pgn_filter 1.1.0

//! Holds information about an individual chess position.

pub mod filter;
use filter::BoardFilter;
pub(super) mod piece;
pub(super) use piece::*;
pub(super) mod piecedefn;
pub(super) use piecedefn::*;
pub(super) mod square;
pub(super) use square::*;

use std::collections::HashMap;
use std::fmt;

/// Holds information about a chess position.
///
/// Including:
/// * location of all pieces
/// * options for castling king or queen side
/// * halfmove and fullmove counts
/// * possible enpassant target
///
/// Methods are also provided to convert boards [`to`](self::to_fen()) and
/// [`from`](self::from_fen()) FEN.
///
#[derive(Clone, Debug)]
pub struct Board {
    // board contents
    board: Vec<Vec<Piece>>,
    // true for white to move next, false for black to move next
    pub(super) white_to_move: bool,
    // true if white king-side castling is valid
    pub(super) white_king_side_castling: bool,
    // true if white queen-side castling is valid
    pub(super) white_queen_side_castling: bool,
    // true if black king-side castling is valid
    pub(super) black_king_side_castling: bool,
    // true if black queen-side castling is valid
    pub(super) black_queen_side_castling: bool,
    // if enpassant is possible, holds the target square, or None
    pub(super) enpassant_target: Option<Square>,
    // count of number of half moves since last pawn move or capture
    pub(super) halfmove_clock: usize,
    // count of number of full moves, as on a score sheet.
    // So fullmove_number starts at 1 and increases every time black moves.
    pub(super) fullmove_number: usize,
}

impl PartialEq for Board {
    fn eq(&self, other: &Self) -> bool {
        if self.white_to_move != other.white_to_move
            || self.white_king_side_castling != other.white_king_side_castling
            || self.white_queen_side_castling != other.white_queen_side_castling
            || self.black_king_side_castling != other.black_king_side_castling
            || self.black_queen_side_castling != other.black_queen_side_castling
            || self.enpassant_target != other.enpassant_target
            || self.halfmove_clock != other.halfmove_clock
            || self.fullmove_number != other.fullmove_number
        {
            return false;
        } else {
            for row in 0..7 {
                for col in 0..7 {
                    if self.board[row][col] != other.board[row][col] {
                        return false;
                    }
                }
            }
        }
        true
    }
}
impl Eq for Board {}

impl fmt::Display for Board {
    /// Displays the board in a 2D representation, suitable for printing to a terminal.
    ///
    /// # Example
    ///
    /// ```no_run
    /// let board = pgn_filter::Board::start_position();
    /// println!("{}", board);
    /// ```
    /// prints:
    /// ```text
    /// rnbqkbnr
    /// pppppppp
    /// ........
    /// ........
    /// ........
    /// ........
    /// PPPPPPPP
    /// RNBQKBNR
    /// ```
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut result = String::from("");

        for row in (0..=7).rev() {
            for col in 0..=7 {
                result.push(match &self.get_coord(col, row).name {
                    Piece::WK => 'K',
                    Piece::WQ => 'Q',
                    Piece::WR => 'R',
                    Piece::WB => 'B',
                    Piece::WN => 'N',
                    Piece::WP => 'P',
                    Piece::BK => 'k',
                    Piece::BQ => 'q',
                    Piece::BR => 'r',
                    Piece::BB => 'b',
                    Piece::BN => 'n',
                    Piece::BP => 'p',
                    Piece::NO => '.',
                });
            }
            result.push_str("\n");
        }

        write!(f, "{}", result)
    }
}

impl Board {
    /// Creates an empty board.
    pub fn new() -> Board {
        Board {
            board: vec![vec![Piece::NO; 8]; 8],
            white_to_move: true,
            white_king_side_castling: false,
            white_queen_side_castling: false,
            black_king_side_castling: false,
            black_queen_side_castling: false,
            enpassant_target: None,
            halfmove_clock: 0,
            fullmove_number: 1,
        }
    }

