From 97fdc89316d31779155af64e4d2af33c2a0497f7 Mon Sep 17 00:00:00 2001
From: Sebastian Hugentobler <shu@vanwa.ch>
Date: Wed, 28 May 2025 21:58:35 +0200
Subject: [PATCH] add argument reading for lox

---
 lox/bf.lox              |  3 ++-
 src/cli.rs              |  3 +++
 src/interpreter.rs      | 10 ++++++---
 src/lib.rs              |  4 ++--
 src/main.rs             |  3 ++-
 src/native_functions.rs | 45 ++++++++++++++++++++++++++++++++++++++++-
 6 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/lox/bf.lox b/lox/bf.lox
index dd99608..6398d59 100644
--- a/lox/bf.lox
+++ b/lox/bf.lox
@@ -96,5 +96,6 @@ class Interpreter {
   }
 }
 
-var interpreter = Interpreter("bf/game_of_life.bf");
+var bfScript = args(0);
+var interpreter = Interpreter(bfScript);
 interpreter.run();
diff --git a/src/cli.rs b/src/cli.rs
index f766d41..8e328fe 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -19,6 +19,9 @@ pub struct RunConfig {
     /// Path to Lox source file.
     #[arg(short, long)]
     pub source: PathBuf,
+    /// Arguments to pass to the Lox script (must be after '--').
+    #[arg(last = true)]
+    pub script_args: Vec<String>,
 }
 
 /// Available commands for the Lox interpreter
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 70b1670..198b4e0 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -60,12 +60,18 @@ pub struct Interpreter {
 /// Default configuration for the interpreter, with builtin native functions.
 impl Default for Interpreter {
     fn default() -> Self {
+        Interpreter::new(Vec::new())
+    }
+}
+
+impl Interpreter {
+    pub fn new(cli_args: Vec<String>) -> Self {
         let env: Rc<RefCell<Environment>> = Default::default();
 
         {
             // add all native functions to global environment
             let mut env = env.borrow_mut();
-            for (name, fun) in native_functions::all() {
+            for (name, fun) in native_functions::all(cli_args) {
                 env.define(name, fun);
             }
         }
@@ -76,9 +82,7 @@ impl Default for Interpreter {
             locals: HashMap::new(),
         }
     }
-}
 
-impl Interpreter {
     /// Execute a list of statements in sequence.
     /// Log errors but continue execution.
     pub fn run(&mut self, statements: Vec<Statement>) -> Result<(), InterpreterError> {
diff --git a/src/lib.rs b/src/lib.rs
index d27e546..0c2d957 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -53,9 +53,9 @@ pub enum RoxError {
 }
 
 /// Read the source code in a file and scan it to tokens.
-pub fn compile(source: &Path) -> Result<(), io::Error> {
+pub fn compile(source: &Path, cli_args: Vec<String>) -> Result<(), io::Error> {
     let input = fs::read_to_string(source)?;
-    let mut interpreter = Interpreter::default();
+    let mut interpreter = Interpreter::new(cli_args);
 
     run(&input, &mut interpreter);
 
diff --git a/src/main.rs b/src/main.rs
index 32caf1a..1539ff8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -23,7 +23,8 @@ fn main() {
                 exit(1);
             }
 
-            if let Err(e) = rox::compile(&compile_config.source) {
+            if let Err(e) = rox::compile(&compile_config.source, compile_config.script_args.clone())
+            {
                 error!(
                     "failed to compile {}: {}",
                     &compile_config.source.to_string_lossy(),
diff --git a/src/native_functions.rs b/src/native_functions.rs
index b33ab72..5639664 100644
--- a/src/native_functions.rs
+++ b/src/native_functions.rs
@@ -224,8 +224,47 @@ impl Callable for PromptAscii {
     }
 }
 
+struct CliArgs {
+    cli_args: Vec<String>,
+}
+impl Callable for CliArgs {
+    fn name(&self) -> String {
+        "args".into()
+    }
+
+    fn arity(&self) -> usize {
+        1
+    }
+
+    fn call(
+        &self,
+        _interpreter: &mut Interpreter,
+        args: Vec<Value>,
+    ) -> Result<Value, CallingError> {
+        if args.len() != self.arity() {
+            return Err(CallingError::ArgumentMismatch(self.arity(), args.len()));
+        }
+
+        let idx = args
+            .first()
+            .ok_or(CallingError::CallFailed("arg not readable".into()))?;
+        if let Value::Number(idx) = idx {
+            let idx: usize = idx.0 as usize;
+            Ok(self
+                .cli_args
+                .get(idx)
+                .map(|x| Value::String(x.clone()))
+                .unwrap_or(Value::Nil))
+        } else {
+            Err(CallingError::CallFailed(
+                "arg index must be a number".into(),
+            ))
+        }
+    }
+}
+
 /// Return all native functions available to the Lox interpreter
-pub fn all() -> Vec<(String, Value)> {
+pub fn all(cli_args: Vec<String>) -> Vec<(String, Value)> {
     vec![
         (
             "asciiOut".into(),
@@ -247,5 +286,9 @@ pub fn all() -> Vec<(String, Value)> {
             "promptAscii".into(),
             Value::Callable((Rc::new(PromptAscii {}), CallableType::Function)),
         ),
+        (
+            "args".into(),
+            Value::Callable((Rc::new(CliArgs { cli_args }), CallableType::Function)),
+        ),
     ]
 }