add back functionality

src/agent.rs

@@ -3,11 +3,18 @@ use rand::prelude::*;
 use std::io;
 use std::io::prelude::*;
 
+#[derive(Debug, Clone, Copy)]
+pub enum AgentMove {
+    CoordPair(CoordPair),
+    Back,
+    Skip,
+}
+
 #[allow(dead_code)]
 // implements `Send` so we can use it in a multithreaded `EloArena`
 pub trait Agent: Send {
     /// Returns the move of an [`Agent`]
-    fn next_move(&mut self, board: &Board) -> Option<CoordPair>;
+    fn next_move(&mut self, board: &Board) -> AgentMove;
     /// Returns the name of the [`Agent`]
     fn name(&self) -> &'static str;
     /// Returns the color the [`Agent`] is playing
@@ -28,16 +35,23 @@ impl ManualAgent {
 
 #[allow(dead_code)]
 impl Agent for ManualAgent {
-    fn next_move(&mut self, board: &Board) -> Option<CoordPair> {
+    fn next_move(&mut self, board: &Board) -> AgentMove {
         let stdin = io::stdin();
         let mut input = String::new();
-        println!("Your turn! ('Skip' to skip)");
+        println!("Your turn! ('Skip' to skip 'back' to go back a move)");
         loop {
             input.clear();
-            stdin.lock().read_line(&mut input).ok()?;
+            if stdin.lock().read_line(&mut input).is_err() {
+                return AgentMove::Skip;
+            };
+
             if input.to_lowercase().trim() == "skip" {
                 // skips move
-                return None;
+                return AgentMove::Skip;
+            }
+            if input.to_lowercase().trim() == "back" {
+                // skips move
+                return AgentMove::Back;
             }
 
             let got = input
@@ -53,7 +67,7 @@ impl Agent for ManualAgent {
                     println!("Invalid move! Try again.");
                     continue;
                 }
-                return Some(got.into());
+                return AgentMove::CoordPair(got.into());
             }
         }
     }
@@ -74,8 +88,11 @@ pub struct RandomAgent {
 
 #[allow(dead_code)]
 impl Agent for RandomAgent {
-    fn next_move(&mut self, board: &Board) -> Option<CoordPair> {
-        board.possible_moves(self.color).choose(&mut rand::rng())
+    fn next_move(&mut self, board: &Board) -> AgentMove {
+        match board.possible_moves(self.color).choose(&mut rand::rng()) {
+            Some(x) => AgentMove::CoordPair(x),
+            None => AgentMove::Skip,
+        }
     }
 
     fn name(&self) -> &'static str {

src/complexagent.rs

@@ -1,7 +1,7 @@
 use crate::{
-    agent::Agent,
+    agent::{Agent, AgentMove},
     logic::{FutureMoveConfig, FutureMoves},
-    repr::{Board, CoordPair, Piece},
+    repr::{Board, Piece},
 };
 
 pub struct ComplexAgent {
@@ -20,13 +20,18 @@ impl ComplexAgent {
 }
 
 impl Agent for ComplexAgent {
-    fn next_move(&mut self, board: &Board) -> Option<CoordPair> {
+    fn next_move(&mut self, board: &Board) -> AgentMove {
         self.future_moves.update_from_board(board);
         self.future_moves.generate();
 
-        self.future_moves
+        match self
+            .future_moves
             .best_move()
             .expect("FutureMoves has no move?")
+        {
+            Some(x) => AgentMove::CoordPair(x),
+            None => AgentMove::Skip,
+        }
     }
 
     fn name(&self) -> &'static str {

src/game_inner.rs

@@ -1,5 +1,5 @@
 use crate::{
-    agent::Agent,
+    agent::{Agent, AgentMove},
     repr::{Board, CoordPair, Piece, Winner},
 };
 
@@ -70,41 +70,48 @@ impl GameInner {
         // when it comes to human input
         loop {
             let player_move = self.players[player_i].next_move(&self.board);
-            self.move_log.push((player_move, player_color));
 
-            if let Some(coord) = player_move {
-                match self.board.place(coord, player_color) {
-                    // Check if its a valid move
-                    Ok(_) => {
-                        if self.do_print {
-                            println!("Player {} placed at {}", player_i, coord);
+            match player_move {
+                AgentMove::CoordPair(coord) => {
+                    self.move_log.push((Some(coord), player_color));
+                    match self.board.place(coord, player_color) {
+                        // Check if its a valid move
+                        Ok(_) => {
+                            if self.do_print {
+                                println!("Player {} placed at {}", player_i, coord);
+                            }
+                            break;
                         }
-                        break;
-                    }
 
-                    Err(err) => {
-                        panic!(
-                            "Invalid move by Player {}: {}. Move: {} State: {:?}",
-                            player_i, err, coord, self
-                        );
+                        Err(err) => {
+                            panic!(
+                                "Invalid move by Player {}: {}. Move: {} State: {:?}",
+                                player_i, err, coord, self
+                            );
+                        }
                     }
                 }
-            } else {
-                if self.do_print {
-                    println!("Player {} did not make a move!", player_i);
+                AgentMove::Back => {
+                    self.back();
                 }
-
-                // players are able to skip a move if they have no valid moves to make
-                if self.board.possible_moves(player_color).next().is_some() {
+                AgentMove::Skip => {
+                    self.move_log.push((None, player_color));
                     if self.do_print {
-                        println!(
-                            "Player {} has possible moves, but skipped (invalid)",
-                            player_i
-                        );
+                        println!("Player {} did not make a move!", player_i);
                     }
-                    continue;
+
+                    // players are able to skip a move if they have no valid moves to make
+                    if self.board.possible_moves(player_color).next().is_some() {
+                        if self.do_print {
+                            println!(
+                                "Player {} has possible moves, but skipped (invalid)",
+                                player_i
+                            );
+                        }
+                        continue;
+                    }
+                    return; // No valid move available
                 }
-                return; // No valid move available
             }
         }
     }
@@ -146,4 +153,19 @@ impl GameInner {
         self.game_loop();
         self.board.game_winner()
     }
+
+    pub fn back(&mut self) {
+        if self.move_log.is_empty() {
+            println!("This is the initial board state!");
+            return;
+        }
+        self.move_log.pop();
+        self.board = self.first_board;
+        for &(l, p) in &self.move_log {
+            if let Some(loc) = l {
+                self.board.place(loc, p).expect("unable to go backwards");
+            }
+        }
+        println!("{}", self);
+    }
 }