    /// Creates a chessboard from a FEN description.
    /// The FEN description may be a single string, representing a board
    /// or a full six-field description.
    ///
    /// # Example
    ///
    /// ```
    /// let start_position = pgn_filter::Board::from_fen(
    ///     "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
    /// ).unwrap();
    /// ```
    ///
    /// # Errors
    ///
    /// An error is returned if given FEN is not valid.
    ///
    pub fn from_fen(fen: &str) -> Result<Board, &'static str> {
        let fields: Vec<&str> = fen.split(' ').collect();
        if fields.len() == 1 || fields.len() == 6 {
            let mut board = Board::new();
            board.setup_board_from_fen(fields[0])?;

            if fields.len() == 6 {
                board.white_to_move = fields[1].to_lowercase() == "w";
                board.white_king_side_castling = fields[2].contains("K");
                board.white_queen_side_castling = fields[2].contains("Q");
                board.black_king_side_castling = fields[2].contains("k");
                board.black_queen_side_castling = fields[2].contains("q");
                board.enpassant_target = if fields[3] == "-" {
                    None
                } else {
                    match Square::from(fields[3]) {
                        Ok(square) => Some(square),
                        Err(e) => panic!("Invalid e.p. target {}", e),
                    }
                };
                if let Ok(count) = fields[4].parse() {
                    board.halfmove_clock = count;
                }
                if let Ok(count) = fields[5].parse() {
                    board.fullmove_number = count;
                }
            }

            Ok(board)
        } else {
            Err("Invalid FEN description")
        }
    }

    /// Returns a FEN description of current chessboard.
    ///
    /// # Example
    ///
    /// ```
    /// let start_fen = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
    /// let start_position = pgn_filter::Board::from_fen(start_fen).unwrap();
    /// assert_eq!(start_fen, start_position.to_fen().as_str());
    /// ```
    ///
    pub fn to_fen(&self) -> String {
        let mut result = String::from("");

        // add board description
        for row in (0..=7).rev() {
            let mut count = 0;
            for col in 0..=7 {
                let piece = &self.board[col][row];
                if *piece == Piece::NO {
                    count += 1;
                } else {
                    if count > 0 {
                        result.push_str(format!("{}", count).as_str());
                        count = 0;
                    }
                    result.push_str(&piece_to_string(&piece));
                }
            }
            if count > 0 {
                result.push_str(format!("{}", count).as_str());
            }
            if row != 0 {
                result.push_str("/")
            }
        }

        // add last fields
        if self.white_to_move {
            result.push_str(" w ");
        } else {
            result.push_str(" b ");
        }
        if self.white_king_side_castling {
            result.push_str("K");
        }
        if self.white_queen_side_castling {
            result.push_str("Q");
        }
        if self.black_king_side_castling {
            result.push_str("k");
        }
        if self.black_queen_side_castling {
            result.push_str("q");
        }
        if let Some(square) = &self.enpassant_target {
            result.push_str(format!(" {} ", square).as_str());
        } else {
            result.push_str(" - ");
        }
        result.push_str(format!("{} {}", &self.halfmove_clock, &self.fullmove_number).as_str());

        result
    }

    /// Creates the start position.
    pub fn start_position() -> Board {
        Board::from_fen("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1").unwrap()
    }

    /// Returns empty filter.
    pub fn must_have() -> BoardFilter {
        BoardFilter::new()
    }

    // --- The following functions provide access to the board's fields ---

    /// Returns "White" or "Black", depending on who is to move next.
    ///
    /// # Example
    ///
    /// ```
    /// let start_position = pgn_filter::Board::start_position();
    /// assert_eq!("White", start_position.player_to_move());
    /// ```
    pub fn player_to_move(&self) -> String {
        if self.white_to_move {
            String::from("White")
        } else {
            String::from("Black")
        }
    }

    /// Returns true if white can castle king-side in given position.
    pub fn can_white_castle_king_side(&self) -> bool {
        self.white_king_side_castling
    }

    /// Returns true if white can castle queen-side in given position.
    pub fn can_white_castle_queen_side(&self) -> bool {
        self.white_queen_side_castling
    }

    /// Returns true if black can castle king-side in given position.
    pub fn can_black_castle_king_side(&self) -> bool {
        self.black_king_side_castling
    }

    /// Returns true if black can castle queen-side in given position.
    pub fn can_black_castle_queen_side(&self) -> bool {
        self.black_queen_side_castling
    }

    /// Returns square which pawn can 'capture' enpassant.
    /// For example, if white has a pawn on e5 and black plays d7-d5,
    /// then d6 is the enpassant target.
    ///
    /// If there is no target square, returns the empty string.
    pub fn enpassant_target(&self) -> String {
        match &self.enpassant_target {
            Some(square) => square.to_string(),
            None => String::from(""),
        }
    }

