@startuml Seq_CanFrameToCloud

title Real-time Data Transfer — CAN Frame to Cloud

participant "CAN Bus\n(SocketCAN)" as CANBUS
participant "Can::CanInterface" as CAN
participant "Can::MessageDispatcher" as DISP
participant "CloudConnectController" as CC
participant "MqttClient" as MQTT
participant "AWS IoT Core\n(MQTT broker)" as AWS

== CAN frame(s) → CAN message ==

CANBUS -> CAN : frame available on the device
CAN -> CC : didFrameReceive(QCanBusFrame)\n→ onCanFrameReceive()
CC -> DISP : onFrameReceive(canId, payload)
DISP -> DISP : MessageBuilder::buildMessage()\nreassembles multi-frame Can::Message
alt Message not yet Complete
    DISP -> DISP : continue accumulating CAN frames
else Complete Message Received
    DISP -> CC : didActionReceive(Can::Message)\n→ onCanMessageReceive()
end

== Publish CAN Message ==

alt msgId not in CAN routing
    CC -> CC : discard (no action defined)
else action == Drop
    CC -> CC : discard
else action == SendDelta AND payload unchanged
    CC -> CC : discard (no change)
else action == SendAlways OR SendDelta with new payload

    CC -> CC : leahi::canMessageToProtobufByteArray()\n→ serialized protobuf

    alt serialization succeeded
        CC -> MQTT : publish(topic, payload, pubId, QoS)

        alt client accepted the publish
            MQTT -> AWS : PUBLISH

            AWS -> MQTT : PUBACK
            MQTT -> CC : didMessageStatusChanged(id, Acknowledged, props)\n→ onCloudMessageStatusChanged()
        else client rejected the publish
            CC -> CC : log warning, message lost
        end
    else serialization failed
        CC -> CC : log warning, message dropped
    end

    CC -> CC : update message cache for SendDelta check
end

@enduml