// Uploads: a whole file, sealed chunk by chunk with several in flight, and the
// folders it lands in.
//
// Methods of MeshBayTransport, copied onto its prototype by extendTransport
// (transport.js, which the shell loads first).

extendTransport(class {
  /**
   * Push a whole file, several chunks in flight at once.
   *
   * One chunk per round trip is 48 KB of throughput per RTT no matter how much
   * bandwidth there is: 4.8 MB/s on a 10 ms path, 480 KB/s on a 100 ms one, and
   * the sender is idle for almost all of it — which also keeps SCTP's congestion
   * window shut, so the transport never gets a chance to speed up either. A
   * window of chunks makes the rate depend on bandwidth rather than distance.
   *
   * Order is not at risk: a DataChannel is ordered and reliable by default, and
   * the node refuses any chunk that is not the one it expects next.
   *
   * The node decides where this lands (uploads/) and under what name — it finds a
   * free one rather than replacing anything. The ack says which, and that is what
   * this returns.
   *
   * `dir` names the folder to upload into, as a virtual path
   * (`Media/Films/1999`) — where the sender is actually looking. The node
   * resolves it against the group's own roots, which refuses `..`, absolute
   * segments and anything escaping its root; it is a place among the group's
   * folders, never a path on the operator's filesystem.
   *
   * `root` is the older, coarser form: the root's name and nothing below it.
   * Kept because a node that predates `dir` reads it, and because Chat has no
   * folder on screen to name. Omitting both leaves the node to pick, which it
   * only does for a client old enough to have had one destination.
   */
  async uploadFile(file, { chunkSize, onProgress, signal, root, dir,
                          tr = '' } = {}) {
    // The same file twice at once would confuse the node, which keys its own
    // upload state by folder and name — and would race for the same
    // destination. The guard uses the same key: by name alone, a dropped folder
    // holding a `cover.jpg` in two albums failed the second one for nothing.
    const inFlightKey = `${dir || ''}/${file.name}`;
    if (this._inFlightUploads.has(inFlightKey)) {
      throw new Error(`${file.name} is already being uploaded`);
    }
    if (!this._gekRaw) throw new Error('This group has no key on this device');
    const C = window.MeshBayCrypto;
    const groupId = (this._connectArgs && this._connectArgs.groupId) || '';
    this._inFlightUploads.add(inFlightKey);
    const uploadId = _hex(crypto.getRandomValues(new Uint8Array(16)));
    const size = chunkSize || UPLOAD_CHUNK_SIZE;
    const total = Math.max(1, Math.ceil(file.size / size));
    let acked = 0;
    let stored = null;
    let failure = null;

    const acks = [];
    const wake = () => {
      acked += 1;
      if (onProgress) onProgress(Math.min(file.size, acked * size), file.size);
      const waiter = acks.shift();
      if (waiter) waiter();
    };
    // "Where am I?" — resolved by the node's answer to the probe chunk below,
    // or by anything that says this node cannot answer it.
    let settleProbe = null;
    const probed = new Promise((r) => { settleProbe = r; });
    const answerProbe = (from) => {
      if (!settleProbe) return false;
      const done = settleProbe;
      settleProbe = null;
      done(from);
      return true;
    };
    this._uploaders.set(uploadId, (msg) => {
      if (msg.type === 'error') {
        // A node that predates the probe refuses its index. That is not a
        // failure — it is the answer "start from the beginning", which is what
        // this client did before there was anything to ask.
        if (answerProbe(0)) return;
        failure = new Error(msg.detail || 'Upload refused');
        wake();
        return;
      }
      // The ack is sealed too — `stored_as` and the folder it landed in name
      // the operator's content. Opening it is what makes the result usable, so
      // a failure here fails the upload rather than being swallowed: a chat
      // attachment that cannot learn its stored name would point at nothing.
      C.openGroup(this._gekRaw, 'upload', 'file_upload_ack', groupId, msg)
        .then((plain) => {
          const payload = msgpack_decode(plain);
          if (payload.stored_as) stored = payload;
          // Only the probe's answer carries this, so the two are told apart
          // without trusting the index the node echoed back in clear.
          if (typeof payload.resume_from === 'number') return answerProbe(payload.resume_from);
          return false;
        })
        .catch((e) => {
          failure = new Error(
            `The node's upload reply did not open under the group key (${e.message})`);
          return false;
        })
        // A probe's answer is not a chunk: waking here would credit the
        // progress bar with a chunk that was never sent.
        .then((wasProbe) => { if (!wasProbe) wake(); });
    });

    const nextAck = () => new Promise(r => acks.push(r));

