// Client for the belt's HTTP API.

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

const KEY = 'wh.key';
export const keyStore = {
  get() {
    try { return localStorage.getItem(KEY); } catch { return null; }
  },
  set(k) {
    try { localStorage.setItem(KEY, k); } catch { /* private mode: session only */ }
    memoryKey = k;
  },
  clear() {
    try { localStorage.removeItem(KEY); } catch { /* ignore */ }
    memoryKey = null;
  },
};
let memoryKey = null;
const currentKey = () => memoryKey ?? keyStore.get();

let unauthorized = () => {};
export function onUnauthorized(cb) { unauthorized = cb; }

async function call(method, path, { json, body, type, auth = true, raw = false, key } = {}) {
  const headers = {};
  // An explicit key (used by login) is tried as given and never triggers the
  // global "session rejected" handler.
  const k = key ?? (auth ? currentKey() : null);
  if (k) headers.Authorization = `Bearer ${k}`;
  let payload = body;
  if (json !== undefined) {
    payload = JSON.stringify(json);
    headers['Content-Type'] = 'application/json';
  } else if (type) {
    headers['Content-Type'] = type;
  }
  let res;
  try {
    res = await fetch(path, { method, headers, body: payload });
  } catch {
    throw new ApiError(0, 'LINK DOWN: cannot reach the server');
  }
  if (!res.ok) {
    let msg = `${res.status} ${res.statusText}`;
    try { msg = (await res.json()).error ?? msg; } catch { /* not JSON */ }
    if (res.status === 401 && auth && key === undefined) unauthorized();
    throw new ApiError(res.status, msg);
  }
  if (raw) return res;
  if ((res.headers.get('Content-Type') ?? '').includes('json')) return res.json();
  return null;
}

export const api = {
  info: () => call('GET', '/info', { auth: false }),
  market: () => call('GET', '/market', { auth: false }),
  register: (name) => call('POST', '/register', { json: { name }, auth: false }),
  me: (key) => call('GET', '/me', { key }),
  ships: () => call('GET', '/ships'),
  assemble: (source) => call('POST', '/assemble', { body: source, type: 'text/plain', auth: false }),
  setProgram: (id, bytes) => call('PUT', `/ships/${id}/program`, { body: bytes, type: 'application/octet-stream' }),
  launch: (id) => call('POST', `/ships/${id}/launch`),
  setUplink: (id, bytes) => call('PUT', `/ships/${id}/uplink`, { body: bytes, type: 'application/octet-stream' }),
  async downlink(id) {
    const res = await call('GET', `/ships/${id}/downlink`, { raw: true });
    return {
      bytes: new Uint8Array(await res.arrayBuffer()),
      day: Number(res.headers.get('X-Downlink-Day')),
    };
  },
  async example(name) {
    const res = await fetch(`/examples/${name}.s`);
    if (!res.ok) throw new ApiError(res.status, `example ${name} not found`);
    return res.text();
  },
  async examples() {
    const res = await fetch('/examples/index.json');
    return res.ok ? res.json() : [];
  },
};

export function b64ToBytes(b64) {
  const bin = atob(b64);
  const out = new Uint8Array(bin.length);
  for (let i = 0; i < bin.length; i++) out[i] = bin.charCodeAt(i);
  return out;
}