@startuml
skinparam BackgroundColor F0F0F0

participant "Connection manager " as manager
participant "Service cellular" as cellular
participant "Phone mode observer " as mode

== Phone is connected to the GSM network==

mode ->cellular : Phone mode change to Connected/ Do not Disturb
cellular -> manager : onPhoneMode()
manager -> cellular :isConnectedToTheNetwork() AT+CFUN?
cellular -> manager : +CFUN: 1

mode ->cellular : Phone mode change to Offline / Message only
cellular -> manager : onPhoneMode()
manager -> cellular :isConnectedToTheNetwork() AT+CFUN?
cellular -> manager : +CFUN: 1
manager -> cellular :hangUpOngoingCall()
manager -> cellular :disconnectFromNetwork() AT+CFUN=4
manager -> cellular :clearNetworkIndicator()
manager->manager : handle switch to selected oflline mode

== Phone is not connected to the GSM network==

mode ->cellular : Phone mode change to CConnected/ Do not Disturb
cellular -> manager : onPhoneMode()
manager -> cellular :isConnectedToTheNetwork() AT+CFUN?
cellular -> manager : +CFUN: 4
manager -> cellular :connectToTheNetwork() AT+CFUN=1

mode ->cellular : Phone mode change to Offline / Message only
cellular -> manager : onPhoneMode()
manager -> cellular :isConnectedToTheNetwork() AT+CFUN?
cellular -> manager : +CFUN: 4
manager->manager : handle switch to selected oflline mode

==handle switch to selected oflline mode==

==handleModeChangeToOfflineMode()==
manager -> cellular : isConnectionTimerActive()
cellular -> manager : timer is active
manager -> cellular : stopConnectionTimer()

==handleModeChangeToOfflineMode()==
manager -> cellular : isConnectionTimerActive()
cellular -> manager : timer is not active
manager -> cellular : startonnectionTimer()

==Connection manager in Messages only mode==
cellular -> manager : service timer tick (60 seconds)
manager -> manager : offline period not expired, online period not expired

manager -> manager : offline period expired onTimTick()
manager -> cellular : connectToNetwork()

manager -> manager : online period expired onTimTick()
manager -> cellular : disconnectFromNetwork()
manager -> cellular :clearNetworkIndicator()
@enduml