capnprotols 0.1.3

//! Shared LSP test client. Spawns the `capnprotols` binary and speaks LSP over stdio,
//! offering synchronous request/notify primitives plus polled response collection.

use std::io::{BufRead, BufReader, Read, Write};
use std::path::PathBuf;
use std::process::{Child, ChildStdin, ChildStdout, Command, Stdio};
use std::sync::mpsc::{self, Receiver};
use std::thread;
use std::time::{Duration, Instant};

use serde_json::{json, Value};

/// Convenient handle on a running language server that we can drive from tests.
pub struct LspClient {
  child:   Option<Child>,
  stdin:   ChildStdin,
  rx:      Receiver<Value>,
  next_id: i64,
}

impl LspClient {
  /// Spawn the server binary and complete the LSP `initialize` handshake.
  pub fn start() -> Self {
    let bin = env!("CARGO_BIN_EXE_capnprotols");
    let mut child = Command::new(bin)
      .stdin(Stdio::piped())
      .stdout(Stdio::piped())
      .stderr(Stdio::piped())
      .env("CAPNPROTOLS_LOG", "warn")
      .spawn()
      .expect("failed to spawn capnprotols binary");

    let stdin = child.stdin.take().expect("stdin");
    let stdout = child.stdout.take().expect("stdout");
    let (tx, rx) = mpsc::channel::<Value>();
    thread::spawn(move || drain_stdout(stdout, tx));

    // Ditch stderr so the child doesn't block on a full pipe in long tests.
    if let Some(stderr) = child.stderr.take() {
      thread::spawn(move || {
        let mut sink = Vec::new();
        let _ = std::io::copy(&mut std::io::BufReader::new(stderr), &mut sink);
      });
    }

    let mut c = Self {
      child: Some(child),
      stdin,
      rx,
      next_id: 1,
    };
    let init = c.request(
      "initialize",
      json!({
          "capabilities": {},
          "processId": std::process::id(),
          "rootUri": null,
      }),
    );
    assert!(init.get("result").is_some(), "initialize failed: {init}");
    c.notify("initialized", json!({}));
    c
  }

  /// Send didOpen and wait for the first publishDiagnostics. Returns the diagnostics
  /// array so tests can assert on them.
  pub fn open(&mut self, uri: &str, text: &str) -> Vec<Value> {
    self.notify(
      "textDocument/didOpen",
      json!({
          "textDocument": {
              "uri": uri,
              "languageId": "capnp",
              "version": 1,
              "text": text,
          }
      }),
    );
    self.next_diagnostics()
  }

  /// Send didChange and wait for the resulting publishDiagnostics.
  pub fn change(&mut self, uri: &str, version: i64, text: &str) -> Vec<Value> {
    self.notify(
      "textDocument/didChange",
      json!({
          "textDocument": { "uri": uri, "version": version },
          "contentChanges": [{ "text": text }],
      }),
    );
    self.next_diagnostics()
  }

  /// Wait for the next `textDocument/publishDiagnostics` and return its diagnostics array.
  pub fn next_diagnostics(&mut self) -> Vec<Value> {
    let pd = self
      .wait_notification(
        "textDocument/publishDiagnostics",
        Duration::from_secs(8),
      )
      .expect("publishDiagnostics");
    pd.pointer("/params/diagnostics")
      .and_then(|v| v.as_array())
      .cloned()
      .unwrap_or_default()
  }

  pub fn shutdown(mut self) {
    let _ = self.request_no_params("shutdown");
    self.notify_no_params("exit");
    if let Some(mut child) = self.child.take() {
      // Don't block forever if the child somehow hangs — tests must always finish.
      let deadline = Instant::now() + Duration::from_secs(3);
      loop {
        match child.try_wait() {
          Ok(Some(_)) => return,
          Ok(None) => {
            if Instant::now() >= deadline {
              let _ = child.kill();
              let _ = child.wait();
              return;
            }
            thread::sleep(Duration::from_millis(20));
          }
          Err(_) => return,
        }
      }
    }
  }

  /// Send a parameterless request (some LSP methods reject explicit null params).
  pub fn request_no_params(&mut self, method: &str) -> Value {
    let id = self.next_id;
    self.next_id += 1;
    self.send(json!({ "jsonrpc": "2.0", "id": id, "method": method }));
    self.await_response(id, method)
  }

  pub fn notify_no_params(&mut self, method: &str) {
    self.send(json!({ "jsonrpc": "2.0", "method": method }));
  }

