115 lines
3.6 KiB
Rust
115 lines
3.6 KiB
Rust
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//! cb-game-runtime — round/phase machinery, commit windows, projections,
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//! and the scenario runner (GameKernel §2.5, §3). Game-agnostic.
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pub mod scenario;
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pub use scenario::{RunOutcome, ScenarioFile};
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use cb_kernel::PlayerId;
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use serde::{Deserialize, Serialize};
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use std::collections::BTreeMap;
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/// A simultaneous commit window (GameKernel K12): the runtime opens it
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/// naming who must submit; submissions are commitment events hidden from
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/// projections until reveal.
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#[derive(Debug, Clone, Serialize, Deserialize)]
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pub struct CommitWindow<C> {
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/// Players who must submit, and their commitment once received.
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pending: BTreeMap<PlayerId, Option<C>>,
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}
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impl<C> CommitWindow<C> {
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pub fn open(players: impl IntoIterator<Item = PlayerId>) -> Self {
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Self {
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pending: players.into_iter().map(|p| (p, None)).collect(),
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}
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}
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/// Record a commitment. Errors on players outside the window or on a
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/// duplicate submission (GameKernel K12).
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pub fn submit(&mut self, player: PlayerId, commitment: C) -> Result<(), CommitError> {
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match self.pending.get_mut(&player) {
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None => Err(CommitError::NotInWindow(player)),
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Some(slot @ None) => {
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*slot = Some(commitment);
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Ok(())
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}
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Some(Some(_)) => Err(CommitError::AlreadyCommitted(player)),
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}
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}
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pub fn is_complete(&self) -> bool {
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self.pending.values().all(Option::is_some)
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}
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/// Consume the window at reveal, yielding commitments in PlayerId
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/// order (deterministic iteration, GameKernel K6).
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pub fn reveal(self) -> Result<Vec<(PlayerId, C)>, CommitError> {
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if !self.is_complete() {
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return Err(CommitError::Incomplete);
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}
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Ok(self
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.pending
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.into_iter()
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.map(|(p, c)| (p, c.expect("checked complete")))
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.collect())
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}
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}
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#[derive(Debug, PartialEq, Eq)]
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pub enum CommitError {
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NotInWindow(PlayerId),
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AlreadyCommitted(PlayerId),
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Incomplete,
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}
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impl core::fmt::Display for CommitError {
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fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
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match self {
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CommitError::NotInWindow(p) => write!(f, "player {p} is not in this window"),
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CommitError::AlreadyCommitted(p) => write!(f, "player {p} already committed"),
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CommitError::Incomplete => write!(f, "window is not complete"),
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}
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}
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}
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/// Per-player projection (GameKernel K13): a total function from state to
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/// what one seat may see. Implemented by game packages; the runtime only
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/// fixes the shape so projections can never feed back into validation.
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pub trait Project {
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type View: Serialize;
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fn project(&self, viewer: Viewer) -> Self::View;
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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pub enum Viewer {
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Player(PlayerId),
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Spectator,
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn commit_window_gates_and_reveals_in_order() {
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let mut w: CommitWindow<u8> = CommitWindow::open([PlayerId(0), PlayerId(1)]);
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assert_eq!(
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w.submit(PlayerId(2), 9),
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Err(CommitError::NotInWindow(PlayerId(2)))
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);
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w.submit(PlayerId(1), 7).unwrap();
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assert_eq!(
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w.submit(PlayerId(1), 8),
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Err(CommitError::AlreadyCommitted(PlayerId(1)))
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);
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assert!(!w.is_complete());
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w.submit(PlayerId(0), 5).unwrap();
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assert!(w.is_complete());
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assert_eq!(
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w.reveal().unwrap(),
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vec![(PlayerId(0), 5), (PlayerId(1), 7)]
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);
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}
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}
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