[oden] Start on custom loader

src/script.rs

@@ -1,9 +1,40 @@
-use oden_js::{Context, Runtime, Value};
+use oden_js::{
+    module::loader::{ModuleLoader, ModuleSource},
+    Context, ContextRef, Result, Runtime, Value,
+};
+use std::ffi::OsStr;
+use std::path::Path;
 use std::sync::mpsc::{channel, Receiver};
 
 pub mod graphics;
 use graphics::GraphicsCommand;
 
+fn transpile_to_javascript(_path: &str, input: String) -> Result<String> {
+    Ok(input)
+}
+
+struct Loader {}
+
+impl Loader {
+    pub fn new() -> Loader {
+        Loader {}
+    }
+}
+
+impl ModuleLoader for Loader {
+    fn load(&self, _context: &ContextRef, name: &str) -> Result<ModuleSource> {
+        let path = Path::new(name);
+        let contents = std::fs::read_to_string(path)?;
+        let contents = if path.extension().and_then(OsStr::to_str) == Some("ts") {
+            transpile_to_javascript(name, contents)?
+        } else {
+            contents
+        };
+
+        Ok(ModuleSource::JavaScript(contents))
+    }
+}
+
 pub struct ScriptContext {
     context: Context,
     init: Value,
@@ -16,7 +47,7 @@ pub struct ScriptContext {
 
 impl ScriptContext {
     pub fn new() -> Self {
-        let runtime = Runtime::new();
+        let runtime = Runtime::with_loader(Loader::new());
 
         let mut context = Context::new(runtime);
         context.add_intrinsic_bigfloat();