syntax = "proto3";

package collab;

/**
 * Rid represents Redis stream message Id, which is a unique identifier
 * in scope of individual Redis stream - here workspace scope - assigned
 * to each update stored in Redis.
 *
 * Default: "0-0"
 */
message Rid {
    // UNIX epoch timestamp in milliseconds.
    fixed64 timestamp = 1;

    // In case when timestamps duplicate, this monotonically increasing
    // sequence number is incremented and assigned.
    uint32 counter = 2;
}

/**
 * SyncRequest message is send by either a server or a client, which informs about the
 * last collab state known to either party.
 *
 * If other side has more recent data, it should send `Update` message in the response.
 * If other side has missing data, it should send its own `SyncRequest` in the response.
 */
message SyncRequest {
    // Last Redis stream ID of the update received from the server, concerning corresponding
    // collab, this message refers to.It
    //
    // The `Rid.timestamp` field can be used to notify clients when was the last time,
    // collab has been synchronised.
    Rid last_message_id = 1;

    // Yjs Doc state vector encoded using lib0 v1 encoding.
    bytes state_vector = 2;
}

/**
 * Update message is send either in response to `SyncRequest` or independently by
 * the client/server. It contains the Yjs doc update that can represent incremental
 * changes made over corresponding collab, or full document state.
 */
message Update {
    // Redis stream message ID assigned to this update, after it has been stored by
    // server in Redis.
    //
    // For updates send by client, this field is not set.
    Rid message_id = 1;

    // Flags used to inform about encoding details:
    // - 0x00 - `payload` encoded using lib0 v1 encoding.
    // - 0x01 - `payload` encoded using lib0 v2 encoding.
    //
    // NOTE: in the future we could also include `payload` compression.
    uint32 flags = 2;

    // Binary update representing incremental changes over the collab,
    // or entire collab state delta.
    bytes payload = 3;
}

/**
 * AwarenessUpdate message is send to inform about the latest changes in the
 * Yjs doc awareness state.
 */
message AwarenessUpdate {
    // Yjs awareness update encoded using lib0 v1 encoding.
    bytes payload = 1;
}

/**
 * AccessChanged message is sent only by the server when we recognise, that
 * connected client has lost the access to a corresponding collab.
 */
message AccessChanged {
    // Flag indicating if user has read access to corresponding collab.
    bool can_read = 1;
    // Flag indicating if user has write access to corresponding collab.
    bool can_write = 2;
    // (Optional) human readable comment about the reason for access change.
    int32 reason = 3;
}

message CollabMessage {
    // Unique collab identifier (UUID), which this message is related to.
    // We're using string here, since it's easier to represent in web browser client.
    string object_id = 1;
    // Collab type - required by some of the collab read operations on the server.
    // NOTE: hopefully we'll be able to get rid of it in the future.
    int32 collab_type = 2;
    oneof data {
        SyncRequest sync_request = 3;
        Update update = 4;
        AwarenessUpdate awareness_update = 5;
        AccessChanged access_changed = 6;
    }
}