// Eryn Wells <eryn@erynwells.me>

mod pieces;

use self::pieces::Pieces;
use crate::bitboard::BitBoard;
use crate::piece::{Piece, PiecePlacementError};
use crate::square::Square;
use std::fmt;
use std::fmt::Write;

#[derive(Clone, Eq, Hash, PartialEq)]
pub struct Position {
    /// Composite bitboards for all the pieces of a particular color.
    pieces_per_color: [BitBoard; 2],

    /// Bitboards representing positions of particular piece types per color.
    pieces_per_type: [[BitBoard; 6]; 2],
}

impl Position {
    fn empty() -> Position {
        Position {
            pieces_per_color: [BitBoard::empty(), BitBoard::empty()],
            pieces_per_type: [
                [
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                ],
                [
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                    BitBoard::empty(),
                ],
            ],
        }
    }

    /// Return a starting position.
    fn starting() -> Position {
        let white_pieces = [
            BitBoard::from_bit_field(0x00FF000000000000),
            BitBoard::from_bit_field(0x4200000000000000),
            BitBoard::from_bit_field(0x2400000000000000),
            BitBoard::from_bit_field(0x8100000000000000),
            BitBoard::from_bit_field(0x1000000000000000),
            BitBoard::from_bit_field(0x8000000000000000),
        ];

        let black_pieces = [
            BitBoard::from_bit_field(0xFF00),
            BitBoard::from_bit_field(0x0042),
            BitBoard::from_bit_field(0x0024),
            BitBoard::from_bit_field(0x0081),
            BitBoard::from_bit_field(0x0010),
            BitBoard::from_bit_field(0x0080),
        ];

        Position {
            pieces_per_color: [
                white_pieces.iter().fold(BitBoard::empty(), |a, b| a | b),
                black_pieces.iter().fold(BitBoard::empty(), |a, b| a | b),
            ],
            pieces_per_type: [white_pieces, black_pieces],
        }
    }

    fn place_piece(&mut self, piece: &Piece, square: &Square) -> Result<(), PiecePlacementError> {
        let bitboard = self.bitboard_for_piece_mut(piece);

        if bitboard.has_piece_at(&square) {
            return Err(PiecePlacementError::PieceExistsOnSquare);
        }

        bitboard.place_piece_at(&square);

        Ok(())
    }

    pub(super) fn bitboard_for_piece(&self, piece: &Piece) -> &BitBoard {
        &self.pieces_per_type[piece.color as usize][piece.shape as usize]
    }

    fn bitboard_for_piece_mut(&mut self, piece: &Piece) -> &mut BitBoard {
        &mut self.pieces_per_type[piece.color as usize][piece.shape as usize]
    }

    fn pieces(&self, color: Color) -> Pieces {
        Pieces::new(&self, color)
    }
}

impl fmt::Debug for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut output = String::new();

        output.push_str("Position {\n");
        write!(output, "    color_to_move: {:?},\n", self.color_to_move)?;

        output.push_str("    pieces_per_color: [\n");
        for bb in self.pieces_per_color {
            write!(output, "        {bb:?},\n")?;
        }
        output.push_str("    ],\n");

        output.push_str("    pieces_per_type: [\n");
        for color_bbs in self.pieces_per_type {
            output.push_str("        [\n");
            for bb in color_bbs {
                write!(output, "            {bb:?},\n")?;
            }
            output.push_str("        ],\n");
        }
        output.push_str("    ],\n");

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

impl fmt::Display for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "abcdefg")

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

    #[test]
    fn place_piece_at() {
        let mut position = Position::empty();

        let piece = Piece::new(Color::White, Shape::Queen);
        let square = Square::from_algebraic_string("e4").expect("Unable to get e4 square");

        position
            .place_piece(&piece, &square)
            .expect("Unable to place white queen on e4");

        position
            .place_piece(&piece, &square)
            .expect_err("Placed white queen on e4 a second time?!");

        println!("{:?}", position);
    }
}