cli: move compilation to build-subcommand

crates/cli/src/main.rs

@@ -5,36 +5,16 @@ use std::{fs::read_to_string, io, process::exit};
 use thiserror::Error;
 
 fn main() {
-    let cli = argh::from_env();
-    if let Err(e) = run(cli) {
+    let cli: Cli = argh::from_env();
+    let res = match cli.command {
+        Commands::Build(cmd) => build(cmd),
+    };
+    if let Err(e) = res {
         eprintln!("error: {}", e);
         exit(1);
     }
 }
 
-fn run(cli: Cli) -> HuffResult {
-    let src = read_to_string(&cli.filename)?;
-    let filename: String = cli.filename;
-    match parse(&src) {
-        Ok(ast) => println!("{:?}", ast),
-        Err(errs) => errs.into_iter().for_each(|e| {
-            Report::build(ReportKind::Error, filename.clone(), e.span().start)
-                .with_config(Config::default().with_index_type(IndexType::Byte))
-                .with_message(e.reason())
-                .with_label(
-                    Label::new((filename.clone(), e.span().into_range()))
-                        .with_message(e.reason())
-                        .with_color(Color::Red),
-                )
-                .finish()
-                .print(sources([(filename.clone(), &src)]))
-                .unwrap()
-        }),
-    }
-
-    Ok(())
-}
-
 #[derive(Error, Debug)]
 enum HuffError {
     /// Wrapper around `io::Error`
@@ -44,12 +24,50 @@ enum HuffError {
     // Parser(Report),
     // Parser(#[from] ParseError<usize, Token<'src>, huff_ast::Error>),
 }
-
 type HuffResult = Result<(), HuffError>;
 
+fn build(cmd: BuildCommand) -> HuffResult {
+    let src = read_to_string(&cmd.filename)?;
+    let filename: String = cmd.filename;
+    match parse(&src) {
+        Ok(ast) => println!("{:?}", ast),
+        Err(errs) => {
+            errs.into_iter().for_each(|e| {
+                Report::build(ReportKind::Error, filename.clone(), e.span().start)
+                    .with_config(Config::default().with_index_type(IndexType::Byte))
+                    // .with_message(e.reason())
+                    .with_label(
+                        Label::new((filename.clone(), e.span().into_range()))
+                            .with_message(e.reason())
+                            .with_color(Color::Red),
+                    )
+                    .finish()
+                    .print(sources([(filename.clone(), &src)]))
+                    .unwrap()
+            });
+        }
+    }
+
+    Ok(())
+}
+
 #[derive(FromArgs)]
 /// Huff Language Compiler
 struct Cli {
+    #[argh(subcommand)]
+    command: Commands,
+}
+
+#[derive(FromArgs)]
+#[argh(subcommand)]
+enum Commands {
+    Build(BuildCommand),
+}
+
+#[derive(FromArgs)]
+#[argh(subcommand, name = "build")]
+/// Build compiles a huff file.
+struct BuildCommand {
     /// filename
     #[argh(positional)]
     filename: String,