1 files changed, 246 insertions, 0 deletions
diff --git a/helix-dap/src/transport.rs b/helix-dap/src/transport.rs
new file mode 100644
index 00000000..afb7694d
--- /dev/null
+++ b/helix-dap/src/transport.rs
@@ -0,0 +1,246 @@
+use crate::{Error, Event, Result};
+use anyhow::Context;
+use log::{error, info, warn};
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use std::collections::HashMap;
+use std::sync::Arc;
+use tokio::{
+    io::{AsyncBufRead, AsyncBufReadExt, AsyncReadExt, AsyncWrite, AsyncWriteExt},
+    sync::{
+        mpsc::{unbounded_channel, Sender, UnboundedReceiver, UnboundedSender},
+        Mutex,
+    },
+};
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct Request {
+    #[serde(skip)]
+    pub back_ch: Option<Sender<Result<Response>>>,
+    pub seq: u64,
+    pub command: String,
+    pub arguments: Option<Value>,
+}
+
+#[derive(Debug, PartialEq, Clone, Deserialize, Serialize)]
+pub struct Response {
+    // seq is omitted as unused and is not sent by some implementations
+    pub request_seq: u64,
+    pub success: bool,
+    pub command: String,
+    pub message: Option<String>,
+    pub body: Option<Value>,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+#[serde(tag = "type", rename_all = "camelCase")]
+pub enum Payload {
+    // type = "event"
+    Event(Event),
+    // type = "response"
+    Response(Response),
+    // type = "request"
+    Request(Request),
+}
+
+#[derive(Debug)]
+pub struct Transport {
+    id: usize,
+    pending_requests: Mutex<HashMap<u64, Sender<Result<Response>>>>,
+}
+
+impl Transport {
+    pub fn start(
+        server_stdout: Box<dyn AsyncBufRead + Unpin + Send>,
+        server_stdin: Box<dyn AsyncWrite + Unpin + Send>,
+        id: usize,
+    ) -> (UnboundedReceiver<Payload>, UnboundedSender<Request>) {
+        let (client_tx, rx) = unbounded_channel();
+        let (tx, client_rx) = unbounded_channel();
+
+        let transport = Self {
+            id,
+            pending_requests: Mutex::new(HashMap::default()),
+        };
+
+        let transport = Arc::new(transport);
+
+        tokio::spawn(Self::recv(transport.clone(), server_stdout, client_tx));
+        tokio::spawn(Self::send(transport, server_stdin, client_rx));
+
+        (rx, tx)
+    }
+
+    async fn recv_server_message(
+        reader: &mut Box<dyn AsyncBufRead + Unpin + Send>,
+        buffer: &mut String,
+    ) -> Result<Payload> {
+        let mut content_length = None;
+        loop {
+            buffer.truncate(0);
+            reader.read_line(buffer).await?;
+            let header = buffer.trim();
+
+            if header.is_empty() {
+                break;
+            }
+
+            let mut parts = header.split(": ");
+
+            match (parts.next(), parts.next(), parts.next()) {
+                (Some("Content-Length"), Some(value), None) => {
+                    content_length = Some(value.parse().context("invalid content length")?);
+                }
+                (Some(_), Some(_), None) => {}
+                _ => {
+                    return Err(std::io::Error::new(
+                        std::io::ErrorKind::Other,
+                        "Failed to parse header",
+                    )
+                    .into());
+                }
+            }
+        }
+
+        let content_length = content_length.context("missing content length")?;
+
+        //TODO: reuse vector
+        let mut content = vec![0; content_length];
+        reader.read_exact(&mut content).await?;
+        let msg = std::str::from_utf8(&content).context("invalid utf8 from server")?;
+
+        info!("<- DAP {}", msg);
+
+        // try parsing as output (server response) or call (server request)
+        let output: serde_json::Result<Payload> = serde_json::from_str(msg);
+
+        Ok(output?)
