ooh at 99% cap

This reverts commit 5a52f2ab7a.

card_game/src/lib.rs

@@ -6,10 +6,10 @@ struct ReadmeDoctests;
 use core::ops::RangeBounds;
 
 // TODO: pub struct ValidInstruction<I>(I);
-pub trait Game {
-	type Stats;
-	type Config;
-	type Instruction;
+pub trait Game: Clone + core::fmt::Debug {
+	type Stats: Clone + core::fmt::Debug;
+	type Config: Clone + core::fmt::Debug;
+	type Instruction: Clone + core::fmt::Debug;
 	fn possible_instructions(&self) -> impl Iterator<Item = Self::Instruction> + use<Self>;
 	fn is_instruction_valid(&self, config: &Self::Config, instruction: Self::Instruction) -> bool;
 	fn process_instruction(
@@ -321,21 +321,36 @@ impl<S> SessionStats<S> {
 	}
 }
 
+#[derive(Debug)]
+pub struct Oom;
+
+#[derive(Clone, Debug)]
 pub struct Session<G: Game> {
 	stats: SessionStats<G::Stats>,
 	config: G::Config,
 	state: SessionState<G>,
 }
-#[derive(Clone, Eq, Hash, PartialEq)]
-pub struct SessionState<G: Game> {
-	seed: G,
+#[derive(Clone, Debug)]
+pub struct StateSnapshot<G: Game> {
 	state: G,
-	history: Vec<G::Instruction>,
+	instruction: G::Instruction,
+}
+impl<G: Game> StateSnapshot<G> {
+	pub const fn state(&self) -> &G {
+		&self.state
+	}
+	pub const fn instruction(&self) -> &G::Instruction {
+		&self.instruction
+	}
+}
+#[derive(Clone, Debug)]
+pub struct SessionState<G: Game> {
+	state: G,
+	history: Vec<StateSnapshot<G>>,
 }
 impl<G: Game + Clone> SessionState<G> {
 	fn new(state: G) -> Self {
 		Self {
-			seed: state.clone(),
 			state,
 			history: Vec::new(),
 		}
@@ -345,6 +360,7 @@ impl<G: Game> Session<G>
 where
 	G: Clone + Eq + core::hash::Hash,
 	G::Stats: Clone + Default,
+	G::Config: Clone,
 	G::Instruction: Clone + Eq + core::hash::Hash,
 {
 	pub fn new(state: G, config: G::Config) -> Self {
@@ -369,7 +385,7 @@ where
 	pub const fn config(&self) -> &G::Config {
 		&self.config
 	}
-	pub fn history(&self) -> &[G::Instruction] {
+	pub fn history(&self) -> &[StateSnapshot<G>] {
 		&self.state.history
 	}
 	pub fn undo(&mut self) {
@@ -389,12 +405,67 @@ where
 	pub fn is_win(&self) -> bool {
 		self.state.is_win()
 	}
+	pub fn is_winnable(&self) -> Result<Option<Vec<StateSnapshot<G>>>, Oom> {
+		const HUGE_CAP: usize = 1 << 25;
+		let mut state_moves = std::collections::HashMap::with_capacity(HUGE_CAP);
+		let mut state = self.clone();
+		while !state.is_win() {
+			// don't look for empty hash map buckets when the hash map is 99% full!
+			if HUGE_CAP * 127 <= state_moves.len() * 128 {
+				return Err(Oom);
+			}
+
+			// Continue existing iterator if it exists
+			let it = state_moves
+				.entry(state.state().clone())
+				.or_insert_with(|| state.state().possible_instructions());
+
+			// Run one possible move
+			if let Some(instruction) = it.next() {
+				state.process_instruction(instruction);
+				continue;
+			}
+
+			// No more moves. If we can't undo we're done
+			if state.history().is_empty() {
+				return Ok(None);
+			} else {
+				state.undo();
+			}
+		}
+
+		// history includes cycles
+		let mut state_index: std::collections::HashMap<_, _> = state
+			.history()
+			.iter()
+			.enumerate()
+			.map(|(i, snapshot)| (snapshot.state().clone(), i))
+			.collect();
+
+		// find the longest range where the start and end are the same state
+		while let Some(longest_range) = state
+			.history()
+			.iter()
+			.enumerate()
+			.filter_map(|(index, snapshot)| {
+				let &last_index = state_index.get(snapshot.state())?;
+				let longness = last_index - index;
+				(longness != 0).then_some(index..last_index)
+			})
+			.max_by_key(|range| range.len())
+		{
+			state.state.history.drain(longest_range);
+			for (i, snapshot) in state.history().iter().enumerate() {
+				state_index.insert(snapshot.state().clone(), i);
+			}
+		}
+
+		Ok(Some(state.state.history))
+	}
 }
 impl<G: Game> Game for SessionState<G>
 where
-	G: Clone,
 	G::Stats: Default,
-	G::Instruction: Clone,
 {
 	type Stats = SessionStats<G::Stats>;
 	type Config = G::Config;
@@ -420,19 +491,16 @@ where
 	) {
 		match instruction {
 			SessionInstruction::Undo => {
-				// replay the entire history of the game except one move
-				self.history.pop();
-				let mut inner_stats = G::Stats::default();
-				let mut state = self.seed.clone();
-				for instruction in &self.history {
-					state.process_instruction(&mut inner_stats, config, instruction.clone());
-				}
-				self.state = state;
-				stats.inner_stats = inner_stats;
+				if let Some(snapshot) = self.history.pop() {
+					self.state = snapshot.state;
 					stats.increment_undos();
 				}
+			}
 			SessionInstruction::InnerInstruction(instruction) => {
-				self.history.push(instruction.clone());
+				self.history.push(StateSnapshot {
+					state: self.state.clone(),
+					instruction: instruction.clone(),
+				});
 				self.state
 					.process_instruction(&mut stats.inner_stats, config, instruction);
 			}