    /// Returns a count of the number of half moves made since the last pawn
    /// move or capture.
    pub fn halfmove_clock(&self) -> usize {
        self.halfmove_clock
    }

    /// Returns the number of the next/current full move, as on a score sheet.
    /// So the fullmove number starts at 1, and increases every time black moves.
    ///
    /// # Example
    /// ```
    /// let start_position = pgn_filter::Board::start_position();
    /// assert_eq!(1, start_position.fullmove_number());
    /// ```
    ///
    pub fn fullmove_number(&self) -> usize {
        self.fullmove_number
    }

    // Counts the number of occurrences of each piece on the board.
    //
    fn piece_counts(&self) -> HashMap<Piece, usize> {
        let mut counts = HashMap::new();
        counts.insert(Piece::WK, 0);
        counts.insert(Piece::WQ, 0);
        counts.insert(Piece::WB, 0);
        counts.insert(Piece::WN, 0);
        counts.insert(Piece::WR, 0);
        counts.insert(Piece::WP, 0);
        counts.insert(Piece::BK, 0);
        counts.insert(Piece::BQ, 0);
        counts.insert(Piece::BB, 0);
        counts.insert(Piece::BN, 0);
        counts.insert(Piece::BR, 0);
        counts.insert(Piece::BP, 0);

        for col in 0..=7 {
            for row in 0..=7 {
                let piece = &self.board[col][row];
                if *piece != Piece::NO {
                    let count = counts.entry(*piece).or_insert(0);
                    *count += 1;
                }
            }
        }

        counts
    }

    // Returns true if given piece can move from start square to finish square on
    // this board
    pub(super) fn can_reach(&self, piece: &Piece, start: &Square, finish: &Square) -> bool {
        match piece {
            Piece::WK | Piece::BK => self.king_can_reach(&start, &finish),
            Piece::WQ | Piece::BQ => self.queen_can_reach(&start, &finish),
            Piece::WB | Piece::BB => self.bishop_can_reach(&start, &finish),
            Piece::WN | Piece::BN => self.knight_can_reach(&start, &finish),
            Piece::WR | Piece::BR => self.rook_can_reach(&start, &finish),
            _ => false, // ? Panic? this should never occur
        }
    }

    fn king_can_reach(&self, start: &Square, finish: &Square) -> bool {
        step_h(&start, &finish) <= 1 && step_v(&start, &finish) <= 1
    }

    fn queen_can_reach(&self, start: &Square, finish: &Square) -> bool {
        self.rook_can_reach(&start, &finish) || self.bishop_can_reach(&start, &finish)
    }

    fn bishop_can_reach(&self, start: &Square, finish: &Square) -> bool {
        let h = step_h(&start, &finish);
        let v = step_v(&start, &finish);

        if h == v {
            let dirn_h = if finish.col > start.col { 1 } else { -1 };
            let dirn_v = if finish.row > start.row { 1 } else { -1 };

            (1..=(h - 1)).all(|i| {
                let i = i as i32;
                let col = if dirn_h > 0 {
                    start.col.checked_add((i * dirn_h) as usize).unwrap()
                } else {
                    start.col.checked_sub((i * -dirn_h) as usize).unwrap()
                };
                let row = if dirn_v > 0 {
                    start.row.checked_add((i * dirn_v) as usize).unwrap()
                } else {
                    start.row.checked_sub((i * -dirn_v) as usize).unwrap()
                };

                let square_to_check = Square { col, row };
                self.get_square(&square_to_check).name == Piece::NO
            })
        } else {
            false
        }
    }

    fn knight_can_reach(&self, start: &Square, finish: &Square) -> bool {
        let h = step_h(&start, &finish);
        let v = step_v(&start, &finish);

        (h == 2 && v == 1) || (h == 1 && v == 2)
    }

    fn rook_can_reach(&self, start: &Square, finish: &Square) -> bool {
        if start.col == finish.col {
            // moving along column
            let row_1 = std::cmp::min(start.row, finish.row) + 1;
            let row_2 = std::cmp::max(start.row, finish.row) - 1;
            (row_1..=row_2).all(|row| self.get_coord(start.col, row).name == Piece::NO)
        } else if start.row == finish.row {
            // moving along row
            let col_1 = std::cmp::min(start.col, finish.col) + 1;
            let col_2 = std::cmp::max(start.col, finish.col) - 1;
            (col_1..=col_2).all(|col| self.get_coord(col, start.row).name == Piece::NO)
        } else {
            false
        }
    }

