Revert "temporarily remove is_winnable because it doesn't work"

This reverts commit 5a52f2ab7a.

card_game/src/lib.rs

@@ -389,6 +389,40 @@ where
 	pub fn is_win(&self) -> bool {
 		self.state.is_win()
 	}
+	pub fn is_winnable(&self) -> Option<Vec<G::Instruction>> {
+		let mut observed = std::collections::HashSet::new();
+		struct StateMachine<G, P, I> {
+			state: G,
+			possible_instructions_iter: P,
+			instruction: I,
+		}
+		let mut dummy_stats = self.stats.inner_stats.clone();
+		let mut state = self.state.state.clone();
+		let mut it = state.possible_instructions();
+		let mut path = Vec::new();
+		'outer: while !state.is_win() {
+			observed.insert(state.clone());
+			for instruction in &mut it {
+				let mut next_state = state.clone();
+				next_state.process_instruction(&mut dummy_stats, &self.config, instruction.clone());
+				if !observed.contains(&next_state) {
+					let possible_instructions_iter =
+						core::mem::replace(&mut it, next_state.possible_instructions());
+					let state = core::mem::replace(&mut state, next_state);
+					path.push(StateMachine {
+						state,
+						possible_instructions_iter,
+						instruction,
+					});
+					continue 'outer;
+				}
+			}
+			let last_state = path.pop()?;
+			state = last_state.state;
+			it = last_state.possible_instructions_iter;
+		}
+		Some(path.into_iter().map(|state| state.instruction).collect())
+	}
 }
 impl<G: Game> Game for SessionState<G>
 where

klondike-cli/src/main.rs

@@ -4,8 +4,8 @@ use klondike::{
 	KlondikePile, KlondikePileStack, KlondikeStats, SkipCards, Tableau, TableauStack,
 };
 
-// #[cfg(test)]
-// mod test;
+#[cfg(test)]
+mod test;
 
 use std::fmt::Display;
 struct Displayed<T>(T);