@startuml

(*) --> "Check if order position with\nscanned ticket secret exists"
--> if "" then
    -down->[yes] ===CHECK===
else
    -->[no] "Check if secret exists\nin revocation list"
    --> if "" then
        --> "Is this a forced upload?"
        --> if "" then
            -->[yes] ===CHECK===
        else
            -right->[no] "Return error REVOKED"
        endif
    else
        -right->[no] "Return error INVALID"
    endif

endif


===CHECK=== -down-> "Is the order in status PAID or PENDING\nand is the position not canceled?"
--> if "" then
    -right->[no] "Return error CANCELED"
else
    -down->[yes] "Is the product part of the check-in list?"
    --> if "" then
        -right->[no] "Return error PRODUCT"
    else
        -down->[yes] "Is the subevent part of the check-in list?"
        --> if "" then
            -right->[no] "Return error PRODUCT "
        else
            -down->[yes] "Is the order in status PAID\nor is this a forced upload?"
            --> if "" then
                -right->[no] "Does the check-in list include pending orders?"
                --> if "" then
                    -right->[no] "Return error UNPAID "
                else
                    -down->[yes] "Is ignore_unpaid set?\n(Has the operator confirmed\nthe checkin?)"
                    --> if "" then
                        -right->[no] "Return error UNPAID "
                    else
                        -down->[yes] "Is this an entry or exit?\nIs the upload forced?"
                    endif
                endif
            else
                -down->[yes] "Is this an entry or exit?\nIs the upload forced?"
            endif
        endif
    endif
endif

"Is this an entry or exit?\nIs the upload forced?" --> if "" then
    -right->[entry && not force] Evaluate custom logic (rules)
    --> if "" then
        -right->[error] "Return error RULES"
    else
        -down->[ok] "Are all required questions answered?"
        --> if "" then
            -right->[no && questions_supported] "Return error INCOMPLETE"
        else
            -down->[yes || not questions_supported] "Does the check-in list allow multi-entry?"
        endif
    endif
else
    -->[exit || force=true] "Return OK "
endif

"Does the check-in list allow multi-entry?" --> if "" then
    -right->[yes] "Return OK"
else
    -down->[no] "Is this the first checkin\nfor this ticket on this list?"
    --> if "" then
        -right->[yes] "Return OK"
    else
        -down->[no] "Are all previous checkins\nfor this ticket on this list exits?"
        --> if "" then
            -right->[yes] "Return OK"
        else
            -down->[no] "Does the check-in list\n allow entry after exit\nand is the last checkin\nan exit?"
            --> if "" then
                -right->[yes] "Return OK"
            else
                -down->[no] "Return error ALREADY_REDEEMED"
            endif
        endif
    endif
endif


@enduml