mc-ingress/src/mc_server.rs

use tokio::{io::AsyncWriteExt, net::TcpStream};

use crate::{
    packets::{
        clientbound::status::{StatusStructNew, StatusTrait},
        serverbound::handshake::Handshake,
        Packet, SendPacket,
    },
    OpaqueError,
};

#[tracing::instrument(skip(client_stream))]
pub async fn handle_ping(client_stream: &mut TcpStream) -> Result<(), OpaqueError> {
    // --- Respond to ping packet ---
    let ping_packet = Packet::parse(client_stream).await?;
    match ping_packet.id.get_int() {
        1 => Ok(ping_packet
            .send_packet(client_stream)
            .await
            .map_err(|_| "Failed to send ping")?),
        _ => Err(OpaqueError::create(&format!(
            "Expected ping packet, got: {}",
            ping_packet.id.get_int()
        ))),
    }
}
/// small helper function for sending `status request` to client
pub async fn complete_status_request(
    client_stream: &mut TcpStream,
    status_struct: StatusStructNew,
) -> Result<(), OpaqueError> {
    let status_res =
        crate::packets::clientbound::status::StatusResponse::set_json(Box::new(status_struct))
            .await;
    status_res
        .send_packet(client_stream)
        .await
        .map_err(|_| "Failed to send status packet")?;
    Ok(())
}

/// Disconnects the client.
///
/// It works if the client is in the login state, and it
/// has *already* and *only* sent the **handshake** and **login_start** packet.
#[tracing::instrument(skip(client_stream))]
pub async fn send_disconnect(
    client_stream: &mut TcpStream,
    reason: &str,
) -> Result<(), OpaqueError> {
    let disconnect_packet =
        crate::packets::clientbound::login::Disconnect::set_reason(reason.to_owned())
            .await
            .ok_or_else(|| "failed to *create* disconnect packet")?;
    disconnect_packet
        .send_packet(client_stream)
        .await
        .map_err(|_| "failed to *send* disconnect packet")?;
    client_stream.flush().await.map_err(|e| e.to_string())?;
    Ok(())
}

pub trait MinecraftServerHandle: Clone {
    async fn start(&self) -> Result<(), OpaqueError>;
    async fn stop(&self) -> Result<(), OpaqueError>;
    async fn query_status(&self) -> Result<ServerDeploymentStatus, OpaqueError>;
    fn get_internal_address(&self) -> Option<String>;
    fn get_internal_port(&self) -> Option<String>;
    fn get_addr(&self) -> Option<String>;
    fn get_port(&self) -> Option<String>;
    fn get_motd(&self) -> Option<String>;

    async fn query_server_connectable(&self) -> Result<TcpStream, OpaqueError> {
        let address = self
            .get_internal_address()
            .ok_or_else(|| "failed to get internal address from server")?;
        let server_stream = TcpStream::connect(address)
            .await
            .map_err(|_| "failed to connect to minecraft server")?;

        tracing::trace!(
            "successfully connected to backend server; (connectibility check) {:?}",
            server_stream.peer_addr()
        );
        Ok(server_stream)
    }

    /// Takes the already received packets, sends them to the server,
    /// and proceeds to proxy the rest of the connection transparently.
    async fn proxy_status(
        &self,
        handshake: &Handshake,
        status_request: &Packet,
        client_stream: &mut TcpStream,
        server_stream: &mut TcpStream,
    ) -> Result<(), OpaqueError> {
        handshake
            .send_packet(server_stream)
            .await
            .map_err(|_| "failed to forward handshake packet to minecraft server")?;
        status_request
            .send_packet(server_stream)
            .await
            .map_err(|_| "failed to forward status request packet to minecraft server")?;

        let data_amount = tokio::io::copy_bidirectional(client_stream, server_stream)
            .await
            .map_err(|e| {
                format!(
                    "error during bidirectional copy between server and client; err={:?}",
                    e
                )
            })?;
        tracing::trace!("data exchanged while proxying status: {:?}", data_amount);
        Ok(())
    }
    // TODO: move the implementation to here, but
    // the async things are *strange* in rust
    fn query_description(
        &self,
    ) -> impl std::future::Future<Output = Result<Box<dyn StatusTrait>, OpaqueError>> + Send;
}

pub trait MinecraftAPI<T> {
    async fn query_server(&self, addr: &str, port: &str) -> Result<T, OpaqueError>;
    async fn start_watch(
        self,
        server: impl MinecraftServerHandle,
        frequency: std::time::Duration,
    ) -> Result<(), OpaqueError>;
}

pub enum ServerDeploymentStatus {
    Connectable(TcpStream),
    Starting,
    PodOk,
    Offline,
}

pub fn sanitize_addr(addr: &str) -> &str {
    // Thanks to a buggy minecraft, when the client sends a join
    // from a SRV DNS record, it will not use the address typed
    // in the game, but use the address redicted *to* by the
    // DNS record as the address for joining, plus a trailing "."
    //
    // For example:
    // server.example.com (_minecraft._tcp.server.example.com)
    // (the typed address)     I (the DNS SRV record which gets read)
    //                         V
    //            5 25565 server.example.com
    //                         I (the response for the DNS SRV query)
    //                         V
    //                server.example.com.
    //         (the address used in the protocol)
    let addr = addr.trim_end_matches(".");

    // Modded minecraft clients send null terminated strings,
    // after which they have extra data. This just removes them
    // from the addr lookup
    let addr = terminate_at_null(addr);
    addr
}

fn terminate_at_null(str: &str) -> &str {
    match str.split('\0').next() {
        Some(x) => x,
        None => str,
    }
}