advent-of-code-2024/day21/src/button.rs

pub trait Button: std::fmt::Debug + Eq {
    fn forbidden_position(&self) -> (i32, i32);
    fn to_position(&self) -> (i32, i32);

    fn distance_with(&self, other: &impl Button) -> Vec<(DirectionalButton, usize)> {
        let source = self.to_position();
        let dest = other.to_position();
        let (dist_v, dist_h) = (dest.0 - source.0, dest.1 - source.1);
        let (mul_v, mul_h) = (dist_v.abs(), dist_h.abs());

        let mut movements = Vec::new();
        if mul_v > 0 {
            movements.push((
                DirectionalButton::from_direction(&(dist_v / mul_v, 0)),
                mul_v as usize,
            ));
        }

        if mul_h > 0 {
            movements.push((
                DirectionalButton::from_direction(&(0, dist_h / mul_h)),
                mul_h as usize,
            ));
        }

        movements
    }

    fn possible_movements(&self, other: &impl Button) -> Vec<Vec<DirectionalButton>> {
        let movements = self.distance_with(other);
        if movements.is_empty() {
            return vec![vec![DirectionalButton::A, DirectionalButton::A]];
        }

        let source = self.to_position();
        let &first_move = movements.first().unwrap();
        let first_move_applied = first_move.0.apply_movement(&source, first_move.1 as i32);
        let &last_move = movements.last().unwrap();
        let last_move_applied = last_move.0.apply_movement(&source, last_move.1 as i32);
        let mut possible_movements = Vec::new();
        if first_move == last_move && first_move_applied != self.forbidden_position() {
            let mut possibility = vec![DirectionalButton::A];
            possibility.extend(vec![first_move.0; first_move.1]);
            possible_movements.push(possibility);
        } else {
            let mut first_possibility = vec![DirectionalButton::A];
            first_possibility.extend(vec![first_move.0; first_move.1]);
            first_possibility.extend(vec![last_move.0; last_move.1]);

            let mut last_possibility = vec![DirectionalButton::A];
            last_possibility.extend(vec![last_move.0; last_move.1]);
            last_possibility.extend(vec![first_move.0; first_move.1]);

            if first_move_applied != self.forbidden_position()
                && last_move_applied != self.forbidden_position()
            {
                possible_movements.push(first_possibility);
                possible_movements.push(last_possibility);
            } else if first_move_applied != self.forbidden_position()
                && last_move_applied == self.forbidden_position()
            {
                possible_movements.push(first_possibility);
            } else if first_move_applied == self.forbidden_position()
                && last_move_applied != self.forbidden_position()
            {
                possible_movements.push(last_possibility);
            } else {
                unreachable!()
            }
        }

        for possible_movement in possible_movements.iter_mut() {
            possible_movement.push(DirectionalButton::A);
        }
        possible_movements
    }
}

#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)]
pub enum NumericButton {
    Zero,
    One,
    Two,
    Three,
    Four,
    Five,
    Six,
    Seven,
    Eight,
    Nine,
    A,
}

impl From<char> for NumericButton {
    fn from(c: char) -> Self {
        match c {
            '0' => Self::Zero,
            '1' => Self::One,
            '2' => Self::Two,
            '3' => Self::Three,
            '4' => Self::Four,
            '5' => Self::Five,
            '6' => Self::Six,
            '7' => Self::Seven,
            '8' => Self::Eight,
            '9' => Self::Nine,
            'A' => Self::A,
            _ => unreachable!(),
        }
    }
}

impl Button for NumericButton {
    fn forbidden_position(&self) -> (i32, i32) {
        (3, 0)
    }

    fn to_position(&self) -> (i32, i32) {
        match self {
            Self::Seven => (0, 0),
            Self::Eight => (0, 1),
            Self::Nine => (0, 2),
            Self::Four => (1, 0),
            Self::Five => (1, 1),
            Self::Six => (1, 2),
            Self::One => (2, 0),
            Self::Two => (2, 1),
            Self::Three => (2, 2),
            Self::Zero => (3, 1),
            Self::A => (3, 2),
        }
    }
}

#[derive(Debug, Clone, Copy, Hash, Eq, PartialEq)]
pub enum DirectionalButton {
    Up,
    Down,
    Left,
    Right,
    A,
}

impl Button for DirectionalButton {
    fn forbidden_position(&self) -> (i32, i32) {
        (0, 0)
    }

    fn to_position(&self) -> (i32, i32) {
        match self {
            Self::Up => (0, 1),
            Self::A => (0, 2),
            Self::Left => (1, 0),
            Self::Down => (1, 1),
            Self::Right => (1, 2),
        }
    }
}

impl DirectionalButton {
    fn from_direction(direction: &(i32, i32)) -> Self {
        match direction {
            (-1, 0) => Self::Up,
            (1, 0) => Self::Down,
            (0, 1) => Self::Right,
            (0, -1) => Self::Left,
            _ => unreachable!(),
        }
    }

    fn to_direction(&self) -> (i32, i32) {
        match self {
            Self::Up => (-1, 0),
            Self::Down => (1, 0),
            Self::Left => (0, -1),
            Self::Right => (0, 1),
            _ => unreachable!(),
        }
    }

    fn apply_movement(&self, position: &(i32, i32), times: i32) -> (i32, i32) {
        let direction = self.to_direction();
        (
            position.0 + direction.0 * times,
            position.1 + direction.1 * times,
        )
    }
}