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States and transitions

The system has two state machines, and they run in parallel: one for the loan (the record that somebody took a device) and one for the equipment (the device itself). They touch at exactly two moments — the pickup and the physical check-in — and run free of each other in between.

That "free in between" is the rule that raises the most questions at the desk, and the cross table at the end of this page exists to answer it once and for all.

How to read the names in capitals

ATIVO, DISPONIVEL, AGUARDANDO_BAIXA are the values stored in the database. The screen hardly ever shows them like that: the inventory writes "Disponível", the record list writes "Ativo". Both names appear side by side here on purpose — this is the page that connects the word on screen to the data stored.

The loan machine

Each item picked up creates a separate loan (see loan). Somebody who takes a laptop and a power strip on the same trip to the desk has two records, which travel through this machine independently.

stateDiagram-v2
    [*] --> ATIVO: pickup on the portal
    ATIVO --> AGUARDANDO_BAIXA: return declared on the portal
    AGUARDANDO_BAIXA --> CONCLUIDO: physical check-in in the panel
    CONCLUIDO --> [*]
Transition Who triggers it On which screen Time stamp written
(born) → ATIVO Student or teacher Portal, Confirmar retirada (Confirm pickup) button data_retirada
ATIVO → AGUARDANDO_BAIXA Student or teacher Portal, Confirmar devolução (Confirm return) button (or Devolver tudo / Return all) data_devolucao
AGUARDANDO_BAIXA → CONCLUIDO Front desk Admin panel, Confirmar Recebimento Físico (Confirm physical receipt) button (or Confirmar Todas as Devoluções / Confirm all returns) data_baixa

The three stamps are three different fields, and each has a single owner. The distance between the last two is the shelf time: how long the device sat on the counter after somebody said they had returned it.

What this machine does not do

  • It does not go back. There is no AGUARDANDO_BAIXA → ATIVO, and no CONCLUIDO → anything. A loan closed by mistake is not reopened by any screen — the way out is to record a new pickup.
  • It does not skip. ATIVO never goes straight to CONCLUIDO. The front desk check is the only path to the end, and that is why it exists.
  • It does not delete. A CONCLUIDO loan stays in the database forever. It is what answers "who had this device last semester".

The equipment machine

stateDiagram-v2
    [*] --> DISPONIVEL: registered
    DISPONIVEL --> EMPRESTADO: pickup
    EMPRESTADO --> DISPONIVEL: check-in
    DISPONIVEL --> MANUTENCAO: repair
    MANUTENCAO --> DISPONIVEL: ready
    DISPONIVEL --> INATIVO: retire
    MANUTENCAO --> INATIVO: retire
    INATIVO --> DISPONIVEL: reactivate
Transition Who triggers it On which screen
(born) → DISPONIVEL Front desk Panel, Inventário (Inventory) tab, registration form
DISPONIVEL → EMPRESTADO Student or teacher Portal, on confirming the pickup
EMPRESTADO → DISPONIVEL Front desk Panel, at the physical check-in
DISPONIVEL → MANUTENCAO Front desk Panel, Manutenção (Maintenance) button on the row
MANUTENCAO → DISPONIVEL Front desk Panel, Disponível (Available) button on the row
DISPONIVEL → INATIVO Front desk Panel, Inativar (Deactivate) button on the row
MANUTENCAO → INATIVO Front desk Panel, Inativar (Deactivate) button on the row
INATIVO → DISPONIVEL Front desk Panel, Reativar (Reactivate) button on the row

The three absences, and the reason for each

EMPRESTADO is not a button

The front desk moves equipment between DISPONIVEL, MANUTENCAO and INATIVO, and that is all. EMPRESTADO comes and goes on its own, through the two gestures that involve a real person carrying the device.

If there were a button, setting it by hand would leave an open loan pointing at an "available" item — and the portal would offer somebody else a device that is in a bag. That is why the row of an item on loan shows the name of whoever has it instead of the button.

INATIVO does not go straight to MANUTENCAO

A retired device goes back to DISPONIVEL first; the repair is decided afterwards. They are two different questions — "is this item going back into circulation?" and "does it need repair?" — and putting them in one click would make the front desk answer both without being asked.

With an open loan, nothing changes

While there is an ATIVO or AGUARDANDO_BAIXA loan pointing at the device, the panel refuses any change of status. The message says who has it, or tells you to confirm the receipt first.

The lock is the opposite of the rule for people, which is loose on purpose — see deactivating a person and deactivating a device.

Both at once

This is the table that answers the most frequent question about the system. It crosses every combination: the three loan states plus the case "no open loan", against the four equipment states.

Open loan Equipment Does it happen? What it means
ATIVO EMPRESTADO Normal The device is with the person. It disappears from the portal; in the inventory it appears with their name and no button.
ATIVO DISPONIVEL Inconsistency The portal would offer somebody else a device that is in a bag. No screen produces this.
ATIVO MANUTENCAO Does not happen The panel refuses to change the status while there is an open loan.
ATIVO INATIVO Does not happen The same refusal.
AGUARDANDO_BAIXA EMPRESTADO Normal The two-phase rule. The person declared the return, the device is on the counter, and it stays out of circulation until the front desk checks it.
AGUARDANDO_BAIXA DISPONIVEL Inconsistency It would be the portal offering a device nobody has collected yet.
AGUARDANDO_BAIXA MANUTENCAO Does not happen The same refusal from the panel.
AGUARDANDO_BAIXA INATIVO Does not happen The same refusal.
None DISPONIVEL Normal The common case: the device is on the shelf, counting in the portal grid.
None MANUTENCAO Normal Under repair. Disappears from the portal, appears in the inventory.
None INATIVO Normal Retired. Disappears from the portal, counts included, and sits in gray in the inventory.
None EMPRESTADO Inconsistency The panel refuses to release it on its own and tells you to check the history: releasing an item somebody might be holding is worse than a message asking for attention.

And the CONCLUIDO loan, where is it in that table?

In the last four rows, in the "None" column. CONCLUIDO means precisely that the loan is no longer open — it does not hold the device anymore, and from then on the equipment can be in any of the four states, including EMPRESTADO again, through a new loan to somebody else.

A device accumulates dozens of CONCLUIDO loans over its life and that says nothing about where it is now. What answers "where is it" is always the equipment status plus the open loan, if there is one.

The three inconsistency rows

The three rows marked "Inconsistency" are not produced by any screen of the system — the writes that create and close loans touch both machines inside the same transaction, and one half does not happen without the other.

If one of them shows up, the source is external: an edit made directly in the database, or a half-finished file restore. The last row is the only one the panel can notice on its own, and its answer is to refuse rather than to "fix".

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