// file: message.fbs
namespace proto;

enum MessageType : byte {
    NONE = 0,
    DATA = 1,
    ACK = 2,
    HEARTBEAT = 3
}

table DataMessage {
    id: string;
    topic: string;
    timestamp: ulong;
    payload: [ubyte];
    metadata: [KeyValue];
}

table AckMessage {
    acked_id: string;
    timestamp: ulong;
}

table HeartBeatMessage {
    client_id: string;
    timestamp: ulong;
}

table KeyValue {
    key: string;
    value: string;
}

union Message {
    DataMessage,
    AckMessage,
    HeartBeatMessage,
}

table Envelope {
    type: MessageType;
    message: Message;
}

root_type Envelope;