    // Returns the PieceDefn (piece name + square) for all pieces on the board
    // which are in the given vector of piece names.
    //
    fn find_pieces(&self, pieces: &Vec<Piece>) -> Vec<PieceDefn> {
        let mut result = vec![];

        for col in 0..=7 {
            for row in 0..=7 {
                if pieces.contains(&self.board[col][row]) {
                    result.push(PieceDefn {
                        name: self.board[col][row].clone(),
                        square: Square { col, row },
                    });
                }
            }
        }

        result
    }

    // Returns the PieceDefn (piece name + square) for all white pieces on the board.
    fn white_pieces(&self) -> Vec<PieceDefn> {
        self.find_pieces(&vec![
            Piece::WK,
            Piece::WQ,
            Piece::WR,
            Piece::WB,
            Piece::WN,
            Piece::WP,
        ])
    }

    // Returns the PieceDefn (piece name + square) for all black pieces on the board.
    fn black_pieces(&self) -> Vec<PieceDefn> {
        self.find_pieces(&vec![
            Piece::BK,
            Piece::BQ,
            Piece::BR,
            Piece::BB,
            Piece::BN,
            Piece::BP,
        ])
    }

    pub(super) fn set_coord(&mut self, col: usize, row: usize, piece: &Piece) {
        self.board[col][row] = piece.clone();
    }

    pub(super) fn set_square(&mut self, square: &Square, piece: &Piece) {
        self.set_coord(square.col, square.row, &piece)
    }

    // Return true if moving the current piece from given start to known
    // destination will leave the moving side's king in check.
    pub(super) fn king_left_in_check(
        &self,
        piece: &Piece,
        start: &Square,
        finish: &Square,
    ) -> bool {
        let mut test_board = self.clone();
        test_board.set_square(&start, &Piece::NO);
        test_board.set_square(&finish, &piece);

        if self.white_to_move {
            test_board.is_white_king_in_check()
        } else {
            test_board.is_black_king_in_check()
        }
    }

    // Returns true if the black king is in check in the current position.
    fn is_black_king_in_check(&self) -> bool {
        let black_king = &self.locations_of(&Piece::BK)[0];
        self.white_pieces()
            .iter()
            .any(|defn| self.can_reach(&defn.name, &defn.square, &black_king))
    }

    // Returns true if the white king is in check in the current position.
    fn is_white_king_in_check(&self) -> bool {
        let white_king = &self.locations_of(&Piece::WK)[0];
        self.black_pieces()
            .iter()
            .any(|defn| self.can_reach(&defn.name, &defn.square, &white_king))
    }

    // Return the locations of a given piece on the board.
    //
    fn locations_of(&self, piece: &Piece) -> Vec<Square> {
        self.locations_within(piece, "")
    }

    // Return the locations of a given piece on the board, limited
    // to a given row or column.
    //
    pub(super) fn locations_within(&self, piece: &Piece, hint: &str) -> Vec<Square> {
        let hint = hint.to_lowercase();
        let mut result = vec![];

        for col in 0..=7 {
            for row in 0..=7 {
                let square = Square { col, row };
                if square.to_string().contains(&hint) && self.board[col][row] == *piece {
                    result.push(square);
                }
            }
        }

        result
    }

    pub(super) fn get_coord(&self, col: usize, row: usize) -> PieceDefn {
        PieceDefn {
            name: self.board[col][row].clone(),
            square: Square { col, row },
        }
    }

    pub(super) fn get_square(&self, square: &Square) -> PieceDefn {
        self.get_coord(square.col, square.row)
    }

    fn setup_board_from_fen(&mut self, fen: &str) -> Result<(), &'static str> {
        let rows: Vec<&str> = fen.split('/').collect();
        let mut result = Ok(());
        if rows.len() == 8 {
            for row in 0..=7 {
                let mut col = 0;
                for ch in rows[row].chars() {
                    match ch {
                        'K' | 'k' | 'Q' | 'q' | 'R' | 'r' | 'B' | 'b' | 'N' | 'n' | 'P' | 'p' => {
                            self.board[col][7 - row] = piece_from(&format!("{}", ch));
                            col += 1;
                            ()
                        }
                        '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' => {
                            if let Some(blanks) = ch.to_digit(10) {
                                col += blanks as usize;
                            }
                        }
                        _ => {
                            result = Err("Invalid character in FEN description");
                        }
                    }
                }
            }
        } else {
            result = Err("Invalid FEN description");
        }
        result
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_must_initialise_empty_board() {
        let board = Board::new();

        for col in 0..=7 {
            for row in 0..=7 {
                assert_eq!(
                    PieceDefn {
                        name: Piece::NO,
                        square: Square { col, row }
                    },
                    board.get_coord(col, row)
                );
            }
        }
    }