+    }
+
+    async fn send_payload_to_server(
+        &self,
+        server_stdin: &mut Box<dyn AsyncWrite + Unpin + Send>,
+        mut req: Request,
+    ) -> Result<()> {
+        let back_ch = req.back_ch.take();
+        let seq = req.seq;
+        let json = serde_json::to_string(&Payload::Request(req))?;
+        if let Some(back) = back_ch {
+            self.pending_requests.lock().await.insert(seq, back);
+        }
+        self.send_string_to_server(server_stdin, json).await
+    }
+
+    async fn send_string_to_server(
+        &self,
+        server_stdin: &mut Box<dyn AsyncWrite + Unpin + Send>,
+        request: String,
+    ) -> Result<()> {
+        info!("-> DAP {}", request);
+
+        // send the headers
+        server_stdin
+            .write_all(format!("Content-Length: {}\r\n\r\n", request.len()).as_bytes())
+            .await?;
+
+        // send the body
+        server_stdin.write_all(request.as_bytes()).await?;
+
+        server_stdin.flush().await?;
+
+        Ok(())
+    }
+
+    fn process_response(res: Response) -> Result<Response> {
+        if res.success {
+            info!("<- DAP success in response to {}", res.request_seq);
+
+            Ok(res)
+        } else {
+            error!(
+                "<- DAP error {:?} ({:?}) for command #{} {}",
+                res.message, res.body, res.request_seq, res.command
+            );
+
+            Err(Error::Other(anyhow::format_err!("{:?}", res.body)))
+        }
+    }
+
+    async fn process_server_message(
+        &self,
+        client_tx: &UnboundedSender<Payload>,
+        msg: Payload,
+    ) -> Result<()> {
+        match msg {
+            Payload::Response(res) => {
+                let request_seq = res.request_seq;
+                let tx = self.pending_requests.lock().await.remove(&request_seq);
+
+                match tx {
+                    Some(tx) => match tx.send(Self::process_response(res)).await {
+                        Ok(_) => (),
+                        Err(_) => error!(
+                            "Tried sending response into a closed channel (id={:?}), original request likely timed out",
+                            request_seq
+                        ),
+                    }
+                    None => {
+                        warn!("Response to nonexistent request #{}", res.request_seq);
+                        client_tx.send(Payload::Response(res)).expect("Failed to send");
+                    }
+                }
+
+                Ok(())
+            }
+            Payload::Request(Request {
+                ref command,
+                ref seq,
+                ..
+            }) => {
+                info!("<- DAP request {} #{}", command, seq);
+                client_tx.send(msg).expect("Failed to send");
+                Ok(())
+            }
+            Payload::Event(ref event) => {
+                info!("<- DAP event {:?}", event);
+                client_tx.send(msg).expect("Failed to send");
+                Ok(())
+            }
+        }
+    }
+
+    async fn recv(
+        transport: Arc<Self>,
+        mut server_stdout: Box<dyn AsyncBufRead + Unpin + Send>,
+        client_tx: UnboundedSender<Payload>,
+    ) {
+        let mut recv_buffer = String::new();
+        loop {
+            match Self::recv_server_message(&mut server_stdout, &mut recv_buffer).await {
+                Ok(msg) => {
+                    transport
+                        .process_server_message(&client_tx, msg)
+                        .await
+                        .unwrap();
+                }
+                Err(err) => {
+                    error!("err: <- {:?}", err);
+                    break;
+                }
+            }
+        }
+    }
+
+    async fn send(
+        transport: Arc<Self>,
+        mut server_stdin: Box<dyn AsyncWrite + Unpin + Send>,
+        mut client_rx: UnboundedReceiver<Request>,
+    ) {
+        while let Some(req) = client_rx.recv().await {
+            transport
+                .send_payload_to_server(&mut server_stdin, req)
+                .await
+                .unwrap()
+        }
+    }
+}