frontend/src/api.js

// api.js — the ONLY network layer. Talks to the backend's GRADIO API endpoints via @gradio/client
// (NOT plain fetch): ZeroGPU only grants the GPU to calls carrying the HF iframe auth headers, and
// @gradio/client is what forwards them. Endpoints: /turn (game loop incl. the GPU dispatcher),
// /game_model (toggle/switch), /announce (VoxCPM voice). One session id per tab, passed as `sid`.

import { Client } from '@gradio/client';

export function sessionId() {
  let sid = sessionStorage.getItem('mlp_session_id');
  if (!sid) {
    sid = `web-${Math.random().toString(36).slice(2, 10)}-${Date.now().toString(36)}`;
    sessionStorage.setItem('mlp_session_id', sid);
  }
  return sid;
}

export class ApiError extends Error {
  constructor(status, message) {
    super(message);
    this.status = status;
  }
}

// Connect once (lazily). On the Space this runs inside the HF iframe, so @gradio/client forwards the
// auth ZeroGPU needs; locally it just hits the dev gr.Server.
let _clientPromise = null;
function client() {
  if (!_clientPromise) {
    _clientPromise = Client.connect(window.location.origin).catch((e) => {
      _clientPromise = null;            // allow retry on next call
      throw new ApiError(0, e?.message || 'could not connect to the game server');
    });
  }
  return _clientPromise;
}

async function call(endpoint, args) {
  const app = await client();
  const res = await app.predict(endpoint, args);
  return res?.data?.[0];
}

/** new_game / play_card / next_turn -> RenderState. Throws ApiError on {error} (rejected -> 409). */
export async function turn(body) {
  const d = await call('/turn', { payload: body, sid: sessionId() });
  if (d && typeof d === 'object' && d.error && !('round' in d)) {
    throw new ApiError(d.rejected ? 409 : 400, d.error);
  }
  return d;
}

/** {on?, model?} -> {on, model, models, tts}. */
export async function gameModel(body) {
  return call('/game_model', { payload: body || {}, sid: sessionId() });
}

/** Voice the last turn's announcement -> {audio: base64|null}. */
export async function announce(round) {
  return call('/announce', { sid: sessionId(), round });
}