use std::fs;
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};
use std::time::{Duration, Instant};
use anyhow::{Context, Result};
use tempfile::{Builder, TempDir};
use super::{
ExecutionOutcome, ExecutionPayload, LanguageEngine, LanguageSession, run_version_command,
};
pub struct REngine {
executable: Option<PathBuf>,
}
impl Default for REngine {
fn default() -> Self {
Self::new()
}
}
impl REngine {
pub fn new() -> Self {
Self {
executable: resolve_r_binary(),
}
}
fn ensure_executable(&self) -> Result<&Path> {
self.executable.as_deref().ok_or_else(|| {
anyhow::anyhow!(
"R support requires the `Rscript` executable. Install R from https://cran.r-project.org/ and ensure `Rscript` is on your PATH."
)
})
}
fn write_temp_source(&self, code: &str) -> Result<(TempDir, PathBuf)> {
let dir = Builder::new()
.prefix("run-r")
.tempdir()
.context("failed to create temporary directory for R source")?;
let path = dir.path().join("snippet.R");
let mut contents = code.to_string();
if !contents.ends_with('\n') {
contents.push('\n');
}
fs::write(&path, contents)
.with_context(|| format!("failed to write temporary R source to {}", path.display()))?;
Ok((dir, path))
}
fn execute_with_path(&self, source: &Path, args: &[String]) -> Result<std::process::Output> {
let executable = self.ensure_executable()?;
let mut cmd = Command::new(executable);
cmd.arg("--vanilla")
.arg(source)
.args(args)
.stdout(Stdio::piped())
.stderr(Stdio::piped());
cmd.stdin(Stdio::inherit());
cmd.output().with_context(|| {
format!(
"failed to invoke {} to run {}",
executable.display(),
source.display()
)
})
}
}
impl LanguageEngine for REngine {
fn id(&self) -> &'static str {
"r"
}
fn display_name(&self) -> &'static str {
"R"
}
fn aliases(&self) -> &[&'static str] {
&["rscript"]
}
fn supports_sessions(&self) -> bool {
self.executable.is_some()
}
fn validate(&self) -> Result<()> {
let executable = self.ensure_executable()?;
let mut cmd = Command::new(executable);
cmd.arg("--version")
.stdout(Stdio::null())
.stderr(Stdio::null());
cmd.status()
.with_context(|| format!("failed to invoke {}", executable.display()))?
.success()
.then_some(())
.ok_or_else(|| anyhow::anyhow!("{} is not executable", executable.display()))
}
fn toolchain_version(&self) -> Result<Option<String>> {
let executable = self.ensure_executable()?;
let mut cmd = Command::new(executable);
cmd.arg("--version");
let context = format!("{}", executable.display());
run_version_command(cmd, &context)
}
fn execute(&self, payload: &ExecutionPayload) -> Result<ExecutionOutcome> {
let start = Instant::now();
let (temp_dir, path) = match payload {
ExecutionPayload::Inline { code, .. } => {
let (dir, path) = self.write_temp_source(code)?;
(Some(dir), path)
}
ExecutionPayload::Stdin { code, .. } => {
let (dir, path) = self.write_temp_source(code)?;
(Some(dir), path)
}
ExecutionPayload::File { path, .. } => (None, path.clone()),
};
let output = self.execute_with_path(&path, payload.args())?;
drop(temp_dir);
Ok(ExecutionOutcome {
language: self.id().to_string(),
exit_code: output.status.code(),
stdout: String::from_utf8_lossy(&output.stdout).into_owned(),
stderr: String::from_utf8_lossy(&output.stderr).into_owned(),
duration: start.elapsed(),
})
}
fn start_session(&self) -> Result<Box<dyn LanguageSession>> {
let executable = self.ensure_executable()?.to_path_buf();
Ok(Box::new(RSession::new(executable)?))