  /// Send a request and synchronously wait for its matching response.
  pub fn request(&mut self, method: &str, params: Value) -> Value {
    let id = self.next_id;
    self.next_id += 1;
    self.send(json!({
        "jsonrpc": "2.0",
        "id": id,
        "method": method,
        "params": params,
    }));
    self.await_response(id, method)
  }

  fn await_response(&mut self, id: i64, method: &str) -> Value {
    let deadline = Instant::now() + Duration::from_secs(8);
    loop {
      let remaining = deadline
        .checked_duration_since(Instant::now())
        .unwrap_or(Duration::ZERO);
      let msg = self.rx.recv_timeout(remaining).unwrap_or_else(|_| {
        panic!("timed out waiting for response to {method}")
      });
      if msg.get("id").and_then(|v| v.as_i64()) == Some(id) {
        return msg;
      }
    }
  }

  pub fn notify(&mut self, method: &str, params: Value) {
    self.send(json!({
        "jsonrpc": "2.0",
        "method": method,
        "params": params,
    }));
  }

  /// Drain notifications until one matching `method` arrives, or the deadline elapses.
  pub fn wait_notification(
    &mut self,
    method: &str,
    max_wait: Duration,
  ) -> Option<Value> {
    let deadline = Instant::now() + max_wait;
    loop {
      let remaining = deadline
        .checked_duration_since(Instant::now())
        .unwrap_or(Duration::ZERO);
      if remaining.is_zero() {
        return None;
      }
      let msg = self.rx.recv_timeout(remaining).ok()?;
      if msg.get("method").and_then(|v| v.as_str()) == Some(method) {
        return Some(msg);
      }
    }
  }

  fn send(&mut self, msg: Value) {
    let body = msg.to_string();
    let header = format!("Content-Length: {}\r\n\r\n", body.len());
    self.stdin.write_all(header.as_bytes()).expect("stdin");
    self.stdin.write_all(body.as_bytes()).expect("stdin");
    self.stdin.flush().expect("stdin flush");
  }
}

impl Drop for LspClient {
  fn drop(&mut self) {
    if let Some(mut child) = self.child.take() {
      let _ = child.kill();
      let _ = child.wait();
    }
  }
}

fn drain_stdout(stdout: ChildStdout, tx: mpsc::Sender<Value>) {
  let mut reader = BufReader::new(stdout);
  loop {
    let mut content_length: Option<usize> = None;
    loop {
      let mut line = String::new();
      if reader.read_line(&mut line).unwrap_or(0) == 0 {
        return;
      }
      let line = line.trim_end_matches(['\r', '\n']);
      if line.is_empty() {
        break;
      }
      if let Some(rest) = line.strip_prefix("Content-Length: ") {
        content_length = rest.trim().parse().ok();
      }
    }
    let len = content_length.expect("missing Content-Length");
    let mut buf = vec![0u8; len];
    if reader.read_exact(&mut buf).is_err() {
      return;
    }
    let value: Value = match serde_json::from_slice(&buf) {
      Ok(v) => v,
      Err(_) => continue,
    };
    if tx.send(value).is_err() {
      return;
    }
  }
}

/// A throwaway project directory with copies of named fixtures. Each test gets its own
/// so the overlay file capnprotols writes alongside the source doesn't collide with
/// other tests running in parallel.
pub struct TempProject {
  dir: PathBuf,
}

impl TempProject {
  /// Create a fresh temp dir and copy the named fixtures (e.g. `["user.capnp", "types.capnp"]`)
  /// into it. The fixtures live under `tests/fixtures/` in the crate.
  pub fn with_fixtures(names: &[&str]) -> Self {
    let mut src_root = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    src_root.push("tests/fixtures");

    static COUNTER: std::sync::atomic::AtomicU64 =
      std::sync::atomic::AtomicU64::new(0);
    let n = COUNTER.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
    let nanos = std::time::SystemTime::now()
      .duration_since(std::time::UNIX_EPOCH)
      .map(|d| d.as_nanos())
      .unwrap_or(0);
    let dir = std::env::temp_dir().join(format!(
      "capnprotols-test-{}-{}-{}",
      std::process::id(),
      nanos,
      n
    ));
    std::fs::create_dir_all(&dir).expect("create temp dir");
    for name in names {
      let src = src_root.join(name);
      let dst = dir.join(name);
      std::fs::copy(&src, &dst).unwrap_or_else(|e| {
        panic!("copy {} -> {}: {e}", src.display(), dst.display())
      });
    }
    Self { dir }
  }

  pub fn path(&self, name: &str) -> PathBuf {
    self.dir.join(name)
  }

  pub fn uri(&self, name: &str) -> String {
    format!("file://{}", self.path(name).display())
  }

  pub fn text(&self, name: &str) -> String {
    let p = self.path(name);
    std::fs::read_to_string(&p)
      .unwrap_or_else(|e| panic!("read {}: {e}", p.display()))
  }
}

impl Drop for TempProject {
  fn drop(&mut self) {
    let _ = std::fs::remove_dir_all(&self.dir);
  }
}