Refactor: Move solver logic to separate module

This commit refactors the Klotski solver logic by moving it from `main.rs` to a new `solver.rs` module. The changes include:

1. Create a new `solver.rs` file containing the `solve_klotski` function and its associated test.
2. Update `main.rs` to use the new `solver` module and remove the moved code.
3. Adjust imports in `main.rs` to reflect the new structure.
4. Fix a documentation comment in `coordinates.rs` by changing the code block type to "test".

These changes improve code organization and modularity, making the project structure cleaner and more maintainable.

*Commit message written with Claude 3.5 Sonnet.*

src/coordinates.rs

@@ -22,7 +22,7 @@ impl Coor {
     ///
     /// This is how the coordinate system looks like:
     ///
-    /// ```
+    /// ```test
     ///      y=0  y=1  y=2  y=3  y=4  ...
     /// x=0
     /// x=1      

src/main.rs

@@ -3,10 +3,10 @@ mod coordinates;
 mod direction;
 mod errors;
 mod piece;
+mod solver;
 
-use board::{Board, SOLUTION};
-use coordinates::Coor;
-use pathfinding::directed::astar;
+use board::Board;
+use solver::solve_klotski;
 
 fn main() {
     let state = Board::new();
@@ -22,39 +22,3 @@ fn main() {
         println!("No solution?");
     }
 }
-
-/// Solves a given Klotski board state using an A* algorithm
-fn solve_klotski(state: Board) -> Option<(Vec<Board>, i32)> {
-    astar::astar(
-        &state,
-        |p| p.next_states(),
-        |s| {
-            // Manhattan distance
-            let Coor {
-                row: target_row,
-                col: target_col,
-            } = s.target_piece().coor;
-
-            let Coor {
-                row: sol_row,
-                col: sol_col,
-            } = SOLUTION;
-
-            (target_row as i32 - sol_row as i32).abs() + (target_col as i32 - sol_col as i32).abs()
-        },
-        |s| s.is_solution(),
-    )
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::{board::Board, solve_klotski};
-
-    #[test]
-    fn can_solve_default_klotski() {
-        // This test may take a few seconds to complete
-        let board = Board::new();
-        let finished = solve_klotski(board);
-        assert!(finished.is_some());
-    }
-}

src/solver.rs

@@ -0,0 +1,41 @@
+use crate::{
+    board::{Board, SOLUTION},
+    coordinates::Coor,
+};
+use pathfinding::directed::astar;
+
+/// Solves a given Klotski board state using an A* algorithm
+pub fn solve_klotski(state: Board) -> Option<(Vec<Board>, i32)> {
+    astar::astar(
+        &state,
+        |p| p.next_states(),
+        |s| {
+            // Manhattan distance
+            let Coor {
+                row: target_row,
+                col: target_col,
+            } = s.target_piece().coor;
+
+            let Coor {
+                row: sol_row,
+                col: sol_col,
+            } = SOLUTION;
+
+            (target_row as i32 - sol_row as i32).abs() + (target_col as i32 - sol_col as i32).abs()
+        },
+        |s| s.is_solution(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{board::Board, solve_klotski};
+
+    #[test]
+    fn can_solve_default_klotski() {
+        // This test may take a few seconds to complete
+        let board = Board::new();
+        let finished = solve_klotski(board);
+        assert!(finished.is_some());
+    }
+}