justcheckers/engine/src/lib.rs

use std::fmt;

pub enum Piece {
    LightPawn,
    LightKing,
    DarkPawn,
    DarkKing,
}

pub enum BoardTile {
    Empty,
    Piece(Piece),
}

pub enum BoardSize {
    American,
    International,
    Canadian,
}

impl BoardSize {
    fn get_size(&self) -> u32 {
        match &self {
            BoardSize::American => 8,
            BoardSize::International => 10,
            BoardSize::Canadian => 12,
        }
    }
}

pub struct Board {
    dimensions: BoardSize,
    tiles: Vec<BoardTile>,
}

impl Board {
    pub fn new(size: BoardSize) -> Board {

        let board_size = size.get_size();
        let width = board_size / 2;
        let height = board_size;
        let starting_rows = board_size / 2 - 1;

        let playing_tiles = (0..width * height)
            .map(|tile|{
                let row = tile / width;
                match row {
                    r if r < starting_rows => BoardTile::Piece(
                        Piece::LightPawn),
                    r if r > height - starting_rows - 1 => BoardTile::Piece(
                        Piece::DarkPawn),
                    _ => BoardTile::Empty,
                }
            })
            .collect();

        Board {
            dimensions: size,
            tiles: playing_tiles,
        }
    }

    fn get_index(&self, row: u32, column: u32) -> usize {
        let width = self.dimensions.get_size() / 2;
        (row * width + (column / 2)) as usize
    }
}

static COLUMN_COORDINATE_BORDER: &str = " ABCDEFGHIJKL";

impl fmt::Display for Board {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {

        let width = self.dimensions.get_size();

        // Create the top level border.
        let mut column_border_chars = COLUMN_COORDINATE_BORDER.chars();
        for _ in 0..width + 1 {
            write!(formatter, "{}", column_border_chars.next().unwrap())?;
        }
        write!(formatter, "\n")?;

        for row in 0..width {

            write!(formatter, "{ }", (row + 1).to_string())?;
            if row % 2 == 0 {
                write!(formatter, " ")?;
            }

            for col in 0..(width / 2) {

                let idx = (row * (width / 2) + col) as usize;

                let token = match self.tiles[idx] {
                    BoardTile::Piece(Piece::LightPawn) => "○",
                    BoardTile::Piece(Piece::LightKing) => "⍟",
                    BoardTile::Piece(Piece::DarkPawn) => "●",
                    BoardTile::Piece(Piece::DarkKing) => "✪",
                    BoardTile::Empty => "◰",
                };

                let adjacent = if row % 2 == 0 && col == (width / 2) - 1 {
                    ""
                } else {
                    " "
                };

                write!(formatter, "{}{}", token, adjacent)?;
            }

            write!(formatter, "\n")?;
        }

        Ok(())
    }
}


#[cfg(test)]
mod tests {
    use crate::Board;
    use crate::BoardSize;

    #[test]
    fn setup_international_board() {

        let expected =
            " \
             ABCDEFGHIJ\n\
            1 ○ ○ ○ ○ ○\n\
            2○ ○ ○ ○ ○ \n\
            3 ○ ○ ○ ○ ○\n\
            4○ ○ ○ ○ ○ \n\
            5 ◰ ◰ ◰ ◰ ◰\n\
            6◰ ◰ ◰ ◰ ◰ \n\
            7 ● ● ● ● ●\n\
            8● ● ● ● ● \n\
            9 ● ● ● ● ●\n\
            10● ● ● ● ● \n\
            ";
        assert_eq!(Board::new(BoardSize::International).to_string(), expected);
    }
}