sequence_chart.puml

@startuml

control EventLoop
participant Adapter
participant HomePort
entity dev
participant Application
activate EventLoop

group An instance of Problem A
    EventLoop -> Adapter: callback()
    activate Adapter #Gold
    Adapter -> HomePort: add_device()
    activate HomePort
    create dev
    HomePort -> dev: create()
    Adapter <-- HomePort
    deactivate HomePort
    EventLoop <-- Adapter
    deactivate Adapter

    EventLoop -> Application: callback()
    activate Application #DarkSalmon
    Application -> HomePort: get_device()
    activate HomePort
    Application <-- HomePort: dev
    note right: Application has pointer to dev
    deactivate HomePort
    Application -> HomePort: request()
    activate HomePort
    HomePort -> Adapter: request()
    activate Adapter #Gold
    Adapter -> HomePort: remove_device()
    activate HomePort
    HomePort -> dev: destroy()
    destroy dev
    Adapter <-- HomePort
    deactivate HomePort
    HomePort <-- Adapter
    deactivate Adapter
    Application <-- HomePort
    note right: Pointer is no longer valid
    deactivate HomePort
    EventLoop <-- Application
    deactivate Application

    deactivate dev
end group

newpage
group A more complicated instance of Problem A
    EventLoop -> Application: callback()
    activate Application #DarkSalmon
    Application -> HomePort: request()
    activate HomePort
    HomePort -> Adapter: request()
    activate Adapter #DarkSalmon
    Adapter -> HomePort: respond()
    activate HomePort
    HomePort -> Application: on_response()
    activate Application #Gold
    HomePort <-- Application
    deactivate Application
    Adapter <-- HomePort
    deactivate HomePort
    HomePort <-- Adapter
    deactivate Adapter
    Application <-- HomePort
    deactivate HomePort
    EventLoop <-- Application
    deactivate Application
end

newpage
'    create dev
'    EventLoop -> dev
'    activate dev
group A solution to problem A
    EventLoop -> Application: callback()
    activate Application #Gold
    Application -> HomePort: get_device()
    activate HomePort
    Application <-- HomePort: dev
    note right: Application has pointer to dev
    deactivate HomePort
    Application -> HomePort: request()
    activate HomePort
    HomePort -> EventLoop: Add a watcher
    Application <-- HomePort
    note right: Pointer is still valid
    deactivate HomePort
    EventLoop <-- Application
    deactivate Application

    EventLoop -> HomePort: Watcher triggers
    activate HomePort
    HomePort -> Adapter: request()
    activate Adapter #Gold
    Adapter -> HomePort: remove_device()
    activate HomePort
    HomePort -> dev: destroy()
    destroy dev
    Adapter <-- HomePort
    deactivate HomePort
    HomePort <-- Adapter
    deactivate Adapter
    EventLoop <-- HomePort
    deactivate HomePort
end

newpage
group An instance of problem B
    EventLoop -> Application: callback()
    activate Application #Gold
    Application -> HomePort: get_device()
    activate HomePort
    Application <-- HomePort: dev
    note right: Application has pointer to dev
    deactivate HomePort
    Application -> HomePort: request()
    activate HomePort
    HomePort -> EventLoop: Add a watcher
    Application <-- HomePort
    note right: Pointer is still valid
    deactivate HomePort
    EventLoop <-- Application
    deactivate Application

    EventLoop -> Adapter: callback()
    activate Adapter #Gold
    Adapter -> HomePort: remove_device()
    activate HomePort
    HomePort -> dev
    destroy dev
    Adapter <-- HomePort
    deactivate HomePort
    EventLoop <-- Adapter
    deactivate Adapter

    EventLoop -> HomePort: Watcher triggers
    activate HomePort
    HomePort -> Adapter: request()
    activate Adapter #Gold
    HomePort <-- Adapter
    deactivate Adapter
    EventLoop <-- HomePort
    deactivate HomePort
end

deactivate EventLoop

@enduml