    try {
      // Ask before sending anything. An upload interrupted at 99% used to start
      // again from zero, because the node kept its position on the connection
      // that was lost — see `uploads.py`. The question goes inside the seal, as
      // a chunk with no bytes, because naming the file on a clear message is
      // exactly what sealing this path was for.
      // Sealed first, spread second — the same shape as the chunk loop below,
      // and not only for symmetry: `test_the_upload_itself_is_sealed` reads
      // this call and fails if a filename appears in it, which is how it can
      // tell a field outside the seal from one inside it.
      const probeSealed = await C.sealGroup(
        this._gekRaw, 'upload', 'file_upload', groupId,
        msgpack_encode({ filename: file.name, data: new Uint8Array(0),
                         dir: dir || '', root: root || '' }));
      this._send({
        type: 'file_upload',
        v: '0.1',
        upload_id: uploadId,
        chunk_index: UPLOAD_PROBE_INDEX,
        total_chunks: total,
        ...(tr ? { tr } : {}),
        ...probeSealed,
      });
      // Bounded: a node that answers neither the probe nor its refusal must not
      // leave an upload waiting for ever. Starting over is always safe.
      let from = await Promise.race([
        probed,
        new Promise((r) => setTimeout(() => { answerProbe(0); r(0); },
                                      UPLOAD_PROBE_TIMEOUT_MS)),
      ]);
      // Defensive: a node reporting a position at or past the end would have
      // renamed the file and dropped its state, so this cannot happen — and if
      // it does, sending everything again is the answer that cannot corrupt.
      if (!(from > 0) || from >= total) from = 0;
      if (from > 0) {
        acked = from;
        if (onProgress) onProgress(Math.min(file.size, from * size), file.size);
      }

      for (let i = from; i < total; i++) {
        if (signal && signal.aborted) throw _aborted();
        // Between two chunks, never inside one — the node refuses a chunk that
        // is not the one it expects, so a position is the only thing worth
        // remembering. Nothing is recorded here beyond that: the node holds the
        // real position, and the probe above is what asks for it on the way
        // back in, which makes resuming correct even across a reconnect.
        if (signal && signal.paused) {
          signal.resumeFrom = i;
          const paused = new Error('Paused');
          paused.name = 'PausedError';
          throw paused;
        }
        // Backpressure: without it the whole file lands in the browser's send
        // buffer in seconds and the progress bar becomes a work of fiction.
        while (this._channel && this._channel.bufferedAmount > UPLOAD_BUFFER_HIGH) {
          if (signal && signal.aborted) throw _aborted();
          await new Promise(r => setTimeout(r, 20));
        }
        while (i - acked >= UPLOAD_WINDOW) {
          await nextAck();
          if (failure) throw failure;
        }
        if (failure) throw failure;

        const buf = new Uint8Array(
          await file.slice(i * size, (i + 1) * size).arrayBuffer());
        // The name, the destination and the bytes go inside the seal together.
        // Mirrors `file_upload_wire` in meshbay_common/protocol.py; only the
        // fields the node routes on stay outside it.
        const sealed = await C.sealGroup(
          this._gekRaw, 'upload', 'file_upload', groupId,
          msgpack_encode({ filename: file.name, data: buf,
                           dir: dir || '', root: root || '' }));
        this._send({
          type: 'file_upload',
          v: '0.1',
          upload_id: uploadId,
          chunk_index: i,
          total_chunks: total,
          ...(tr ? { tr } : {}),
          ...sealed,
        });
      }
      while (acked < total) {
        await nextAck();
        if (failure) throw failure;
      }
    } finally {
      this._uploaders.delete(uploadId);
      this._inFlightUploads.delete(inFlightKey);
    }
    return stored || {};
  }

  /** Create a directory under the current one. Any member may. */
  async createDirectory(dir, name) {
    const msg = await this._sendAndWait({
      type: 'dir_create', v: '0.1', dir: dir || '', name,
    });
    if (msg.type === 'error') throw new Error(msg.detail);
    return msg;
  }
});

// 48 KB is what fits comfortably in one SCTP message across stacks; the window is
// what makes the rate independent of the round trip. 32 × 48 KB = 1.5 MB in
// flight, which saturates any path up to roughly 100 Mb/s at 100 ms.
const UPLOAD_CHUNK_SIZE = 48 * 1024;
const UPLOAD_WINDOW = 32;
// "Where am I?", asked as an ordinary sealed upload chunk with no bytes rather
// than on a clear message. Mirrors UPLOAD_PROBE_INDEX in
// meshbay_common/protocol.py; the node writes nothing and answers with
// `resume_from`, and one that predates it refuses the index, which reads as
// "start from the beginning".
const UPLOAD_PROBE_INDEX = -1;
// How long to wait for that answer before assuming there is none. A node that
// answers neither the probe nor its refusal must not leave an upload waiting
// for ever, and starting over is always safe.
const UPLOAD_PROBE_TIMEOUT_MS = 5000;
const UPLOAD_BUFFER_HIGH = 1024 * 1024;