syntax = "proto3";

/**
 * This is just a helper message type that allows us to use a "base interface"
 * in code to describe that all messages should at least have a 'type field'.
 */
message base_message {
  // The type of the message.
  string type = 1;
}

/**
 * This is a user defined structure that is sent as part of the `config`
 * message. Left empty here because everything is optional.
 */
message peerConnectionOptions {
}

/**
 * A config message is sent to each connecting peer when it connects to
 * describe to them the setup of the signalling server they're
 * connecting to.
 */
message config {
  // Should always be 'config'
  string type = 1;
  // The user defined peer connnection options
  peerConnectionOptions peerConnectionOptions = 2;
  // The signalling protocol version the signalling server is using
  optional string protocolVersion = 3;
}

/**
 * A request for a new streamer to give itself an ID. The flow for these
 * messages should be connect->identify->endpointId->endpointIdConfirm
 */
message identify {
  // Should always be 'identify'
  string type = 1;
}

/**
 * Message is consumed by the Signalling Server. Specifies an id for the
 * streamer. This is used to uniquely identify multiple streamers connected
 * to the same Signalling Server.
 * Note: to preserve backward compatibility when Streamer IDs were optional,
 * when a Streamer first connects it is assigned a temporary ID which
 * allows use of older Streamers if needed.
 * Note: Streamer IDs must be unique and so if the ID provided here clashes
 * with an existing ID, the ID may be altered slightly (usually just an
 * appended number). The streamer will be sent an `endpointIdConfirm`
 * message to notify it of it's final ID.
 */
message endpointId {
  // Should always be 'endpointId'
  string type = 1;
  // The requested ID of the streamer.
  string id = 2;
  // The signalling protocol version the streamer is using
  optional string protocolVersion = 3;
}

/**
 * A response to `endpointId` that will notify the streamer of its final
 * ID given. Since streamer IDs must be unique the requested ID may not be
 * available and may need to be altered.
 */
message endpointIdConfirm {
  // Should always be 'endpointIdConfirm'
  string type = 1;
  // The final ID of the streamer.
  string committedId = 2;
}

/**
 * Message is used to communicate to players that the streamer it is currently
 * subscribed to is changing its ID. This allows players to keep track of it's
 * currently subscribed streamer and allow auto reconnects to the correct
 * streamer. This happens if a streamer sends an `endpointID` message after it
 * already has an ID assigned. (Can happen if it is late to respond to the
 * `identify` message and is auto assigned a legacy ID.)
 */
message streamerIdChanged {
  // Should always be 'streamerIdChanged'
  string type = 1;
  // The new ID of the streamer.
  string newID = 2;
}

/**
 * A request to the signalling server to send the player a list of
 * available streamers it could possibly subscribe to.
 */
message listStreamers {
  // Should always be 'listStreamers'
  string type = 1;
}

/**
 * Message is a reply to `listStreamers` from a player. Replies with a list of
 * currently active streamers connected to this server.
 */
message streamerList {
  // Should always be 'streamerList'
  string type = 1;
  // A list of streamer IDs active on the server.
  repeated string ids = 2;
}

/**
 * Message is consumed by the signalling server. Tells the signalling server
 * that the player requests to subscribe to the given stream.
 */
message subscribe {
  // Should always be 'subscribe'
  string type = 1;
  // The ID of the streamer the player wishes to subscribe to.
  string streamerId = 2;
}

/**
 * Message is consumed by the signalling server. Tells the signalling server
 * that the player wishes to unsubscribe from the current stream. The player
 * must have previously used the `subscribe` message for this to have any effect.
 */
message unsubscribe {
  // Should always be 'unsubscribe'
  string type = 1;
}

/**
 * Sent in response to a subscribe message when something goes wrong.
 */
 message subscribeFailed {
     // Should always be 'subscribeFailed'
     string type = 1;
     // A description of what went wrong.
     string message = 2;
 }

/**
 * A message sent to a streamer to notify it that a player has just
 * subscribed to it.
 */
message playerConnected {
  // Should always be 'playerConnected'
  string type = 1;
  // True if the player should be given a datachannel for stream control purposes.
  bool dataChannel = 2;
  // True if the player connected is an SFU
  bool sfu = 3;
  // The ID of the player that connected.
  string playerId = 5;
}

/**
 * Message is used to notify a streamer that a player has
 * unsubscribed/disconnected from the stream.
 */
message playerDisconnected {
  // Should always be 'playerDisconnected'
  string type = 1;
  // The ID of the player that disconnected.
  string playerId = 2;
}

/**
 * An offer message is an offer of a WebRTC stream.
 * When a player subscribes to a streamer the streamer will offer the
 * stream to the new player.
 */
message offer {
  // Should always be 'offer'
  string type = 1;
  // The SDP payload from WebRTC
  string sdp = 2;
  // If being sent to a player this should be a valid player ID
  optional string playerId = 3;
  // Indiates that this offer is coming from an SFU.
  optional bool sfu = 4;
  //Indicates that the streamer is multiplexing data channels
  optional bool multiplex = 5;
  // Indicates the scalability mode of the video stream
  optional string scalabilityMode = 6;
}

