use std::{
    io::{BufRead, BufReader},
    net::{IpAddr, SocketAddr, TcpListener, TcpStream},
};

use anyhow::Result;
use tokio::spawn;

pub struct SmtpServer {
    listener: TcpListener,
    running: bool,
}

impl SmtpServer {
    pub fn new(ip: [u8; 4], port: u16) -> Result<Self> {
        Ok(Self {
            listener: TcpListener::bind((IpAddr::from(ip), port))?,
            running: false,
        })
    }

    // TODO: trap SIGINT to stop server?
    pub async fn run(&mut self) -> Result<()> {
        self.running = true;
        while self.running {
            let (stream, addr) = self.listener.accept()?;
            let session = SessionHandler {
                stream,
                addr,
                state: SessionState::default(),
            };
            spawn(session.run());
        }
        Ok(())
    }
}

struct SessionHandler {
    stream: TcpStream,
    addr: SocketAddr,
    state: SessionState,
}

impl SessionHandler {
    async fn run(mut self) -> Result<()> {
        let mut r = BufReader::new(&self.stream);
        let mut buffer = String::new();

        loop {
            if r.read_line(&mut buffer)? == 0 {
                break;
            }

            log::debug!("Received '{}' from '{}'", buffer.trim(), self.addr);
            self.state.apply().await;
            buffer.clear();
        }

        log::info!("Connection closed by {}", self.addr);
        Ok(())
    }
}

#[derive(Default)]
struct SessionState {}

impl SessionState {
    async fn apply(&mut self) {
        todo!()
    }
}