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: http_logger.rs
    path of file: ./repos/dufs/src
    
    the code of the file until where you have to start completion: use std::{collections::HashMap, str::FromStr};

use crate::{auth::get_auth_user, server::Request};

pub const DEFAULT_LOG_FORMAT: &str = r#"$remote_addr "$request" $status"#;

#[derive(Debug, Clone, PartialEq)]
pub struct HttpLogger {
    elements: Vec<LogElement>,
}

impl Default for HttpLogger {
    fn default() -> Self {
        DEFAULT_LOG_FORMAT.parse().unwrap()
    }
}

#[derive(Debug, Clone, PartialEq)]
enum LogElement {
    Variable(String),
    Header(String),
    Literal(String),
}

impl HttpLogger {
    pub fn data(&self, req: &Request) -> Has
    
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let mut elements = vec![];
        let mut is_var = false;
        let mut cache = String::new();
        for c in format!("{s} ").chars() {
            if c == '$' {
                if !cache.is_empty() {
                    elements.push(LogElement::Literal(cache.to_string()));
                }
                cache.clear();
                is_var = true;
            } else if is_var && !(c.is_alphanumeric() || c == '_') {
                if let Some(value) = cache.strip_prefix("$http_") {
                    elements.push(LogElement::Header(value.replace('_', "-").to_string()));
                } else if let Some(value) = cache.strip_prefix('$') {
                    elements.push(LogElement::Variable(value.to_string()));
                }
                cache.clear();
                is_var = false;
            }
            cache.push(c);
        }
        let cache = cache.trim();
        if !cache.is_empty() {
            elements.push(LogElement::Literal(cache.to_string()));
        }
        Ok(Self { elements })
    }