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);

klondike-cli/src/test.rs

@@ -1,33 +1,15 @@
-use klondike::Klondike;
 use card_game::Session;
+use klondike::Klondike;
 #[test]
 fn test_is_winnable() {
 	// is winnable
-	let is_winnable = Session::new_default(Klondike::with_seed(123)).is_winnable();
-	println!("is_winnable = {is_winnable:?}");
-}
-#[test]
-fn test_klondike() {
-	// create game session
-	let game = Klondike::with_seed(123);
-	let mut session = Session::new_default(game);
-
-	// is winnable
-	let is_winnable = session.is_winnable();
-	println!("is_winnable = {is_winnable:?}");
-
-	// play game
-	while let Some(instruction) = session.possible_instructions().next() {
-		session.process_instruction(instruction);
+	let is_winnable = Session::new_default(Klondike::with_seed(0)).is_winnable().unwrap();
+	if let Some(win_moves) = is_winnable {
+		// for (i, ins) in win_moves.into_iter().enumerate() {
+		// 	println!("{i} = {:?}", ins.instruction());
+		// }
+		println!("Game is winnable with {} moves", win_moves.len());
+	} else {
+		println!("Game is not winnable");
 	}
-
-	// did win
-	let is_win = session.is_win();
-
-	// print session history
-	for (i, instruction) in session.history().iter().enumerate() {
-		println!("move {i} = {instruction:?}");
-	}
-
-	println!("is_win = {is_win}");
 }

klondike/src/lib.rs

@@ -533,6 +533,10 @@ impl Iterator for KlondikeIter {
 		instruction
 	}
 }
+#[test]
+fn test_klondike_iter() {
+	assert_eq!(KlondikeIter::new().count(), 721);
+}
 
 #[derive(Clone, Debug, Eq, Hash, PartialEq)]
 pub struct Klondike {