From 01b456b4fef8ce4a002f870e5385424614a2a5fb Mon Sep 17 00:00:00 2001
From: Mike White <botahamec@outlook.com>
Date: Wed, 15 Sep 2021 20:49:13 -0400
Subject: Added best move function

---
 ai/src/lib.rs      | 20 +++++++++++++++++++-
 cli/src/eval.rs    |  6 +++++-
 cli/src/main.rs    | 24 ++++++++++++++++++++++++
 model/src/moves.rs | 14 +++++++++++++-
 4 files changed, 61 insertions(+), 3 deletions(-)

diff --git a/ai/src/lib.rs b/ai/src/lib.rs
index 405c88d..89fd345 100644
--- a/ai/src/lib.rs
+++ b/ai/src/lib.rs
@@ -1,4 +1,5 @@
 pub use model::{CheckersBitBoard, Move, PieceColor, PossibleMoves};
+use std::mem::MaybeUninit;
 
 const KING_WORTH: u32 = 2;
 
@@ -22,7 +23,7 @@ fn eval_position(board: CheckersBitBoard) -> f32 {
 	if dark_eval + light_eval != 0.0 {
 		light_eval / (dark_eval + light_eval)
 	} else {
-		0.0
+		0.5
 	}
 }
 
@@ -55,3 +56,20 @@ pub fn eval(depth: usize, mut alpha: f32, beta: f32, board: CheckersBitBoard) ->
 		best_eval
 	}
 }
+
+pub fn best_move(depth: usize, board: CheckersBitBoard) -> Move {
+	let mut best_eval = 0.0;
+	let mut best_move = MaybeUninit::uninit();
+	for current_move in PossibleMoves::moves(board) {
+		let current_eval = eval(depth - 1, best_eval, 1.0, unsafe {
+			current_move.apply_to(board)
+		});
+		println!("{} {}", current_move, current_eval);
+		if current_eval > best_eval {
+			best_eval = current_eval;
+			best_move = MaybeUninit::new(current_move);
+		}
+	}
+
+	unsafe { best_move.assume_init() }
+}
diff --git a/cli/src/eval.rs b/cli/src/eval.rs
index d078c5f..72fa32a 100644
--- a/cli/src/eval.rs
+++ b/cli/src/eval.rs
@@ -1,4 +1,8 @@
-use ai::CheckersBitBoard;
+use ai::{CheckersBitBoard, Move};
 pub fn eval(depth: usize) -> f32 {
 	ai::eval(depth, 0.0, 1.0, CheckersBitBoard::starting_position())
 }
+
+pub fn best_move(depth: usize) -> Move {
+	ai::best_move(depth, CheckersBitBoard::starting_position())
+}
diff --git a/cli/src/main.rs b/cli/src/main.rs
index a550092..d230398 100644
--- a/cli/src/main.rs
+++ b/cli/src/main.rs
@@ -31,6 +31,17 @@ fn main() {
 						.help("The depth to go to"),
 				),
 		)
+		.subcommand(
+			SubCommand::with_name("best")
+				.about("Calculate the best move")
+				.arg(
+					Arg::with_name("depth")
+						.required(true)
+						.short("d")
+						.takes_value(true)
+						.help("The depth to go to"),
+				),
+		)
 		.get_matches();
 
 	if let Some(matches) = matches.subcommand_matches("perft") {
@@ -59,4 +70,17 @@ fn main() {
 			)
 		);
 	}
+
+	if let Some(matches) = matches.subcommand_matches("best") {
+		println!(
+			"{}",
+			eval::best_move(
+				matches
+					.value_of("depth")
+					.unwrap()
+					.parse()
+					.expect("Error: not a valid number")
+			)
+		)
+	}
 }
diff --git a/model/src/moves.rs b/model/src/moves.rs
index 720e11a..f6b1fce 100644
--- a/model/src/moves.rs
+++ b/model/src/moves.rs
@@ -1,4 +1,5 @@
-use crate::CheckersBitBoard;
+use crate::{CheckersBitBoard, SquareCoordinate};
+use std::fmt::{Display, Formatter};
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 pub enum MoveDirection {
@@ -122,6 +123,17 @@ impl Move {
 	}
 }
 
+impl Display for Move {
+	fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+		write!(
+			f,
+			"{}-{}",
+			SquareCoordinate::from_value(self.start as usize),
+			SquareCoordinate::from_value(self.end_position())
+		)
+	}
+}
+
 #[cfg(test)]
 mod tests {
 
-- 
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