Decisions, drafts, and Undo

Intents

Two rules follow, and a game must keep both:

1. Every state inside an open decision offers at least one Choice or Confirm. A bot ignores Cancel, so it must always have something else to take.
2. A Choice never returns the decision to a state it had before. A bot taking only Choice and Confirm must always reach the end.

Worked example: a draft of 12 cards

The seat stages one card, may switch to another, and then takes the staged card.

• Nothing staged: each of the 12 cards is a Choice.
• One card staged: the other 11 cards are still offered, so the seat can switch, but as Cancel. The take command is a Confirm.

#[derive(Default, Serialize, Deserialize)]
#[serde(crate = "boardweaver_sdk::serde", default)]
struct Pick {
    staged: Option<usize>,
}

fn offers(table: &Table, player_id: PlayerId) -> Vec<Offer> {
    let pick: Pick = table.state().read(StateOf::PlayerPrivate(player_id));
    let switch = if pick.staged.is_some() { Intent::Cancel } else { Intent::Choice };
    let mut offers: Vec<Offer> = (0..table.state().space("market").pieces.len())
        .filter(|&index| pick.staged != Some(index))
        .map(|index| {
            Offer::new(Action::PieceClick { space_id: "market".into(), index }, switch)
                .label(msg!("offer.stage", card = index))
        })
        .collect();
    if pick.staged.is_some() {
        offers.push(Offer::new(Action::command("take"), Intent::Confirm).label(msg!("offer.take-staged")));
    }
    offers
}

The common mistake is to tag the 11 switches as Choice. Then staging card A, then card B, then card A again returns the decision to a state it had, and a bot can switch between cards forever.

What ends a decision

A decision stays open, as the seat's draft, until a step ends it. The first rule that applies decides:

1. The step drew from Rng: the decision ends, whatever the step's intent.
2. The step is a reveal: the decision ends.
3. The step's intent is Confirm: the decision ends.
4. Otherwise the decision stays open.

So only the last step of a decision can draw randomness or reveal. Plan multi-step moves so the random or revealing part comes last.

Undo

Undo is not an intent and not an action: it is the platform's, and the client shows its button. The game logic allows it with table.allow_undo() (Changing the state).