use std::{
	sync::Arc,
};

use tokio::{
	io::{
		AsyncReadExt,
		AsyncWriteExt,
	},
	net::{
		UdpSocket,
		tcp,
	}
};

pub async fn rx (
	udp_sock: Arc <UdpSocket>,
	mut tcp_read: tcp::OwnedReadHalf,
) -> anyhow::Result <()> {
	loop {
		let mut tag = [0u8, 0, 0, 0];
		let bytes_read = tcp_read.read (&mut tag).await?;
		if bytes_read != 4 {
			anyhow::anyhow! ("loops::rx: Couldn't read 4 bytes for tag");
		}
		if tag != [1, 0, 0, 0] {
			anyhow::anyhow! ("loops::rx: unexpected tag in framing");
		}
		
		let mut length = [0u8, 0, 0, 0];
		let bytes_read = tcp_read.read (&mut length).await?;
		if bytes_read != 4 {
			anyhow::anyhow! ("loops::rx: Couldn't read 4 bytes for tag");
		}
		
		let length = usize::try_from (u32::from_le_bytes (length))?;
		if length >= 8_192 {
			anyhow::anyhow! ("loops::rx: Length too big for UDP packets");
		}
		
		let mut buf = vec! [0u8; length];
		let bytes_read = tcp_read.read_exact (&mut buf).await?;
		if length != bytes_read {
			anyhow::anyhow! ("loops::rx: read_exact failed");
		}
		buf.truncate (bytes_read);
		
		udp_sock.send (&buf).await?;
	}
}

pub async fn tx (
	udp_sock: Arc <UdpSocket>,
	mut tcp_write: tcp::OwnedWriteHalf,
) -> anyhow::Result <()> 
{
	loop {
		let mut buf = vec! [0u8; 8_192];
		let bytes_read = udp_sock.recv (&mut buf).await?;
		buf.truncate (bytes_read);
		
		let tag = [1u8, 0, 0, 0];
		let length = u32::try_from (bytes_read)?.to_le_bytes ();
		
		tcp_write.write_all (&tag).await?;
		tcp_write.write_all (&length).await?;
		tcp_write.write_all (&buf).await?;
	}
}