Implemented host interface

ablescript/src/error.rs

@@ -14,6 +14,7 @@ pub enum ErrorKind {
     UnknownVariable(String),
     MeloVariable(String),
     TopLevelEnough,
+    NonExitingRlyeh(i32),
     MissingLhs,
     Brian(InterpretError),
     Io(io::Error),
@@ -51,6 +52,7 @@ impl Display for ErrorKind {
             ErrorKind::UnknownVariable(name) => write!(f, "unknown identifier \"{}\"", name),
             ErrorKind::MeloVariable(name) => write!(f, "banned variable \"{}\"", name),
             ErrorKind::TopLevelEnough => write!(f, "can only `enough` out of a loop"),
+            &ErrorKind::NonExitingRlyeh(code) => write!(f, "program exited with code {code}"),
             ErrorKind::Brian(err) => write!(f, "brainfuck error: {}", err),
             // TODO: give concrete numbers here.
             ErrorKind::MissingLhs => write!(f, "missing expression before binary operation"),

ablescript/src/host_interface.rs

@@ -0,0 +1,47 @@
+/// Host Environment Interface
+pub trait HostInterface {
+    type Data;
+
+    /// Print a string
+    fn print(&mut self, string: &str, new_line: bool) -> std::io::Result<()>;
+
+    /// Read a byte
+    fn read_byte(&mut self) -> std::io::Result<u8>;
+
+    /// This function should exit the program with specified code.
+    ///
+    /// For cases where exit is not desired, just let the function return
+    /// and interpreter will terminate with an error.
+    fn exit(&mut self, code: i32);
+}
+
+/// Standard [HostInterface] implementation
+#[derive(Clone, Copy, Default)]
+pub struct Standard;
+impl HostInterface for Standard {
+    type Data = ();
+
+    fn print(&mut self, string: &str, new_line: bool) -> std::io::Result<()> {
+        use std::io::Write;
+
+        let mut stdout = std::io::stdout();
+        stdout.write_all(string.as_bytes())?;
+        if new_line {
+            stdout.write_all(b"\n")?;
+        }
+
+        Ok(())
+    }
+
+    fn read_byte(&mut self) -> std::io::Result<u8> {
+        use std::io::Read;
+
+        let mut buf = [0];
+        std::io::stdin().read_exact(&mut buf)?;
+        Ok(buf[0])
+    }
+
+    fn exit(&mut self, code: i32) {
+        std::process::exit(code);
+    }
+}

ablescript/src/interpret.rs

@@ -12,20 +12,19 @@ use crate::{
     ast::{Assignable, AssignableKind, Block, Expr, Spanned, Stmt},
     consts::ablescript_consts,
     error::{Error, ErrorKind},
+    host_interface::HostInterface,
     value::{Functio, Value, ValueRef, Variable},
 };
 use rand::random;
 use std::{
     cmp::Ordering,
     collections::{HashMap, VecDeque},
-    io::{stdin, stdout, Read, Write},
     mem::take,
     ops::Range,
-    process::exit,
 };
 
 /// An environment for executing AbleScript code.
-pub struct ExecEnv {
+pub struct ExecEnv<H> {
     /// The stack, ordered such that `stack[stack.len() - 1]` is the
     /// top-most (newest) stack frame, and `stack[0]` is the
     /// bottom-most (oldest) stack frame.
@@ -38,6 +37,9 @@ pub struct ExecEnv {
     /// booleans to facilitate easy manipulation.
     read_buf: VecDeque<bool>,
 
+    /// Interface to interact with the host interface
+    host_interface: H,
+
     /// Vector of blocks to be executed at the end of the program
     finalisers: Vec<Block>,
 }
@@ -49,13 +51,12 @@ struct Scope {
     variables: HashMap<String, Variable>,
 }
 
-impl Default for ExecEnv {
+impl<H> Default for ExecEnv<H>
+where
+    H: Default + HostInterface,
+{
     fn default() -> Self {
-        Self {
-            stack: vec![Default::default()],
-            read_buf: Default::default(),
-            finalisers: vec![],
-        }
+        Self::with_host_interface(H::default())
     }
 }
 
@@ -85,15 +86,20 @@ enum HaltStatus {
 /// standard input.
 pub const READ_BITS: u8 = 3;
 
-impl ExecEnv {
+impl<H: HostInterface> ExecEnv<H> {
     /// Create a new Scope with no predefined variable definitions or
     /// other information.
-    pub fn new() -> Self {
-        Self::default()
+    pub fn with_host_interface(host_interface: H) -> Self {
+        Self {
+            stack: vec![Default::default()],
+            read_buf: Default::default(),
+            finalisers: vec![],
+            host_interface,
+        }
     }
 
     /// Create a new Scope with predefined variables
-    pub fn new_with_vars<I>(vars: I) -> Self
+    pub fn new_with_vars<I>(host_interface: H, vars: I) -> Self
     where
         I: IntoIterator<Item = (String, Variable)>,
     {
@@ -103,7 +109,9 @@ impl ExecEnv {
 
         Self {
             stack: vec![scope],
-            ..Default::default()
+            read_buf: Default::default(),
+            finalisers: vec![],
+            host_interface,
         }
     }
 
