@startuml HDF
    participant TD                  as TD
    participant SW                  as SW
    participant UI                  as UI
    actor       USER                as US

    'Possible actions and interaction types
    ' External on CANBus
    ' TD -> SW: MSG: Message
    ' SW -> TD: MSG: Message

    ' Internal to the application
    ' XX -> YY: CMD: Command
    ' XX -> XX: ACT: Action

    ' External on OS/FS
    ' SW -> Script: ACT: Command
    ' Script -> OS: CMD: Command
    ' Script -> SW: MSG: Message
    ' OS -> Script: MSG: Message

    ' US -> UI: User actions are:
    '   ASK: Display a <message>
    '   ENT: User enters a value or string
    '   TCH: User touches a button (RadioButton, CheckBox, ...)
    '   SCL: User scrolls a flip-able area

  == Main TX HDF ==
    UI ->o UI: ⟲: Main Treatment Screen
    US -> UI: TCH: HDF Menu Option
    UI -> US: ACT: Display HDF Screen   \
                    \n\t  - Pressures   \
                    \n\t  - Pressures Graph \
                    \n\t  - HDF

    group Plot Timer (1 min)
        UI --> UI: ...
    end

    group Pressures Data
        TD --> UI: ...
    end

    group HDF Data
        TD --> UI: ...
    end

 == Pause/ Resume Button ==
    US -> UI: TCH: Pause/ Resume HDF button
    UI -> SW: ACT: : Pause/ Resume Command

    alt Pause
        SW -> TD: MSG: [xXX: Req #1] Pause/ Resume Command Request\n\
            \t(U32) cmd=HDF_PAUSE_COMMAND (0)
    else Resume 
        SW -> TD: MSG: [xXX: Req #1] Pause/ Resume Command Request\n\
            \t(U32) cmd=HDF_RESUME_COMMAND (1)
    end

    TD -> SW: MSG: [xXX: Rsp #2] \nPause/ Resume Command Response   \
                        \n\t(U32)  mAccept                      \
                        \n\t(U32)  mRejectionReason

    SW -> UI: CMD: Pause/ Resume Command Response   \
                        \n\t(U32)  mAccept                      \
                        \n\t(U32)  mRejectionReason
    alt Accept
        UI -> US: ACT: Display status tags for paused or resumed
    else #Pink Reject 
        UI -> US: ACT: Show rejection reason
    end         

 == Auto-Substitution  Button ==
    US -> UI: TCH: Auto-Substitution switch
    UI -> SW: ACT: Auto-Substitution Command

    alt Off
        SW -> TD: MSG: [xXX: Req #1] Auto-Substitution Command Request\n\
            \t(U32) cmd=HDF_AUTO_SUB_OFF_COMMAND (0)
    else On 
        SW -> TD: MSG: [xXX: Req #1] Auto-Substitution Command Request\n\
            \t(U32) cmd=HDF_AUTO_SUB_ON_COMMAND (1)
    end

    TD -> SW: MSG: [xXX: Rsp #2] \nAuto-Substitution Command Response   \
                        \n\t(U32)  mAccept                      \
                        \n\t(U32)  mRejectionReason

    SW -> UI: CMD: Auto-Substitution Command Response   \
                        \n\t(U32)  mAccept                      \
                        \n\t(U32)  mRejectionReason
    alt Accept
        group HDF Data
            TD --> UI: (U32)autoSubState= OFF (0) / ON(1)
        end
        UI -> US: ACT: Display state of auto sub
    else #Pink Reject 
        UI -> US: ACT: Show rejection reason
    end      

 == Edit HDF  Button ==
    US -> UI: TCH: Edit HDF Icon 
    UI -> UI: ACT: Open HDF adjustment dialog
    US -> UI: TCH: Edit : \
                \n\t Treatment Mode \
                \n\t Prescribed Substitution Fluid Volume
    US -> UI: TCH: Confirm Button
    UI -> SW: ACT: Adjust HDF Request
    SW -> TD: MSG: [xXX: Req #2] Adjust HDF Request\
            \n\t(U32) Treatment Mode   \
            \n\t(F32) Prescribed Substitution Fluid Volume
    TD -> SW: MSG: [xXX: Rsp #3] \nAdjust HDF Response   \
                        \n\t(U32)  mAccept                              \
                        \n\t(U32)  mTxModeRejectionReason               \
                        \n\t(U32)  mPrescSubFluidVolumeRejectionReason
    SW -> UI: CMD: Adjust HDF Response    \
                        \n\t(U32)  mAccept                      \
                        \n\t(U32)  mTxModeRejectionReason               \
                        \n\t(U32)  mPrescSubFluidVolumeRejectionReason
    alt Accept
        UI -> US: ACT: Close Dialog
    else #Pink Reject 
        UI -> US: ACT: Highlight rejected parameter
    end   

 == Pressures Data ==
    TD -> SW: MSG: [x24: #12] \nTD Pressures Data\n(F32) artPress, \n(F32) venPres\n(U32) limitState\n(S32) artMin\n(S32) artMax\n(S32) venMin\n(s32) venMax\n(F32) artLong\n(U32) venLong\n(F32) tmpPress\n(F32) tmpMin\n(F32) tmpMax 
    SW -> UI: CMD: Update TD Pressures\n(F32) artPress, \n(F32) venPres\n(U32) limitState\n(S32) artMin\n(S32) artMax\n(S32) venMin\n(s32) venMax\n(F32) artLong\n(U32) venLong\n(F32) tmpPress\n(F32) tmpMin\n(F32) tmpMax 

 == HDF Data ==
    TD -> SW: MSG: [xXX: #5]\nHDF Data      \
            \n\t(F32) setSubVolume          \
            \n\t(F32) subRate               \
            \n\t(F32) subVolumeDelivered    \
            \n\t(U32) state                 \
            \n\t(U32) autoSubState
    SW -> UI: CMD: Display HDF Data         \
            \n\t(F32) setSubVolume          \
            \n\t(F32) subRate               \
            \n\t(F32) subVolumeDelivered    \
            \n\t(U32) state                 \
            \n\t(U32) autoSubState

@enduml