// The page's session: wai-app's WebAssembly build, the program as it streams, and the log
// every action a person takes on the page is sealed into (joule-ui SPEC §6, §7).
//
// `fire(action, inputs, handler)` is the interaction lifecycle around an asynchronous
// handler: authorized first (a denied action's handler never runs), the handler run and
// timed on the page's clock, then sealed as the next link of the log under the page's own
// key. A page has no energy meter: the figure is the estimator's, from the handler's wall
// time, and the log says so (`Estimator`).
import init, { Session, verifyLog, registry, guide, check } from "./pkg/wai_app.js";

export { verifyLog, registry, guide, check };

export async function openSession() {
  await init();
  const seed = crypto.getRandomValues(new Uint8Array(32));
  const s = new Session(seed);
  seed.fill(0);
  return new PageSession(s);
}

export class PageSession {
  constructor(wasm) {
    this.w = wasm;
    this.listeners = new Set();
    this.actor = wasm.actor();
  }
  push(chunk) { return JSON.parse(this.w.push(chunk)); }
  finish() { return JSON.parse(this.w.finish()); }
  reset() { this.w.reset(); }
  program() { return this.w.program(); }
  canonical() { return this.w.canonical(); }
  log() { return JSON.parse(this.w.log()); }
  logRaw() { return this.w.logRaw(); }
  verify() { return JSON.parse(this.w.verify()); }
  totalUj() { return this.w.totalUj(); }
  on(f) { this.listeners.add(f); return () => this.listeners.delete(f); }
  note(entry) { for (const f of this.listeners) { try { f(entry); } catch { /* a view's own fault */ } } }

  async fire(action, inputs, handler) {
    const b = JSON.parse(this.w.beginAction(action, JSON.stringify(inputs === undefined ? null : inputs)));
    if (b.sealed) {
      this.note(b.sealed);
      throw new Error(`${action} was denied: ${b.sealed.reason}`);
    }
    const t0 = performance.now();
    let out;
    let err = null;
    try { out = await handler(); } catch (e) { err = e; }
    const wall = performance.now() - t0;
    const output = err ? { error: String((err && err.message) || err) } : out === undefined ? null : out;
    let text;
    try { text = JSON.stringify(output); } catch { text = JSON.stringify(String(output)); }
    const entry = JSON.parse(this.w.finishAction(b.pending, text === undefined ? "null" : text, wall));
    this.note(entry);
    if (err) throw err;
    return out;
  }
}