refactor(tvix): Break out REPL into its own module r/8187

In preparation for adding some new functionality to the tvix REPL, break
it out into its own module.

Change-Id: I4fb78320e92562e3474a3724536cb22c1d893e57
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11733
Tested-by: BuildkiteCI
Autosubmit: aspen <root@gws.fyi>
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 117 insertions, 0 deletions

diff --git a/tvix/cli/src/repl.rs b/tvix/cli/src/repl.rs
new file mode 100644
index 000000000000..8dde9d9bfdc0
--- /dev/null
+++ b/tvix/cli/src/repl.rs
@@ -0,0 +1,117 @@
+use std::{path::PathBuf, rc::Rc};
+
+use rustyline::{error::ReadlineError, Editor};
+use tvix_glue::tvix_store_io::TvixStoreIO;
+
+use crate::{interpret, AllowIncomplete, Args, IncompleteInput};
+
+fn state_dir() -> Option<PathBuf> {
+    let mut path = dirs::data_dir();
+    if let Some(p) = path.as_mut() {
+        p.push("tvix")
+    }
+    path
+}
+
+#[derive(Debug)]
+pub struct Repl {
+    /// In-progress multiline input, when the input so far doesn't parse as a complete expression
+    multiline_input: Option<String>,
+    rl: Editor<()>,
+}
+
+impl Repl {
+    pub fn new() -> Self {
+        let rl = Editor::<()>::new().expect("should be able to launch rustyline");
+        Self {
+            multiline_input: None,
+            rl,
+        }
+    }
+
+    pub fn run(&mut self, io_handle: Rc<TvixStoreIO>, args: &Args) {
+        if args.compile_only {
+            eprintln!("warning: `--compile-only` has no effect on REPL usage!");
+        }
+
+        let history_path = match state_dir() {
+            // Attempt to set up these paths, but do not hard fail if it
+            // doesn't work.
+            Some(mut path) => {
+                let _ = std::fs::create_dir_all(&path);
+                path.push("history.txt");
+                let _ = self.rl.load_history(&path);
+                Some(path)
+            }
+
+            None => None,
+        };
+
+        loop {
+            let prompt = if self.multiline_input.is_some() {
+                "         > "
+            } else {
+                "tvix-repl> "
+            };
+
+            let readline = self.rl.readline(prompt);
+            match readline {
+                Ok(line) => {
+                    if line.is_empty() {
+                        continue;
+                    }
+
+                    let input = if let Some(mi) = &mut self.multiline_input {
+                        mi.push('\n');
+                        mi.push_str(&line);
+                        mi
+                    } else {
+                        &line
+                    };
+
+                    let res = if let Some(without_prefix) = input.strip_prefix(":d ") {
+                        interpret(
+                            Rc::clone(&io_handle),
+                            without_prefix,
+                            None,
+                            args,
+                            true,
+                            AllowIncomplete::Allow,
+                        )
+                    } else {
+                        interpret(
+                            Rc::clone(&io_handle),
+                            input,
+                            None,
+                            args,
+                            false,
+                            AllowIncomplete::Allow,
+                        )
+                    };
+
+                    match res {
+                        Ok(_) => {
+                            self.rl.add_history_entry(input);
+                            self.multiline_input = None;
+                        }
+                        Err(IncompleteInput) => {
+                            if self.multiline_input.is_none() {
+                                self.multiline_input = Some(line);
+                            }
+                        }
+                    }
+                }
+                Err(ReadlineError::Interrupted) | Err(ReadlineError::Eof) => break,
+
+                Err(err) => {
+                    eprintln!("error: {}", err);
+                    break;
+                }
+            }
+        }
+
+        if let Some(path) = history_path {
+            self.rl.save_history(&path).unwrap();
+        }
+    }
+}