@@ -226,16 +234,10 @@ impl ExecEnv {
         match &stmt.item {
             Stmt::Print { expr, newline } => {
                 let value = self.eval_expr(expr)?;
-                if *newline {
-                    println!("{value}");
-                } else {
-                    print!("{value}");
-                    stdout()
-                        .lock()
-                        .flush()
+                self.host_interface
+                    .print(&value.to_string(), *newline)
                     .map_err(|e| Error::new(e.into(), stmt.span.clone()))?;
             }
-            }
             Stmt::Dim { ident, init } => {
                 let init = match init {
                     Some(e) => self.eval_expr(e)?,
@@ -315,12 +317,17 @@ impl ExecEnv {
             Stmt::Rlyeh => {
                 // Maybe print a creepy error message or something
                 // here at some point. ~~Alex
-                exit(random());
+                let code = random();
+                self.host_interface.exit(code);
+                return Err(Error::new(
+                    ErrorKind::NonExitingRlyeh(code),
+                    stmt.span.clone(),
+                ));
             }
             Stmt::Rickroll => {
-                stdout()
-                    .write_all(include_str!("rickroll").as_bytes())
-                    .expect("Failed to write to stdout");
+                self.host_interface
+                    .print(include_str!("rickroll"), false)
+                    .map_err(|e| Error::new(e.into(), stmt.span.clone()))?;
             }
             Stmt::Read(assignable) => {
                 let mut value = 0;
@@ -442,9 +449,13 @@ impl ExecEnv {
                     span: span.to_owned(),
                 })?;
 
-                stdout()
-                    .write_all(&output)
-                    .expect("Failed to write to stdout");
+                match String::from_utf8(output) {
+                    Ok(string) => self.host_interface.print(&string, false),
+                    Err(e) => self
+                        .host_interface
+                        .print(&format!("{:?}", e.as_bytes()), true),
+                }
+                .map_err(|e| Error::new(e.into(), span.clone()))?;
 
                 Ok(HaltStatus::Finished)
             }
@@ -537,11 +548,10 @@ impl ExecEnv {
         const BITS_PER_BYTE: u8 = 8;
 
         if self.read_buf.is_empty() {
-            let mut data = [0];
-            stdin().read_exact(&mut data)?;
+            let byte = self.host_interface.read_byte()?;
 
             for n in (0..BITS_PER_BYTE).rev() {
-                self.read_buf.push_back(((data[0] >> n) & 1) != 0);
+                self.read_buf.push_back(((byte >> n) & 1) != 0);
             }
         }
 
@@ -619,12 +629,15 @@ impl ExecEnv {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::ast::{Expr, Literal};
+    use crate::{
+        ast::{Expr, Literal},
+        host_interface::Standard,
+    };
 
     #[test]
     fn basic_expression_test() {
         // Check that 2 + 2 = 4.
-        let env = ExecEnv::new();
+        let env = ExecEnv::<Standard>::default();
         assert_eq!(
             env.eval_expr(&Spanned {
                 item: Expr::BinOp {
@@ -650,7 +663,7 @@ mod tests {
         // The sum of an integer and an aboolean causes an aboolean
         // coercion.
 
-        let env = ExecEnv::new();
+        let env = ExecEnv::<Standard>::default();
         assert_eq!(
             env.eval_expr(&Spanned {
                 item: Expr::BinOp {
@@ -675,7 +688,7 @@ mod tests {
     fn overflow_should_not_panic() {
         // Integer overflow should throw a recoverable error instead
         // of panicking.
-        let env = ExecEnv::new();
+        let env = ExecEnv::<Standard>::default();
         assert_eq!(
             env.eval_expr(&Spanned {
                 item: Expr::BinOp {
@@ -719,7 +732,7 @@ mod tests {
     // From here on out, I'll use this function to parse and run
     // expressions, because writing out abstract syntax trees by hand
     // takes forever and is error-prone.
-    fn eval(env: &mut ExecEnv, src: &str) -> Result<Value, Error> {
+    fn eval(env: &mut ExecEnv<Standard>, src: &str) -> Result<Value, Error> {
         // We can assume there won't be any syntax errors in the
         // interpreter tests.
         let ast = crate::parser::parse(src).unwrap();
@@ -731,7 +744,7 @@ mod tests {
         // Functions have no return values, so use some
         // pass-by-reference hacks to detect the correct
         // functionality.
-        let mut env = ExecEnv::new();
+        let mut env = ExecEnv::<Standard>::default();
 
         // Declaring and reading from a variable.
         eval(&mut env, "foo dim 32; bar dim foo + 1;").unwrap();
@@ -765,7 +778,7 @@ mod tests {
         // Declaration and assignment of variables declared in an `if`
         // statement should have no effect on those declared outside
         // of it.
-        let mut env = ExecEnv::new();
+        let mut env = ExecEnv::<Standard>::default();
         eval(
             &mut env,
             "foo dim 1; 2 =: foo; unless (never) { foo dim 3; 4 =: foo; }",

ablescript/src/lib.rs

@@ -6,6 +6,7 @@
 
 pub mod ast;
 pub mod error;
+pub mod host_interface;
 pub mod interpret;
 pub mod parser;
 pub mod value;

ablescript_cli/src/main.rs

@@ -46,7 +46,7 @@ fn main() {
                 if ast_print {
                     println!("{:#?}", ast);
                 }
-                ExecEnv::new().eval_stmts(&ast)
+                ExecEnv::<ablescript::host_interface::Standard>::default().eval_stmts(&ast)
             }) {
                 println!(
                     "Error `{:?}` occurred at span: {:?} = `{:?}`",

ablescript_cli/src/repl.rs

@@ -4,7 +4,7 @@ use rustyline::Editor;
 
 pub fn repl(ast_print: bool) {
     let mut rl = Editor::<()>::new();
-    let mut env = ExecEnv::new();
+    let mut env = ExecEnv::<ablescript::host_interface::Standard>::default();
 
     // If this is `Some`, the user has previously entered an
     // incomplete statement and is now completing it; otherwise, the