// #![feature(if_let_guard)]

use std::{ io::{ BufRead, BufReader, Write }, net::TcpListener };
use anyhow::Result;
use thiserror::Error;

macro_rules! d { () => { Default::default() }; }
macro_rules! f { ($s: expr) => { format!($s) }; }

#[derive(Clone, Debug, Error)]
enum E {
    #[error("Invalid request data found during parsing")]
    InvalidRequest,
}

fn main() -> Result<()> {
    let listener = TcpListener::bind("127.0.0.1:4221").unwrap();

    for stream in listener.incoming() {
        match stream {
            Ok(mut stream) => {
                let buf_reader = BufReader::new(&mut stream);

                let mut data = buf_reader
                    .lines()
                    .map(|result| result.unwrap())
                    .take_while(|line| !line.is_empty());

                let (_method, path, _ver) = {
                    let start_line = data.next().ok_or(E::InvalidRequest)?; // should be 500;
                    let mut parts = start_line.split_whitespace().map(ToOwned::to_owned);
                    let method = parts.next().ok_or(E::InvalidRequest)?;
                    let path   = parts.next().ok_or(E::InvalidRequest)?;
                    let ver    = parts.next().ok_or(E::InvalidRequest)?;

                    (method, path, ver)
                };

                let response = match path.as_str() {
                    "/" => Response::Empty,
                    // p if let Some(echo) = p.strip_prefix("/echo/") => Response::TextPlain(echo), // a nicer way to do that, not available in stable yet
                    p if p.starts_with("/echo/") => Response::TextPlain(p.trim_start_matches("/echo/")),
                    _ => Response::_404,
                };

                println!("accepted new connection");

                let _ = stream.write(response.build().as_bytes());
                let _ = stream.flush();

            }
            Err(e) => {
                println!("error: {}", e);
            }
        }
    }

    Ok(())
}

#[derive(Debug, Clone)]
enum Response <'a> {
    _404,
    Empty,
    TextPlain (&'a str),
}


#[allow(non_upper_case_globals)]
impl Response <'_> {
    fn build (self) -> String {

        let (code, body) = match self {
            Self::_404 => ("404 Not Found", d!()),
            Self::Empty => ("200 OK", d!()),
            Self::TextPlain(text) => ("200 OK", text)
        };

        let headers = self.headers().join("\r\n");

        f!("HTTP/1.1 {code}\r\n{headers}\r\n\r\n{body}").into()
    }

    fn headers (&self) -> Vec<String> {
        match self {
            Self::TextPlain(text) => vec![f!("Content-Type: text/plain"), format!("Content-Length: {}", text.len())],
            _ => d!()
        }
    }
}