    #[test]
    fn test_invalid_fen() {
        assert_eq!(
            Err("Invalid FEN description"),
            Board::from_fen("1 2 3 4 5 6")
        );
        assert_eq!(Err("Invalid FEN description"), Board::from_fen("1"));
        assert_eq!(Err("Invalid FEN description"), Board::from_fen("1 2 3"));
    }

    fn test_piece(board: &Board, col: usize, row: usize, piece: &str) {
        assert_eq!(
            PieceDefn {
                name: piece_from(&piece),
                square: Square { col, row }
            },
            board.get_coord(col, row)
        );
    }

    #[test]
    fn test_setup_fen() {
        if let Ok(board) = Board::from_fen("3k4/7p/8/8/8/8/2P5/R7 b Kq - 5 46") {
            test_piece(&board, 0, 0, "R");
            test_piece(&board, 2, 1, "P");
            test_piece(&board, 7, 6, "p");
            test_piece(&board, 3, 7, "k");
            assert!(!board.white_to_move);
            assert!(board.white_king_side_castling);
            assert!(!board.white_queen_side_castling);
            assert!(!board.black_king_side_castling);
            assert!(board.black_queen_side_castling);
            assert_eq!(None, board.enpassant_target);
            assert_eq!(5, board.halfmove_clock);
            assert_eq!(46, board.fullmove_number);
        } else {
            assert!(false);
        }
    }

    #[test]
    fn test_to_fen() {
        let fens = [
            "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
            "3k4/7p/8/8/8/8/2P5/R7 b Kq - 5 46",
        ];
        for fen in fens.iter() {
            let position = Board::from_fen(fen).unwrap();
            assert_eq!(fen, &position.to_fen());
        }
    }

    #[test]
    fn test_makes_start() {
        let board = Board::start_position();
        assert!(board.white_to_move);
        assert!(board.white_king_side_castling);
        assert!(board.white_queen_side_castling);
        assert!(board.black_king_side_castling);
        assert!(board.black_queen_side_castling);
        assert_eq!(None, board.enpassant_target);
        assert_eq!(0, board.halfmove_clock);
        assert_eq!(1, board.fullmove_number);
        test_piece(&board, 0, 0, "R");
        test_piece(&board, 1, 0, "N");
        test_piece(&board, 2, 0, "B");
        test_piece(&board, 3, 0, "Q");
        test_piece(&board, 4, 0, "K");
        test_piece(&board, 5, 0, "B");
        test_piece(&board, 6, 0, "N");
        test_piece(&board, 7, 0, "R");
        test_piece(&board, 0, 7, "r");
        test_piece(&board, 1, 7, "n");
        test_piece(&board, 2, 7, "b");
        test_piece(&board, 3, 7, "q");
        test_piece(&board, 4, 7, "k");
        test_piece(&board, 5, 7, "b");
        test_piece(&board, 6, 7, "n");
        test_piece(&board, 7, 7, "r");
        for col in 0..=7 {
            test_piece(&board, col, 1, "P");
            test_piece(&board, col, 6, "p");
            for row in 2..=5 {
                assert_eq!(
                    PieceDefn {
                        name: Piece::NO,
                        square: Square { col, row }
                    },
                    board.get_coord(col, row)
                );
            }
        }
    }

    #[test]
    fn test_piece_counts() {
        let board = Board::start_position();
        let mut counts = board.piece_counts();
        assert_eq!(12, counts.keys().len());

        let count = counts.entry(Piece::WR).or_insert(0);
        assert_eq!(2, *count);
        let count = counts.entry(Piece::WB).or_insert(0);
        assert_eq!(2, *count);
        let count = counts.entry(Piece::WN).or_insert(0);
        assert_eq!(2, *count);
        let count = counts.entry(Piece::WK).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::WQ).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::WP).or_insert(0);
        assert_eq!(8, *count);
        let count = counts.entry(Piece::BR).or_insert(0);
        assert_eq!(2, *count);
        let count = counts.entry(Piece::BB).or_insert(0);
        assert_eq!(2, *count);
        let count = counts.entry(Piece::BN).or_insert(0);
        assert_eq!(2, *count);
        let count = counts.entry(Piece::BK).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::BQ).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::BP).or_insert(0);
        assert_eq!(8, *count);

