// wire format is <len>(<header><message>)
// header is a varint, channel << 4 | <4-bit-type>

// type=0, should be the first message sent on a channel
message Feed {
  required bytes discoveryKey = 1;
  optional bytes nonce = 2;
}

// type=1, overall connection handshake. should be send just after the feed message on the first channel only
message Handshake {
  optional bytes id = 1;
  optional bool live = 2; // keep the connection open forever? both ends have to agree
  optional bytes userData = 3;
  repeated string extensions = 4;
  optional bool ack = 5; // Should all blocks be explicitly acknowledged?
}

// type=2, message indicating state changes etc.
// initial state for uploading/downloading is true
// if both ends are not downloading and not live it is safe to consider the stream ended
message Info {
  optional bool uploading = 1;
  optional bool downloading = 2;
}

// type=3, what do we have?
message Have {
  required uint64 start = 1;
  optional uint64 length = 2 [default = 1]; // defaults to 1
  optional bytes bitfield = 3;
}

// type=4, what did we lose?
message Unhave {
  required uint64 start = 1;
  optional uint64 length = 2 [default = 1]; // defaults to 1
}

// type=5, what do we want? remote should start sending have messages in this range
message Want {
  required uint64 start = 1;
  optional uint64 length = 2; // defaults to Infinity or feed.length (if not live)
}

// type=6, what don't we want anymore?
message Unwant {
  required uint64 start = 1;
  optional uint64 length = 2; // defaults to Infinity or feed.length (if not live)
}

// type=7, ask for data
message Request {
  required uint64 index = 1;
  optional uint64 bytes = 2;
  optional bool hash = 3;
  optional uint64 nodes = 4;
}

// type=8, cancel a request
message Cancel {
  required uint64 index = 1;
  optional uint64 bytes = 2;
  optional bool hash = 3;
}

// type=9, get some data
message Data {
  message Node {
    required uint64 index = 1;
    required bytes hash = 2;
    required uint64 size = 3;
  }

  required uint64 index = 1;
  optional bytes value = 2;
  repeated Node nodes = 3;
  optional bytes signature = 4;
}

// type=15 (last message) is an extension message
// that is encoded like this <varint user-type><payload>