martian-chess/src/game.rs

use crate::prelude::*;

pub(crate) struct GamePlugin;

impl Plugin for GamePlugin {
    fn build(&self, app: &mut App) {
        app.add_event::<GameEvent>()
            .init_resource::<ActiveTile>()
            .add_systems(Startup, setup_board)
            .add_systems(
                PostUpdate,
                (
                    debug_hovering
                        .run_if(resource_exists::<debug::DebugEnabled>())
                        .run_if(resource_changed::<ActiveTile>()),
                    debug_board.run_if(resource_exists::<debug::DebugEnabled>()),
                ),
            );
    }
}

#[derive(Debug, Component, Clone)]
pub(crate) enum Piece {
    Pawn,
    Drone,
    Queen,
}

// manually for the type.
impl std::fmt::Display for Piece {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            Piece::Queen => write!(f, "@"),
            Piece::Drone => write!(f, "^"),
            Piece::Pawn => write!(f, "*"),
        }
    }
}

#[derive(Debug)]
pub(crate) enum GameError {
    NullMove,
    InvalidMove,
}

#[derive(Debug, Event)]
pub(crate) enum GameEvent {
    SelectPiece,
    PlacePiece,
}

/// The board is setup like this:
/// ```text
///       0  1  2  3  4  5  6  7
///     +--+--+--+--+--+--+--+--+
/// a   |  |  |  |  I  | d| Q| Q|
///     +--+--+--+--+--+--+--+--+
/// b   |d |p |p |  I  | p| d| Q|
///     +--+--+--+--+--+--+--+--+
/// c   |Q |d |p |  I  | p| p| d|
///     +--+--+--+--+--+--+--+--+
/// d   |Q |Q |d |  I  |  |  |  |
///     +--+--+--+--+--+--+--+--+
/// ````
#[derive(Debug, Resource)]
pub(crate) struct Board {
    inner: Vec<Vec<Option<Piece>>>,
}

#[derive(Debug, Component, PartialEq, Clone)]
pub(crate) struct BoardIndex {
    pub x: usize,
    pub y: usize,
}

impl Board {
    /// Returns the piece at the given location
    pub(crate) fn at(&self, BoardIndex { x, y }: &BoardIndex) -> Option<Piece> {
        self.inner[*y][*x].clone()
    }

    /// Returns a list of all pieces on the board with their location
    pub(crate) fn pieces(&self) -> Vec<(BoardIndex, Piece)> {
        self.inner
            .iter()
            .enumerate()
            .flat_map(|(y, nested)| {
                nested.iter().enumerate().filter_map(move |(x, p)| {
                    p.as_ref().map(|val| (BoardIndex { x, y }, val.clone()))
                })
            })
            .collect()
    }

    pub(crate) fn move_piece(
        &mut self,
        from: &BoardIndex,
        to: &BoardIndex,
    ) -> Result<(), GameError> {
        if from == to {
            Err(GameError::NullMove)
        } else if self.at(to).is_none() {
            self.at(from).map_or(Err(GameError::NullMove), |from_val| {
                // TODO: We can self.inner.swap(to, from) if board is single vec
                self.inner[to.y][to.x] = Some(from_val);
                self.inner[from.y][from.x] = None;
                Ok(())
            })
        } else {
            Err(GameError::InvalidMove)
        }
    }
}

impl std::fmt::Display for Board {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        self.inner.iter().rev().for_each(|row| {
            let _ = write!(f, "+--+--+--+--+--+--+--+--+\n");
            let _ = write!(f, "|");
            row.iter().for_each(|piece| {
                let _ = match piece {
                    Some(p) => write!(f, "{} |", p),
                    None => write!(f, "  |"),
                };
            });
            let _ = write!(f, "\n");
        });
        let _ = write!(f, "+--+--+--+--+--+--+--+--+");
        Ok(())
    }
}

#[derive(Debug, Default, Resource)]
pub(crate) struct ActiveTile {
    pub idx: Option<BoardIndex>,
}

#[derive(Debug, Default, Component)]
pub(crate) struct Selected;

fn setup_board(mut commands: Commands) {
    use Piece::*;
    commands.insert_resource(Board {
        inner: vec![
            vec![
                Some(Queen),
                Some(Queen),
                Some(Drone),
                None,
                None,
                None,
                None,
                None,
            ],
            vec![
                Some(Queen),
                Some(Drone),
                Some(Pawn),
                None,
                None,
                Some(Pawn),
                Some(Pawn),
                Some(Drone),
            ],
            vec![
                Some(Drone),
                Some(Pawn),
                Some(Pawn),
                None,
                None,
                Some(Pawn),
                Some(Drone),
                Some(Queen),
            ],
            vec![
                None,
                None,
                None,
                None,
                None,
                Some(Drone),
                Some(Queen),
                Some(Queen),
            ],
        ],
    });
}

/// TODO: only run_if debug enabled
fn debug_hovering(
    selected: Res<ActiveTile>,
    board: Res<Board>,
    mut debug_info: ResMut<debug::DebugInfo>,
) {
    match &selected.idx {
        Some(idx) => debug_info.set(
            "hovering".into(),
            format!("{:?}@({},{})", board.at(&idx), idx.x, idx.y,),
        ),
        None => debug_info.set("selected".into(), format!("N/A")),
    };
}

fn debug_board(board: Res<Board>, mut debug_info: ResMut<debug::DebugInfo>) {
    debug_info.set("board".into(), format!("\n{}", *board));
}