refactoring builtins

src/builtins.rs

@@ -1,29 +1,36 @@
 use crate::{
     error::ExecError,
-    runtime::{State, Value},
+    run::{Call, Context, Value},
 };
+use std::{boxed::Box, collections::HashMap, io::Write};
 
+#[derive(Clone, Copy)]
 pub enum Builtin {
     Echo,
 }
 
-impl Builtin {
-    pub fn lookup(name: &str) -> Option<Self> {
-        match name {
-            "echo" => Some(Self::Echo),
-            _ => None,
+impl Call for Builtin {
+    fn call(&self, ctx: &mut Context, args: &[Value]) -> Result<Value, ExecError> {
+        match self {
+            Builtin::Echo => Echo.call(ctx, args),
         }
     }
+}
 
-    pub fn call(&self, _: &mut State, args: &Vec<Value>) -> Result<Value, ExecError> {
-        match self {
-            Builtin::Echo => {
-                let args: Result<Vec<String>, ExecError> =
-                    args.into_iter().map(|arg| arg.try_as_string()).collect();
-                let args = args?;
-                println!("{}", args.join(" "));
-                Ok(Value::None)
-            }
-        }
+pub struct Echo;
+
+impl Call for Echo {
+    fn call(&self, ctx: &mut Context, args: &[Value]) -> Result<Value, ExecError> {
+        let args = args
+            .into_iter()
+            .map(|v| v.try_as_str())
+            .collect::<Result<Vec<_>, _>>()?;
+        _ = write!(ctx.stdout, "{}\n", args.join(" "));
+        Ok(Value::None)
     }
 }
+
+pub fn all() -> HashMap<&'static str, Builtin> {
+    use Builtin::*;
+    HashMap::from([("echo", Echo)])
+}

src/interactive.rs

@@ -1,8 +1,8 @@
 use crate::{
-    edit,
+    builtins, edit,
     log::*,
     output,
-    runtime::{self, Eval},
+    run::{self, Eval},
     syntax::parse,
 };
 
@@ -21,7 +21,6 @@ pub struct Session {
     pub editor: edit::Editor,
     pub stdout: output::Writer,
     pub stderr: output::Writer,
-    pub state: runtime::State,
 }
 
 impl Session {
@@ -30,11 +29,16 @@ impl Session {
             editor: edit::Editor::new()?,
             stdout: output::Writer::stdout()?,
             stderr: output::Writer::stderr()?,
-            state: runtime::State::new(),
         })
     }
 
     pub fn run(mut self) -> Result<()> {
+        let mut state = run::State::new();
+        let mut ctx = run::Context {
+            stdout: self.stdout.clone(),
+            stderr: self.stderr.clone(),
+            state: &mut state,
+        };
         info!("» shell session start --------");
         loop {
             self.editor.show_prompt()?;
@@ -49,7 +53,7 @@ impl Session {
                     continue;
                 }
             };
-            if let Err(e) = command.eval(&mut self.state) {
+            if let Err(e) = command.eval(&mut ctx) {
                 self.render_error(e)?;
             }
         }

src/main.rs

@@ -34,7 +34,7 @@ mod parse;
 mod prompt;
 
 /// the runtime state of the shell process
-mod runtime;
+mod run;
 
 /// syntax and semantic analysis
 mod syntax;

src/output.rs

@@ -94,6 +94,7 @@ fn log_output_mode(mode: Console::CONSOLE_MODE) {
     }
 }
 
+#[derive(Clone)]
 pub struct Writer {
     output: HANDLE,
 }

src/run.rs

@@ -1,10 +1,10 @@
-use crate::error::ExecError;
+use crate::{builtins, error::ExecError, input, output};
 use std::{collections::HashMap, process};
 
 /// Eval represents anything that can be evaluated at runtime.
 pub trait Eval {
     /// Evaluates the receiver, given the current runtime state.
-    fn eval(&self, ctx: &mut State) -> Result<Value, ExecError>;
+    fn eval(&self, ctx: &mut Context) -> Result<Value, ExecError>;
 }
 
 /// An individual value at runtime.
@@ -23,19 +23,13 @@ pub enum Value {
 
 impl Value {
     pub fn try_to_string(self) -> Result<String, ExecError> {
-        match self {
-            Value::None => Err(ExecError::type_error("expected text value, saw None value")),
-            Value::Text(v) => Ok(v),
-            Value::ExitStatus(_) => Err(ExecError::type_error(
-                "expected text value, saw ExitStatus value",
-            )),
-        }
+        Ok(self.try_as_str()?.to_string())
     }
 
