100-days-of-rust/Week-03/Day-21_Random-Maze-Generator/day21/src/lib.rs

use std::time::{SystemTime, UNIX_EPOCH};

pub fn draw_maze(height: usize, width: usize) -> String {
    let mut maze = vec![vec![(false, false, false); width]; height];
    let mut rng = Rng::new();

    bfs_make_maze(
        (
            rng.random_number(0, height as u128) as usize,
            rng.random_number(0, width as u128) as usize,
        ),
        &mut maze,
        &mut rng,
    );

    let mut res = "+---".repeat(width) + "+";
    for c in 0..height {
        res = format!("{}\n|", res);
        for r in maze.get(c).unwrap() {
            res = format!("{}   ", res);
            if r.1 {
                res = format!("{} ", res);
            } else {
                res = format!("{}|", res);
            }
        }
        res = format!("{}\n+", res);
        for r in maze.get(c).unwrap() {
            if r.0 {
                res = format!("{}   +", res);
            } else {
                res = format!("{}---+", res);
            }
        }
    }

    res
}

fn bfs_make_maze(position: (usize, usize), maze: &mut Vec<Vec<(bool, bool, bool)>>, rng: &mut Rng) {
    maze[position.0][position.1].2 = true;
    let mut nums = [0, 1, 2, 3];
    for i in (0..4).rev() {
        let rand_index = rng.random_number(0, i + 1);
        nums.swap(rand_index as usize, i as usize);
    }
    for num in nums {
        if num == 0 && position.1 + 1 < maze[0].len() && !maze[position.0][position.1 + 1].2 {
            let mut new_position = position;
            new_position.1 += 1;
            maze[position.0][position.1].1 = true;
            bfs_make_maze(new_position, maze, rng);
        }
        if num == 1 && position.1 > 0 && !maze[position.0][position.1 - 1].2 {
            let mut new_position = position;
            new_position.1 -= 1;
            maze[new_position.0][new_position.1].1 = true;
            bfs_make_maze(new_position, maze, rng);
        }
        if num == 2 && position.0 + 1 < maze.len() && !maze[position.0 + 1][position.1].2 {
            let mut new_position = position;
            new_position.0 += 1;
            maze[position.0][position.1].0 = true;
            bfs_make_maze(new_position, maze, rng);
        }
        if num == 3 && position.0 > 0 && !maze[position.0 - 1][position.1].2 {
            let mut new_position = position;
            new_position.0 -= 1;
            maze[new_position.0][new_position.1].0 = true;
            bfs_make_maze(new_position, maze, rng);
        }
    }
}

pub struct Rng {
    seed: u128,
}

impl Rng {
    pub fn new() -> Rng {
        let time_since_epoch = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .expect("Error in getting time")
            .as_millis();
        Rng {
            seed: time_since_epoch,
        }
    }

    fn linear_congruent_generator(&mut self, a: u128, c: u128, m: u128) -> u128 {
        let result = (a * self.seed + c) % m;
        self.seed = result;
        result
    }

    pub fn random_number(&mut self, from: u128, to: u128) -> u128 {
        let random_number = self.linear_congruent_generator(1103515245, 12345, 2u128.pow(31));
        (random_number % (to - from)) + from
    }
}

impl Default for Rng {
    fn default() -> Self {
        Self::new()
    }
}