src/main.rs

use std::{io::Result, collections::HashMap};
use tokio::{net::{TcpListener, TcpStream}, io::{AsyncReadExt, AsyncWriteExt}};


use itertools::Itertools;
use nom::AsChar;

async fn process_socket(mut stream: TcpStream) {
    println!("accepted new connection");

    let mut request: HashMap<String, String> = HashMap::new();
    let mut line_num: usize = 0;
    loop {
        let mut line = String::default();

        loop {
            let mut buf: [u8; 1] = [0; 1];
            stream.read_exact(&mut buf).await.unwrap();

            let character = buf[0].as_char();
            if character == '\n' {
                break
            } else if character != '\r' {
                line.push(character);
            }
        }

        if line_num == 0 {
            let mut splits = line.split(' ');
            request.insert("method".to_owned(), splits.next().unwrap().to_owned());
            request.insert("path".to_owned(), splits.next().unwrap().to_owned());
        } else {
            let mut splits = line.split(":");
            let key = splits.next().unwrap();
            let value = splits.next().unwrap_or_default().trim();
            request.insert(key.to_owned(), value.to_owned());
        }

        if request.get("path").unwrap() != "/user-agent" || request.contains_key("User-Agent") { break };
        line_num += 1;
    }

    // println!("{:?}", request);

    let mut path = request.get("path").unwrap().split("/");

    let response_status: String;
    let mut response_headers: Vec<String> = vec![];
    let response_body: String;

    // println!("{:?}", path);

    path.next().unwrap();

    match path.next().unwrap() {
        "" => {
            response_status = "200 OK".into();
            response_body = "".into();
        },
        "echo" => {
            response_status = "200 OK".into();
            response_body = path.join("/");
            response_headers.push("Content-Type: text/plain".into());
        },
        "user-agent" => {
            response_status = "200 OK".into();
            response_body = request.get("User-Agent").unwrap().into();
            response_headers.push("Content-Type: text/plain".into());
        },
        _ => {
            response_status = "404 Not Found".into();
            response_body = "".into();
        }
    }

    if response_body.len() > 0 {
        response_headers.push(format!("Content-Length: {}", response_body.len()));
    }

    stream.write(format!("HTTP/1.1 {response_status}\r\n{}\r\n\r\n{response_body}", response_headers.join("\r\n")).as_bytes()).await.unwrap();

}

#[tokio::main]
async fn main() -> Result<()> {
    let listener = TcpListener::bind("127.0.0.1:4221").await?;
    let mut futures = vec![];

    loop {
        let (socket, _) = listener.accept().await?;
        futures.push(tokio::spawn(process_socket(socket)));
    }
}