1 files changed, 39 insertions, 7 deletions

diff --git a/src/game.rs b/src/game.rs
index 5db2c48..4a80ce7 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -743,23 +743,28 @@ impl Game {
         self.size
     }
 
-    pub fn query_action_lines(&self) -> String {
-        let mut result = String::new();
+    pub fn query_action_lines(&self) -> Vec<String> {
+        let mut result = Vec::new();
         let mut newline = true;
         let num_actions = self.actions.len();
         if num_actions > 0 {
-            result += "1. ";
+            let mut line = String::new();
+            line += "1. ";
             for i in 0..num_actions {
                 if i > 1 && newline {
                     // TODO: Is placing the opponent's first stone the zeroeth action?
-                    result += &format!("{}. ", i / 2 + 1);
+                    line += &format!("{}. ", i / 2 + 1);
                 }
-                result += &format!("{} ", self.actions[i]);
+                line += &format!("{}  ", self.actions[i].to_string());
                 if i > 0 && !newline {
-                    result.push('\n');
+                    result.push(line);
+                    line = String::new();
                 }
                 newline = !newline;
             }
+            if !line.is_empty() {
+                result.push(line);
+            }
         }
         result
     }
@@ -834,6 +839,33 @@ impl Game {
             }
         }
     }
+
+    pub fn undo(&mut self) -> Result<Vec<Position>, String> {
+        if self.actions.len() > 0 {
+            self.actions.pop();
+            self.states.pop();
+            self.turn_order = match self.actions.len() {
+                0 => TurnOrder::WhitePlacesBlack,
+                1 => TurnOrder::BlackPlacesWhite,
+                _ => TurnOrder::Normal,
+            };
+            self.current_player = match self.current_player {
+                Player::Black => Player::White,
+                Player::White => Player::Black,
+            };
+            // I'm too lazy to work out exactly which squares must be
+            // redrawn when an action is undone
+            let mut redraw_all: Vec<Position> = Vec::new();
+            for x in 0..self.size {
+                for y in 0..self.size {
+                    redraw_all.push(Position { x, y });
+                }
+            }
+            Ok(redraw_all)
+        } else {
+            Err(String::from("Cannot undo in an empty game!"))
+        }
+    }
 }
 
 impl fmt::Display for Game {
@@ -845,7 +877,7 @@ impl fmt::Display for Game {
             self.white_player_name,
             self.black_player_name,
             self.size,
-            self.query_action_lines()
+            self.query_action_lines().join("\n")
         )
     }
 }