-    pub fn try_as_string(&self) -> Result<String, ExecError> {
+    pub fn try_as_str(&self) -> Result<&str, ExecError> {
         match self {
             Value::None => Err(ExecError::type_error("expected text value, saw None value")),
-            Value::Text(v) => Ok(v.clone()),
+            Value::Text(v) => Ok(&v),
             Value::ExitStatus(_) => Err(ExecError::type_error(
                 "expected text value, saw ExitStatus value",
             )),
@@ -44,7 +38,7 @@ impl Value {
 }
 
 impl Eval for Value {
-    fn eval(&self, _: &mut State) -> Result<Value, ExecError> {
+    fn eval(&self, _: &mut Context) -> Result<Value, ExecError> {
         Ok(self.clone())
     }
 }
@@ -56,12 +50,32 @@ impl Eval for Value {
 pub struct State {
     #[allow(unused)]
     variables: HashMap<&'static str, Value>,
+    pub(crate) builtins: HashMap<&'static str, builtins::Builtin>,
 }
 
 impl State {
     pub fn new() -> Self {
         Self {
             variables: HashMap::new(),
+            builtins: builtins::all(),
         }
     }
+
+    pub fn has_builtin(&self, name: &str) -> bool {
+        self.builtins.contains_key(name)
+    }
+
+    pub fn builtin(&self, name: &str) -> Option<builtins::Builtin> {
+        self.builtins.get(name).copied()
+    }
+}
+
+pub trait Call {
+    fn call(&self, ctx: &mut Context, args: &[Value]) -> Result<Value, ExecError>;
+}
+
+pub struct Context<'s> {
+    pub(crate) stdout: output::Writer,
+    pub(crate) stderr: output::Writer,
+    pub(crate) state: &'s mut State,
 }

src/syntax.rs

@@ -3,7 +3,7 @@ use crate::{
     error::{ExecError, ParseError},
     lex::{Lexer, Token},
     parse,
-    runtime::{Eval, State, Value},
+    run::{Call, Context, Eval, Value},
 };
 use std::{collections::HashSet, process};
 
@@ -15,7 +15,7 @@ pub enum Element {
 }
 
 impl Eval for Element {
-    fn eval(&self, ctx: &mut State) -> Result<Value, ExecError> {
+    fn eval(&self, ctx: &mut Context) -> Result<Value, ExecError> {
         use Element::*;
         match self {
             Block(block) => block.eval(ctx),
@@ -39,7 +39,7 @@ impl Block {
 }
 
 impl Eval for Block {
-    fn eval(&self, ctx: &mut State) -> Result<Value, ExecError> {
+    fn eval(&self, ctx: &mut Context) -> Result<Value, ExecError> {
         let mut v = Value::None;
         for cmd in self.commands.iter() {
             v = cmd.eval(ctx)?;
@@ -55,21 +55,27 @@ pub struct Command {
 }
 
 impl Command {
-    fn eval_args(&self, ctx: &mut State) -> Result<Vec<Value>, ExecError> {
-        self.args.iter().map(|elem| elem.eval(ctx)).collect()
+    fn exec_builtin(&self, ctx: &mut Context, builtin: Builtin) -> Result<Value, ExecError> {
+        let args = self
+            .args
+            .iter()
+            .map(|elem| elem.eval(ctx))
+            .collect::<Result<Vec<_>, _>>()?;
+        builtin.call(ctx, &args)
     }
 
-    fn exec_command(&self, ctx: &mut State, name: &str) -> Result<Value, ExecError> {
-        let mut proc = process::Command::new(&name);
+    fn exec_command(&self, ctx: &mut Context, name: &str) -> Result<Value, ExecError> {
+        let args = self
+            .args
+            .iter()
+            .map(|elem| elem.eval(ctx)?.try_to_string())
+            .collect::<Result<Vec<_>, _>>()?;
 
-        if self.args.len() > 0 {
-            let args = self
-                .args
-                .iter()
-                .map(|elem| elem.eval(ctx)?.try_to_string())
-                .collect::<Result<Vec<String>, ExecError>>()?;
+        let mut proc = process::Command::new(&name);
+        if args.len() > 0 {
             proc.args(args);
         }
+
         let mut child = proc.spawn().map_err(|e| ExecError::ProcessSpawnError {
             name: name.to_string(),
             source: e,
@@ -85,17 +91,12 @@ impl Command {
 }
 
 impl Eval for Command {
-    fn eval(&self, ctx: &mut State) -> Result<Value, ExecError> {
-        let name = self.name.eval(ctx)?.try_to_string()?;
-
-        match Builtin::lookup(&name) {
-            Some(builtin) => {
-                let args = self.eval_args(ctx)?;
-                // let args: Vec<&str> = args.into_iter().map(|arg| arg).collect();
-
-                builtin.call(ctx, &args)
-            }
-            None => self.exec_command(ctx, &name),
+    fn eval(&self, ctx: &mut Context) -> Result<Value, ExecError> {
+        let name = self.name.eval(ctx)?;
+        let name = name.try_as_str()?;
+        match ctx.state.builtin(name) {
+            Some(builtin) => self.exec_builtin(ctx, builtin),
+            None => self.exec_command(ctx, name),
         }
     }
 }