@startuml
skinparam sequenceMessageAlign center

collections "BLE broadcaster" as thingy
participant "Gateway\n(Raspberry Pi)" as gw
participant "MQTT Broker\n(RabbitMQ)" as broker
participant "Database\n(InfluxDB)" as db

== Data collection ==
thingy -> gw : BLE advertising packet

alt company_id != 0xffff
    gw -> gw : discard packet
else
    gw -> gw : check payload size

    alt payload size != 14 bytes
        gw -> gw : discard packet\n(non-Thingy device)
    else
        gw -> gw : decode_payload()

        alt unknown key in payload
            gw -> gw : discard packet\nlog debug
        else
            alt CO2 == 0xFFFFFFFF
                gw -> gw : discard CO2 value\n(sensor not ready)
            end

            alt duplicate within 10 seconds
                gw -> gw : discard packet\n(deduplication)
            else
                gw -> gw : add UTC timestamp
                gw -> broker : publish JSON\n{gateway_id}/{mac}/update
                broker --> gw : on_publish confirmed
            end
        end
    end
end

@enduml