refactor: platform trait, platform-specific code handling into platform module

src/platform/emscripten.rs

@@ -0,0 +1,61 @@
+//! Emscripten platform implementation.
+
+use std::borrow::Cow;
+use std::time::Duration;
+
+use crate::asset::{Asset, AssetError};
+use crate::platform::{Platform, PlatformError};
+
+/// Emscripten platform implementation.
+pub struct EmscriptenPlatform;
+
+impl Platform for EmscriptenPlatform {
+    fn sleep(&self, duration: Duration) {
+        unsafe {
+            emscripten_sleep(duration.as_millis() as u32);
+        }
+    }
+
+    fn get_time(&self) -> f64 {
+        unsafe { emscripten_get_now() }
+    }
+
+    fn init_console(&self) -> Result<(), PlatformError> {
+        Ok(()) // No-op for Emscripten
+    }
+
+    fn get_canvas_size(&self) -> Option<(u32, u32)> {
+        Some(unsafe { get_canvas_size() })
+    }
+
+    fn get_asset_bytes(&self, asset: Asset) -> Result<Cow<'static, [u8]>, AssetError> {
+        use sdl2::rwops::RWops;
+        use std::io::Read;
+
+        let path = format!("assets/game/{}", asset.path());
+        let mut rwops = RWops::from_file(&path, "rb").map_err(|_| AssetError::NotFound(asset.path().to_string()))?;
+
+        let len = rwops.len().ok_or_else(|| AssetError::NotFound(asset.path().to_string()))?;
+
+        let mut buf = vec![0u8; len];
+        rwops
+            .read_exact(&mut buf)
+            .map_err(|e| AssetError::Io(std::io::Error::new(std::io::ErrorKind::Other, e)))?;
+
+        Ok(Cow::Owned(buf))
+    }
+}
+
+// Emscripten FFI functions
+extern "C" {
+    fn emscripten_get_now() -> f64;
+    fn emscripten_sleep(ms: u32);
+    fn emscripten_get_element_css_size(target: *const u8, width: *mut f64, height: *mut f64) -> i32;
+}
+
+unsafe fn get_canvas_size() -> (u32, u32) {
+    let mut width = 0.0;
+    let mut height = 0.0;
+    emscripten_get_element_css_size("canvas\0".as_ptr(), &mut width, &mut height);
+    (width as u32, height as u32)
+}