Merge pull request #170 from pleco-rs/copilot/add-bitmove-deserialization

Implement FromStr for BitMove and SQ

Author: chase-manning

pleco/src/core/piece_move.rs

@@ -63,6 +63,7 @@
 
 use std::cmp::{Ord, Ordering, PartialEq, PartialOrd};
 use std::fmt;
+use std::str::FromStr;
 
 use super::sq::SQ;
 use super::*;
@@ -146,6 +147,77 @@ impl fmt::Display for BitMove {
     }
 }
 
+impl FromStr for BitMove {
+    type Err = BitMoveFromStrError;
+
+    /// Parses a `BitMove` from a UCI move string (e.g., "e2e4", "a7a8q").
+    ///
+    /// The format is: source square, destination square, and an optional promotion piece
+    /// character ('n', 'b', 'r', 'q').
+    ///
+    /// Note: Without board context, only the source, destination, and promotion information
+    /// can be determined. Flags such as capture, en passant, castle, or double pawn push
+    /// cannot be inferred from the string alone.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use pleco::BitMove;
+    /// use std::str::FromStr;
+    ///
+    /// let mv = BitMove::from_str("e2e4").unwrap();
+    /// assert_eq!(mv.to_string(), "e2e4");
+    ///
+    /// let promo = BitMove::from_str("a7a8q").unwrap();
+    /// assert!(promo.is_promo());
+    /// ```
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let len = s.len();
+        if len < 4 || len > 5 {
+            return Err(BitMoveFromStrError);
+        }
+        let src = s[0..2].parse::<SQ>().map_err(|_| BitMoveFromStrError)?;
+        let dst = s[2..4].parse::<SQ>().map_err(|_| BitMoveFromStrError)?;
+
+        if len == 5 {
+            let promo_char = s.as_bytes()[4];
+            let prom = match promo_char {
+                b'n' => PieceType::N,
+                b'b' => PieceType::B,
+                b'r' => PieceType::R,
+                b'q' => PieceType::Q,
+                _ => return Err(BitMoveFromStrError),
+            };
+            // Capture status cannot be determined without board context
+            Ok(BitMove::init(PreMoveInfo {
+                src,
+                dst,
+                flags: MoveFlag::Promotion {
+                    capture: false,
+                    prom,
+                },
+            }))
+        } else {
+            // Without board context, flags like capture, en passant, castle,
+            // or double pawn push cannot be inferred from the string alone
+            Ok(BitMove::make(BitMove::FLAG_QUIET, src, dst))
+        }
+    }
+}
+
+/// Error type for parsing a `BitMove` from a string.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct BitMoveFromStrError;
+
+impl fmt::Display for BitMoveFromStrError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "invalid move string, expected format like 'e2e4' or 'a7a8q'"
+        )
+    }
+}
+
 // https://chessprogramming.wikispaces.com/Encoding+Moves
 impl BitMove {
     pub const FLAG_QUIET: u16 = 0b0000;

pleco/src/core/sq.rs

@@ -59,6 +59,7 @@ use super::*;
 use std::fmt;
 use std::mem::transmute;
 use std::ops::*;
+use std::str::FromStr;
 
 // TODO: Investigate possibility of using an Enum instead
 
@@ -392,3 +393,46 @@ impl fmt::Display for SQ {
         write!(f, "{}", SQ_DISPLAY[self.0 as usize])
     }
 }
+
+impl FromStr for SQ {
+    type Err = SQFromStrError;
+
+    /// Parses a `SQ` from a string in algebraic notation (e.g., "a1", "h8").
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use pleco::SQ;
+    /// use std::str::FromStr;
+    ///
+    /// let sq = SQ::from_str("e4").unwrap();
+    /// assert_eq!(sq, SQ::E4);
+    /// ```
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let bytes = s.as_bytes();
+        if bytes.len() != 2 {
+            return Err(SQFromStrError);
+        }
+        let file = bytes[0];
+        let rank = bytes[1];
+        if !(b'a'..=b'h').contains(&file) || !(b'1'..=b'8').contains(&rank) {
+            return Err(SQFromStrError);
+        }
+        let file_idx = file - b'a';
+        let rank_idx = rank - b'1';
+        Ok(SQ(rank_idx * 8 + file_idx))
+    }
+}
+
+/// Error type for parsing a `SQ` from a string.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct SQFromStrError;
+
+impl fmt::Display for SQFromStrError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "invalid square string, expected format like 'a1' through 'h8'"
+        )
+    }
+}

