use crate::{board::Board, square::Square, strategy::Strategy};

pub struct NakedSingle {
    index: usize,
    value: u8,
}

impl Strategy for NakedSingle {
    fn find_instance(board: &crate::board::Board) -> Option<Self>
    where
        Self: Sized,
    {
        board
            .squares
            .iter()
            .enumerate()
            .filter_map(|(index, square)| match square {
                Square::Options(marks) => Some((index, marks)),
                _ => None,
            })
            .find(|(_index, marks)| marks.len() == 1)
            .map(|(index, marks)| NakedSingle {
                index,
                value: marks.first_index().unwrap() as u8 + 1,
            })
    }

    fn apply(&self, mut board: Board) -> Board {
        board.squares[self.index] = Square::Value(self.value);
        board.restrict_marks();
        board
    }
}