// Run the SHIPPED transport through a change of network, and see whether the
// connection follows.
//
// A phone moving between mobile data and the Wi-Fi the node is on keeps a
// connection whose candidate pair runs over the network it left. Reported on
// the Android application: the group stopped answering and the application had
// to be killed. transport.js is executed whole; what is modelled is the
// environment: a clock, the window's events, `navigator.connection`, a peer
// connection that opens its channel after the answer, a hub that answers the
// offer and the token (or does not, while the device is offline), and a node
// that answers the handshake and pings until it is cut off.
//
// Usage: node network_change_harness.mjs <transport sources> <json>
//   {"scenario": "change-dead" | "change-alive" | "backoff" | "ice-dead" | "ice-alive"
//                | "events" | "closed" | "refused"
//                | "refused-during"}
import { readFileSync } from 'fs';
import { delimiter } from 'path';

const transportSrc = process.argv[2].split(delimiter)
  .map((p) => readFileSync(p, 'utf8')).join('\n');
const { scenario } = JSON.parse(process.argv[3] || '{}');

for (const level of ['log', 'warn', 'error', 'info', 'debug']) {
  console[level] = (...args) => process.stderr.write(args.join(' ') + '\n');
}
process.on('unhandledRejection', () => {});

// ── The clock ────────────────────────────────────────────────────────────────

let now = 0;
let nextId = 1;
let timers = [];
globalThis.setTimeout = (fn, ms) => {
  const t = { at: now + (ms || 0), fn, id: nextId++ };
  timers.push(t);
  return t.id;
};
globalThis.setInterval = (fn, ms) => {
  const t = { at: now + ms, fn, id: nextId++, every: ms };
  timers.push(t);
  return t.id;
};
globalThis.clearTimeout = (id) => { timers = timers.filter((t) => t.id !== id); };
globalThis.clearInterval = globalThis.clearTimeout;
Date.now = () => now;
globalThis.performance = { now: () => now };
const flush = async () => { for (let i = 0; i < 50; i++) await Promise.resolve(); };
async function run(until) {
  await flush();
  while (timers.length) {
    const due = timers.reduce((a, b) => (b.at < a.at ? b : a));
    if (due.at > until) break;
    if (due.every) due.at += due.every;
    else timers = timers.filter((t) => t !== due);
    now = Math.max(now, due.every ? due.at - due.every : due.at);
    due.fn();
    await flush();
  }
  now = until;
}

// ── The page around the transport ────────────────────────────────────────────

function eventTarget(obj) {
  const listeners = new Map();
  obj.addEventListener = (type, fn) => {
    if (!listeners.has(type)) listeners.set(type, new Set());
    listeners.get(type).add(fn);
  };
  obj.removeEventListener = (type, fn) => { listeners.get(type)?.delete(fn); };
  obj.dispatch = (type) => { for (const fn of [...(listeners.get(type) || [])]) fn({ type }); };
  obj.listening = () => [...listeners.values()].reduce((n, s) => n + s.size, 0);
  return obj;
}

globalThis.window = globalThis;
eventTarget(globalThis);
const connection = eventTarget({ type: 'cellular', effectiveType: '4g' });
Object.defineProperty(globalThis, 'navigator',
  { value: { userAgent: 'harness', connection }, configurable: true });
globalThis.location = { hash: '' };
globalThis.document = {
  addEventListener() {}, removeEventListener() {}, visibilityState: 'visible',
};
globalThis.localStorage = { getItem: () => null, setItem() {}, removeItem() {} };

const b64 = (u8) => Buffer.from(u8).toString('base64');
window.MeshBayCrypto = {
  b64encode: (u8) => b64(u8),
  b64decode: (s) => new Uint8Array(Buffer.from(String(s), 'base64')),
  verifyNodeSignature: async () => true,
  challengeTranscript: () => new Uint8Array(1),
  webrtcBinding: () => new Uint8Array(1),
  handshakeProof: async () => new Uint8Array([7]),
  handshakeTranscript: () => new Uint8Array(1),
  constantTimeEqual: () => true,
  openGroup: async () => window.__codec.msgpack_encode({ chat_epoch: 1 }),
};

