Cli

src/main.rs

@@ -2,6 +2,99 @@ pub mod codegen;
 pub mod errors;
 pub mod parser;
 
+use std::fs;
+use std::path::PathBuf;
+use std::process;
+
 fn main() {
-    println!("Hello, world!");
+    let args: Vec<String> = std::env::args().collect();
+
+    if args.len() < 2 {
+        print_usage();
+        process::exit(1);
+    }
+
+    match args[1].as_str() {
+        "build" => {
+            if args.len() < 3 {
+                eprintln!("error: expected a file path\n  usage: mist build <file.ms>");
+                process::exit(1);
+            }
+            cmd_build(&args[2]);
+        }
+        "check" => {
+            if args.len() < 3 {
+                eprintln!("error: expected a file path\n  usage: mist check <file.ms>");
+                process::exit(1);
+            }
+            cmd_check(&args[2]);
+        }
+        "version" | "--version" | "-v" => {
+            println!("mist {}", env!("CARGO_PKG_VERSION"));
+        }
+        "help" | "--help" | "-h" => {
+            print_usage();
+        }
+        unknown => {
+            eprintln!("error: unknown command '{}'\n", unknown);
+            print_usage();
+            process::exit(1);
+        }
+    }
+}
+
+fn cmd_build(path: &str) {
+    let source = read_ms_file(path);
+    match parser::parse(&source) {
+        Ok(ast) => {
+            println!("parsed {} top-level items", ast.statements.len());
+            // codegen will go here
+        }
+        Err(e) => {
+            eprintln!("parse error:\n{}", e);
+            process::exit(1);
+        }
+    }
+}
+
+fn cmd_check(path: &str) {
+    let source = read_ms_file(path);
+    match parser::parse(&source) {
+        Ok(_) => {
+            println!("ok");
+        }
+        Err(e) => {
+            eprintln!("parse error:\n{}", e);
+            process::exit(1);
+        }
+    }
+}
+
+fn read_ms_file(path: &str) -> String {
+    let pb = PathBuf::from(path);
+
+    if !pb.exists() {
+        eprintln!("error: file '{}' not found", path);
+        process::exit(1);
+    }
+
+    if pb.extension().and_then(|e| e.to_str()) != Some("ms") {
+        eprintln!("error: expected a .ms file, got '{}'", path);
+        process::exit(1);
+    }
+
+    fs::read_to_string(&pb).unwrap_or_else(|e| {
+        eprintln!("error: could not read '{}': {}", path, e);
+        process::exit(1);
+    })
+}
+
+fn print_usage() {
+    println!("mist - the mist compiler");
+    println!();
+    println!("usage:");
+    println!("  mist build <file.ms>   compile a .ms file to go");
+    println!("  mist check <file.ms>   parse and validate without compiling");
+    println!("  mist version           print the compiler version");
+    println!("  mist help              print this message");
 }