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fix(core): validate moved tableau stack forms a legal run

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move_cards only checked that the *bottom* card of a moved stack landed
legally on the destination — the cards above the bottom went through
unverified. A player could lift an arbitrary selection from one column
and drop it on another whenever the bottom happened to match, even if
the upper cards didn't form a descending alternating-colour sequence.

Adds is_valid_tableau_sequence(&[Card]) -> bool to rules.rs (4 lines)
and one call site in move_cards's tableau-destination branch. One
focused test covering single-card / valid-run / same-colour /
rank-gap cases.

Reported by Quat: "stack 4 onto stack 2" was accepted when illegal.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
funman300
2026-05-05 17:26:14 +00:00
parent 000143231b
commit f1aeb24157
2 changed files with 47 additions and 1 deletions
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solitaire_core/src/game_state.rs
+13 -1
View File
@@ -4,7 +4,7 @@ use crate::card::Card;
use crate::deck::{deal_klondike, Deck};
use crate::error::MoveError;
use crate::pile::{Pile, PileType};
use crate::rules::{can_place_on_foundation, can_place_on_tableau};
use crate::rules::{can_place_on_foundation, can_place_on_tableau, is_valid_tableau_sequence};
use crate::scoring::{compute_time_bonus as scoring_time_bonus, score_move, score_undo as scoring_undo};
const MAX_UNDO_STACK: usize = 64;
@@ -283,6 +283,18 @@ impl GameState {
if !can_place_on_tableau(&bottom_card, dest) {
return Err(MoveError::RuleViolation("invalid tableau placement".into()));
}
// The previous check only validates that the *bottom* of the
// moved stack lands on the destination's top card. Without
// this guard, a player could lift an arbitrary multi-card
// selection from one column and drop it onto another whenever
// the bottom card happens to match — even if the cards
// above the bottom don't form a legal descending
// alternating-colour run.
if !is_valid_tableau_sequence(&from_pile.cards[start..]) {
return Err(MoveError::RuleViolation(
"moved cards must form a valid tableau run".into(),
));
}
}
_ => return Err(MoveError::InvalidDestination),
}