refactor(tazjin/rlox): Move entrypoints into interpreters r/2123

Right now this introduces a simple mechanism to flip between the
interpreters.

Change-Id: I92ee920c53d76ab6b664ac671993a6d6426af61a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2412
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

1 files changed, 50 insertions, 0 deletions

diff --git a/users/tazjin/rlox/src/treewalk/mod.rs b/users/tazjin/rlox/src/treewalk/mod.rs
index d76045b91b9c..95136b2fa141 100644
--- a/users/tazjin/rlox/src/treewalk/mod.rs
+++ b/users/tazjin/rlox/src/treewalk/mod.rs
@@ -1,2 +1,52 @@
+use crate::*;
+
 pub mod interpreter;
 mod resolver;
+
+pub fn main() {
+    let mut args = env::args();
+
+    if args.len() > 2 {
+        println!("Usage: rlox [script]");
+        process::exit(1);
+    } else if let Some(file) = args.nth(1) {
+        run_file(&file);
+    } else {
+        run_prompt();
+    }
+}
+
+// Run Lox code from a file and print results to stdout
+fn run_file(file: &str) {
+    let contents = fs::read_to_string(file).expect("failed to read the input file");
+    let mut lox = treewalk::interpreter::Interpreter::create();
+    run(&mut lox, &contents);
+}
+
+// Evaluate Lox code interactively in a shitty REPL.
+fn run_prompt() {
+    let mut line = String::new();
+    let mut lox = treewalk::interpreter::Interpreter::create();
+
+    loop {
+        print!("> ");
+        io::stdout().flush().unwrap();
+        io::stdin()
+            .read_line(&mut line)
+            .expect("failed to read user input");
+        run(&mut lox, &line);
+        line.clear();
+    }
+}
+
+fn run(lox: &mut treewalk::interpreter::Interpreter, code: &str) {
+    let chars: Vec<char> = code.chars().collect();
+
+    let result = scanner::scan(&chars)
+        .and_then(|tokens| parser::parse(tokens))
+        .and_then(|program| lox.interpret(program).map_err(|e| vec![e]));
+
+    if let Err(errors) = result {
+        report_errors(errors);
+    }
+}