use bytes::BytesMut;
use std::net::SocketAddr;
use tokio::net::UdpSocket;
use niom_turn::constants::*;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    tracing_subscriber::fmt::init();
    let server: SocketAddr = "127.0.0.1:3478".parse()?;
    let local = UdpSocket::bind("0.0.0.0:0").await?;

    // Build a minimal STUN Binding Request with USERNAME and placeholder MESSAGE-INTEGRITY
    let username = "testuser";
    let password = "secretpassword"; // matches server's in-memory creds

    let mut buf = BytesMut::new();
    buf.extend_from_slice(&METHOD_BINDING.to_be_bytes()); // Binding Request
    buf.extend_from_slice(&0u16.to_be_bytes()); // length placeholder
    buf.extend_from_slice(&MAGIC_COOKIE_U32.to_be_bytes());
    let trans = [7u8; 12];
    buf.extend_from_slice(&trans);

    // USERNAME
    let uname = username.as_bytes();
    buf.extend_from_slice(&ATTR_USERNAME.to_be_bytes());
    buf.extend_from_slice(&(uname.len() as u16).to_be_bytes());
    buf.extend_from_slice(uname);
    while (buf.len() % 4) != 0 { buf.extend_from_slice(&[0u8]); }

    // MESSAGE-INTEGRITY placeholder
    let mi_attr_offset = buf.len();
    buf.extend_from_slice(&ATTR_MESSAGE_INTEGRITY.to_be_bytes());
    buf.extend_from_slice(&(20u16).to_be_bytes());
    let mi_val_pos = buf.len();
    buf.extend_from_slice(&[0u8;20]);
    while (buf.len() % 4) != 0 { buf.extend_from_slice(&[0u8]); }

    // fix length
    let total_len = (buf.len() - 20) as u16;
    let len_bytes = total_len.to_be_bytes();
    buf[2] = len_bytes[0];
    buf[3] = len_bytes[1];

    // compute HMAC over bytes up to MI attribute header
    {
        use hmac::{Hmac, Mac};
        use sha1::Sha1;
        type HmacSha1 = Hmac<Sha1>;
        let mut mac = HmacSha1::new_from_slice(password.as_bytes()).expect("HMAC key");
        mac.update(&buf[..mi_attr_offset]);
        let res = mac.finalize().into_bytes();
        for i in 0..20 { buf[mi_val_pos + i] = res[i]; }
    }

    // send
    local.send_to(&buf, server).await?;

    let mut r = vec![0u8; 1500];
    let (len, addr) = local.recv_from(&mut r).await?;
    println!("got {} bytes from {}", len, addr);
    // dump hex
    println!("{:02x?}", &r[..len]);
    Ok(())
}