/**
 * This is a response to an `offer` message. It contains the answer `SDP`.
 * Part of the normal subscribe flow. A peer will subscribe to a streamer
 * and depending on whether `offer_to_receive` is set, one peer will make
 * an offer and the other should answer.
 */
message answer {
  // Should always be 'answer'
  string type = 1;
  // The WebRTC SDP payload
  string sdp = 2;
  // If being sent to a player this should be set to a valid player ID.
  optional string playerId = 3;
  // Specifies the minimum bitrate requested for streams.
  optional int32 minBitrateBps = 4;
  // Specifies the maximum bitrate requested for streams.
  optional int32 maxBitrateBps = 5;
}

/**
 * A submessage that contains data from a WebRTC ICE candidate.
 */
message iceCandidateData {
  string candidate = 1;
  string sdpMid = 2;
  int32 sdpMLineIndex = 3;
  optional string usernameFragment = 4;
}

/**
 * A single ICE candidate entry from WebRTC. Notifies a peer of a possible
 * connection option to another peer.
 */
message iceCandidate {
  // Should always be 'iceCandidate'
  string type = 1;
  // The ICE candidate data from WebRTC
  iceCandidateData candidate = 2;
  // If being sent to a player this should be a valid player ID.
  optional string playerId = 3;
}

/**
 * Message is consumed by the Signalling Server. Requests that the
 * signalling server disconnect the given player matching the player ID.
 */
message disconnectPlayer {
  // Should always be 'disconnectPlayer'
  string type = 1;
  // The ID of the player to disconnect.
  string playerId = 2;
  // An optional reason string to send to the player.
  optional string reason = 3;
}

/**
 * A keepalive ping message used to test that the connection is still open.
 */
message ping {
  // Should always be 'ping'
  string type = 1;
  // The current time
  int32 time = 2;
}

/**
 * Message is a reply to `ping` from a streamer. Replies with the time from the
 * ping message.
 */
message pong {
  // Should always be 'pong'
  string type = 1;
  // The echoed time from the ping message
  int32 time = 2;
}

/**
 * Message is used to notify players when a Streamer disconnects from the
 * signalling server.
 */
message streamerDisconnected {
  // Should always be 'streamerDisconnected'
  string type = 1;
}

/**
 * Message is forwarded to a connected SFU. Sends a preferred layer index to a
 * connected SFU for a specified player. Useful for switching between SFU
 * quality layers to force a certain resolution/quality option either as part
 * of UX or testing.
 */
message layerPreference {
  // Should always be 'layerPreference'
  string type = 1;
  // The requested spatial layer
  int32 spatialLayer = 2;
  // The requested temporal layer
  int32 temporalLayer = 3;
  // The player ID this preference refers to
  string playerId = 4;
}

/**
 * Message is forwarded to a connected SFU. Tells the SFU that the player
 * requests data channels to the streamer.
 */
message dataChannelRequest {
  // Should always be 'dataChannelRequest'
  string type = 1;
}

/**
 * Message is forwarded to a player. Sends information to the player about what
 * data channels to use for sending/receiving with the streamer.
 */
message peerDataChannels {
  // Should always be 'peerDataChannels'
  string type = 1;
  // The player ID this message refers to.
  string playerId = 2;
  // The channel ID to use for sending data.
  int32 sendStreamId = 3;
  // The channel ID to use for receiving data.
  int32 recvStreamId = 4;
}

/**
 * Message is forwarded to a connected SFU. Tells the SFU that the player is
 * ready for data channels to be negotiated.
 */
message peerDataChannelsReady {
  // Should always be 'peerDataChannelsReady'
  string type = 1;
}

/**
 * Message is forwarded to the streamer. Sends a request to the streamer to
 * open up data channels for a given player.
 */
message streamerDataChannels {
  // Should always be 'streamerDataChannels'
  string type = 1;
  // The SFU the player is connected to
  string sfuId = 2;
  // The channel ID to use for sending data.
  int32 sendStreamId = 3;
  // The channel ID to use for receiving data.
  int32 recvStreamId = 4;
}

/**
 * Sent by the SFU to indicate that it is now streaming.
 */
message startStreaming {
  // Should always be 'startStreaming'
  string type = 1;
}

/**
 * Sent by the SFU to indicate that it is now no longer streaming.
 */
message stopStreaming {
  // Should always be 'stopStreaming'
  string type = 1;
}

/**
 * DEPRECATED Message is sent to players to indicate how many currently connected players
 * there are on this signalling server. (Note: This is mostly old behaviour and
 * is not influenced by multi streamers or who is subscribed to what streamer.
 * It just reports the number of players it knows about.)
 */
message playerCount {
  // Should always be 'playerCount'
  string type = 1;
  // The number of players connected.
  int32 count = 2;
}

/**
 * DEPRECATED Message is consumed by the signalling server. Will print out the provided
 * stats data on the console.
 */
message stats {
  // Should always be 'stats'
  string type = 1;
  // The stats data to echo.
  string data = 2;
}