        let board = Board::from_fen("3k4/7p/8/8/8/8/2P5/R7").unwrap();
        let mut counts = board.piece_counts();
        assert_eq!(12, counts.keys().len());

        let count = counts.entry(Piece::WR).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::WB).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::WN).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::WK).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::WQ).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::WP).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::BR).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::BB).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::BN).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::BK).or_insert(0);
        assert_eq!(1, *count);
        let count = counts.entry(Piece::BQ).or_insert(0);
        assert_eq!(0, *count);
        let count = counts.entry(Piece::BP).or_insert(0);
        assert_eq!(1, *count);
    }

    #[test]
    fn test_locations() {
        let c1 = Square { col: 2, row: 0 };
        let f1 = Square { col: 5, row: 0 };
        assert_eq!(
            vec![c1.clone(), f1.clone()],
            Board::start_position().locations_of(&Piece::WB)
        );
        assert!(Board::start_position()
            .locations_within(&Piece::WB, "Q")
            .is_empty());
        assert_eq!(
            vec![f1.clone()],
            Board::start_position().locations_within(&Piece::WB, "f")
        );
        assert_eq!(
            vec![c1.clone(), f1.clone()],
            Board::start_position().locations_within(&Piece::WB, "1")
        );
    }

    #[test]
    fn test_find_pieces() {
        let start = Board::start_position();
        let knights = start.find_pieces(&vec![Piece::WN, Piece::BN]);
        assert_eq!(4, knights.len());
        let squares: Vec<String> = knights
            .iter()
            .map(|piece| piece.square.to_string())
            .collect();
        assert_eq!(vec!["b1", "b8", "g1", "g8"], squares);
    }

    const DEFNS: &[(&str, &str, &str, bool, &str)] = &[
        // rook moves
        ("R", "e4", "e8", true, "8/8/8/8/4R3/8/8/8"),
        ("R", "e4", "d8", false, "8/8/8/8/4R3/8/8/8"),
        ("r", "e4", "c4", true, "8/8/8/8/4r3/8/8/8"),
        // bishop moves
        ("B", "d4", "h8", true, "8/8/8/8/3R4/8/8/8"),
        ("b", "g8", "a2", true, "6b1/8/8/8/8/8/8/8"),
        ("B", "d4", "d8", false, "8/8/8/8/3B4/8/8/8"),
        ("b", "b4", "e1", false, "8/8/8/8/1b6/2N5/8/4K3"),
        // queen moves
        ("Q", "e4", "e8", true, "8/8/8/8/4Q3/8/8/8"),
        ("Q", "e4", "d8", false, "8/8/8/8/4Q3/8/8/8"),
        ("Q", "e4", "h1", true, "8/8/8/8/4Q3/8/8/8"),
        ("Q", "e4", "a1", false, "8/8/8/8/4Q3/8/8/8"),
        // king moves
        ("K", "e1", "f1", true, "8/8/8/8/8/8/8/4K3"),
        ("K", "e1", "f2", true, "8/8/8/8/8/8/8/4K3"),
        ("K", "e1", "f3", false, "8/8/8/8/8/8/8/4K3"),
        ("K", "e1", "g1", false, "8/8/8/8/8/8/8/4K3"),
        ("K", "e4", "d3", true, "8/8/8/8/4R3/8/8/8"),
        // knight moves
        ("N", "g1", "f3", true, "8/8/8/8/8/8/8/6N1"),
        ("N", "g1", "g3", false, "8/8/8/8/8/8/8/6N1"),
        ("n", "e5", "d7", true, "8/8/8/4n3/8/8/8/8"),
    ];

    #[test]
    fn test_reach_squares() {
        for defn in DEFNS {
            let board = Board::from_fen(&defn.4).expect("Internal error in tests");
            let start = Square::from(&defn.1).unwrap();
            let finish = Square::from(&defn.2).unwrap();

            if defn.3 {
                assert!(board.can_reach(&piece_from(defn.0), &start, &finish));
            } else {
                assert!(!board.can_reach(&piece_from(defn.0), &start, &finish));
            }
        }
    }
}