HTTP Request Parser

use std::collections::BTreeMap;
use std::io::{self, Read};

#[derive(Debug)]
struct Request {
    method: String,
    path: String,
    version: String,
    headers: BTreeMap<String, String>,
}

fn main() -> io::Result<()> {
    let mut input = String::new();
    io::stdin().read_to_string(&mut input)?;

    if input.trim().is_empty() {
        input = "GET /products?city=riyadh HTTP/1.1\r\nHost: example.test\r\nAccept: text/html\r\n\r\n".to_string();
    }

    match parse_request(&input) {
        Some(request) => {
            println!("Method: {}", request.method);
            println!("Path: {}", request.path);
            println!("Version: {}", request.version);
            for (name, value) in request.headers {
                println!("{name}: {value}");
            }
        }
        None => println!("Invalid request"),
    }

    Ok(())
}

fn parse_request(input: &str) -> Option<Request> {
    let mut lines = input.lines();
    let first = lines.next()?;
    let mut parts = first.split_whitespace();
    let method = parts.next()?.to_string();
    let path = parts.next()?.to_string();
    let version = parts.next()?.to_string();
    let mut headers = BTreeMap::new();

    for line in lines {
        if line.trim().is_empty() {
            break;
        }

        let (name, value) = line.split_once(':')?;
        headers.insert(name.trim().to_string(), value.trim().to_string());
    }

    Some(Request {
        method,
        path,
        version,
        headers,
    })
}