const SDP = 'v=0\r\na=fingerprint:sha-256 AA:BB\r\n';
const candidate = (address, kind) => `a=candidate:1 1 udp 2130706431 ${address} 50000 typ ${kind}\r\n`;
// On the node's Wi-Fi without the permission (test_local_network_refused.py):
// the phone's offer and the node's answer as measured, and the node's address
// on the phone's subnet missing from what the browser paired.
const WIFI_OFFER = SDP + candidate('192.168.1.13', 'host') + candidate('90.112.206.172', 'srflx');
const NODE_ANSWER = SDP + candidate('192.168.1.22', 'host') + candidate('90.112.206.172', 'srflx');
const KEPT_WHEN_REFUSED = ['90.112.206.172'];
let offline = false;
let lanRefused = false;
globalThis.fetch = async (url) => {
  if (offline) throw new TypeError('Failed to fetch');
  return {
    ok: true, status: 200, headers: { get: () => null },
    json: async () => (url.endsWith('/mnp-token') ? { mnp_token: 't' }
      : { sdp: lanRefused ? NODE_ANSWER : SDP }),
  };
};

// ── The node ─────────────────────────────────────────────────────────────────

let pings = 0;
const pcs = [];

class NodeSession {
  constructor(channel) { this.channel = channel; this.cut = false; }
  reply(obj, ms) {
    setTimeout(() => {
      if (this.cut || this.channel.readyState !== 'open') return;
      const body = window.__codec.msgpack_encode(obj);
      const frame = new Uint8Array(4 + body.byteLength);
      new DataView(frame.buffer).setUint32(0, body.byteLength, false);
      frame.set(body, 4);
      this.channel.onmessage({ data: frame.buffer });
    }, ms);
  }
  receive(frame) {
    if (this.cut) return;
    const msg = window.__codec.msgpack_decode(frame.slice(4));
    const req_id = msg.req_id;
    switch (msg.type) {
      case 'handshake':
        return this.reply({ type: 'handshake_challenge', v: '99.0', v_min: '0.0',
          nonce: b64(new Uint8Array(32)), node_pk: 'pk', sig: 's', req_id }, 50);
      case 'handshake_response':
        return this.reply({ type: 'handshake_ack', proof: 'AA==', node_pk: 'pk', sig: 's',
          nonce: 'n', ct: 'c', req_id }, 50);
      case 'device_hello':
        return this.reply({ type: 'device_hello_ack', req_id }, 50);
      case 'ping':
        pings += 1;
        return this.reply({ type: 'pong', token: msg.token, req_id }, 30);
      default:
        return undefined;
    }
  }
}

class FakeChannel {
  constructor() { this.readyState = 'connecting'; this.binaryType = 'arraybuffer'; }
  send(frame) {
    if (this.readyState !== 'open') throw new Error('InvalidStateError');
    this.session.receive(frame);
  }
  close() {
    if (this.readyState === 'closed') return;
    this.readyState = 'closed';
    if (this.onclose) this.onclose({});
  }
}

class FakePC {
  constructor() {
    this.connectionState = 'new';
    this.iceConnectionState = 'new';
    this.iceGatheringState = 'complete';
    pcs.push(this);
  }
  createDataChannel() { this.channel = new FakeChannel(); return this.channel; }
  async createOffer() { return { type: 'offer', sdp: lanRefused ? WIFI_OFFER : SDP }; }
  async setLocalDescription(d) { this.localDescription = d; }
  async getStats() {
    const reports = new Map();
    if (this.refused) {
      KEPT_WHEN_REFUSED.forEach((address, i) => {
        reports.set(`R${i}`, { id: `R${i}`, type: 'remote-candidate', address });
      });
    }
    return reports;
  }
  async setRemoteDescription() {
    if (lanRefused) {
      // ICE gives up, and the channel goes with it, as Chrome reports it:
      // there after thirty seconds, here after fifteen.
      this.refused = true;
      setTimeout(() => {
        if (this.connectionState === 'closed') return;
        this.iceConnectionState = 'failed';
        this.connectionState = 'failed';
        this.channel.close();
      }, 15000);
      return;
    }
    setTimeout(() => {
      if (this.connectionState === 'closed') return;
      this.channel.session = new NodeSession(this.channel);
      this.channel.readyState = 'open';
      this.connectionState = 'connected';
      this.iceConnectionState = 'connected';
      if (this.channel.onopen) this.channel.onopen();
    }, 100);
  }
  close() {
    this.connectionState = 'closed';
    if (this.channel) this.channel.close();
  }
}
globalThis.RTCPeerConnection = FakePC;