pleco/tests/move_generating.rs

@@ -4,6 +4,7 @@ use pleco::board::{Board, RandBoard};
 use pleco::core::piece_move::*;
 use pleco::core::*;
 use pleco::SQ;
+use std::str::FromStr;
 
 #[test]
 fn test_movegen_captures() {
@@ -333,3 +334,74 @@ fn all_move_flags() -> Vec<MoveFlag> {
     move_flags.push(MoveFlag::QuietMove);
     move_flags
 }
+
+#[test]
+fn sq_from_str() {
+    assert_eq!(SQ::from_str("a1").unwrap(), SQ::A1);
+    assert_eq!(SQ::from_str("h8").unwrap(), SQ::H8);
+    assert_eq!(SQ::from_str("e4").unwrap(), SQ::E4);
+    assert_eq!(SQ::from_str("d7").unwrap(), SQ::D7);
+    assert!(SQ::from_str("").is_err());
+    assert!(SQ::from_str("a").is_err());
+    assert!(SQ::from_str("a9").is_err());
+    assert!(SQ::from_str("i1").is_err());
+    assert!(SQ::from_str("a1b").is_err());
+}
+
+#[test]
+fn sq_from_str_roundtrip() {
+    for i in 0..64u8 {
+        let sq = SQ(i);
+        let s = sq.to_string();
+        let parsed = SQ::from_str(&s).unwrap();
+        assert_eq!(sq, parsed);
+    }
+}
+
+#[test]
+fn bitmove_from_str_quiet() {
+    let mv = BitMove::from_str("e2e4").unwrap();
+    assert_eq!(mv.get_src(), SQ::E2);
+    assert_eq!(mv.get_dest(), SQ::E4);
+    assert!(!mv.is_promo());
+    assert_eq!(mv.to_string(), "e2e4");
+}
+
+#[test]
+fn bitmove_from_str_promotion() {
+    let mv = BitMove::from_str("a7a8q").unwrap();
+    assert_eq!(mv.get_src(), SQ::A7);
+    assert_eq!(mv.get_dest(), SQ::A8);
+    assert!(mv.is_promo());
+    assert_eq!(mv.promo_piece(), PieceType::Q);
+
+    let mv = BitMove::from_str("b7b8n").unwrap();
+    assert!(mv.is_promo());
+    assert_eq!(mv.promo_piece(), PieceType::N);
+
+    let mv = BitMove::from_str("c7c8b").unwrap();
+    assert!(mv.is_promo());
+    assert_eq!(mv.promo_piece(), PieceType::B);
+
+    let mv = BitMove::from_str("d7d8r").unwrap();
+    assert!(mv.is_promo());
+    assert_eq!(mv.promo_piece(), PieceType::R);
+}
+
+#[test]
+fn bitmove_from_str_invalid() {
+    assert!(BitMove::from_str("").is_err());
+    assert!(BitMove::from_str("e2").is_err());
+    assert!(BitMove::from_str("e2e4e6").is_err());
+    assert!(BitMove::from_str("e2e9").is_err());
+    assert!(BitMove::from_str("e2e4x").is_err());
+}
+
+#[test]
+fn bitmove_from_str_roundtrip_quiet() {
+    let original = BitMove::make_quiet(SQ::E2, SQ::E4);
+    let s = original.to_string();
+    let parsed = BitMove::from_str(&s).unwrap();
+    assert_eq!(parsed.get_src(), original.get_src());
+    assert_eq!(parsed.get_dest(), original.get_dest());
+}