import { ProtocolError } from './validation.js';

export function exhibitURL(value, base) {
  if (!value.trim()) throw new Error('Enter an exhibit URL or served path.');
  const url = new URL(value.trim(), base);
  if (!['http:', 'https:'].includes(url.protocol) || url.origin !== new URL(base).origin || url.username || url.password) {
    throw new Error('Enter a same-origin HTTP exhibit URL or served path.');
  }
  return url.href;
}

// Frame lifecycle only; protocol negotiation remains in ExhibitHost.
export class ExhibitConnection {
  constructor({ host, createFrame, transport, base, changed = () => {}, loadTimeoutMs = 15000 }) {
    Object.assign(this, { host, createFrame, transport, base, changed, loadTimeoutMs });
    this.frame = null; this.url = ''; this.loading = false; this.generation = 0;
  }
  disconnect() {
    this.generation++; clearTimeout(this.timer); this.loading = false;
    this.frame?.remove(); this.frame = null; this.host.disconnect(); this.changed();
  }
  load(value) {
    const url = exhibitURL(value, this.base); // Invalid input preserves the active exhibit.
    this.disconnect(); this.url = url; this.loading = true;
    const generation = this.generation;
    const frame = this.createFrame(); this.frame = frame;
    frame.addEventListener('load', () => {
      if (generation !== this.generation) return;
      clearTimeout(this.timer); this.loading = false; this.attach();
    });
    this.timer = setTimeout(() => {
      if (generation !== this.generation) return;
      this.disconnect();
      this.host.report(new ProtocolError('LOAD_TIMEOUT', 'Exhibit did not finish loading. Check the served path and reconnect.'));
    }, this.loadTimeoutMs);
    frame.src = url; this.changed();
  }
  async attach() {
    if (!this.frame || this.loading) return;
    const generation = this.generation;
    try { await this.host.connect(this.transport(this.frame), this.url); }
    catch (error) { if (generation === this.generation && !error.code) this.host.report(error); }
    this.changed();
  }
  reconnect() {
    if (this.frame && !this.loading) return this.attach();
    if (this.url) this.load(this.url);
  }
}