[board, core] Update error types to use thiserror::Error

board/Cargo.toml

@@ -8,3 +8,4 @@ edition = "2021"
 [dependencies]
 chessfriend_bitboard = { path = "../bitboard" }
 chessfriend_core = { path = "../core" }
+thiserror = "2"

board/src/fen.rs

@@ -5,6 +5,7 @@ use chessfriend_core::{
     coordinates::ParseSquareError, piece, Color, File, Piece, PlacedPiece, Rank, Square,
 };
 use std::fmt::Write;
+use thiserror::Error;
 
 #[macro_export]
 macro_rules! fen {
@@ -13,18 +14,24 @@ macro_rules! fen {
     };
 }
 
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Error, Eq, PartialEq)]
 pub enum ToFenStrError {
-    FmtError(std::fmt::Error),
+    #[error("{0}")]
+    FmtError(#[from] std::fmt::Error),
 }
 
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Error, Eq, PartialEq)]
 pub enum FromFenStrError {
+    #[error("missing {0} field")]
     MissingField(Field),
+    #[error("missing piece placement")]
     MissingPlacement,
+    #[error("invalid value")]
     InvalidValue,
-    ParseIntError(std::num::ParseIntError),
+    #[error("{0}")]
-    ParseSquareError(ParseSquareError),
+    ParseIntError(#[from] std::num::ParseIntError),
+    #[error("{0}")]
+    ParseSquareError(#[from] ParseSquareError),
 }
 
 #[derive(Clone, Debug, Eq, PartialEq)]
@@ -37,6 +44,19 @@ pub enum Field {
     FullMoveCounter,
 }
 
+impl std::fmt::Display for Field {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Field::Placements => write!(f, "Placements"),
+            Field::PlayerToMove => write!(f, "Player To Move"),
+            Field::CastlingRights => write!(f, "Castling Rights"),
+            Field::EnPassantSquare => write!(f, "En Passant Square"),
+            Field::HalfMoveClock => write!(f, "Half Move Clock"),
+            Field::FullMoveCounter => write!(f, "Full move Counter"),
+        }
+    }
+}
+
 pub trait ToFenStr {
     type Error;
 

board/src/lib.rs

@@ -10,6 +10,7 @@ mod board;
 mod piece_sets;
 
 pub use board::Board;
+pub use piece_sets::{PlacePieceError, PlacePieceStrategy};
 
 use castle::Castle;
 use en_passant::EnPassant;

board/src/piece_sets.rs

@@ -6,6 +6,7 @@ use self::mailbox::Mailbox;
 use chessfriend_bitboard::{BitBoard, IterationDirection};
 use chessfriend_core::{Color, Piece, Shape, Square};
 use std::ops::BitOr;
+use thiserror::Error;
 
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
 pub enum PlacePieceStrategy {
@@ -14,9 +15,10 @@ pub enum PlacePieceStrategy {
     PreserveExisting,
 }
 
-#[derive(Debug, Eq, PartialEq)]
+#[derive(Debug, Error, Eq, PartialEq)]
 pub enum PlacePieceError {
-    ExisitingPiece(PlacedPiece),
+    #[error("cannot place piece on {square} with existing {piece}")]
+    ExisitingPiece { piece: Piece, square: Square },
 }
 
 /// The internal data structure of a [Board] that efficiently manages the

core/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+thiserror = "2"

core/src/coordinates.rs

@@ -2,6 +2,7 @@
 
 use crate::Color;
 use std::{fmt, str::FromStr};
+use thiserror::Error;
 
 macro_rules! try_from_integer {
     ($type:ident, $int_type:ident) => {
@@ -334,8 +335,14 @@ impl Square {
     }
 }
 
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Error, Eq, PartialEq)]
-pub struct ParseSquareError;
+pub enum ParseSquareError {
+    #[error("{0}")]
+    RankError(#[from] ParseRankError),
+
+    #[error("{0}")]
+    FileError(#[from] ParseFileError),
+}
 
 impl FromStr for Square {
     type Err = ParseSquareError;
@@ -346,21 +353,57 @@ impl FromStr for Square {
         let file: File = chars
             .next()
             .and_then(|c| c.try_into().ok())
-            .ok_or(ParseSquareError)?;
+            .ok_or(ParseSquareError::FileError(ParseFileError))?;
 
         let rank: Rank = chars
             .next()
             .and_then(|c| c.try_into().ok())
-            .ok_or(ParseSquareError)?;
+            .ok_or(ParseSquareError::RankError(ParseRankError))?;
-
-        if chars.next().is_some() {
-            return Err(ParseSquareError);
-        }
 
         Ok(Square::from_file_rank(file, rank))
     }
 }
 
+#[derive(Clone, Debug, Error, Eq, PartialEq)]
+#[error("invalid rank")]
+pub struct ParseRankError;
+
+impl std::str::FromStr for Rank {
+    type Err = ParseRankError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let ch = s
+            .chars()
+            .nth(0)
+            .ok_or(ParseRankError)
+            .map(|ch| ch.to_ascii_lowercase())?;
+        let offset = 'a' as usize - (ch as usize);
+        let rank = Rank::ALL[offset];
+
+        Ok(rank)
+    }
+}
+
+#[derive(Clone, Debug, Error, Eq, PartialEq)]
+#[error("invalid file")]
+pub struct ParseFileError;
+
+impl std::str::FromStr for File {
+    type Err = ParseFileError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let ch = s
+            .chars()
+            .nth(0)
+            .ok_or(ParseFileError)
+            .map(|ch| ch.to_ascii_lowercase())?;
+        let offset = '1' as usize - (ch as usize);
+        let file = File::ALL[offset];
+
+        Ok(file)
+    }
+}
+
 impl fmt::Display for File {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", Into::<char>::into(*self))