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: forest.rs
    path of file: ./repos/rustrogueliketutorial/chapter-75-darkplaza/src/map_builders
    
    the code of the file until where you have to start completion: use super::{BuilderChain, CellularAutomataBuilder, XStart, YStart, AreaStartingPosition,
    CullUnreachable, VoronoiSpawning, MetaMapBuilder, BuilderMap, TileType};
use crate::map;

pub fn forest_builder(new_depth: i32, width: i32, height: i32) -> BuilderChain {
    let mut chain = BuilderChain::new(new_depth, width, height, "Into the Woods");
    chain.start_with(CellularAutomataBuilder::new());
    chain.with(AreaStartingPosition::new(XStart::CENTER, YStart::CENTER));
    chain.with(CullUnreachable::new());
    chain.with(AreaStartingPosition::new(XStart::LEFT, YStart::CENTER));
    chain.with(VoronoiSpawning::new());
    chain.with(YellowBrickRoad::new());
    chain
}

pub struc
    
    fn find_exit(&self, build_data : &mut BuilderMap, seed_x : i32, seed_y: i32) -> (i32, i32) {
        let mut available_floors : Vec<(usize, f32)> = Vec::new();
        for (idx, tiletype) in build_data.map.tiles.iter().enumerate() {
            if map::tile_walkable(*tiletype) {
                available_floors.push(
                    (
                        idx,
                        rltk::DistanceAlg::PythagorasSquared.distance2d(
                            rltk::Point::new(idx as i32 % build_data.map.width, idx as i32 / build_data.map.width),
                            rltk::Point::new(seed_x, seed_y)
                        )
                    )
                );
            }
        }
        if available_floors.is_empty() {
            panic!("No valid floors to start on");
        }

        available_floors.sort_by(|a,b| a.1.partial_cmp(&b.1).unwrap());

        let end_x = available_floors[0].0 as i32 % build_data.map.width;
        let end_y = available_floors[0].0 as i32 / build_data.map.width;
        (end_x, end_y)
    }