) => {
      const ws = new WebSocket(this.wsUrl);
      this.ws = ws;
      const timer = setTimeout(() => { try { ws.close(); } catch {} reject(new Error('connect timeout')); }, timeoutMs);
      ws.onopen = () => { clearTimeout(timer); resolve(this); };
      ws.onerror = () => { clearTimeout(timer); reject(new Error('ws error')); };
      ws.onclose = () => {
        this.closed = true;
        for (const [, p] of this.pending) p.rej(new Error('ws closed'));
        this.pending.clear();
      };
      ws.onmessage = (ev) => {
        let m;
        try { m = JSON.parse(ev.data); } catch { return; }
        if (m.id && this.pending.has(m.id)) {
          const p = this.pending.get(m.id);
          this.pending.delete(m.id);
          if (m.error) p.rej(new Error(m.error.message || 'cdp error'));
          else p.res(m.result);
        }
      };
    });
  }

  send(method, params = {}, timeoutMs = 15000) {
    if (this.closed) return Promise.reject(new Error('ws closed'));
    const id = ++this.id;
    return new Promise((res, rej) => {
      this.pending.set(id, { res, rej });
      this.ws.send(JSON.stringify({ id, method, params }));
      setTimeout(() => {
        if (this.pending.has(id)) { this.pending.delete(id); rej(new Error('cdp timeout: ' + method)); }
      }, timeoutMs);
    });
  }

  async eval(expression, timeoutMs = 15000) {
    const r = await this.send('Runtime.evaluate', {
      expression,
      returnByValue: true,
      awaitPromise: true,
      userGesture: true
    }, timeoutMs);
    if (r.exceptionDetails) {
      throw new Error(r.exceptionDetails.exception?.description || r.exceptionDetails.text || 'eval failed');
    }
    return r.result ? r.result.value : undefined;
  }

  close() { try { this.ws.close(); } catch {} this.closed = true; }
}

async function listPages(port, urlMatch) {
  const res = await fetch(`http://127.0.0.1:${port}/json/list`, { signal: AbortSignal.timeout(5000) });
  const all = await res.json();
  return all.filter(t => t.type === 'page' && typeof t.url === 'string'
    && t.url.includes(urlMatch) && !t.url.startsWith('devtools://'));
}

const EXPR = fs.readFileSync(path.join(__dirname, 'probe-expression.js'), 'utf8');

module.exports = { CDP, listPages, EXPR };