use crate::repr::{Board, Piece, PosMap};

pub struct BoardValueMap(PosMap<i64>);

impl BoardValueMap {
    pub fn board_value(&self, board: &Board, color: Piece) -> i64 {
        Board::all_positions()
            .filter_map(|(i, j)| board.get(i, j).map(|p| (i, j, p)))
            .map(|(i, j, pos_p)| (*self.0.get(i, j), pos_p))
            .map(|(value, pos_p)| {
                if pos_p != color {
                    // enemy has position
                    return -value;
                }
                // target has position
                value
            })
            .sum()
    }

    /// Weights from: https://repub.eur.nl/pub/7142/ei2005-47.pdf
    pub fn new() -> Self {
        let mut map = PosMap::new();
        assert_eq!(
            Board::BOARD_SIZE,
            8,
            "BVM only supports Board::BOARD_SIZE of 8"
        );

        const POSITION_VALUES: [[i64; 8]; 8] = [
            [100, -20, 10, 5, 5, 10, -20, 100],
            [-20, -50, -2, -2, -2, -2, -50, -20],
            [10, -2, -1, -1, -1, -1, -2, 10],
            [5, -2, -1, -1, -1, -1, -2, 5],
            [5, -2, -1, -1, -1, -1, -2, 5],
            [10, -2, -1, -1, -1, -1, -2, 10],
            [-20, -50, -2, -2, -2, -2, -50, -20],
            [100, -20, 10, 5, 5, 10, -20, 100],
        ];

        for (i, j) in Board::all_positions() {
            map.set(i, j, POSITION_VALUES[i][j])
        }

        Self(map)
    }
}