You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: prefab.rs
    path of file: ./repos/HandsOnRust/InventoryAndPowerUps/carrying_items/src/map_builder
    
    the code of the file until where you have to start completion: use crate::prelude::*;

const FORTRESS : (&str, i32, i32) = ("
------------
---######---
---#----#---
---#-M--#---
-###----###-
--M------M--
-###----###-
---#----#---
---#----#---
---######---
------------
", 12, 11);

pub fn apply_prefab(mb: &mut MapBuilder, rng: &mut RandomNumberGenerator) {
    let mut placement = None;

    let dijkstra_map = DijkstraMap::new(
        SCREEN_WIDTH,
        SCREEN_HEIGHT,
        &vec![mb.map.point2d_to_index(mb.player_start)],
        &mb.map,
        1024.0
    );

    let mut attempts = 0;// (1)
    while placement.is_none() && attempts < 10 {// (2)
        let dimensions = Rect::with_size(// (3)
            rng.range(0, SCREEN_WIDTH - FORTRESS.1),
            rng.range(0, SCREEN_HEIGHT - FORTRESS.2),
            FORTRESS.1,
            FORTRESS.2
        );

        let mut can_place = false;// (4)
        dimensions.for_each(|pt| {// (5)
            let idx = mb.ma
    
pub fn apply_prefab(mb: &mut MapBuilder, rng: &mut RandomNumberGenerator) {
    let mut placement = None;

    let dijkstra_map = DijkstraMap::new(
        SCREEN_WIDTH,
        SCREEN_HEIGHT,
        &vec![mb.map.point2d_to_index(mb.player_start)],
        &mb.map,
        1024.0
    );

    let mut attempts = 0;// (1)
    while placement.is_none() && attempts < 10 {// (2)
        let dimensions = Rect::with_size(// (3)
            rng.range(0, SCREEN_WIDTH - FORTRESS.1),
            rng.range(0, SCREEN_HEIGHT - FORTRESS.2),
            FORTRESS.1,
            FORTRESS.2
        );

        let mut can_place = false;// (4)
        dimensions.for_each(|pt| {// (5)
            let idx = mb.map.point2d_to_index(pt);
            let distance = dijkstra_map.map[idx];
            if distance < 2000.0 && distance > 20.0 && mb.amulet_start != pt {// (6)
                can_place = true;
            }
        });

        if can_place {// (7)
            placement = Some(Point::new(dimensions.x1, dimensions.y1));
            let points = dimensions.point_set();
            mb.monster_spawns.retain(|pt| !points.contains(pt) );// (8)
        }
        attempts += 1;
    }

    if let Some(placement) = placement {// (9)
        let string_vec : Vec<char> = FORTRESS.0
            .chars().filter(|a| *a != '\r' && *a !='\n')
            .collect();// (10)
        let mut i = 0;// (11)
        for ty in placement.y .. placement.y + FORTRESS.2 {// (12)
            for tx in placement.x .. placement.x + FORTRESS.1 {
                let idx = map_idx(tx, ty);
                let c = string_vec[i];// (13)
                match c {// (14)
                    'M' => {// (15)
                        mb.map.tiles[idx] = TileType::Floor;
                        mb.monster_spawns.push(Point::new(tx, ty));
                    }
                    '-' => mb.map.tiles[idx] = TileType::Floor,// (16)
                    '#' => mb.map.tiles[idx] = TileType::Wall,
                    _ => println!("No idea what to do with [{}]", c)// (17)
                }
                i += 1;
            }
        }
    }
}