}
}
fn resolve_r_binary() -> Option<PathBuf> {
which::which("Rscript").ok()
}
struct RSession {
executable: PathBuf,
dir: TempDir,
script_path: PathBuf,
statements: Vec<String>,
previous_stdout: String,
previous_stderr: String,
}
impl RSession {
fn new(executable: PathBuf) -> Result<Self> {
let dir = Builder::new()
.prefix("run-r-repl")
.tempdir()
.context("failed to create temporary directory for R repl")?;
let script_path = dir.path().join("session.R");
fs::write(&script_path, "options(warn=1)\n")
.with_context(|| format!("failed to initialize {}", script_path.display()))?;
Ok(Self {
executable,
dir,
script_path,
statements: Vec::new(),
previous_stdout: String::new(),
previous_stderr: String::new(),
})
}
fn render_script(&self) -> String {
let mut script = String::from("options(warn=1)\n");
for stmt in &self.statements {
script.push_str(stmt);
if !stmt.ends_with('\n') {
script.push('\n');
}
}
script
}
fn write_script(&self, contents: &str) -> Result<()> {
fs::write(&self.script_path, contents).with_context(|| {
format!(
"failed to write generated R REPL script to {}",
self.script_path.display()
)
})
}
fn run_current(&mut self, start: Instant) -> Result<(ExecutionOutcome, bool)> {
let script = self.render_script();
self.write_script(&script)?;
let mut cmd = Command::new(&self.executable);
cmd.arg("--vanilla")
.arg(&self.script_path)
.stdout(Stdio::piped())
.stderr(Stdio::piped())
.current_dir(self.dir.path());
let output = cmd.output().with_context(|| {
format!(
"failed to execute R session script {} with {}",
self.script_path.display(),
self.executable.display()
)
})?;
let stdout_full = normalize_output(&output.stdout);
let stderr_full = normalize_output(&output.stderr);
let stdout_delta = diff_output(&self.previous_stdout, &stdout_full);
let stderr_delta = diff_output(&self.previous_stderr, &stderr_full);
let success = output.status.success();
if success {
self.previous_stdout = stdout_full;
self.previous_stderr = stderr_full;
}
let outcome = ExecutionOutcome {
language: "r".to_string(),
exit_code: output.status.code(),
stdout: stdout_delta,
stderr: stderr_delta,
duration: start.elapsed(),
};
Ok((outcome, success))
}
fn run_snippet(&mut self, snippet: String) -> Result<ExecutionOutcome> {
self.statements.push(snippet);
let start = Instant::now();
let (outcome, success) = self.run_current(start)?;
if !success {
let _ = self.statements.pop();
let script = self.render_script();
self.write_script(&script)?;
}
Ok(outcome)
}
fn reset_state(&mut self) -> Result<()> {
self.statements.clear();
self.previous_stdout.clear();
self.previous_stderr.clear();
let script = self.render_script();
self.write_script(&script)
}
}
impl LanguageSession for RSession {
fn language_id(&self) -> &str {
"r"
}
fn eval(&mut self, code: &str) -> Result<ExecutionOutcome> {
let trimmed = code.trim();
if trimmed.is_empty() {
return Ok(ExecutionOutcome {
language: self.language_id().to_string(),
exit_code: None,
stdout: String::new(),
stderr: String::new(),
duration: Duration::default(),
});
}
if trimmed.eq_ignore_ascii_case(":reset") {
self.reset_state()?;
return Ok(ExecutionOutcome {
language: self.language_id().to_string(),
exit_code: None,
stdout: String::new(),
stderr: String::new(),
duration: Duration::default(),
});
}
if trimmed.eq_ignore_ascii_case(":help") {
return Ok(ExecutionOutcome {
language: self.language_id().to_string(),
exit_code: None,
stdout:
"R commands:\n :reset - clear session state\n :help - show this message\n"
.to_string(),
stderr: String::new(),
duration: Duration::default(),
});
}
let snippet = if should_wrap_expression(trimmed) {
wrap_expression(trimmed)
} else {
ensure_trailing_newline(code)
};
self.run_snippet(snippet)
}
fn shutdown(&mut self) -> Result<()> {
Ok(())
}
}
fn should_wrap_expression(code: &str) -> bool {
if code.contains('\n') {
return false;
}
let lowered = code.trim_start().to_ascii_lowercase();
const STATEMENT_PREFIXES: [&str; 12] = [
"if ", "for ", "while ", "repeat", "function", "library", "require", "print", "cat",
"source", "options", "setwd",
];
if STATEMENT_PREFIXES
.iter()
.any(|prefix| lowered.starts_with(prefix))
{
return false;
}
if code.contains("<-") || code.contains("=") {
return false;
}
true
}
fn wrap_expression(code: &str) -> String {
format!("print(({}))\n", code)
}
fn ensure_trailing_newline(code: &str) -> String {
let mut owned = code.to_string();
if !owned.ends_with('\n') {
owned.push('\n');
}
owned
}
fn diff_output(previous: &str, current: &str) -> String {
if let Some(stripped) = current.strip_prefix(previous) {
stripped.to_string()
} else {
current.to_string()
}
}
fn normalize_output(bytes: &[u8]) -> String {
String::from_utf8_lossy(bytes)
.replace("\r\n", "\n")
.replace('\r', "")
}