use std::env;
use std::io::{self, BufRead, BufReader, Write};
use std::net::TcpStream;

fn read_messages(mut reader: impl BufRead) -> u64 {
    // Read the message count
    let mut buf = String::new();
    reader.read_line(&mut buf).unwrap();
    let count = buf.trim().parse::<u64>().unwrap();

    // Read and print each message
    for _ in 0..count {
        buf.clear();
        reader.read_line(&mut buf).unwrap();
        print!("{buf}");
    }

    // Read and return the message index
    buf.clear();
    reader.read_line(&mut buf).unwrap();
    buf.trim().parse::<u64>().unwrap()
}

fn main() {
    // Read the configuration
    let mut args = env::args().skip(1);
    let username = args.next().expect("need username");
    let host = args.next().expect("need hostname");
    let port = args.next().unwrap_or("44322".into());
    let port = port.parse::<u16>().expect("port should be an integer");

    // Connect to the server
    let mut writer = TcpStream::connect((host, port)).unwrap();
    let mut reader = BufReader::new(writer.try_clone().unwrap());

    // Get message history
    writer.write_all(b"LAST 20\n").unwrap();
    let mut last_index = read_messages(&mut reader);

    // Process user input
    print!("> ");
    io::stdout().flush().unwrap();
    let lines = io::stdin().lines();
    for line in lines.map(Result::unwrap) {
        // Send non-empty lines
        if !line.is_empty() {
            writer
                .write_all(format!("SEND {username}: {line}\n").as_bytes())
                .unwrap();
            let mut discard = String::new();
            reader.read_line(&mut discard).unwrap();
        }

        // Get new messages
        writer
            .write_all(format!("SKIP {last_index}\n").as_bytes())
            .unwrap();
        last_index = read_messages(&mut reader);

        print!("> ");
        io::stdout().flush().unwrap();
    }
}