// ── The shipped transport ────────────────────────────────────────────────────

new Function(`${transportSrc}\nwindow.__codec = { msgpack_encode, msgpack_decode };`)();
const Transport = window.MeshBayTransport;
// What the transport's own module listens to, before any connection exists.
const moduleListeners = window.listening() + connection.listening();
const out = {};

if (scenario === 'events') {
  // The helper alone: which events count as another network, and how many.
  let calls = 0;
  const off = Transport.onNetworkChange(() => { calls += 1; });
  const at = [];
  const step = async (fire) => { fire(); await run(now + 5000); at.push(calls); };
  await step(() => connection.dispatch('change'));                  // a bandwidth estimate
  await step(() => { connection.type = 'wifi'; connection.dispatch('change'); });
  await step(() => window.dispatch('online'));
  await step(() => window.dispatch('meshbay-default-network'));
  await step(() => {                                                 // one change, three events
    connection.type = 'cellular'; connection.dispatch('change');
    window.dispatch('online');
    window.dispatch('meshbay-default-network');
  });
  off();
  await step(() => window.dispatch('online'));
  out.calls = at;
  out.leftListening = window.listening() + connection.listening() - moduleListeners;
} else {
  const main = new Transport('https://hub.invalid', 'token');
  let reconnectedAt = null;
  main.addReconnectListener(() => { if (reconnectedAt === null) reconnectedAt = now; });
  const failures = [];
  main.addReconnectFailureListener((err) => { failures.push(err.reason || null); });
  let connected = false;
  const identity = { pkEdB64: 'ed', signAs: async () => 'sig', native: false };
  main.connect('node', 'token', 'group', new Uint8Array(32), identity, null, 'u', 'uid',
               undefined, undefined, '', 'pk')
    .then(() => { connected = true; }, (err) => { out.connectError = err.message; });
  await run(5000);
  out.connected = connected;

  const first = pcs[0];
  if (scenario === 'change-dead' || scenario === 'change-alive') {
    // Mobile data to Wi-Fi. The pair in use ran over mobile data; when it is
    // gone, the node hears nothing more on it.
    if (scenario === 'change-dead') first.channel.session.cut = true;
    connection.type = 'wifi';
    connection.dispatch('change');
    await run(25000);
  } else if (scenario === 'ice-dead' || scenario === 'ice-alive') {
    if (scenario === 'ice-dead') first.channel.session.cut = true;
    first.iceConnectionState = 'disconnected';
    first.oniceconnectionstatechange();
    await run(25000);
  } else if (scenario === 'backoff') {
    // The connection fails while the device has no network, and every attempt
    // fails with it until the backoff has grown long. Then Wi-Fi comes back.
    offline = true;
    first.channel.session.cut = true;
    first.connectionState = 'failed';
    first.onconnectionstatechange();
    await run(40000);
    offline = false;
    connection.type = 'wifi';
    connection.dispatch('change');
    out.backAt = now;
    await run(80000);
  } else if (scenario === 'refused-during') {
    // The same, with the permission granted while an attempt set up before it
    // is still waiting on ICE: that attempt is given up, the next goes at once.
    lanRefused = true;
    first.channel.session.cut = true;
    connection.type = 'wifi';
    connection.dispatch('change');
    await run(40000);
    const attempts = pcs.length;
    while (pcs.length === attempts) await run(now + 100);
    await run(now + 2000);
    lanRefused = false;
    out.backAt = now;
    main.retryNow();
    await run(now + 40000);
  } else if (scenario === 'refused') {
    // Connected on mobile data, then on the node's Wi-Fi without the local
    // network permission: every attempt is refused, and says so. The
    // permission is granted after a while, and the page asks to try now.
    lanRefused = true;
    first.channel.session.cut = true;
    connection.type = 'wifi';
    connection.dispatch('change');
    await run(60000);
    out.failures = [...failures];
    out.stillReconnecting = main.reconnecting;
    lanRefused = false;
    out.backAt = now;
    main.retryNow();
    await run(80000);
  } else if (scenario === 'closed') {
    main.close();
    connection.type = 'wifi';
    connection.dispatch('change');
    await run(25000);
    out.leftListening = window.listening() + connection.listening() - moduleListeners;
  }
  out.reconnectedAt = reconnectedAt;
  out.connections = pcs.length;
  out.pings = pings;
}

process.stdout.write(JSON.stringify(out));